Targeting multivalent receptor tyrosine kinases to enhance the efficacy of anti-PD-1 immunotherapy in gastric cancer

Background: Gastric cancer (GC) is the fifth most common cancer and the fifth leading cause of cancer-related deaths globally. The response to immune checkpoint blockade (ICB) therapy in GC is relatively poor with almost two thirds of the patients not responding due to the tumor's ability to maintain an immunosuppressive microenvironment and develop resistance to immunotherapy. Previously, we demonstrated that dovitinib, a multi-target receptor tyrosine kinases (RTKs) inhibitor, suppresses tumor growth and remodels the tumor microenvironment (TME) by facilitating the recruitment of CD8+ T cells into immune-suppressive types of mouse gastric cancer. This study aimed to assess whether dovitinib enhances the therapeutic effectiveness of PD-1 blockade. Methods: ATP-GLO to measure cell viability in vitro. A syngeneic murine gastric tumor model with two distinct mouse GC cell lines was utilized to assess the synergistic effects of dovitinib and anti-PD-1 treatment. IF and flow cytometry to immunophenotyping. Results: The combination of dovitinib and PD-1 blockade was significantly more effective than either treatment alone, leading to reduced tumor growth and increased animal survival in both models (p<0.01). IF analysis revealed that while dovitinib alone increased CD8+ T cell infiltration in the tumor core, the combination treatment further enhanced the infiltration of cytotoxic T cells (Perforin+ CD8+) compared to the other groups (p<0.01). Furthermore, multiparametric flow cytometry combined with FlowSOM clustering analysis showed an increase in CD4+ and CD8+ T cell clusters with higher activation (CD69+) and lower or absent expression of exhaustion markers (PD-1, CTLA-4). In contrast, dovitinib alone was associated with a more exhausted T cell phenotype. Notably, only the combination treatment increased the tumor killing capacity of the cytotoxic T cells. Conclusion: Our findings demonstrate that the combination of dovitinib and PD-1 blockade is significantly more effective than either treatment alone, as the two therapies synergistically remodel the TME beyond their direct cytotoxic effects. This synergy is achieved by increasing the infiltration of activated tumor-infiltrating lymphocytes (TILs) and reducing the exhaustion phenotype typically seen with monotherapy. This study supports the rationale for combining multi-target RTKs inhibitors with immunotherapies as an effective therapeutic strategy for gastric cancer.