Distinct Profiles of Epigenetic Evolution between Colorectal Cancers with and without Metastasis

Abstract

Liver metastasis is a fatal step in the progression of colorectal cancer (CRC); however, the epigenetic evolution of this process is largely unknown. To decipher the epigenetic alterations during the development of liver metastasis, the DNA methylation status of 12 genes, including 5 classical CpG island methylator phenotype (CIMP) markers, was analyzed in 62 liver metastases and in 78 primary CRCs (53 stage I-III; 25 stage IV). Genome-wide methylation analysis was also performed in stage I-III CRCs and in paired primary and liver metastatic cancers. Methylation frequencies of MGMT and TIMP3 increased progressively from stage I-III CRCs to liver metastasis (P = 0.043 and P = 0.028, respectively). The CIMP-positive cases showed significantly earlier recurrence of disease than did CIMP-negative cases with liver metastasis (P = 0.030), whereas no such difference was found in stage I-III CRCs. Genome-wide analysis revealed that more genes were methylated in stage I-III CRCs than in paired stage IV samples (P = 0.008). Hierarchical cluster analysis showed that stage I-III CRCs and stage IV CRCs were clustered into two distinct subgroups, whereas most paired primary and metastatic cancers showed similar methylation profiles. This analysis revealed distinct methylation profiles between stage I-III CRCs and stage IV CRCs, which may reflect differences in epigenetic evolution during progression of the disease. In addition, most methylation status in stage IV CRCs seems to be established before metastasis.

Aberrant TET1 Methylation Closely Associated with CpG Island Methylator Phenotype in Colorectal Cancer

“…All cell lines were supplemented with 10% fetal bovine serum (Life Technologies) and antibiotic-antimycotic reagent (Life Technologies) at 37 C in a humidified incubator with 5% CO 2 . SW48, RKO, and HT29 cells were treated with 1 mmol/L 5-aza-2 0 -deoxycytidine (DAC; SigmaAldrich) as described previously for 72 hours, with the drug and medium replaced every 24 hours (14).…”

“…Next, genome-wide CpG methylation status was compared between colorectal cancers with and without TET methylation using MCAM technology (14,16). We assessed 22 colorectal cancers in this context: five CIMP-P colorectal cancers with TET1 methylation, six CIMP-P tumors without TET1 methylation and 11 CIMP-N tumors without TET1 methylation.…”

“…Global analysis using methylated CpG island amplificationmicroarray technology was carried out using DNA from 22 colorectal cancer samples (five CIMP-P with TET1 methylation, six CIMP-P without TET1 methylation, and 11 CIMP-N colorectal cancers) as described previously (14,16,19).…”

Combined analysis of KRAS and PIK3CA mutations, MET and PTEN expression in primary tumors and corresponding metastases in colorectal cancer

“…15,16 Moreover, several reports have shown that more genes were methylated in primary colorectal tumors than in corresponding metastatic lesions and metastases can exhibit substantial differences in gene expression patterns compared with primary tumors. [17][18][19] In view of these data, the heterogeneity between primary tumors and metastases emerged as an additional reason for the failure of targeted therapies in colorectal cancer; thus, the current study was conducted in order to determine the degree of discordance between potential predictive and/or prognostic molecular markers in primary tumors and corresponding metastases, and to investigate the possible associations between these biomarkers in primary tumors, as well as in metastases.…”

The Colorectal Tumor Microenvironment: The Next Decade

“…Yet, the enormous research efforts of the last decade promise major discoveries and novel implementation relative to potential treatments for CRC that will hopefully be available within the next 10 years. New findings implicating mutations in metastasis suppressor genes [1] or in known oncogenic pathways such as KRAS, BRAF, PTEN, IGFR1 and EGFR [2-4] as well as epigenetic alterations involving DNA methylation dysregulation and/or chromatin remodeling [5] and miRNA control of gene expression [6] have greatly expanded the knowledge of how metastatic dissemination proceeds. The constant interplay between the tumor and its surrounding microenvironment continuously modifies their synergistic mechanisms and responses generally to the tumor's advantage, such that attacking the lesions on all fronts becomes a necessity.…”