Keywords BCR-ABL - arterial thrombotic events - tyrosine kinase inhibitors - chronic myeloid
leukemia
Introduction
In 2001, the approval of imatinib , the first-in-class tyrosine kinase inhibitor (TKI) targeting BCR-ABL, transformed
the prognosis of patients with chronic-phase (CP) chronic myeloid leukemia (CML) from
a life-threatening condition to a manageable and chronic disease.[1 ] Yet, despite satisfactory outcomes, 33% of patients did not achieved optimal response
because of treatment resistance or intolerance.[1 ] The identification of the predominant resistance mechanism (i.e., point mutations
in the kinase domain of Bcr-Abl) led to the development of second-generation BCR-ABL
TKIs (dasatinib, nilotinib, and bosutinib, respectively, approved in 2006, 2007, and
2012) active against most of the BCR-ABL mutated forms.[2 ]
[3 ] Second-generation TKIs demonstrated no or little improvement of the overall survival
compared with imatinib,[4 ]
[5 ]
[6 ] but two of these (i.e., dasatinib and nilotinib) improve surrogate outcomes and
permit quicker and deeper achievement of molecular response, which is criteria to
try treatment cessation (i.e., MR[4 ] or higher molecular response stable for at least 2 years).[7 ] Based on these results, dasatinib and nilotinib were approved in 2010 for frontline
management of CML, whereas bosutinib is used only after failure or intolerance of
first-line BCR-ABL TKIs. Unfortunately, these treatments were ineffective against
a common mutation (14% of all mutations) in the gatekeeper residue of BCR-ABL (i.e.,
the T315I[a ] mutation),[8 ]
[9 ]
[10 ] requiring the development of a third-generation TKI (ponatinib), efficient against
this mutation. Ponatinib is currently the only treatment active against the T315I
mutation and is therefore reserved for patients with this mutation or for patients
resistant to frontline treatments.[11 ]
Since its approval, the first-generation TKI, imatinib, has demonstrated reassuring
safety profile, with low rate of grade 3/4 adverse events and excellent tolerability.[12 ]
[13 ] Conversely, new-generation BCR-ABL TKIs—nilotinib, dasatinib, bosutinib, and ponatinib—are
more recent and display different safety profile. Dasatinib, nilotinib, and ponatinib
are largely associated with fluid retention and dasatinib specifically induces high
rate of pleural effusions.[14 ]
[15 ]
[16 ]
[17 ]
[18 ] Nilotinib induces metabolic disorders such as dyslipidemia and hyperglycemia, whereas
bosutinib safety profile is mainly characterized by gastrointestinal events (i.e.,
diarrhea, nausea, vomiting).[19 ]
[20 ] Finally, ponatinib has been rapidly associated with high rate of vascular occlusion.[21 ]
Recently, meta-analyses of randomized clinical trials established that ponatinib is
not the only new-generation TKI that increases the cardiovascular risk.[22 ]
[23 ] The four new-generation BCR-ABL TKIs increase the risk of vascular occlusive events
compared with imatinib, especially arterial occlusive diseases, and this is in accordance
with clinical trial data.[22 ]
[23 ]
[24 ]
[25 ] However, this cardiovascular risk is controversy for dasatinib because of the low
incidence (1.1 per 100 patient-year) of cardiovascular events in clinical trials.[26 ]
[27 ] Recently, a large retrospective analysis of CP-CML patients treated with BCR-ABL
TKIs at the MD Anderson Cancer Center confirmed the increased risk of vascular occlusive events with dasatinib.[28 ] Another controversial point is the effect of imatinib on the cardiovascular system.
Indeed, imatinib is associated with low risk of cardiovascular events and it was therefore
hypothesized that imatinib prevents their occurrence.[29 ]
[30 ] Clinical data indicate that most patients developing arterial occlusive events with
new-generation BCR-ABL TKIs are high-risk patients, but cardiovascular events also
occurred in young and healthy patients. Additional information on clinical safety
of BCR-ABL TKIs is described in the Supplementary Material ([Table S1 ]). We assume that the mechanism underlying arterial thrombosis with BCR-ABL TKIs
might be multiple. The predominance of arterial events raised concerns about the impact
of BCR-ABL TKIs on platelet functions, atherosclerosis, and metabolism, and precluded
prothrombotic states to be responsible of these events.[31 ]
This review particularly focuses on the contribution of glucose and lipid metabolism,
atherosclerosis, and platelets in the occurrence of cardiovascular events with new-generation
TKIs. The last section discusses relevant off-targets that might be implicated in
the cardiovascular toxicity. The discovery of the mechanism(s) by which arterial occlusive
events arose in CML patients would help in the management of patients treated with
BCR-ABL TKIs and implement risk minimization measures. Discovery of the pathophysiology
of these events in CML patients might also led to the development of predictive biomarkers
or to the development of new therapies with no or reduced cardiovascular toxicity
profile while keeping an unaltered efficacy.
Impact on Platelet Functions
Impact on Platelet Functions
BCR-ABL TKIs are associated with both bleeding and thrombotic complications. [Table 1 ] describes experiments assessing the impact of BCR-ABL TKIs on platelet production
and functions. Imatinib and dasatinib induce hemorrhagic events in patients with CML.
Interestingly, dasatinib-associated hemorrhages occurred both in patients with and
without thrombocytopenia.[32 ] In vitro and in vivo investigations demonstrated that dasatinib affects both platelet
functions (i.e., platelet aggregation, secretion, and activation) and platelet formation
by impairment of megakaryocyte migration.[33 ]
[34 ]
[35 ]
[36 ] Furthermore, dasatinib decreases thrombus formation in vitro, in vivo, and ex vivo,[34 ] and decreases the number of procoagulant platelets (i.e., phosphatidylserine-exposing
platelets).[35 ] Several dasatinib off-targets are implicated in platelet signaling and functions
including members of the SFKs (e.g., Src, Lyn, Fyn, Lck, and Yes) ([Fig. 1 ]).[37 ]
[38 ] However, SFKs are also inhibited by bosutinib without disturbance of platelet aggregation
and adhesion. Dasatinib also inhibits Syk, BTK, and members of the ephrin family[b ] (e.g., EphA2), all known to be involved in platelet functions.
Table 1
In vitro and ex vivo investigations of the effects of BCR-ABL TKIs on platelet production
and functions
Endpoints
Methods
Models
TKIs
Findings
Ref.
