Serum- and Glucocorticoid-induced Kinase Sgk1 Directly Promotes the Differentiation of Colorectal Cancer Cells and Restrains Metastasis.

Abstract

The molecular events that determine intestinal cell differentiation are poorly understood and it is unclear whether it is primarily a passive event or an active process. It is clinically important to gain a greater understanding of the process, because in colorectal cancer, the degree of differentiation of a tumor is associated with patient survival. <i>SGK1</i> has previously been identified as a gene that is principally expressed in differentiated intestinal cells. In colorectal cancer, there is marked downregulation of <i>SGK1</i> compared with normal tissue.<b>Experimental Design:</b> An inducible <i>SGK1</i> viral overexpression system was utilized to induce reexpression of <i>SGK1</i> in colorectal cancer cell lines. Transcriptomic and phenotypic analyses of these colorectal cancer lines was performed and validation in mouse and human cohorts was performed. We demonstrate that <i>SGK1</i> is upregulated in response to, and an important controller of, intestinal cell differentiation. Reexpression of <i>SGK1</i> in colorectal cancer cell lines results in features of differentiation, decreased migration rates, and inhibition of metastasis in an orthotopic xenograft model. These effects may be mediated, in part, by SGK1-induced PKP3 expression and increased degradation of MYC. Our results suggest that <i>SGK1</i> is an important mediator of differentiation of colorectal cells and may inhibit colorectal cancer metastasis.