RPS6KA2 and breast cancer: Consistently, JunD and RSK3 both had much higher mRNA and protein levels in luminal and HER2+ breast cancer cell lines (MCF7, BT474 and MDA-MB-453) compared with BLBC cells (SUM1315, MDA-MB-231, BT549 and MDA-MB-157) (Fig. 3c, d).