Platelet production
Platelet count
Murine whole blood
Dasatinib
Thrombocytopenia
platelet production
[33 ]
Flow cytometry (DNA ploidy)
Migration assay (Dunn chamber)
Megakaryocyte primary culture
Dasatinib
megakaryocyte differentiation
megakaryocyte migration
proplatelet formation
[33 ]
Platelet aggregation
Born aggregometry; Light transmission aggregometry
Washed human platelet
Imatinib
= CRP-, collagen- and thrombin-induced platelet aggregation
[38 ]
[39 ]
[42 ]
Light transmission aggregometry
Human platelet (PRP)
Imatinib
ADP-induced platelet aggregation
collagen- and CRP-induced platelet aggregation
[34 ]
Light transmission aggregometry, immunostaining (PAC-1)
Human platelet (PRP); patient blood
Dasatinib
ADP-, collagen-, thrombin- and CRP-induced platelet aggregation
[34 ]
[35 ]
[38 ]
Light transmission aggregometry; Born aggregometry
Human platelet (PRP); Washed human platelet
Nilotinib
= platelet aggregation
[34 ]
[39 ]
[42 ]
Born aggregometry
Washed human platelet
Ponatinib
CRP-induced platelet aggregation
= thrombin-induced platelet aggregation
[42 ]
Platelet activation
Immunostaining (PS)
Washed human platelet
Imatinib
= PS exposure
[42 ]
Western blot
Human platelet lysate
Imatinib
= Src, Lyn, LAT, and BTK activation
[42 ]
Immunostaining (PS)
Patient blood
Dasatinib
PS exposure
[35 ]
Immunostaining (PS)
Washed human platelet
Nilotinib
= PS exposure
[42 ]
Immunostaining (PS)
Patient blood
Nilotinib
PS exposure
[35 ]
Western blot
Human platelet lysate
Nilotinib
= Src, Lyn, LAT and BTK activation
[42 ]
Immunostaining (PS)
Patient blood
Bosutinib
PS exposure
[35 ]
Immunostaining (PS)
Washed human platelet, patient blood
Ponatinib
PS exposure
[35 ]
[42 ]
Western blot
Human platelet lysate
Ponatinib
Src, Lyn, LAT and BTK activation
[42 ]
Granule release
Immunostaining (P-selectin)
Human platelet
Imatinib
thrombin-, PAR-1- and CRP-mediated α-granule release
= PAR-4-mediated α-granule release
[34 ]
Immunostaining (P-selectin)
Washed human platelet
Imatinib
= α-granule release
[42 ]
Immunostaining (P-selectin)
Human platelet
Dasatinib
thrombin-, PAR-1-, PAR-4- and CRP-mediated α-granule release
[34 ]
Immunostaining (P-selectin)
Washed human platelet
Nilotinib
= PAR-4-, CRP- and thrombin-mediated α-granule release
[34 ]
[42 ]
Immunostaining (P-selectin)
Murine platelet
Nilotinib
CRP-, PAR-4- and thrombin-mediated α-granule release
[34 ]
Immunostaining (P-selectin)
Human platelet
Nilotinib
PAR-1-mediated α-granule release
[34 ]
Immunostaining (P-selectin)
Washed human platelet
Ponatinib
α-granule release
[42 ]
Platelet spreading
Microscopy (platelet spreading)
Washed human platelet
Imatinib
= platelet spreading and lamellipodia formation
[42 ]
Microscopy (platelet spreading)
Washed human platelet
Nilotinib
= platelet spreading and lamellipodia formation
[42 ]
Microscopy (platelet spreading)
Washed human platelet
Ponatinib
platelet spreading and lamellipodia formation
[42 ]
Thrombus formation
In vitro flow study, PFA-100
Human blood, murine whole blood
Imatinib
= platelet deposition and thrombus volume
= closure time
[34 ]
[36 ]
[44 ]
Ex vivo and in vitro flow study
Murine whole blood, human whole blood
Imatinib
thrombus volume and aggregate formation
[34 ]
[42 ]
In vitro and ex vivo flow study
Human blood, murine whole blood, patient whole blood
Dasatinib
thrombus volume and platelet deposition
[34 ]
[35 ]
[36 ]
PFA-100
Human whole blood
Dasatinib
closure time (collagen/epinephrine activation)
= closure time (collagen/ADP activation)
[44 ]
Ex vivo flow study
Murine whole blood, patient whole blood
Nilotinib
thrombus volume (growth and stability)
[34 ]
In vitro flow study
Human whole blood, murine whole blood
Nilotinib
= platelet deposition and thrombus volume
[34 ]
[36 ]
[42 ]
In vitro flow study
Human blood
Bosutinib
platelet deposition (late)
[36 ]
PFA-100
Patient blood
Ponatinib
closure time
[41 ]
In vitro flow study
Human whole blood
Ponatinib
aggregate formation
[42 ]
Abbreviations: ADP, adenosine diphosphate; BTK, Bruton's tyrosine kinase; CRP, C-reactive
protein; DNA, deoxyribonucleic acid; LAT, linker for activation of T-cells; PAR, protease-activated
receptor; PFA, platelet function assay; PRP, platelet-rich plasma; PS, phosphatidyl
serine.
Fig. 1 Signaling pathways supporting platelet adhesion, activation, and aggregation. Tyrosine
kinases are involved in several pathways and contribute to platelet adhesion, aggregation,
and activation. Important players in platelet signaling are members of the Src family
kinases; particularly Lyn, Fyn, and cSRC. These three tyrosine kinases are inhibited
by dasatinib which might explain platelet dysfunction encountered with this treatment.
Additionally, dasatinib also inhibits BTK, Syk, EphA4, and EphB1—four tyrosine kinases
involved in platelet activation and aggregate stabilization. 5HT, 5-hydroxytryptamine;
ADP, adenosine diphosphate; Btk, Bruton's tyrosine kinase; Ca, calcium; Eph, ephrin;
FcR, Fc receptor; GP, glycoprotein; PAR, protease-activated receptor; PI3K, phosphoinositide
3-kinase; PLC, phospholipase C; TXA2, thromboxane A2; vWF, Von Willebrand factor.
Experimental assessments of platelet functions with imatinib demonstrate less pronounced
effects on platelets. Imatinib inhibits platelet aggregation only at high doses,[34 ] and does not interfere with platelet aggregation in vivo.[39 ] However, in vitro studies also indicate decreased platelet secretion and activation
by imatinib.[34 ] The mechanism by which imatinib inhibits platelet functions is unknown. Oppositely
to dasatinib, imatinib does not inhibit SFKs, ephrins, BTK, and Syk. A hypothesis
also suggests that imatinib induces bleeding disorders because of BCR-ABL rearrangements
in megakaryocytic cell lines, leading to clonal expansion of dysfunctional megakaryocytes.[40 ]
Even if ponatinib induces very few bleeding disorders, assessment of primary hemostasis
in CML patients demonstrated that ponatinib induces defect in platelet aggregation.
This impairment was found at all ponatinib dosage, in patients with or without low
platelet counts.[41 ] These results were in accordance with in vitro studies which previously demonstrated
similar characteristics than dasatinib (i.e., decrease of platelet spreading, aggregation,
P-selectin secretion, and phosphatidylserine exposure).[35 ]
[42 ] However, in vitro assays tested ponatinib at 1 µM, a dose far higher than the concentration
observed in patients on treatment.[43 ] Nilotinib and bosutinib are not associated with bleeding disorders in CML patients.
First in vitro studies demonstrated little or no effect on platelet aggregation and
activation with these two TKIs.[36 ]
[39 ]
[44 ] However, recent experiments described prothrombotic phenotype of platelets induced
by nilotinib, with increase of PAR-1[c ]–mediated platelet secretion, adhesion, and activation, without disturbing platelet
aggregation.[34 ] Additional studies demonstrated that nilotinib increases secretion of adhesive molecules
as well as thrombus formation and stability ex vivo.[34 ]
To summarize, dasatinib and imatinib induce hemorrhagic events through alteration
of platelet functions, but the molecular mechanism needs to be better determined.
Ponatinib also impairs platelet functions. Therefore, no current data involve platelets
in the pathogenesis of arterial thrombosis occurring with dasatinib and ponatinib.
Oppositely, nilotinib might induce arterial thrombosis through alteration of platelet
secretion, adhesion, and activation.
