Deciphering the mammary stem cell niche: a role for laminin-binding integrins

Integrin dimers a3/b1, a6/b1 and a6/b4 are the receptors of mammary epithelial cells for Laminin, major component of the mammary basement membrane. Antibodies against a6 and a3 integrin chains serve to isolate stem cell enriched populations from mammary epithelium, however, role of integrin dimers comprising these chains in the control of mammary stem cell activity are not known. To investigate the role of Laminin-binding integrins in the control of mammary stem cell function, a3 and a6 chains were deleted from mammary basal cells in vitro using Cre-recombinase carrying adenovirus. We found that deletion of single integrin chain (either a3, or a6) did not significantly affect stem cell potential as evaluated by transplantation and mammosphere assays, whereas basal cells depleted of both a3 and a6 integrin chains (a3a6KO) presented severely diminished stem cell activity. In this study the transcriptional profiles of a3a6KO were analysed and compared to those of control cells.