Signature in Renal Carcinoma Figure 7. Epithelial mesenchymal transition in ccRCC. a. A heatmap showing the increased expression of some markers associated with EMT. Upregulation of genes is indicated in red, downregulation is indicated in green, and similar expression is indicated in black. b. IHC validation of two known markers of EMT: vimentin and N-cadherin. Sum scores are shown with n, as indicated. *p,0.01 when comparing ccRCC to normal match. doi:10.1371/journal.pone.0010696.g007 Figure 8. Proposed model for cellular differentiation in ccRCC. During normal renal development, mesenchymal stem cells undergo mesenchymal epithelial transition (MET) to develop into normal renal epithelial cells (NREs). In renal carcinogenesis, NREs undergo de- differentiation and epithelial mesenchymal transition (EMT), followed by adipogenic differentiation to develop into ccRCC. doi:10.1371/journal.pone.0010696.g008 than the blood supply can deliver nutrients. TLR2 can interact with a number of damage-associated molecular patterns (DAMPs) that are generated in the wake of cell death [37];[38];[39]. TLR2:DAMP interactions are important in the generation and maintenance of chronic inflammation that is integral to the disease process. Similarly, the homeostatic chemokine stromal cell-derived factor-1 (CXCL12/SDF-1) regulates many vital biological process- es, including neovascularization and tumorigenesis via binding to the widely expressed receptor CXCR4 [40]. CXCR4-expressing tumor cells preferentially metastasize to tissues that highly express CXCL12, including the lung, liver, LN, and bone marrow [41];[42]. Interestingly, CXCR4 expression within a tumor increases, through HIF-1a, as the oxygen concentration decreases; this action enhances the metastatic potential of the tumor cells [43]. Consequently, there is a great deal of interest in developing anti- cancer therapeutics targeting CXCR4 [44]; [45]. It has been previously shown that other immune genes such as TLR3 [46] and B7-H1 ligand [47], are aberrantly expressed in ccRCC cells. The activated immune state may be linked to the responsiveness of ccRCC to immunotherapies, which makes ccRCC one of only a few cancers that responds to immune therapies [48]; [49]. Our data indicate that ccRCC has undergone EMT with an acquisition of mesenchymal/adipogenic differentiation signature and a loss of epithelial differentiation. Our work confirms a recent PLoS ONE | www.plosone.org 10 May 2010 | Volume 5 | Issue 5 | e10696