Interestingly, women with altered production of melatonin, caused by a circadian disruption after exposure to dim light at night, have intrinsic resistance to paclitaxel via epigenetic mechanisms, which increase signal transducer and activator of transcription 3 (STAT3) expression, which is frequently overexpressed in paclitaxel-resistant breast cancer. This evidence concerns the gene STAT3 and breast cancer.