Triple negative (negative for expression of estrogen receptor, progesterone receptor, and overexpression of HER2) breast cancer cell lines dervied from metastatic cancer (Cal51 and MDA-MB-231) were treated with increasing concentrations of microtubule poisons classically considered to be stabilizers (docetaxel, ixabepilone, epothilone B) or destabilizers (vinblastine, vinorelbine, eribulin). The gene discussed is PGR; the disease is metastatic malignant neoplasm.