Following various
immunotherapies, lack of proper anti-
tumor immune responses is considered a significant problem in novel
cancer therapeutic approaches. The expression of
inhibitory checkpoint molecules on
tumor-infiltrating T cells is one of the main reasons for the ineffectiveness of various
immunotherapies. Therefore, we decided to inhibit two of the most important immune checkpoints expressed on
tumor-associated T cells, PD-1 and A2aR.
Ligation of PD-1 with PD-L1 and A2aR with
adenosine significantly suppress T cell responses against
tumor cells. Whitin
tumors, specific inhibition of these molecules on T cells is of particular importance for successful
immunotherapy as well as the elimination of treatment-associated side-effects. Thus, in this study, superparamagnetic
iron oxide (SPION) nanoparticles (NPs) were covered by
chitosan lactate (CL), functionalized with TAT
peptide, and loaded with
siRNA molecules against PD-1 and A2aR. Appropriate physicochemical properties of the prepared NPs resulted in efficient delivery of
siRNA to
tumor-derived T cells and suppressed the expression of A2aR and PD-1, ex vivo. T cell functions such as
cytokine secretion and proliferation were considerably enhanced by the downregulation of these molecules which led to an increase in their survival time. Interestingly, treatment of CT26 and 4T1 mouse
tumors with
siRNA-loaded NPs not only inhibited
tumor growth but also markedly increased anti-
tumor immune responses and survival time. The results strongly support the efficacy of SPION-CL-TAT NPs loaded with anti-PD-1/A2aR siRNAs in
cancer therapy and their further development for
cancer patients in the near future.