Metabolic Dysregulation
Glucose Metabolism
BCR-ABL TKIs have contradictory effect on glucose metabolism. Imatinib and dasatinib
improve glucose metabolism and type 2 diabetes management in CML patients (i.e., decrease
of antidiabetic drug dosage and reversal of type 2 diabetes).[14 ]
[45 ]
[46 ]
[47 ]
[48 ]
[49 ] This clinical profile is in accordance with in vivo studies in which imatinib is
effective to prevent the development of type 1 diabetes in prediabetic mice, without
impacting the adaptive immune system.[50 ] Therefore, imatinib is currently tested in clinical trials for patients suffering
from type 1 diabetes mellitus (NCT01781975). The mechanism(s) by which dasatinib and
imatinib improve glucose metabolism remains unknown. Global hypotheses suggest that
imatinib increases peripheral insulin sensitivity, promotes β-cell survival, or decreases
hepatic glucose production ([Fig. 2 ]).[51 ]
[52 ]
[53 ]
[54 ] This latter hypothesis (i.e., decreased hepatic glucose production by imatinib)
is not currently the preferred theory, whereas it was demonstrated that imatinib weakly
affects hepatic glucose production.[51 ] Several targets might be involved in this metabolic effect. PDGFR has already been
linked with type 1 diabetes reversal.[50 ] Hägerkvist et al hypothesized that c-Abl inhibition by imatinib promotes β-cell
survival through activation of NF-κB signaling and inhibition of proapoptotic pathways
([Fig. 2 ]).[53 ]
[54 ] Inhibition of c-Abl in β-cells might also increase insulin production and contribute
to the glucose regulation by imatinib.[55 ] It was also speculated that imatinib decreases insulin resistance in peripheral
tissues due to c-Abl-dependent JNK inactivation.[d ]
[51 ] Similar hypotheses might be translated to dasatinib because of the similar off-target
inhibitory profile (i.e., dasatinib also inhibits c-Abl and PDGFR). It was hypothesized
that imatinib and dasatinib impact glucose metabolism through reduced adipose mass.[51 ]
[56 ] However, clinical data do not demonstrate weight loss in CML patients and do not
favor this hypothesis. In both imatinib- and dasatinib-treated patients, increased
circulating adiponectin[e ] level correlates with decreased insulin resistance.[57 ]
[58 ] This correlation might be explained by the translocation of the glucose transporter
GLUT4[f ] from the cytoplasm to the cell membrane following adiponectin signaling.[59 ] Additionally, adiponectin has been related to decreased hepatic glucose production
which could be an additional mechanism by which imatinib and dasatinib improve glucose
metabolism.[60 ] It was speculated that the raise of adiponectin level with imatinib and dasatinib
is the consequence of increased adipogenesis subsequent to PDGFR inhibition.[61 ]
Fig. 2 Effects of BCR-ABL TKIs on glucose metabolism. Imatinib and dasatinib possess hypoglycemic
effects, whereas nilotinib increases blood glucose level and diabetes development.
The figure describes glucose metabolism and boxes contain emitted hypotheses for effects
of imatinib, dasatinib, and nilotinib on glucose metabolism. Four major hypotheses
have been emitted including impact on insulin production by β-cells, β-cell survival,
peripheral insulin sensitivity, and hepatic glucose production. ABL, Abelson; FAK,
focal adhesion kinase; GLUT, glucose transporter; IRS-1, insulin receptor substrate
1; JNK, c-Jun N-terminal kinases; MEKK1, MAPK/ERK kinase kinase 1; NF-κB, nuclear
factor-kappa B; PDK1, pyruvate dehydrogenase kinase 1; PI3K, phosphoinositide 3-kinase;
ROS, reactive oxygen species.
Oppositely to imatinib and dasatinib, case reports and clinical trials indicate that
nilotinib increases blood glucose level and promotes diabetes mellitus.[62 ]
[63 ]
[64 ]
[65 ] Indeed, 20% of nilotinib-treated patients developed diabetes after 3 years of treatment,[65 ] whereas 29% of patients suffer from increase of fasting glucose after 1 year of
therapy.[64 ] However, no variations of glycated hemoglobin were reported.[64 ]
[65 ] Clinical data indicate no direct effect of nilotinib on β-cells, but suggest fasting
insulin increase, fasting C-peptide decrease, and an increase of HOMA-IR values (i.e.,
a model to assess insulin resistance).[64 ]
[66 ]
[67 ] Therefore, the preferred hypothesis to explain the development of hyperglycemia
is the manifestation of insulin resistance. Weakened insulin secretion occurred sometimes,
but it is likely that this impairment is the consequence of β-cell exhaustion.[68 ] However, in vitro experiments demonstrated inhibitory effect of nilotinib on pancreatic
cell growth.[69 ] Breccia et al proposed an additional hypothesis linking development of hyperglycemia
and body mass index. They suggested that the development of hyperglycemia might be
the consequence of increase fat level tissue resulting in decrease peripheral insulin
sensitivity.[70 ] However, dietetic measures to restrict glucose exogenous uptake in patients who
developed hyperglycemia were not successful,[63 ] and nilotinib does not induce changes in patient body weight.[71 ] Little is known regarding the mechanism by which nilotinib induces insulin resistance.
Racil et al suggested that peripheral insulin resistance is mediated by c-Abl inhibition
which is involved in insulin receptor signaling ([Fig. 2 ]).[67 ] This hypothesis is contrary to the hypothesis described with dasatinib and imatinib
in which c-Abl enhances insulin sensitivity through c-Abl inhibition. These two hypotheses
describe different pathways involving c-Abl but with opposite outcomes. To date, no
hypothesis is preferred and additional studies are required to understand the opposite
effect on glucose metabolism between TKIs, whereas both have been attributed to c-Abl
inhibition. Interestingly, Frasca et al described opposite role of c-Abl in insulin
signaling depending on the receptor involved, the signaling pathway, and the cell
context.[72 ] Similar investigations should be performed in the context of c-Abl inhibition by
BCR-ABL TKIs. For bosutinib and ponatinib, little is known regarding their impact
on glucose metabolism, but no drastic changes in glucose profile has been reported
during clinical trials.
Lipid Metabolism
Similarly with glucose metabolism, effects on lipid metabolism are conflicting between
TKIs. Oppositely to in vivo study which demonstrated no impact of imatinib on total
cholesterol and triglycerides levels in diabetic mice,[29 ] imatinib is associated in CML patients with a rapid and progressive decrease of
cholesterol and triglycerides levels.[66 ]
[73 ]
[74 ]
[75 ] First hypothesis relates the inhibition of PDGFR by imatinib ([Fig. 3 ]). PDGFR is involved in the synthesis of the lipoprotein lipase (LPL) and in the
regulation of the lipoprotein receptor-related protein (LRP).[73 ]
[74 ] However, all BCR-ABL TKIs possess inhibitory activity against PDGFR but do not share
this positive impact on lipid profile. Recently, Ellis et al described that imatinib
impairs gene expression of proteins involved in plasma lipid regulation. Indeed, in
in vitro model of CML cells, imatinib affects gene expression of four genes implicated
in lipid synthesis (HMG-CoA reductase[g ] gene and apobec1[h ]), lipid clearance (LDLR gene[i ]) and in exchange of lipids from very low-density lipoprotein (VLDL) or low-density
lipoprotein (LDL) to high-density lipoprotein (HDL) (CETP[j ] gene). However, these studies were performed in a model of CML cells and need to
be confirmed in more relevant models (e.g., primary cell lines, hepatocytes).[76 ] Franceschino et al suggested that imatinib decreases diarrhea-related lipid absorption
due to inhibition of c-kit in interstitial Cajal cells (i.e., c-kit signaling is critical
for the survival and development of these cells).[73 ] However, this hypothesis is unlikely, few patients (3.3%) developed grade 3/4 diarrhea,
and patients treated with interferon-α and cytarabine developed diarrhea at a same
rate and do not present lipid level reduction in the phase 3 clinical trial (NCT00333840).
