The Chemokine Receptor CXCR4 is Regulated by DNA Methylation in Pancreatic Cancer

Abstract

Despite the biological and clinical importance of the interaction between the chemokinereceptor CXCR4 and its ligand CXCL12 (SDF-1?) in human cancers, little is known abouttranscriptional regulation of the CXCR4 gene. Although aberrant hypermethylation in cancer hasbeen described typically in genes with tumor-suppressor properties, this epigenetic alteration hasalso been observed to affect potential cancer-promoting genes. We now demonstrate that DNAmethylation influences CXCR4 expression in human pancreatic cancer. Gene expression profilingand reverse transcription-PCR identified a significant proportion of pancreatic cancer cell lines thatdisplayed little or no CXCR4 mRNA expression. Using methylation-specific PCR, combinedbisulfite restriction analysis, and bisulfite sequencing, we found the 5' CpG islands of the CXCR4gene to be unmethylated in normal pancreas, whereas promoter hypermethylation was detected in45% (9 of 20) of pancreatic cancer cell lines and in 46% (46 of 100) of primary pancreaticadenocarcinomas. There was a significant inverse correlation between methylation and mRNAexpression level of CXCR4 (P = 0.008) in a large panel of pancreatic cancer cell lines. Constitutiveas well as inducible expression of CXCR4 could be restored in methylated cell linespharmacologically using epigenetic modifying drugs. These findings demonstrate the firstevidence for epigenetic regulation of CXCR4 in human cancers, providing new insights into therole of CXCR4/CXCL12 interactions in tumor progression.