NDRG1 and neoplasm: Similarly, the side population was modified only in SUM159 cells (Fig. 5C; Fig. S4D), although Multi-Drug Resistance 1 (MDR1), or p-glycoprotein, was reduced in both SUM159 and MDA-MB-231 cells only upon activation with TGFβ1 (Fig. S5A), what endorses the notion that NDRG1 is involved in tumor chemoresistance.