Fig. 3 Effects of BCR-ABL TKIs on lipid metabolism. Several hypotheses have been emitted
to explain the imatinib-induced hypolipidemic effect. Imatinib regulates expression
of genes involved in lipid metabolism: Apobec1 that regulates ApoB expression through
the introduction of a stop codon into ApoB mRNA (ApoB is essential for VLDL production),
and LDLR that is implicated in lipid clearance. Imatinib-induced PDGFR inhibition
influences LPL synthesis and dysregulates LRP. Dasatinib and nilotinib increase cholesterol
plasma level through an unknown mechanism. Global hypotheses can be emitted and include
increased hepatic lipid synthesis (possibly related to hyperinsulinemia) and decreased
lipid clearance through LDLR functional defect or decreased LPL synthesis. ABC, ATP-binding
cassette; C, cholesterol; CETP, cholesteryl ester transfer protein; CM, chylomicron;
FA, fatty acid; HMGCoA reductase, hydroxymethylglutaryl-CoA reductase; IDL, intermediate-density
lipoprotein; LDL, low-density lipoprotein; LDLR, low-density lipoprotein receptor;
LPL, lipoprotein lipase; LRP, lipoprotein receptor-related protein; PDGFR, platelet-derived
growth factor receptor; VLDL, very low-density lipoprotein.
Oppositely, dasatinib and mostly nilotinib are associated with an increase of cholesterol
level.[26 ]
[66 ]
[77 ] Nilotinib induces quick rise of total cholesterol, HDL, and LDL (i.e., within 3
months). Nilotinib-induced dyslipidemia are responsive to statin and lipid level normalized
after nilotinib discontinuation.[78 ] To date, the mechanism by which dasatinib and nilotinib impact lipid metabolism
is unknown. Future researches should determine how these treatments induce dyslipidemia.
Global hypotheses could be formulated and include an increase of lipid synthesis that
might be secondary to insulin resistance and hyperinsulinemia. This hypothesis is
particularly relevant with nilotinib and it is also associated with hyperglycemia.
Dasatinib and nilotinib might also decrease blood lipid clearance (e.g., disturbance
of LDLR and LPL synthesis). The development of dyslipidemia might contribute to the
occurrence of arterial occlusive events that occurred with nilotinib and dasatinib.
However, the relationship between impaired lipid metabolism and cardiovascular occlusive
events is unknown with BCR-ABL TKIs, and there is no indication that correct management
of lipid metabolism can prevent arterial thrombosis (e.g., stenosis occurred in a
nilotinib-treated patient despite the management of its hyperlipidemia through statin
treatment).[79 ] On their side, bosutinib and ponatinib do not disturb lipid metabolism.[78 ]
[80 ]
Effects on Atherosclerosis
Effects on Atherosclerosis
Endothelial Dysfunction
[Fig. S1 ] in the [Supplementary Material ] details the role of endothelial cells (ECs) in atherosclerosis. Several in vitro
and in vivo experiments assess the impact of imatinib on EC viability and functions
([Table 2 ]). These studies demonstrate that imatinib does not affect EC viability nor induce
apoptosis but increases EC proliferation.[39 ]
[81 ]
[82 ]
[83 ]
[84 ] Only one study reports a proapoptotic effect of imatinib on ECs, but their experiments
were performed on a cell line (i.e., EA.hy926 cells),[85 ] a model less reliable than primary cultures (e.g., HUVEC,[k ] HCAEC[l ]). In vitro studies also assessed the effect of imatinib on EC functions. In these
studies, imatinib does not influence adhesion molecule expressions (i.e., ICAM-1[m ] and VCAM-1[n ]), EC migration, reactive oxygen species (ROS) production, nor angiogenesis.[81 ]
[82 ]
[85 ]
[86 ]
[87 ] Letsiou et al suggested that imatinib decreases EC inflammation by decreasing the
secretion of proinflammatory mediators.[86 ] The impact of imatinib on endothelial permeability is not clear. Indeed, in vitro
studies demonstrate that imatinib increases endothelial permeability by decreasing
the level of plasma membrane VE-cadherin,[o ]
[85 ]
[86 ] whereas in vivo experiments indicate decreased vascular leak following imatinib
treatment in a murine model of acute lung injury.[88 ] Additionally, imatinib has been tested in patients suffering from acute lung injury,
a disease characterized by vascular leakage, and demonstrate promising clinical efficacy.
Therefore, imatinib might positively affect atherogenesis by decreasing endothelial
inflammation and reducing vascular leakage.
Table 2
In vivo and in vitro investigations of the effects of BCR-ABL TKIs on endothelial
cell viability and major functions
Endpoints
Methods
Models
TKIs
Findings
Ref.
EC proliferation/survival
Cell counting; trypan blue staining
EA.hy 926 cell; HCAEC
Imatinib
= EC viability <10µM
[84 ]
[85 ]
Caspase assay; Annexin V staining; Hoechst staining; TUNEL assay
HMEC-1; HUVEC; Human pulmonary EC; Mouse EC
Imatinib
= EC apoptosis
[81 ]
[82 ]
[87 ]
TUNEL assay; Annexin V staining
EA.hy 926 cell
Imatinib
EC apoptosis
[85 ]
MTT cell proliferation assay; 3 H-thymidine incorporation; WST-1 assay; cell counting
HMEC-1; HUVEC; HCAEC
Imatinib
= EC proliferation
[39 ]
[81 ]
[82 ]
[84 ]
Resazurin proliferation assay; PCNA expression
HUVEC; BAEC
Imatinib
EC proliferation (≥1.2 µM)
[83 ]
Caspase assay; Hoechst staining; Annexin V staining; TUNEL assay
Human pulmonary EC
Dasatinib
EC apoptosis
[87 ]
3 H-thymidine incorporation; WST-1 assay; MTT assay
HUVEC; HCAEC; HMEC-1; HCtAEC
Nilotinib
EC proliferation
[39 ]
[82 ]
[89 ]
Annexin V staining
HUVEC
Nilotinib
= EC apoptosis
[82 ]
Caspase assay; Annexin V staining
HCAEC; HUVEC
Ponatinib
EC apoptosis
[82 ]
[90 ]
3 H-thymidine incorporation; WST-1 assay
HUVEC; HMEC-1; EPC
Ponatinib
EC proliferation
[82 ]
[90 ]
Oxidative stress
Fluorescent ROS detection; Immunofluorescence (8-oxo-dG)
Human Pulmonary EC; Rat lung
Imatinib
= endothelial ROS
[87 ]
Fluorescent ROS detection; Immunofluorescence (8-oxo-dG)
Human Pulmonary EC; Rat lung
Dasatinib
endothelial ROS
[87 ]
EC migration
Wound scratch assay; Microchemotaxis assay; Transwell migration assay
HMEC-1; HUVEC; EA.hy 926 cell; HCAEC
Imatinib
= EC migration
[81 ]
[82 ]
[84 ]
[85 ]
Wound scratch assay
HUVEC; HCAEC; HMEC-1
Nilotinib
EC migration
[39 ]
Transwell migration assay
HUVEC
Nilotinib
= EC migration
[82 ]
Transwell migration assay
HUVEC
Ponatinib
EC migration
[82 ]
Angiogenesis
Tube-formation assay
HMEC-1; HUVEC
Imatinib
= angiogenesis
[81 ]
[82 ]
Tube-formation assay
HUVEC; HCAEC; HMEC-1
Nilotinib
angiogenesis
[39 ]
Tube-formation assay
HUVEC
Nilotinib
= angiogenesis
[82 ]
Tube-formation assay
HUVEC
Ponatinib
angiogenesis
[82 ]
Permeability
Permeability to albumin
EA.hy 926 cell
Imatinib
endothelial permeability (10 µM)
[85 ]
Immunofluorescence (VE-cadherin)
EA.hy 926 cell; HPAEC
Imatinib
membrane VE-cadherin (10 µM)
[85 ]
[86 ]
BAL protein levels
Mice (2-hit model of ALI)
Imatinib
BAL protein levels
