ERBB2 and breast cancer: The second possible mechanism is that the cis-interaction of necin-4 with other transmembrane proteins, such as integrin β4, affects the degrees of the cis-interaction of nectin-4 with ErbB2, p95-ErbB2, or ErbB2∆Ex16 through their extracellular regions, because in human breast cancer SUM190-PT cells, nectin-4 cis-interacts with integrin β4, eventually promoting anchorage-independent survival through the c-Src signaling41.