Objective The aim of this study was to investigate whether there are differences in the expression spectrums of RSK4 in different tumor cells and to predict the possible protein subtypes and their biological characteris-tics.Methods RNA was extracted from glioma cells GL261,ovarian cancer cells ID8,breast cancer cells 4T1 and 168FARN,colon cancer cells mc38 and CT26,gastric cancer cells MFC and lung cancer cells LLC1.The expres-sions and splicing isomers of RSK4 were detected by RT-PCR.The biological characteristics and functions of RSK4 were analyzed by bioinformatics.Results RT-PCR results showed that RSK4 was expressed in GL261,4T1,mc38,CT26,MFC and LLC1;and multiple splicing isomers were expressed in different tumor cells.Open reading frame analysis revealed RSK4 may encode at least 11 protein subtypes.Secondary structure analysis showed that these protein subtypes encoded by the splicing isomers were composed of α-helix,extended strand,β-turn and random coil,and had the same conserved domain.The results of protein interaction network enrichment analysis showed that RSK4 exerted kinase activity in the nucleus and cytoplasm mainly through the mTOR signaling pathway and long-term potentiation.Conclusions RSK4 has different expression spectrums in different tumor cells,and may produces a variety of protein isoforms with different nitrogen terminals,which can be involved in different biological processes through multiple signaling pathways.