To investigate the functional role of KLF11 in BC, we performed siRNA-mediated loss-of-function of KLF11 with cell viability, cell proliferation, and cell apoptosis assays in ER-positive luminal type (MCF7), HER2 amplified type (SK-BR-3), and TNBC (MDA-MB-231) cell lines. The gene discussed is KLF11; the disease is breast cancer.