Introduction:
Presence of cytotoxic CD8+ T cells (CTLs) in tumor microenvironment (TME) is critical
for the effectiveness of immune therapies and patients' outcome, while regulatory
T® cells and myeloid derived suppressor cells (MDSC) promote cancer progression.
Methods:
A unique tissue explant culture method was used for solid tumors. With this ex vivo
culture model, the whole TME can be stimulated. mRNA measurements were performed and
culture supernatants were analyzed for chemokine concentrations. Alternatively, monocyte-derived
macrophages or adult fibroblasts were used in analogous experiments. Chemotaxis assays
were performed using pre-activated CD8+ T-cells (top chamber) and supernatants from
cancer specimens. Western blot experiments were used to evaluate the impact of NFκB.
Results:
We show that two TLR3 ligands, both activate human TLR3 pathway, involving TRAF3 and
IRF-3, and induce IFNα, ISG-60 and CXCL10, thus promoting CTLs chemotaxis to the ex
vivo-treated tumors. However, in contrast to poly I:C, rintatolimod does not activate
human MAVS/helicase pathway, thus avoiding the NFκB- and TNFα-dependent induction
of COX-2, and induction of IDO, IL-10, CCL22 and CXCL12.
Conclusions:
With this work we have shown that a selective targeting of TLR3 and elimination of
the NFkB-COX-2-TNFa pathway may allow for selective enhancement of type-1 immunity
in human TME. The next steps will be to test other immunomodulating adjuvants as Checkpoint
Inhibitors in HNSCC explant cultures and their effects on a) NFκB pathway, b) induction
of a type-1 immunity with c) enhancement of the desired CTL attracting chemokines
instead of Treg and MDSC attracting ones.
