Parallel-Reaction-Monitoring-Based Proteome-Wide Profiling of Differential Kinase Protein Expression during Prostate Cancer Metastasis in Vitro

Prostate cancer is the most common type of cancer in men, and kinases are heavily pursued as drug targets for anticancer therapy. In this study, we applied our recently reported parallel-reaction-monitoring (PRM)-based targeted proteomic method to examine the reprogramming of the human kinome associated with bone metastasis of prostate cancer in vitro. The method displayed superior sensitivity over the shotgun-proteomic approach, and it facilitated the quantification of the relative expression of 276 kinase proteins in a pair of bone metastatic prostate cancer cells. Among the differentially expressed kinases, mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4) stimulates the migration and invasion of cultured prostate cancer cells, partially by modulating the activity of secreted matrix metalloproteinases 9 (MMP-9). We also found that the upregulation of MAP4K4 in metastatic prostate cancer cells is driven by the MYC proto-oncogene. Cumulatively, we identify MAP4K4 as a potential promoter for prostate cancer metastasis in vitro.