[86 ]
[88 ]
Permeability to FITC-Dextran; permeability to HRP
HMEC-1; HUVEC; Human lung microvascular EC
Imatinib
= endothelial permeability
[94 ]
[147 ]
Immunostaining
HUVEC
Imatinib
intercellular gaps
[147 ]
Evans blue/albumin extravasation
Mice
Imatinib
Evans blue extravasation
[147 ]
Pulmonary microvascular permeability assay; permeability assay (FITC-Dextran)
Mice; HMEC-1; HPAEC
Dasatinib
endothelial permeability
[94 ]
Permeability assay (FITC-Dextran)
HRMEC
Dasatinib
VEGF-induced permeability
[148 ]
CAM expression
Confocal microscopy; ELISA; qRT-PCR; flow cytometry
HMEC-1; Pulmonary EC (rat lung); EA.hy926
Imatinib
= ICAM-1, VCAM-1 and E-selectin expression
= soluble ICAM-1, VCAM-1 and E-selectin
[81 ]
[87 ]
[149 ]
Immunoblotting (VCAM-1)
Human lung EC
Imatinib
VCAM-1 expression
[86 ]
Confocal microscopy
Pulmonary EC (rat lung)
Dasatinib
ICAM-1, VCAM-1 and E-selectin expression
[87 ]
ELISA
Rat
Dasatinib
soluble ICAM-1, VCAM-1 and E-selectin
[87 ]
qRT-PCR; flow cytometry
EA.hy926
Dasatinib
= ICAM-1, VCAM-1 and E-selectin expression
[149 ]
Unknown
HUVEC
Nilotinib
ICAM-1, VCAM-1 and E-selectin expression (≥1 µM)
[39 ]
qRT-PCR; flow cytometry
EA.hy926
Nilotinib
ICAM-1, VCAM-1 and E-selectin expression
[149 ]
Secretory
ELISA (IL-6; IL-8)
Stimulated HPAEC
Imatinib
IL-8 and IL-6 (LPS induced)
[86 ]
qRT-PCR ; ELISA (IL-1β; IL-6; TNF-α)
EA.hy926 cell ; HUVEC
Imatinib
= IL-1β, IL-6 and TNF-α expression and production
[149 ]
qRT-PCR ; ELISA (IL-1β; IL-6; TNF-α)
EA.hy926 cell ; HUVEC
Dasatinib
= IL-1β, IL-6 and TNF-α expression and production
[149 ]
qRT-PCR ; ELISA (IL-1β; IL-6; TNF-α)
EA.hy926 cell ; HUVEC
Nilotinib
= IL-6 and TNF-α expression and production
IL-1β expression and production
[149 ]
ELISA (t-PA; PAI-1; ET-1; vWF; total NO)
HCtAEC
Nilotinib
t-PA
PAI-1, ET-1, vWF and total NO
[89 ]
Adhesion
Unknown
HUVEC
Ponatinib
adhesion to plastic surface at 1 µM
[90 ]
Abbreviations: 8-oxo-dG, 8-hydroxy-2′-deoxyguanosine; ALI, acute lung injury; BAEC,
bovine aortic endothelial cell; BAL, bronchoalveolar level ; EC, endothelial cell;
ELISA, enzyme-linked immunosorbent assay; EPC, endothelial progenitor cell; ET-1,
endothelin 1; FITC, fluorescein isothiocyanate; HCAEC, human coronary artery endothelial
cell; HCtAEC, human carotid artery endothelial cell; HMEC-1, human microvascular endothelial
cell; HPAEC, human pulmonary artery endothelial cell; HRMEC, human retinal microvascular
endothelial cells; HUVEC, human umbilical vein endothelial cell; ICAM-1, intercellular
adhesion molecule 1; IL, interleukin; LPS, lipopolysaccharide; NO, nitric oxide; PAI-1,
plasminogen activator inhibitor-1; ROS, reactive oxygen species; t-PA, tissue plasminogen
activator; TUNEL, terminal deoxynucleotidyl transferase dUTP nick end labeling; VCAM-1,
vascular cell adhesion molecule 1; VE-cadherin, vascular endothelial cadherin; vWF,
Von Willebrand factor.
Nilotinib and ponatinib reduce EC proliferation and might impaired endothelial regeneration.[39 ]
[82 ]
[89 ]
[90 ] Additionally, ponatinib induces EC apoptosis, although it is well recognized that
high glucose concentration induces EC death,[91 ] suggesting that nilotinib might, by this intermediary, affect EC viability. Moreover,
clinical data indicate that dasatinib induces pulmonary arterial hypertension, whereas
imatinib is possibly beneficial in this disease.[92 ]
[93 ] This pathology is initiated by dysfunction or injury of pulmonary ECs.[87 ] Therefore, in vivo and in vitro studies investigated effect of imatinib and dasatinib
on pulmonary ECs and demonstrate that dasatinib induces apoptosis on pulmonary ECs
mediated by increased mitochondrial ROS production.[87 ] Future researches should assess if this effect is also found in arterial ECs and
ROS production should also be tested with other new-generation BCR-ABL TKIs.
In addition to their effect on EC viability, nilotinib and ponatinib also influence
EC functions, inhibit their migration, and decrease angiogenesis.[39 ]
[82 ] It was suggested that the antiangiogenic effect of ponatinib is the consequence
of VEGFR[p ] inhibition, but this hypothesis cannot explain the antiangiogenic effect of nilotinib
(i.e., nilotinib does not inhibit VEGFR).[82 ] Nilotinib also increases adhesion molecule expressions (i.e., ICAM-1, VCAM-1, and
E-selectin) in vitro,[39 ] suggesting that nilotinib might increase leukocyte recruitment. However, further
experiments are needed to validate this hypothesis (e.g., assessment of endothelium
permeability and transendothelial migration). Dasatinib also induces endothelium leakage
in vitro, and the RhoA-ROCK[q ] pathway is involved in this phenomenon.[94 ] It was demonstrated that RhoA activation induces the phosphorylation of myosin light
chain that increases the actomyosin contractibility and disrupt endothelial barrier.[94 ] Therefore, increased endothelium permeability is a potential mechanism by which
dasatinib and nilotinib promote atherosclerosis development and arterial thrombosis.
Likewise, it is plausible that ponatinib affects endothelium integrity because of
its inhibitory activity against VEGFR, which is recognized as a permeability-inducing
agent. Additional hypotheses suggest that inhibition of Abl kinase (i.e., Arg[r ] and c-Abl) and PDGFR might also be implicated in vascular leakage.[85 ] Finally, Guignabert et al demonstrated that both in rats and in CML patients taking
dasatinib, there is an increase of soluble adhesion molecules, which are well-known
markers of endothelial dysfunction.[87 ]
Inflammation
[Fig. S2 ] in the [Supplementary Material ] describes the role of immune cells and inflammation process during atherosclerosis.
[Table 3 ] summarizes in vitro studies that investigate impacts of BCR-ABL TKIs on survival,
proliferation, and major functions of monocytes, macrophages, and T-lymphocytes. Globally,
in vitro studies demonstrate that imatinib inhibits the development and maturation
of monocytes and alters monocyte functions.[95 ]
[96 ] Imatinib decreases production of proinflammatory cytokines (i.e., TNF-α[s ] and IL-6[t ]) and diminishes the potential of monocytes to phagocytose.[97 ]
[98 ] These impacts on monocyte functions are possibly related to c-fms[u ] inhibition.[99 ] Imatinib also inhibits macrophage functions in vitro. Imatinib decreases lipid uptake
without impacting the lipid efflux and decreases activity and secretion of two matrix
metalloproteinases (MMPs; i.e., MMP-2 and MMP-9[v ]) on a posttranscriptional level.[100 ] Additionally, imatinib inhibits T-lymphocyte activation and proliferation and decreases
proinflammatory cytokines secretion (i.e., IFN-γ[w ]).[101 ] The inhibition of monocyte, macrophage, and T-cell functions by imatinib might prevent
the development of atherosclerosis or reduce the risk of atherosclerotic plaque rupture.
