CD27 and cancer: As previously reported, in the cancer-immunity cycle, CD28: (CD80, CD86), CD40, CD27, HVEM, GITR: GITRL, ICOS, and TLR-2 are stimulatory factors, while TIM-3, PD-L1: PD-1, PD-L1: (CD80, CD86), CTLA-4: (CD80, CD86), BTLA, and LAG-3 are inhibitory factors [13–15].