Given that the immunosuppressive nature of the tumor microenvironment is a major obstacle to achieving favorable outcome in treating cancer using PD-1/PD-L1 blockade, we hypothesized that Salmonella-induced changes in the tumor tissue could ameliorate the immunosuppressive microenvironment and, therefore, enhance the response rate and therapeutic efficacy of PD-1/PD-L1 blockade. Here, PDCD1 is linked to cancer.