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Fig. 1. RA receptor expression in human breast epithelial cells. A, semiquantitative RT-PCR analysis of RAR{alpha}1, RAR{alpha}2, and RARß2 expression in immortalized nontumorigenic MTSV1–7 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{alpha} 1 and RAR{alpha}2 (see "Materials and Methods" for details of coamplification and unambiguous identification of each amplicon). The low but detectable RAR{alpha}1 expression in MTSV1–7 cells was more readily apparent in experiments in which RAR{alpha}1 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 RAR{alpha}2 (RAR{alpha}1 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 RAR{alpha}2 and RARß2 was confirmed in a second cell preparation. C, Western blot analysis of RAR{alpha} and RARß expression in MTSV1–7 and MCF-7 cells under basal conditions and after RA treatment as in A (see "Materials and Methods" and "Results" for details).