TIGIT and melanoma: Eighteen genes identified in our study were consistent with those reported by earlier studies in melanoma, breast, colon, lung and liver cancers, including coinhibitory receptors CTLA4 and TIGIT and costimulatory receptors TNFRSF4 and TNFRSF18. Previous studies have proven that CTLA4, TIGIT, TNFRSF4 and TNFRSF18 cannot promote and instead suppress the proliferation and immunosuppression of Tregs [45–47].