ESR1 and breast cancer: A band migrating at the expected molecular weight (~75 kDa) was observed in the two ERα-negative breast cancer lines that had the highest levels of AR-V7 mRNA, MDA-MD-453 and MFM-223, but was not apparent in lines with lower (ZR-75–1, T47D) or no (MDA-MB-231) expression of AR-V7 and AR-FL transcripts (Figure 3C).