PTK6 is critical not only for the growth of ER+ breast cancer cells that are resistant to tamoxifen, but also for the growth of ER+ breast cancer cells made resistant to long-term estrogen deprivation (MCF-7-EDR; T47D-EDR) or to the selective ER degrader fulvestrant (MCF-7-FulvR). This evidence concerns the gene PTK6 and breast carcinoma.