The deletion of PTPN2 in syngeneic tumors in mice, including xenografted B16F10A melanomas and MC38 colorectal adenocarcinomas, as well as orthotopic AT3 mammary tumors, can enhance T cell mediated anti-tumor immunity and the response to PD-1 checkpoint blockade6,10. The gene discussed is PTPN2; the disease is melanoma.