Growth factors in mouse mammary cell interactions in vitro.

Paracrine interactions may be important in homeostasis of mammary gland. We have previously reported that normal mammary epithelial cells and stromal cells stimulate the growth of mammary tumor cells in 3-dimensional cultures in collagen gels. We now describe the ability of EGF, TGF beta, bFGF, aFGF, and PDGF to directly affect growth of tumor cells in 3-dimensional cultures in collagen gels. In addition, we assessed the ability of neutralizing antibodies against each growth factor to disrupt interactions between normal mammary cells and mammary tumor cells. Only bFGF and PDGF directly stimulated growth of the mouse mammary tumor cells. However, neither anti-bFGF nor anti-PDGF abrogated the stimulation of tumor cells by normal mammary epithelial cells or normal mammary stromal cell.