Table 3
In vitro studies on effects of BCR-ABL TKIs on proliferation, survival, and major
functions of monocytes, macrophages, and T-lymphocytes
Endpoints
Methods
Models
TKIs
Findings
Ref.
Monocytes/Macrophages
Proliferation/survival
Propidium iodide staining
PBMC
Imatinib
= viability
[150 ]
Cell counting
Ovarian tumor ascites samples
Imatinib
macrophage production
[96 ]
Cell counting
Ovarian tumor ascites samples
Dasatinib
macrophage production
[96 ]
WST-1 assay
Human macrophages
Ponatinib
= macrophage viability
[82 ]
Monocyte differentiation
Morphology assessment
Human monocyte
Imatinib
differentiation into macrophages
[95 ]
Secretion
ELISA; qPCR
Human monocyte and macrophage; PBMC
Imatinib
TNF-α, IL-6 and IL-8 production
[97 ]
[150 ]
ELISA
PBMC; Human monocyte and macrophage
Imatinib
= IL-10 production
[150 ]
ELISA; Bioplex system; nitrite assay
Raw 264.7; bone-marrow derived macrophage
Dasatinib
TNF-α, IL-6, IL-12p40 and NO production
[103 ]
[151 ]
qPCR; Bioplex system
Primary macrophage (mice)
Dasatinib
IL-10 production
[103 ]
Bioplex system
Bone-marrow derived macrophage
Bosutinib
IL-6, IL-12p40 and TNF-α production
[103 ]
qPCR; Bioplex system
Primary macrophage (mice)
Bosutinib
IL-10 production
[103 ]
Phagocytosis
Antigen-uptake assay
Human monocyte
Imatinib
phagocytosis
[97 ]
Cholesterol uptake
Cholesterol uptake assay
THP-1; PBMC
Imatinib
LDL uptake
[100 ]
Cholesterol uptake assay
THP-1
Bosutinib
LDL uptake
[100 ]
MMP production/activity
Zymography
THP-1
Imatinib
MMP-2 and MMP-9 secretion and activity
[100 ]
T Lymphocytes
Proliferation/survival
3 H-TdR incorporation; CFSE staining; titrated thymidine
Naïve CD4+ T cell; Human T cell
Imatinib
T-cell proliferation
[101 ]
[152 ]
[153 ]
Annexin V staining; Caspase assay
Human T cell
Imatinib
= T-cell apoptosis
[101 ]
[152 ]
[153 ]
Annexin V staining
Human T cell
Imatinib
= T cell apoptosis
CFSE dye
Human T cell
Dasatinib
T-cell proliferation
[107 ]
Annexin V staining
PBMC; Human T cell
Dasatinib
= T cell viability
[105 ]
[107 ]
CFSE dye
CD8+ T cell; PBMC
Nilotinib
T cell proliferation
[106 ]
[154 ]
Secretion
ELISA
Human T cell; CD8+ and CD4+ T cell
Imatinib
IFN-γ production
[101 ]
[107 ]
ELISA; proteome profile array
Human T cell; PBMC
Dasatinib
TNF-α, IFN-γ, IL-2, IL-6, IL-17 production
[105 ]
[107 ]
Proteome profile array
PBMC
Dasatinib
chemotactic factors secretion
(SDF-1, MIP-1α, MIP-1β, MCP-1, CXCL-1)
[105 ]
ELISPOT assay
CD8+ T cell
Nilotinib
IFN-γ production
[154 ]
Activation
Immunofluorescence
Human T cell
Imatinib
T cell activation
[101 ]
Flow cytometry (CD25, CD69)
Human T cell
Imatinib
= T cell activation
[153 ]
Flow cytometry (CD25, CD69)
Human T cell; PBMC
Dasatinib
T cell activation
[105 ]
[107 ]
Flow cytometry (CD25, CD69)
Human T cell
Nilotinib
T cell activation
[154 ]
Abbreviations: CFSE, carboxyfluorescein succinimidyl ester; CXCL1, (C-X-C motif) ligand
1; ELISA, enzyme-linked immunosorbent assay; ELISPOT, enzyme-linked immunospot; IFN,
interferon; IL, interleukin; MCP, monocyte chemoattractant protein-1; MIP-1, macrophage
inflammatory protein 1; NO, nitric oxide; PBMC, peripheral blood mononuclear cell;
qPCR, quantitative polymerase chain reaction; SDF-1, stromal cell-derived factor 1;
TNF, tumor necrosis factor.
Effects of new-generation TKIs on inflammatory cells were less studied, but first
experiments indicate similarities with imatinib about its impact on monocytes and
macrophages. Both dasatinib and nilotinib have similar inhibitory profile on macrophage-colony
formation that has been linked to CSFR inhibition.[96 ]
[102 ] Dasatinib also possesses anti-inflammatory functions by attenuating proinflammatory
cytokines production (i.e., TNF-α, IL-6, and IL-12[x ]) by macrophages and increasing production of anti-inflammatory mediator (i.e., IL-10[y ]).[103 ] These effects are thought to be mediated by SIK[z ] inhibition, a subfamily of three serine/threonine kinases that regulate macrophage
polarization.[103 ]
[104 ] Finally, dasatinib is associated with decreased T-cell functions and particularly
it decreases the production of proinflammatory cytokines (e.g., TNF-α, IFN-γ) and
chemotactic mediators.[105 ] Nilotinib and bosutinib also possess anti-inflammatory activity and decrease cytokine
production and T-cell activation.[103 ]
[106 ] Inhibition of Lck,[ai ] a tyrosine kinase implicated in T-cell receptor signaling, is implicated in the
impairment of T-cell functions by dasatinib and nilotinib.[107 ]
[108 ] It has been hypothesized that nilotinib decreases mast cell activity through c-kit
inhibition,[62 ]
[109 ] which might result in a decrease of the vascular repair system.[39 ]
[62 ] Clinical profile of nilotinib in patients with CML consolidates this hypothesis
and demonstrates a decreased of mast cell level.[39 ] However, similar decreased of mast cell is also reported with imatinib without high
rate of arterial thrombosis.[110 ]
Globally, BCR-ABL TKIs possess reassuring profile on inflammatory cells. However,
impact of new-generation TKIs on several functions of macrophages have not been assessed
(e.g., MMP secretion and activity, lipid uptake, and foam cell formation), whereas
effect of ponatinib on inflammatory cells is unknown. The assessment of lipid uptake
and foam cell formation is particularly relevant with new-generation TKIs because
there are numerous interactions between TKIs and ABC transporters.[aii ]
[111 ]
[112 ]
Fibrous Cap Thickness
[Fig. S3 ] in the [Supplementary Material ] describes the mechanism by which atherosclerotic plaque ruptures and induces arterial
thrombosis. [Table 4 ] summarizes in vitro and in vivo experiments performed on VSMCs and fibroblasts.
