To investigate the functional role of DLL1 in these BC cells, MCF-7, BT474, and MDA-MB-231 cells were transfected with two DLL1 specific siRNAs (DLL1-siRNA1 and DLL1-siRNA2), to downregulate DLL1 expression, and with a non-targeting siRNA (Ctr), as a negative control. Here, DLL1 is linked to breast cancer.