Fig. 1. RA receptor expression in human breast epithelial cells. A, semiquantitative RT-PCR analysis of RAR1, RAR2, and RARß2 expression in immortalized nontumorigenic MTSV17 cells and MCF-7 breast carcinoma cells under basal conditions (Lanes labeled C) and after treatment with 1 µM RA for 24 h (Lanes labeled RA). The results shown are representative of at least three experiments. The first and second panels from the top, ethidium bromide staining and RT-PCR Southern data, respectively, for RAR 1 and RAR2 (see "Materials and Methods" for details of coamplification and unambiguous identification of each amplicon). The low but detectable RAR1 expression in MTSV17 cells was more readily apparent in experiments in which RAR1 was amplified separately (not shown). The third and fourth panels, RARß2 and GAPDH RT-PCR Southern data, respectively. B, semiquantitative RT-PCR Southern analysis of RAR2 (RAR1 primer not included) and RARß2 expression in primary normal HMECs enriched in luminal cells; the ethidium bromide signal for GAPDH is shown to demonstrate even loading. RA treatment was as in A. Expression of RAR2 and RARß2 was confirmed in a second cell preparation. C, Western blot analysis of RAR and RARß expression in MTSV17 and MCF-7 cells under basal conditions and after RA treatment as in A (see "Materials and Methods" and "Results" for details).