Integrated genomic analysis of colorectal cancer progression reveals activation of EGFR through demethylation of the EREG promoter

Abstract

Key molecular drivers that underlie transformation of colonic epithelium into colorectal adenocarcinoma (CRC) are well described. However, the mechanisms through which clinically targeted pathways are activated during CRC progression have yet to be elucidated. Here, we used an integrative genomics approach to examine CRC progression. We used laser capture microdissection to isolate colonic crypt cells, differentiated surface epithelium, adenomas, carcinomas and metastases, and used gene expression profiling to identify pathways that were differentially expressed between the different cell types. We identified a number of potentially important transcriptional changes in developmental and oncogenic pathways, and noted a marked upregulation of EREG in primary and metastatic cancer cells. We confirmed this pattern of gene expression by in situ hybridization and observed staining consistent with autocrine expression in the tumor cells. Upregulation of EREG during the adenoma–carcinoma transition was associated with demethylation of two key sites within its promoter, and this was accompanied by an increase in the levels of epidermal growth factor receptor (EGFR) phosphorylation, as assessed by reverse-phase protein analysis. In CRC cell lines, we demonstrated that EREG demethylation led to its transcriptional upregulation, higher levels of EGFR phosphorylation, and sensitization to EGFR inhibitors. Low levels of EREG methylation in patients who received cetuximab as part of a phase II study were associated with high expression of the ligand and a favorable response to therapy. Conversely, high levels of promoter methylation and low levels of EREG expression were observed in tumors that progressed after treatment. We also noted an inverse correlation between EREG methylation and expression levels in several other cancers, including those of the head and neck, lung and bladder. Therefore, we propose that upregulation of EREG expression through promoter demethylation might be an important means of activating the EGFR pathway during the genesis of CRC and potentially other cancers.

Distinguishable Prognostic Signatures of Left- and Right-Sided Colon Cancer: a Study Based on Sequencing Data

“…Overexpression of GNG4 inhibits cell growth of glioblastoma cell lines and in vitro transformation of immortalized human astrocytes, hence indicating a probable tumor suppressor character of GNG4 in glioblastoma [38]. Palma P et al identified increased GNG4 expression level in treatment-responsive rectal cancer samples compared with nonresponsive rectal tumor patients [30]. Our results reveled that GNG4 is highly expressed in the left-side colon.…”

“…Qu X et al found that in those patients treated with cetuximab, low EREG methylation was correlated with increased expression of the ligand of EREG, also was related to a better response to the cetuximab treatment. On the contrary, high EREG methylation was correlated with decreased expression of the ligand of EREG, as well as was related to the worse response of therapy [30]. Lee MS et al found that there were noteworthy inverse correlations between EREG expression and methylation, as well as tumor position, BRAF mutation, and CIMP-high status [31].…”

Genome-wide DNA methylation profiles of low- and high-grade adenoma reveals potential biomarkers for early detection of colorectal carcinoma

“…To ensure consistency of data processing, we only compared our samples with publically accessible samples with raw idat files. GSE68060, GSE68838, GSE77954, GSE77965, GSE81211, GSE101764, GSE107352, and GSE75546 were collected from GEO while E-MTAB-6450 was collected from ArrayExpress [43][44][45][46][47][48] (Additional file 1: Table S6). Some cell line samples and metastatic cancer samples were removed upon further study.…”

Localization and Accumulation Studies of Dacomitinib in Rat Intestines and Skin by Immunohistochemistry

“…The expression of ErbB-1, -2 and -4 tends to be higher in the ileum than in other areas of the intestines tract [10]. Qu et al reported that epiregulin expression is confined to epithelial cells in the colon [6]. These findings suggest that the intensity of immunostaining in the intestines is proportional to ErbB family expression in the intestines.…”