Semi-quantitative analysis of SSTR1-5 and ErbB1-4 mRNA and protein expression in MCF-7 and MDA-MB-231 breast cancer cells. A. Upper panel shows western blot analysis of SSTR1-5 in MCF-7 (left) and MDA-MB-231 (right) cells. Membrane protein (25 μg) was fractionated by SDS-PAGE and probed with affinity-purified SSTR antibodies. Major protein bands of 53 (SSTR1), 57 (SSTR2), 60 (SSTR3), 44 (SSTR4) and 58 kDa (SSTR5) were obtained. Lower panel shows RT-PCR anlaysis of SSTR1-5 mRNA expression in both cell lines. 5 μg of DNA-free RNA was reverse transcribed and coamplified with primers specific for SSTR1-5 and β-actin. 8 μL of PCR products were fractionated on agarose gels stained with ethidium bromide, visualized under UV lighting and photographed. B. Western blot (upper panel) and RT-PCR (lower panel) analysis of ErbB1-4 expression in MCF-7 (left) and MDA-MB-231 (right) breast tumor cells. Major protein bands of 170 (ErbB1), 185 (ErbB2), 200 (ErbB3) and 175 kDa (ErbB4) were obtained. Experimental conditions were the same as described for panel A except for the specific antibodies and primers.