CTLA4 and melanoma: In melanoma cell lines, ICOS mRNA showed variable expression levels ranging from 0 to 2.44 RMA (mean 0.42 RMA, median 0.057 RMA, 95%CI 0.19–0.65 RMA, N = 33), confirming a tumor-intrinsic mRNA expression of ICOS. CTLA-4 protein and CTLA4 mRNA expression by melanoma cells has been reported [22, 35].