Expression of estrogen receptor on MM cell lines and MM patient cells. Lysates from ARH-77, OCI My-5, RPMI 8226, S6B45, and U266 MM cells (A) as well as purified MM cells from 3 patients (B) were examined by Western immunoblotting for the presence of ER- using the TE1115011 MoAb. MCF-7 breast cancer cells and DU145 prostatic cancer cells served as positive and negative controls, respectively, for ER- expression. Immunoblotting with anti–tubulin- MoAb assured equivalent protein loading.