ESR1 and breast cancer: Although very low expression was observed in only two (LS174T and Colo320DM) of the six CC cell lines tested, two (MKN1 and MKN7) of the four GC cell lines expressed GPNMB. We also examined the gene expression of various receptors, including ERα, HER2, and EGFR; however, GPNMB expression was independent from that of other receptors related to BC (Fig.1A).