Novel Regulation by Glucocorticoids of C-FMS Proto-Oncogene RNA Protein Binding and Breast Cancer Invasion

摘要

We propose to explore the role of c-fms RNA protein binding as well as the mechanism by which the c-fms proto-oncogene contributes to aggressive invasive behavior of breast cancer. We have found by Northwestern analysis that there are several proteins which bind to the 3, untranslated region of c-fms RNA. Protein purification has yielded several proteins, some of which are abundant enough for sequencing analysis. The final fraction was confirmed to be active in 3UTR c-fms RNA gel shift assays. Further, we have successfully utilized microarray analysis to identify 5 genes which are consistently differentially overexpressed by dexamethasone in BT20 breast cancer cells. One such gene, which was confirmed to be sensitive to dexamethasone by Western Blot, is sgk, a serine threonine kinase. The sgk protein is phosphorylated by PI3- kinase. We have demonstrated that inhibition of PI3-kinase results in a significant decrease in dexamethasone and CSF-1 (growth factor ligand for c-fms) induced adhesiveness of BT20 cells to extracellular matrix, This suggests that sgk may be a downstream mediator of the c-fms related invasive phenotype. Sgk has not been previously been identified as a gene involved in c-fms related aggressive behavior, thus may represent a potential new target for therapeutic intervention.