sodium-bisulfite and Pancreatic-Neoplasms

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive tumor and still remains a challenge for its lack of effective therapeutic strategies, which is due to the late diagnosis of this disease. Methylation markers might improve early detection and surveillance of PDAC. Furthermore, analysis of hypermethylation in the tumor tissue might help to identify new targets for therapeutic intervention and improve the understanding of the pathophysiological changes occurring in pancreatic cancer. Methylation specific PCR is the method of choice if a small number of genes will be tested in a larger set of patient samples. After DNA isolation by standard procedure, the DNA is then modified using sodium bisulfite. This DNA can then be used in qualitative and quantitative PCR assays.

Topics: Carcinoma, Pancreatic Ductal; DNA; DNA Methylation; Humans; Pancreatic Neoplasms; Polymerase Chain Reaction; Sulfites

Pancreatic adenocarcinoma (PaC) is one of most difficult tumors to treat. Much of this is attributed to the late diagnosis. To identify biomarkers for early detection, we examined DNA methylation differences in leukocyte DNA between PaC cases and controls in a two-phase study. In phase I, we measured methylation levels at 1,505 CpG sites in treatment-naïve leukocyte DNA from 132 never-smoker PaC patients and 60 never-smoker healthy controls. We found significant differences in 110 CpG sites (false discovery rate <0.05). In phase II, we tested and validated 88 of 96 phase I selected CpG sites in 240 PaC cases and 240 matched controls (p≤0.05). Using penalized logistic regression, we built a prediction model consisting of five CpG sites (IL10_P348, LCN2_P86, ZAP70_P220, AIM2_P624, TAL1_P817) that discriminated PaC patients from controls (C-statistic = 0.85 in phase I; 0.76 in phase II). Interestingly, one CpG site (LCN2_P86) alone could discriminate resectable patients from controls (C-statistic= 0.78 in phase I; 0.74 in phase II). We also performed methylation quantitative trait loci (methQTL) analysis and identified three CpG sites (AGXT_P180_F, ALOX12_E85_R, JAK3_P1075_R) where the methylation levels were significantly associated with single nucleotide polymorphisms (SNPs) (false discovery rate <0.05). Our results demonstrate that epigenetic variation in easily obtainable leukocyte DNA, manifested by reproducible methylation differences, may be used to detect PaC patients. The methylation differences at certain CpG sites are partially attributable to genetic variation. This study strongly supports future epigenome-wide association study using leukocyte DNA for biomarker discovery in human diseases.

Topics: Aged; Aged, 80 and over; CpG Islands; DNA Methylation; Female; Humans; Leukocytes; Male; Middle Aged; Pancreatic Neoplasms; Quantitative Trait Loci; Sulfites