THE ROLE OF INTEGRINS AND EXTRACELLULAR-MATRIX IN ANCHORAGE-INDEPENDENT GROWTH OF A MAMMARY-CARCINOMA CELL-LINE

Anchorage-independent growth is a property of malignant cells. Extrace llular matrix proteins are present in tumor spheroids but their functi on is not clearly defined. In this paper we show that a murine mammary carcinoma cell line, SPL, which expresses the fibronectin receptor al pha(5) beta(1) requires fibronectin for anchorage-independent growth i n soft agar. Growth factors (hepatocyte growth factor and transforming growth factor-beta) also promote SP1 colony growth. In contrast, coll agen types I and IV have an inhibitory effect on SP1 colony growth. A clone isolated from SP1 cells which expresses the collagen/laminin rec eptor alpha(2) beta(1) as well as the fibronectin receptor alpha(5) be ta(1) demonstrates increased colony formation in the presence of fibro nectin and collagen. These data suggest a role for both the alpha(5) b eta(1) and alpha(2) beta(1) integrin receptors in the regulation of an chorage-independent growth of mammary carcinoma cells.