Analysis of DNA Methylation in Tissues Exposed to Inflammation.

Induction of aberrant DNA methylation is one of the most important mechanisms mediating the effect of inflammation on cancer development. Aberrant methylation of promoter CpG islands of tumor suppressor genes can silence their downstream genes, and that in cancer tissues is associated with prognosis or therapeutic effects. In addition, aberrant methylation can occur in tissues exposed to specific types of inflammation, producing a so-called "epigenetic field for cancerization," and its accumulation is correlated with cancer risk. Thus, aberrant methylation at specific loci is an important biomarker and mediator of the carcinogenic effect of inflammation. DNA methylation at specific genomic regions can be analyzed by various methods based upon bisulfite-mediated DNA conversion, which specifically converts unmethylated cytosines into uracils under appropriate conditions. Methylation-specific PCR (MSP), quantitative MSP, and bisulfite sequencing are widely used, and this chapter provides protocols for bisulfite-mediated conversion, quantitative MSP, and bisulfite sequencing.