Apatinib combined with PD-L1 blockade synergistically enhances antitumor immune responses and promotes HEV formation in gastric cancer.

PURPOSE: Apatinib, an antiangiogenic drug, has shown beneficial effects only in a fraction of advanced gastric cancer (GC) patients. Given the recent success of immunotherapies, combination of apatinib with immune checkpoint inhibitor may provide sustained and potent antitumor responses. METHODS: Immunocompetent mice with subcutaneous MFC tumors grown were given a combination of apatinib and anti-PD-L1 antibody therapy. GC tissues from patients undergoing curative resection in China were collected, and the density of HEVs, MSI status and tumor-infiltrated lymphocytes were analyzed by immunohistochemical staining. RESULTS: Combined apatinib and PD-L1 blockade therapy synergistically delayed tumor growth and increased survival in MFC-bearing immunocompetent mice. The combination therapy promoted antitumor immunity by increasing the ratio of CD8(+) cytotoxic T cells to Foxp3(+) Treg cells, the accumulation of CD20(+) B cells and the Th1/Th2 cytokine ratio (IFN-γ/IL-10). The combination therapy induced the formation of HEVs through activation of LTβR signaling, thus promoting CD8(+) cytotoxic T cell and CD20(+) B cell infiltration in tumors. In clinical GC samples, the density of HEVs positively correlated with the intratumoral infiltration of CD8(+) cytotoxic T cells and CD20(+) B cells. MSI-high GC showed a higher density of HEVs, CD8(+) cytotoxic T cells and CD20(+) B cells than MSS/MSI-low GC. GC patients with high densities of HEVs, CD8(+) cytotoxic T cells and CD20(+) B cells had an improved prognosis with superior overall survival. CONCLUSION: Combining apatinib with PD-L1 blockade treatment synergistically enhances antitumor immune responses and promotes HEV formation in GC.