Z Gastroenterol 2013; 51 - A56
DOI: 10.1055/s-0033-1347506

DNA methylation markers of left-sided colorectal cancer based on gene expression screening

B Péterfia 1, P Hollósi 2, A Kalmár 1, O Galamb 3, S Spisák 3, B Wichmann 3, K Tóth 1, K Leiszter 1, VÁ Patai 1, V Kubák 2, K Kiss 2, Z Horváth 2, Z Tulassay 3, I Kovalszky 2, B Molnár 3
  • 12nd Department of Internal Medicine, Semmelweis University, Budapest, Hungary
  • 21st Department of Pathology and Experimental Cancer Research, Semmelweis University, Budapest, Hungary
  • 3Molecular Medicine Research Unit, Semmelweis University, Budapest, Hungary

Background and aims: Aberrant DNA methylation can lead to dysregulated expression of certain genes that is proven to contribute to colorectal cancer (CRC) formation and progression. However, our knowledge of the methylation markers of CRC development remains incomplete. Our aims were to identify DNA methylation markers in left-sided CRC samples on the basis of gene expression and to analyze their methylation levels along the colorectal adenoma-carcinoma sequence.

Materials and methods: Whole genome expression profiling was performed by using HGU133 Plus 2.0 microarrays (Affymetrix) on healthy colonic (n = 49), colorectal adenoma (n = 49) and left-sided CRC (n = 49) biopsy samples and also on laser microdissected (LCM) epithelial and stromal cells from healthy (n = 6) and CRC (n = 6) samples. Transcripts with gradually decreasing or increasing expression along the adenoma-carcinoma sequence were selected on the basis of Spearman and Kendall analysis. Methylation status of the identified genes were analyzed on macrodissected (n = 10) and LCM (n = 5) healthy colonic, adenomatous biopsy (n = 10) and LCM (n = 5), macrodissected (n = 10) and LCM (n = 5) left-sided colorectal cancer samples using bisulfite-sequencing PCR (BS-PCR) followed by pyrosequencing.

Results: A set of transcripts (including MAL, SFRP1, SULT1A1, PRIMA1) showed decreasing expression (p ≤0,01) in the biopsy samples along the adenoma-carcinoma sequence. Expression of SULT1A1 gene were found to be significantly downregulated (p ≤0,01) in the tumor epithelial cells, whereas MAL and PRIMA1 showed significantly decreased expression (p ≤0,05) in the tumor stromal cells compared to the healthy samples. Hypermethylation of SFRP2 (10/10 cases), COL1A2 (9/10 cases), SOCS3 (9/10 cases) could be detected in CRC samples compared to the healthy specimens. According to the pyrosequencing results of LCM samples increased methylation levels were found predominantly in tumor epithelial cells.

Conclusion: Genome-wide gene expression-based screening was found to be a suitable approach for the idetification of genes, that can be potentially regulated by DNA methylation. Hypermethylation of the selected markers (COL1A2, SFRP2, SOCS3) might result in reduced expression and could contribute to the formation of colorectal cancer.