In MDA-MB-231 and H358 cells, LJI308 blocks cellular inhibition of RSK and its phosphorylation of YB1 on Ser102 with EC50 of 0.2–0.3 μM, and thus inhibits cell growth. In TNBC HTRY-LT cells, LJI308 also suppresses cell growth correlative with YB-1 inhibition.