RECAPITULATION OF A NORMAL CELLULAR GROWTH PROGRAM IN EARLY INVASIVE BREAST-CANCER

With a view to identifying markers reflecting not the evidence of, but the potential for, neoplastic progression of the breast we have compa red the normal invasive mammary epithelial cell growth seen at puberty with invasive and non-invasive carcinogenesis using the mouse as a mo del. We have analyzed cell proliferation, the expression of the metall oproteinase stromelysin-1 and of the extracellular matrix protein tena scin. Striking parallels were observed between pubertal growth and the development of invasive, metastasizing mouse mammary tumors. In parti cular, the myoepithelial to epithelial transition of proliferation and stromelysin-1 expression was a hallmark of both normal growth at pube rty and the early development of aggressive tumors. Investigation of n eoplastic lesions in the human breast indicated that the pubertal grow th characteristics are recapitulated only in the development of ductal carcinomas and may define early stages of invasive and potentially ma lignant growth.