PDCD1 and endometrial cancer: Although PD-1 blockade therapy has been approved for several types of cancers, approximately half of the patients treated with immune-checkpoint inhibitors do not benefit from these therapies,15 and the clinical responses to PD-1 signal inhibitors, such as anti-PD-1 or PD-L1 antibodies, have been unsatisfactory for both ovarian (11.5–15% overall) and endometrial cancers (13% overall).7,16–18 Therefore, combinatorial treatments, using conventional chemotherapy and new treatment strategies, must be developed to successfully treat cancers that are refractory or resistant to anti-PD-1 therapy.