Interestingly, BLBC cells usually have lower endogenous level of JunD/RSK3 signalling and are more sensitive to JQ1 than other subtypes of breast cancer; silencing of JUND/RPS6KA2 can restore the sensitivity in JQ1-resistant luminal or HER2+ breast cancer cells, suggesting that besides adaption to BET inhibition, JunD/RSK3 signalling is also an intrinsic safeguard mechanism. Here, ERBB2 is linked to breast cancer.