It was shown that the consensus sequence of p90 ribosomal S6 kinase (RSK) is RXRXXS/T as same as that of p70S6K1 and the enzyme phosphorylates, the Ser76 and Ser457, as well as Ser67 of human PDCD4-protein in melanoma cells [71]. The gene discussed is PDCD4; the disease is melanoma.