Characterization of the Src-regulated kinome identifies SGK1 as a key mediator of Src-induced transformation

Despite significant progress, our understanding of how specific oncogenes transform cells is still limited and likely underestimates the complexity of downstream signalling events. Herein, we describe a novel, integrated approach that addresses this knowledge gap. This utilizes mass spectrometry-based chemical proteomics to characterize the global impact of an oncogene on the expressed kinome, and then functionally annotates the regulated kinases. As an example, we identified approximately seventy protein kinases exhibiting altered expression and/or phosphorylation in Src-transformed mammary epithelial cells. An integrated siRNA screen identified nine kinases, including SGK1, as being essential for Src-induced transformation. In triple negative breast cancer cells, which exhibit a prominent signalling network governed by src family kinases, Src positively regulated SGK1 expression and combined inhibition of Src and SGK1 was more effective at inhibiting colony formation in vitro, and xenograft growth in vivo, than either treatment alone. Therefore, this approach not only provides major mechanistic insights into oncogenic transformation but also aids the design of improved therapeutic strategies.