CD28 and melanoma: The expression of immune checkpoint molecules (PD-1, PD-L1, CTLA4, BTLA, CD28, CD80, CD86, HAVCR2, ICOS, LAG3, and TIGIT) in the low-risk group was significantly higher than that in the high-risk group (Fig. 9B), indicating that the melanoma patients in the low-risk group may have a more favorable response to immune checkpoint inhibition.