Imatinib decreases VSMC proliferation and growth but results are conflicting about
its impact on apoptosis. Some studies demonstrate no impact on SMC apoptosis, whereas
others indicate increased SMC death.[83 ]
[113 ]
[114 ]
[115 ]
[116 ] Imatinib also affects VSMC functions and decreases their migration and LDL binding,
inducing decreased LDL retention by the sub-endothelium.[113 ]
[117 ] Imatinib also exerts negative effect on the synthesis of major ECM components (type
I collagen and fibronectin A) by fibroblasts, correlating to decreased ECM accumulation
in vivo.[118 ] The impact of imatinib on SMCs is thought to be mediated by PDGFR inhibition,[114 ] which is involved in several VSMC functions including VSMC survival and plasticity.[113 ] Subsequent to the hypothesis that imatinib inhibits PDGFR signaling, prevents abundant
SMC and fibroblast proliferation, and inhibits abundant ECM accumulation, imatinib
has been tested for the management of several fibrotic diseases (e.g., dermal and
liver pulmonary fibrosis, systemic sclerosis).[30 ]
[118 ]
[119 ] Imatinib successfully acts on pulmonary fibrosis and pulmonary arterial hypertension
(i.e., a disease involving vascular remodeling mediated by pulmonary SMC proliferation),[93 ]
[114 ] and has beneficial activity in sclerotic chronic graft-versus-host disease.[120 ] Finally, imatinib was tested in vivo for the prevention of cardiovascular diseases
and demonstrates efficacy for the treatment of myocardial fibrosis by reducing ECM
component synthesis (i.e., procollagen I and III).[30 ] In a rat model, imatinib successfully inhibits stenosis after balloon injury and
presents interest in intimal hyperplasia and stenosis after bypass grafts.[115 ]
[116 ]
[121 ]
[122 ]
[123 ] Imatinib also successfully prevents arterial thrombosis following microvascular
surgery in rabbits.[124 ] Imatinib was also encompassed in a stent but do not demonstrate efficacy in restenosis
prevention.[84 ]
Table 4
In vitro and in vivo studies on effects of BCR-ABL TKIs on proliferation, survival,
and major functions of smooth muscle cells and fibroblasts
Endpoints
Methods
Models
TKIs
Findings
Ref.
Proliferation/survival
Resazurin assay; immunofluorescence; 3 H-thymidine incorporation; BrdU incorporation; MTT assay
HVSMC; BAoSMC; PASMC; ASMC; VSMC; HAoSMC; HCASMC; Rabbit
Imatinib
SMC proliferation
[83 ]
[84 ]
[114 ]
[115 ]
[116 ]
[123 ]
[155 ]
Caspase assay; PARP (Western blot); JC-1 dye; Annexin V staining
BAoSMC; Dermal fibroblast; PASMC
Imatinib
= SMC/fibroblast apoptosis
[83 ]
[118 ]
[155 ]
TUNEL; caspase assay
PASMC; HAoSMC; Rabbit
Imatinib
SMC apoptosis (PDGF-stimulated)
[114 ]
[116 ]
[123 ]
Trypan blue exclusion
HCASMC; A10 cell line
Imatinib
= SMC viability
[84 ]
Cell counting; Propidium iodide staining
A10 cell line, HAoSMC
Dasatinib
SMC proliferation
[113 ]
[125 ]
Migration
Transwell cell migration assay
HAoSMC; PASMC; HCASMC; A10 cell
Imatinib
SMC migration
[84 ]
[116 ]
[155 ]
Transwell cell migration assay
HAoSMC; A10 cell
Dasatinib
SMC migration
[113 ]
[125 ]
Secretion/synthesis
Radiolabel incorporation
Human VSMC
Imatinib
proteoglycan synthesis
[117 ]
RT-PCR; Western blot; Sircol collagen assay
Dermal fibroblast
Imatinib
COL1A1, COL1A2, fibronectin 1 synthesis
collagen synthesis
[118 ]
RT-PCR
Dermal fibroblast
Imatinib
= MMP-1, MMP-2, TIMP-1, TIMP-2, TIMP-3 and TIMP-4
[118 ]
qRT-PCR
Human fibroblast
Nilotinib
Decreases COL1A1 and COL1A2 synthesis
[127 ]
Fibrosis
Sirius red staining
Rat
Imatinib
myocardial fibrosis, liver fibrosis
[30 ]
[119 ]
Intima/media ratio
Rat (Balloon injury model)
Imatinib
stenosis
[121 ]
[122 ]
Intima/media ratio
Rabbit
Imatinib
intimal thickness
[124 ]
Hydroxyproline, collagen content
Rat liver
Imatinib
hydroxyproline and collagen content
[128 ]
Hydroxyproline, collagen content
Rat liver
Nilotinib
hydroxyproline and collagen content
[128 ]
Sirius red staining
Rat liver
Nilotinib
liver fibrosis
[128 ]
Abbreviations: ASMC, arterial smooth muscle cell; BAoSMC, bovine aortic smooth muscle
cell; BrdU, bromodeoxyuridine; COL, collagen; HaOSMC, human aortic smooth muscle cell;
HCASMC, human coronary artery smooth muscle cell; HVSMC, human vascular smooth muscle
cell; MMP, matrix metalloproteinase; PARP, poly(ADP-ribose) polymerase; PASMC, pulmonary
smooth muscle cell; PDGF, platelet-derived growth factor; qRT-PCR, quantitative reverse
transcription polymerase chain reaction; SMC, smooth muscle cell; TIMP, tissue inhibitor
of metalloproteinase; TUNEL, terminal deoxynucleotidyl transferase dUTP nick end labeling;
VSMC, vascular smooth muscle cell.
Impact of new-generation TKIs on fibrosis was less studied but demonstrate similar
inhibitory effect on VSMCs and fibroblasts. Indeed, dasatinib inhibits PDGFR more
potently than imatinib,[113 ] and the hypothesis that dasatinib prevents restenosis similarly with imatinib was
emitted. Therefore, a patent has been filed claiming the use of dasatinib for the
prevention of stenosis and restenosis.[125 ] Compared with imatinib, dasatinib has additional off-targets and is able to inhibit
Src,[aiii ] a kinase involved in dermal fibrosis in addition to PDGFR.[126 ] Therefore, dasatinib was tested in patients with scleroderma-like chronic graft-versus-host
disease, a disease resulting from inflammation and progressive fibrosis of the dermis
and subcutaneous tissues, and first results are encouraging.[126 ] Nilotinib also appears to be clinically efficient in scleroderma-like graft-versus-host
disease by reducing collagen expression.[127 ] Finally, nilotinib was tested in vivo for the treatment of liver fibrosis and demonstrates
decreased fibrotic markers and inflammatory cytokines (IL-1α, IL-1β, IFN-γ, IL-6).[128 ] However, only low-dose nilotinib was found to be efficient against fibrosis and
normalized collagen content.[128 ] This lack of antifibrotic effect at higher doses might be explained by inhibition
of additional off-targets by nilotinib that affect the benefit of low-dose nilotinib
against fibrosis. Arterial thrombosis occurring with dasatinib and nilotinib are probably
not the consequence of VSMC impairment, but investigations should be performed on
VSMCs rather than on fibroblasts. Additional investigations are warranted to complete
impact of BCR-ABL TKIs on VSMC functions (e.g., VSMC apoptosis, proliferation, and
migration) and confirm their safety toward VSMCs.
Off-targets
BCR-ABL TKIs bind the highly conserved ATP binding site and are therefore not very
specific to BCR-ABL and possess multiple cellular targets (kinases and nonkinase proteins).[129 ]
[130 ] This allowed the possibility to exploit them in other indications (e.g., PDGFR inhibition
by imatinib is used in BCR-ABL-negative chronic myeloid disorders),[131 ] but this may also induce toxicities and side effects.[129 ] The development of arterial thrombotic events with new-generation BCR-ABL TKIs is
likely to be related to inhibition of off-targets, as described throughout this review.
[Fig. 4 ] describes inhibitory profiles of imatinib, dasatinib, nilotinib, bosutinib, and
ponatinib. Globally, imatinib is the most selective BCR-ABL TKIs, whereas dasatinib
and ponatinib inhibit numerous off-targets.
Fig. 4 Specificity of imatinib, dasatinib, nilotinib, and ponatinib toward tyrosine kinases.
