Although this result suggests that ERα is strongly implicated in TNF-α-triggered apoptotic cell death in breast cancer cells, we could not conclusively infer that ERα is a positive regulator of the stimulation of caspase-dependent apoptosis in breast cancer, because our data obviously showed the dramatic decrease in ERα after TNF-α administration to MCF-7 cells, in accordance with a previous study [40]. Here, ESR1 is linked to breast cancer.