Commercially available GBM cell lines A172 and U251, cell lines derived from primary GBM tumor biopsies (designated MZ-327 and MZ-18), along with cells established from a recurrent tumor biopsy (MZ-256 and MZ-304) (Hetschko et al., 2008; Murphy et al., 2014) were used in assessing the effects of pre-treating GBM cells with MRP1 small molecule inhibitors. The gene discussed is ABCC1; the disease is neoplasm.