Zielsetzung:
CD38 is overexpressed by lymphomas and other hematological tumors and represents a
promising target for immunotherapy. We aimed to develop CD38-specific nanobody-Fc
fusion proteins for imaging and treatment of hematological tumors and to test them
in a bioluminescent lymphoma model.
Material und Methodik:
We generated CD38-specific nanobodies (15kDa) by phage-display technology from immunized
llamas. Specific binding, affinity and epitope specificity of selected nanobodies
were analyzed by flow cytometry. Nanobodies were fused to the Fc-domains of human
IgG1. The capacity of Nb-Fc fusion proteins (60kDa) to induce complement-dependent
cytotoxicity (CDC) of human lymphoma cell lines and bone marrow cells of multiple
myeloma patients were analyzed by flow cytometry. In vivo effects of Nb-Fc fusion
proteins on tumor growth were assessed in SCID-mice injected with luciferase-transduced
human Burkitt lymphoma cells. Therapeutic response was determined via bioluminescence
imaging of disseminated tumors (IVIS200,PerkinElmer) and survival curves.
Ergebnisse:
We selected 22 families of CD38-specific nanobodies. Crossblockade analyses indicate
that most of these bind to 3 non-overlapping epitopes. While single Nb-Fc fusion proteins
showed little if any capacity to induce CDC, the combination of two Nb-Fc-fusion proteins
recognizing distinct epitopes showed very potent CDC toward CD38-expressing cell lines
as well as toward primary CD38+ tumor cells from bone marrow samples of myeloma patients.
In vivo bioluminescence imaging of luciferase-transduced CD38+ Burkitt lymphoma cells
confirmed the therapeutic efficacy of combinations of two Fc-fusion proteins recognizing
distinct epitopes. Such combinations significantly reduced tumor growth and significantly
prolonged survival of treated mice compared to controls.
Schlussfolgerungen:
Bioluminescence imaging is a reliable tool for monitoring diffuse tumor growth and
therapy response. CD38-specific nanobody-Fc fusion proteins hold promise as therapeutics
for CD38-expressing lymphomas.