Alterations in integrin and basement-membrane protein expression by malignant breast cells

We investigated expression of eight integrin subunits and four basement membrane proteins by normal and malignant human mammary epithelial cells (HMEC) in culture and in tissue sections. Normal HMEC expressed the same six integrin subunits in culture and in vivo. Expression of some of these was altered in vivo in breast carcinomas: alpha1 was not observed and beta4 was missing from some cells-changes that were not genetic, as malignant cells in primary culture could express these subunits. Nor was expression of these subunits related to expression of their basement membrane protein ligands. Other integrin subunits were reduced in culture, and expression of basement membrane proteins differed between normal and malignant cells and cells in vivo and in culture. Our results suggest that breast carcinoma cells have altered regulation of expression of adhesion receptors and their ligands, and these alterations can be manipulated in culture for further study.