Changes in expression of integrin heterodimer in primary and metastatic breast cancer

Abstract

The integrin complex has been shown to be expressed in murine tissues at the basolateral aspect of most epithelial cells including the mammary epithelium, thus suggesting that this heterodimer may interact with components of the basement membrane. Because transformation of mammary epithelium frequently results in disappearance of basement membranes and loss of cell polarisation we have analysed in the present study whether expression of the oc6/04 complex is altered in human breast tumours. The results of the present study confirm that in human mammary gland 6 and 4 subunits colocalise at the basolateral aspect of the epithelium. While in benign breast lesions this distribution pattern remains mostly unchanged, in primary carcinomas the expression of both chains is either redistributed over the cell surface or significantly reduced. This altered pattern of expression is paralleled by the lack of detection of basement membrane laminin and collagen type IV. In metastatic lesions the expression of the heterodimer is maintained in most of the lymphonodal foci, but less frequently detected in metastasis localised in the pleural cavity and in parenchymal tissues. These findings indicate that in breast epithelium expression of the a6/04 heterodimer is modulated by the presence of basement membrane and is possibly influenced by microenvironmental factors as suggested by the different pattern of 6/04 expression in nodal and extranodal metastatic foci. © Macmillan Press Ltd., 1992.