RSV + tamoxifen significantly reduced tumor cell viability more than either drug aloneRSV + tamoxifen effectively blocked breast cancer growthReduced the STAT3 acetylation, restored ERα expression and sensitized TNBC (triple-negative breast cancer) cells to antiestrogen therapyInhibited the tumor growth in mice bearing A2058 human melanoma tumors, accompanied by disruption of STAT3- DNMT1 complex formation and demethylation of several tumor-suppressor gene promoters. This evidence concerns the gene ESR1 and triple-negative breast carcinoma.