Taken together, these results indicate the potential of targeting HIF 1 and CXCR4 CXCL12 in colorectal cancer. Results In vivo CXCR4 and CXCR7 expression in human carcinomas Lenalidomide We measured CXCR4 Inhibitors,Modulators,Libraries and CXCR7 mRNA levels in human polyps and carcinomas. Tumor stages were classified according to UICC recommendations. The expression of CXCR4 and CXCR7 mRNA in these tumors was compared to that of a pool of healthy colonic mucosa samples. Over all, the expression levels of both CXCR4 and CXCR7 were identical to those of the normal mucosa. In Inhibitors,Modulators,Libraries carcinomas, CXCR4 expression significantly increased between early stage tumors and late stage tumors but without significance between stages III IV and metastases Figure 1C. CXCR7 ex pression significantly increased Inhibitors,Modulators,Libraries between early stage tumors and metastases.
Similarly, the CXCR4 and CXCR7 protein expression was absent in polyps and early stages carcinomas but increased Inhibitors,Modulators,Libraries between stage II and III, to be highest in the stage IV carcinomas. Expression was maintained in the liver me tastases. Concerning CXCR7, a weak expres sion Inhibitors,Modulators,Libraries was found in the normal mucosa and stages I to IV, which increased in the liver metastases due to increased number of cells expressing CXCR7. In vitro CXCR4 expression is regulated by HIF 1 Transcript expression We studied CXCR4 mRNA expression in normoxia and hypoxia in SW480, HCT116 and HT29 cells. In hypoxia, there was a significant increase in CXCR4 mRNA level for the three cell lines with a higher increase at 1% O2 than at 3% O2.
On the other hand, as compared to SW480 cells, HT29 and HCT116 cell lines express low rates of CXCR7, and in SW480 cells, no www.selleckchem.com/products/Trichostatin-A.html change in CXCR7 mRNA level was observed between the normoxic and hyp oxic conditions. To determine if the hypoxia related increase of CXCR4 mRNA expression is regulated by HIF 1, we used two different HIF 1 siRNAs. HIF 1 mRNA expression was inhibited by 90% with both HIF 1 siRNAs, and CXCR4 expression was concomi tantly inhibited by more than 90%. Protein expression We then studied the regulation of CXCR4 and CXCR7 pro tein expression at the cell membrane in hypoxia using flow cytometry. For the three cell lines, hypoxia upregu lated the expression of CXCR4 protein at the cell mem brane, whereas CXCR7 expression remained unchanged, confirming the transcriptional data. The HIF 1 and CXCR4 siRNAs led to decreased CXCR4 protein expression, but not to the basal level observed in nor moxia. These data demonstrate that hypoxia induces a strong expression of CXCR4 at the cell mem brane that is regulated by HIF 1, whereas CXCR7 ex pression is independent of hypoxia, HIF 1 and CXCR4. Flow cytometry confirmed our previous observation that CXCR7 is absent in the HCT116 and HT29 cells but highly expressed in the SW480 cells.