RPS6KA2 and breast cancer: Lastly, to further confirm the role of JunD/RSK3 signalling in BET resistance, RPS6KA2 and JUND were respectively knocked down in two JQ1-resistant breast cancer cell lines (BT474 and MDA-MB-453) (Supplementary Fig. 3B), and showed that the silencing of both RPS6KA2 and JUND restored the JQ1 sensitivity of these cells (Fig. 3f).