To determine the role of MST4 in breast cancer, the level of MST4 expression was analyzed in six human breast cancer cell lines—MCF7, MDA-MB-231, MDA-MB-468, MDA-MB-453, BT-474, and SKBR3—and two non-cancerous cell lines, MCF10A and MCF12A (Figure 1a). This evidence concerns the gene STK26 and breast carcinoma.