Therefore, re-expression of CD133 ARQ197 msds by treatment of demethylation agent is expected to discover the functions of CD133 gene in cancer. The failure to detect methylated or unmethylated DNA bands in MS-PCR SNU-61 cells warrants comment. We believe that there are some problems with the quality of the modified DNA. This remains to be confirmed. The strong expression of CD133 by Caco-2 cells, in which promoter hypermethylation was detected, supports the suggestion that regulation of CD133 expression might be caused by another mechanism. In conclusion, we observed hypermethylation in the promoter region of the CD133 gene in 13 of 32 colorectal cancer cell lines. We confirmed the methylation status by MS-PCR, bisulfite sequencing analysis and treatment of 5-aza-2��-deoxycytidine.

The expression status of the CD133, one of CSC markers, was correlated with methylation status of CpG islands in the CD133 promoter. These results may contribute to the understanding of the role of CD133 inactivation in the pathogenesis of colorectal cancers. COMMENTS Background The caner stem cell theory is a newly emerged concept of cancer initiation and development. These cells have the ability to self-renew and to recapitulate the bulk tumor population. In colorectal cancer, a CD133-positive population of colon cancer cells was recently demonstrated to be highly enriched in tumor-initiating colon cancer stem cells. Research frontiers It is reported that tumor initiating cells in colorectal cancer cells express CD133, the cell surface glycoprotein. However, the CD133 gene transcriptional regulation is rather complicated and poorly understood.

This study demonstrates that CD133 expression could be regulated by methylation status of promoter of the gene. Innovations and breakthroughs Recently, a CD133 has become a matter of common interest in the research of colorectal cancer stem cells. This study suggests that transcriptional repression of CD133 is caused by promoter hypermethylation of the CD133 in some of colorectal cancer cell lines. Moreover, each colorectal cancer cell line represented different methylation status of promoter and each colony of cell lines exhibited different levels of methylation. Applications Cancer stem cells lost their potential during differentiation by loss of expression of stem cell-specific expressed genes.

Therefore, this study may contribute to the understanding of the role of CD133 inactivation in the progression of colorectal cancers. Terminology Promoter methylation is one of the most essential epigenetic characteristics. The importance of DNA methylation is highlighted by the finding that Dacomitinib many human diseases result from its abnormal control. Moreover, the aberrant methylation of CpG islands is characteristic of many human cancers and is detected during early carcinogenesis.