B7-1 is not expressed on most tumor cells; therefore, if tumors express MHC-I and trigger the first signal, they may not fully activate anti-tumor specific T cells [3]; however, transfecting the B7-1 gene into tumor cells can render them capable of effectively stimulating antitumor T-cell activation, leading to cancer eradication in vivo[4]–[8]. This evidence concerns the gene CD80 and cancer.