The CYT-1 isoform has antiproliferative activity in SUM102 mammary cancer cells, 32D bone marrow cells, and HC11 and MCF10A mammary epithelial cells, while CYT-1 ERBB4 promotes tumorigenesis in ovarian OVCAR-3 and SKOV-3 cancer cell lines [23]-[27]. This evidence concerns the gene ERBB4 and breast cancer.