Tamoxifen resistance is a major therapeutic problem in breast cancer and a significant correlation between STAT3-RANTES autocrine signaling and acquisition of tamoxifen resistance has been reported: STAT3 and RANTES in tamoxifen-resistant MCF-7 cells regulate each other via autocrine signaling, leading to the induction of an antiapoptotic signal. The gene discussed is CCL5; the disease is breast cancer.