Green, yellow, red, and blue circles contain tyrosine kinase inhibited by dasatinib,
nilotinib, bosutinib, and ponatinib, respectively. Tyrosine kinases in white represent
imatinib off-targets. This figure summarizes results from 13 experiments.[39 ]
[43 ]
[130 ]
[132 ]
[133 ]
[134 ]
[135 ]
[136 ]
[137 ]
[156 ]
[157 ]
[158 ]
[159 ] In case of conflictual results between studies, a conservative approach has been
applied. Additional information is provided in the [Supplementary Material ].
However, inhibitory profiles are difficult to determine and several researches published
discrepancies. For conflicting results, a conservative approach has been applied in
[Fig. 4 ], but [supplementary information ] ([Table S2 ]) describes the tyrosine kinase selectivity profile of the five BCR-ABL TKIs and
indicates divergences between studies.[43 ]
[130 ]
[132 ]
[133 ]
[134 ] These discrepancies can be explained by the difference in drug concentration and
methodologies. To date, several methods have been used to determine inhibitory profile
of BCR-ABL TKIs including in vitro kinase assay,[133 ]
[134 ]
[135 ] kinase expression in bacteriophages,[136 ] and affinity purification methods combined with mass spectrophotometry.[130 ]
[132 ] However, all these methods suffer from caveats, including the incompatibility to
perform live-cell studies. A cell-permeable kinase probe was developed to figure out
this problem, but this assay is still limited by the number of off-target tested (i.e.,
it requires to predefine tested off-targets) and therefore, the missing of targets
is possible.[137 ] For this reason, the inhibitory activity of each TKI has not been tested toward
all tyrosine kinase and [Fig. 4 ] includes only off-targets for which at least one of the five BCR-ABL TKI has been
tested. Thus, inhibitory profiles need to be carefully considered and it has to keep
in mind that BCR-ABL TKI metabolites may possess activity against supplemental off-targets.
As described over this review, PDGF signaling has countless effects on several cells
and tissues and is involved in several proatherogenic mechanisms (e.g., adipogenesis,
vascular leakage, VSMC viability, and functions) and vascular homeostasis, which led
to the suggestion of its implication in the potential beneficial cardiovascular effect
of imatinib.[116 ]
[123 ]
[138 ] However, dasatinib, nilotinib, and ponatinib also inhibit PDGFR but increase the
risk of arterial occlusive events. This difference of clinical outcome might be explained
by the concentration of BCR-ABL TKIs necessary to obtain a same degree of PDGFR inhibition.[43 ] Indeed, Rivera et al reported that when adjusted to the maximum serum concentration,
imatinib inhibits more profoundly PDGFR than dasatinib, nilotinib, and ponatinib.[43 ] Therefore, at effective concentration, it is probable that the degree of PDGFR inhibition
is too low with dasatinib, nilotinib, and ponatinib to obtain the beneficial effect
of PDGFR inhibition on atherosclerosis. Another possible hypothesis concerns the less
conclusive specificity of new-generation TKIs which leads to inhibition of additional
off-targets that might counterbalance the positive effect of PDGFR inhibition.
Other tyrosine kinases have been incriminated in the occurrence of arterial thrombosis
with new-generation TKIs. DDR-1[aiv ] possesses functions in vascular homeostasis, atherogenesis, and is expressed in
pancreatic islet cells. However, and similarly with PDGFR, it is inhibited by all
BCR-ABL TKIs.[26 ]
[62 ] Other hypotheses include impairment of VEGF signaling by ponatinib[43 ]
[90 ] or the inhibition of several ephrin receptors by new-generation TKIs but not by
imatinib which might inhibit monocyte recruitment.[139 ] Finally, it has been suggested that the inhibition of c-Abl itself is implicated
in the increase of the cardiovascular risk. Indeed, imatinib possesses lower inhibitory
effect on c-Abl than new-generation TKIs, which might further explain the difference
in cardiovascular safety.[43 ] Additionally, c-Abl modulates Tie-2,[av ] a tyrosine kinase that possesses important effect on endothelial cell function,
angiogenesis, and inflammation.[140 ]
[141 ]
Perspectives and Conclusions
Perspectives and Conclusions
This review summarizes the data underlying the potential preventive effect of imatinib
on the occurrence of arterial thrombosis. Globally, in vitro and in vivo experiments
demonstrate that imatinib possesses antiplatelet activity, hypolipidemic and hypoglycemic
effects, and inhibits inflammation and atherosclerosis development in several cell
types (i.e., decreases of inflammatory cell and VSMC functions and increased vascular
permeability). These benefits were largely attributed to PDGFR inhibition. It is currently
unknown why new-generation TKIs that also inhibit PDGFR present opposite cardiovascular
safety profile and this point needs to be elucidated.
New-generation BCR-ABL TKIs increase the risk of arterial thromboembolism with different
clinical features (e.g., time-to-event and absolute rate) and are associated with
different safety profiles, suggesting different pathways to explain the pathophysiology.
The safety profile of nilotinib is mostly characterized by impaired glucose and lipid
metabolism. However, both the molecular mechanism of these alterations and their impact
on the occurrence of arterial thrombosis are unknown. Both dasatinib and ponatinib
exhibit antiplatelet effect, whereas it was recently suggested that nilotinib potentially
induces prothrombotic phenotype of platelets. Based on the clinical characteristics
and case reports, atherosclerosis appears the most plausible mechanisms by which new-generation
TKIs induce arterial thrombosis. However, in vitro and in vivo studies of viability
and functions of SMCs and inflammatory cells demonstrate reassuring impact of dasatinib
and nilotinib, even if additional studies are required to complete this evaluation.
However, first experiments indicate that dasatinib, nilotinib, and ponatinib influence
EC survival and/or endothelium integrity, suggesting a reasonable hypothesis by which
new-generation TKIs induce atherosclerosis development and, subsequently, arterial
thrombosis. Additional studies on the shedding of functional extracellular vesicles
by endothelial cells might be interesting regarding their important role in coronary
artery diseases.[142 ] Finally, the impact of new-generation TKIs on human blood coagulation and fibrinolysis
has never been studied and should be addressed.
To conclude, new-generation TKIs increase the risk of arterial thrombosis in patients
with CML, whereas imatinib, the first-generation TKI, might prevent the development
of cardiovascular events. To date, the cellular events and signaling pathways by which
these events occurred are unknown and researches are extremely limited focusing mainly
on imatinib and nilotinib. Researches need to be extended to all new-generation BCR-ABL
TKIs (i.e., dasatinib, bosutinib, and ponatinib). The understanding of the mechanisms
by which new-generation BCR-ABL TKIs induce or promote arterial occlusive events will
improve the clinical uses of these therapies. To date, only general risk minimization
measures have been proposed (e.g., management of dyslipidemia, diabetes, arterial
hypertension following standard of care).[14 ]
[22 ]
[23 ]
[143 ]
[144 ]
[145 ]
[146 ] The understanding of the pathophysiology is required to implement the most appropriate
risk minimization strategies for thrombotic events and to select patients to whom
the prescription of these drugs should be avoided when applicable. Finally, the understanding
of the pathophysiology will help in the design of new BCR-ABL inhibitors sparing the
toxic targets.
Review Criteria
Relevant articles published from the database inception to July 11, 2017, were identified
from an electronic database (PubMed) using the keywords “vascular,” “thrombosis,”
“atherosclerosis,” “arteriosclerosis,” “venous,” “arterial,” “hemostasis,” “metabolic,”
“metabolism,” “glycemia,” “glycaemia,” “cholesterol,” “triglycerides,” and “platelet”
combined with the five approved BCR-ABL TKIs. The search strategy is presented in
supplementary files. Articles published in languages other than English were excluded
from the analysis. Primary criteria were pathophysiological explanation of arterial
thrombotic events. Abstracts and full-text articles were reviewed with a focus on
atherogenesis, plaque rupture, platelet functions, and their link with the development
of arterial thrombosis with BCR-ABL TKIs. The reference section of identified articles
was also examined.