ESR1 and breast cancer: We found that human ERα+ breast cancer cell lines (ZR-75-1, CAMA1, T47D and BT474) express variable, but detectable levels of aromatase transcripts by real time RT PCR (Fig. 1A), and ZR-75-1 and CAMA1 cell lines also express detectable aromatase protein levels with Western immunoblotting (Fig. 1B).