BCL2 and breast carcinoma: We showed that treatment of both MCF-7 and MDA-MB-231 breast cancer cell lines with (1) and (2) results in the transcriptional down-regulation of BCL2. DNA damage by ROS is thought to lead to transcriptional activation of the tumour suppressor gene, p53, leading to the down-regulation of BCL2 and up-regulation of various pro-apoptotic genes [22].