Studies On New CpG Island Methylation Phenotype Markers And Clinicopathologicalfeatures In Colorectal Cancer

Object:CpG island methylator phenotype (CIMP) was first proposed in 1999 to describe a subset of colorectal cancer (CRC) that are characterized by vast hypermethylation of promoter CpG island sites, resulting in the inactivation of several tumor suppressor genes or other tumor-related genes. The CIMP trait was found to be associated with a variety of distinct clinical and molecular features, i.e., it has the worse prognosis, with apparently lower responsiveness to 5-FU and Cetuximb. However, the accurate clinical and molecular features of CIMP have not been equal among studies. Possible explanations for this inconsistency include the use of small case-control studies, differences in the methylation markers used to define CIMP, and different hypermethylation assays used. Which specific methylated gene or loci should be used to define CIMP is the main challenge in studying and evaluation of CIMP tumors, we selected a new panel of five loci at SHISA3, STC2, TMEM200B, CTSL1 and LRIFlgenes for CIMP analysis.In addition, to quantify the methylation more accurately, we used a new technique of droplet digital PCR (ddPCR) to detect the methylation status.Methods:Based on our previous DNA methylomes studies on CIMP/non-CIMP colon cancers, we selected five CpG islands in the promoter regions of SHISA3, STC2, TMEM200B, CTSL1 and LRIF1, which is specifically methylated in CIMP tumors as a set of new surrogate panel markers for CIMP analysis. In addition, to quantify the methylation more accurately, we used a new technique of droplet digital PCR (ddPCR) to detect the methylation status.Results:Of the 216 tumors we investigated, our new panel delivered more sensitivity and specificity for CIMP analysis than previously validated five gene panel (classic panel) includes CACNA1G, IGF2, NEUROG1, RUNX3, and SOCS1.Conclusions:The new five gene panel for CIMP analysis is more sensitive and specific than the classic panels.