Figure 3.

Brca1 and Brca2 expression are induced by glucocorticoids during mammary epithelial differentiation. (A) mRNA expression of Brca1, Brca2, histone H2B, β-casein, and actin in HC11 mammary epithelial cells that were either actively growing (Active) or postconfluent at the times indicated after induction with lactogenic hormones (insulin, hydrocortisone, and prolactin) in the presence of whole serum. mRNA expression was quantitated by RNase protection (Brca1 and actin) or Northern blot hybridization (β-casein, Brca2, and histone H2B). The 28S RNA band from an ethidium bromide-stained nitrocellulose blot used as a loading control is shown. (B) [³H]Thymdine incorporation (corrected for number of cells) of actively growing or differentiating HC11 cells shown in A. (C) Hormonal requirements for Brca1 and Brca2 up-regulation in HC11 cells. mRNA expression of Brca1, Brca2, histone H2B, β-casein, and actin as measured by Northern blot hybridization in HC11 mammary epithelial cells that were either actively growing (Active), confluent for 3 days in growth medium (Con), or postconfluent and treated with the indicated hormones for 7 days in differentiation medium. HC, hydrocortisone; Ins, insulin; Prl, prolactin.