Background: Cytokine-induced killer cells which were induced with tumor antigen-pulsed dendritic cells (DC-CIK) immunotherapy is a promising strategy for the treatment of malignant tumors. However, the efficacy was restricted by the immunosuppression of tumor microenvironment mediated by the cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) pathway. We, therefore, screened a nanobody which is targeted for CTLA-4 (Nb36), and blocked the CTLA-4 signaling with Nb36 to overcome the negative co-stimulation of effector T cells.
Methods: Peripheral blood mononuclear cells (PBMCs) were collected from healthy donors and used to induce CIK cells in vitro, then co-cultured with DC cells that have received tumor antigens. We tested whether blocking CTLA-4 signaling with Nb36 could promote DC-CIK cells proliferation, pro-inflammatory cytokine production and cytotoxicity in vitro. In vivo experiments, The NOD/SCID mice were injected subcutaneously with HepG2 cells to induce solid tumor. We observe whether this therapy can more effectively inhibit tumor growth in mice.
Results: After being stimulated with Nb36, DC-CIK cells presented enhanced proliferation and production of IFN-γ in vitro, thereby strengthening the killing effect on tumor cells. For in vivo experiments, Nb36-treated DC-CIK cells significantly inhibited the growth of subcutaneously transplanted tumors of liver cancer, reduced tumor weight and prolonged the survival of tumor-bearing NOD/SCID mice.
Conclusions: These findings demonstrated that in response to CTLA-4 specific nanobody stimulation, DC-CIK cells exhibited superior anti-tumor efficacy. Our findings suggested that DC-CIK cells + Nb36 has potential to treat malignant tumors through in vivo adoptive therapy.