CTLA-4 and PD-1 are expressed in human solid tumor-derived cells [10,12,46,47], and recent studies have shown that BTLA is expressed in a small subpopulation of cancer cells from clinical tumor specimens mainly identified by immunohistochemical including NSCLC [22], gastric cancer [20], and ovarian cancer cells [19]. This evidence concerns the gene BTLA and ovarian carcinoma.