RPS6KA3 and plasma cell myeloma: This is because the level of RSK2 expression and phosphorylation is significantly higher in a subset of MAPK driven cancer cell lines as compared to non-cancer controls, and RSK2 is therefore considered to be a viable cancer drug target [10–13], specifically in the treatment of breast [14] and prostate tumors [15–17], myeloma [18, 19], T-cell lymphoma [20] and melanoma [21].