Aberrant expression of integrin and erbB subunits in breast cancer cell lines

Integrin and growth factor receptors play an important role in cell functions and their aberrant expressions are implicated in breast cancer malignancy. Recent studies have shown that integrins physically and functionally associate with growth factor receptors suggesting the cooperative regulation of these two signals. We studied the expression of integrin and erbB subunits by flow cytometer in human normal mammary epithelial (HME) cell, non-metastatic (MCF-7, ZR-75-1, MDA-MB453) and metastatic tumor cell lines (MDA-MB231, MDA-MB435). Compared with HME cells, all of non-metastatic and metastatic cell lines showed decreased expressions of α2 and β4 integrin subunits. Two metastatic cell lines, but not three non-metastatic tumor cell lines, expressed α5 and α6 comparable to HME cells. There was no correlation of erbB2 expression with integrin expressions. We isolated MDA-MB435 subpopulations expressing lower amount of α6 integrin and found that α5, but not α2 and αv integrins, was concomitantly decreased while erbB family was not affected. Then we transfected erbB2 gene into MDA-MB435 and found the induction of erbB3 expression but not erbB1 and erbB4. However, erbB2 transfection had no effect on the expression of α6 and β4 integrin subunits. These data suggest that the expression of α5 and α6 integrins may contribute to metastasis, and that the regulation of erbB2 and α6 integrin expressions is independent in breast cancer cells.