RPS6KA3 and neoplasm: Furthermore, palbociclib-insensitive tumours (two-cycles) showed reduced phosphorylation in AKT (p = 0.03) and RSK2 (p = 0.003), as well as the tumour suppressors p38 (p = 0.04) and GSK3a (p = 0.04) and GSK3b (p = 0.004) compared to palbociclib-sensitive tumours (one-cycle).