Enhanced CXCR4 Expression Associates with Increased Gene Body 5-Hydroxymethylcytosine Modification but not Decreased Promoter Methylation in Colorectal Cancer

Abstract

In colorectal cancer (CRC), upregulation of the C-X-C motif chemokine receptor 4 (CXCR4) is correlated with metastasis and poor prognosis, highlighting the need to further elucidate CXCR4’s regulation in CRC. For the first time, DNA methylation and 5-hydroxymethylcytosine aberrations were investigated to better understand the epigenetic regulation of CXCR4 in CRC. CXCR4 expression levels were measured using qPCR and immunoblotting in normal colon tissues, primary colon cancer tissues and CRC cell lines. Publicly available RNA-seq and methylation data from The Cancer Genome Atlas (TCGA) were extracted from tumors from CRC patients. The DNA methylation status spanning CXCR4 gene was evaluated using combined bisulfite restriction analysis (COBRA). The methylation status in the CXCR4 gene body was analyzed using previously performed nano-hmC-seal data from colon cancers and adjacent normal colonic mucosa. CXCR4 expression levels were significantly increased in tumor stromal cells and in tumor colonocytes, compared to matched cell types from adjacent normal-appearing mucosa. CXCR4 promoter methylation was detected in a minority of colorectal tumors in the TCGA. The CpG island of the CXCR4 promoter showed increased methylation in three of four CRC cell lines. CXCR4 protein expression differences were also notable between microsatellite stable (MSS) and microsatellite instable (MSI) tumor cell lines. While differential methylation was not detected in CXCR4, enrichment of 5-hydroxymethylcytosine (5hmC) in CXCR4 gene bodies in CRC was observed compared to adjacent mucosa.

CXCR4 Mediates Enhanced Cell Migration in CALM-AF10 Leukemia

“…CXCR4 expression and signaling is regulated through a variety of mechanisms. At a transcriptional level, CXCR4 expression may be modified through DNA methylation, directly activated by multiple transcription factors, and impacted by a range of physiologic stimuli ( 19 , 36 ). Protein expression may be impacted by tyrosine sulfation or glycosylation or modified by oligomerization.…”

Comprehensive analysis of lncRNA‑associated ceRNA network reveals the novel potential of lncRNA, miRNA and mRNA biomarkers in human rectosigmoid junction cancer

“…CRC is the result of multiple etiological effects, one of which is the assemblage of diverse genetic or epigenetic alterations and their complex connections (21)(22)(23). Accumulating evidence has demonstrated that lncRNAs have considerable biological roles by modulating gene expression at multiple levels in tumorigenesis and tumor progression (24), and lncRNAs also form the main part of the ceRNA network of CRC.…”

Colorectal Cancer: The Contribution of CXCL12 and Its Receptors CXCR4 and CXCR7

“…A recent work by Stuckel et al showed that the overexpression of CXCR4 in human CRCs is observed in both colonocytes and stromal cells. The authors found that this overexpression is not the result of hypermethylation of the CpG islands of the CXCR4 promoter but rather of an increase in 5-hydroxymethylcytosine (5hmC), a marker of active demethylation of a gene [ 183 ]; and in this case, the accumulation of 5hmC would reflect increased transcription of CXCR4 in the CRC [ 184 ]. This work complements other studies demonstrating the regulation of CXCR4 expression by epigenetic processes associated with genome methylation.…”