Invasiveness in vitro of mixed aggregates composed of two human mammary cell lines MCF-7 and HBL-100.

Interactions between invasive and noninvasive cells were studied via confronting cultures between mixed cell aggregates and embryonic chick heart fragments in vitro. The mixed aggregates were composed of MCF-7 and HBL-100 cells, both derived from human mammary epithelium. HBL-100 cells invade into the heart fragments when confronted as unmixed aggregates, while MCF-7 cells do not. Using mixed aggregates HBL-100 cells still invade into the heart tissue, but MCF-7 cells sort out to the periphery of the cultures and do not invade. Two mechanisms concerning the noninvasiveness of MCF-7 cells in vitro are discussed: the homotypic adhesion of the MCF-7 cell population due to the presence of numerous desmosomes, and the incapability of MCF-7 cells to migrate on extracellular laminin present in the embryonic chick heart and in the HBL-100 cell population.