RPS6KB1 and T-cell leukemia: Interestingly, micro-RNA 21 suppresses the expression of the S6K1 substrate and translational inhibitor PDCD4 to regulate cell survival in T cell leukemia (44), whereas elevated levels of T cell micro-RNA 21 expression and subsequent suppression of PDCD4 are associated with active disease in systemic lupus erythematosus (45).