DIFFERENTIATION OF BREAST-CANCER CELLS IN-VITRO IS PROMOTED BY THE CONCURRENT INFLUENCE OF MYOEPITHELIAL CELLS AND RELAXIN

Our previous studies showed that relaxin promotes differentiation of M CF-7 breast adenocarcinoma cells. In the current investigation, we aim ed to elucidate whether the effect of the hormone is potentiated when MCF-7 cells are grown together with myoepithelial cells, thus creating a microenvironment reminiscent of the organised tissue architecture o f the mammary parenchyma in vivo. The findings obtained reveal that mo st MCF-7 cells cultured alone have an undifferentiated, blast-like phe notype, only a minority showing a more differentiated phenotype with m ore organelles and rudimentary intercellular junctions. When co-cultur ed with myoepithelial cells more MCF-7 cells acquire ultrastructural f eatures consistent with a more differentiated phenotype, such as a ric h organellular complement, apical microvilli and intercellular junctio ns. When relaxin was added to the co-cultures, the ultrastructural sig ns of differentiation could be observed in even more MCF-7 cells and b ecame more pronounced than in the absence of the hormone, judged by th e appearance of a clear-cut polarisation of cytoplasmic organelles, an almost continuous coat of apical microvilli and numerous intracellula r pseudolumina.