preproenkephalin and Adenocarcinoma

To examine the profiles of K-ras mutations and p16 and preproenkephalin (ppENK) promoter hypermethylation and their associations with cigarette smoking in pancreatic cancer patients.. In plasma DNA of 83 patients with untreated primary pancreatic ductal adenocarcinoma, DNA hypermethylation was determined by methylation-specific polymerase chain reaction and K-ras codon 12 mutations by enriched-nested polymerase chain reaction followed by direct sequencing. Information on smoking exposure was collected by in-person interview. Pearson chi test and Fisher exact test were used in statistical analysis.. K-ras mutations, ppENK, and p16 promoter hypermethylation were detected in 32.5%, 29.3%, and 24.6% of the patients, respectively. Sixty-three percent (52/83) of patients exhibited at least one of the alterations. Smoking was associated with the presence of K-ras mutations (P = 0.003). A codon 12 G-to-A mutation was predominantly observed in regular smokers and in heavy smokers (pack-year of smoking > or =36). Smoking was not associated with p16 or ppENK hypermethylation.. These preliminary observations suggest that plasma DNA might be a useful surrogate in detecting genetic and epigenetic alterations of pancreatic cancer. The findings on the association between K-ras mutation and smoking were in consistency with previous studies. Further studies on environmental modulators of epigenetic changes in pancreatic cancer are warranted.

Topics: Adenocarcinoma; Adult; Aged; DNA Methylation; Enkephalins; Epigenesis, Genetic; Female; Gene Expression Regulation, Neoplastic; Genes, p16; Genes, ras; Genetic Predisposition to Disease; Humans; Male; Middle Aged; Mutation; Pancreatic Neoplasms; Promoter Regions, Genetic; Protein Precursors; Smoking

A higher prevalence of epigenetic inactivation of tumor suppressor genes has been reported in cancer cell line populations compared to primary cancer populations. Cancer-related genes are commonly methylated in cancer cell lines but it is not known the extent to which tumor suppressor genes may be artificially methylated in vitro. We therefore examined 10 pancreatic cancer cell lines and corresponding primary tumors for aberrant DNA methylation of promoter CpG islands of eight genes and seven CpG islands. Using methylation-specific PCR (MSP), methylation was not detected at any of the 15 CpG islands in 15 normal pancreata or in an immortalized normal pancreatic duct epithelial (HPDE) cell line. Of 150 loci examined, 49 loci were methylated in both primary carcinomas and their corresponding cell lines, 95 loci were not methylated in either cell lines or their corresponding primary carcinomas. There were four loci methylated only in cell lines while another two loci were methylated only in primary carcinomas. Overall, the methylation status of primary carcinomas and their cell lines were concordant in 96% of cases (144 of 150) (J statistic; J=0.92, P<0.0001). We conclude that most of the DNA methylation of tumor suppressor genes observed in cancer cell lines is present in the primary carcinomas from which they were derived.

Topics: Adenocarcinoma; Calcium Channels, T-Type; Cell Line; CpG Islands; DNA Methylation; DNA, Neoplasm; Enkephalins; Genes, Tumor Suppressor; Humans; Neoplasm Proteins; Pancreatic Neoplasms; Polymerase Chain Reaction; Promoter Regions, Genetic; Protein Precursors; Receptors, Retinoic Acid; Thrombospondin 1; Tissue Inhibitor of Metalloproteinase-3; Tumor Cells, Cultured

To identify CpG islands differentially methylated in pancreatic adenocarcinoma, we used methylated CpG island amplification (MCA) coupled with representational difference analysis. Of 42 CpG islands identified by MCA/representational difference analysis, 7 CpG islands [methylated in carcinoma of the pancreas (MICP)] were differentially methylated in a panel of eight pancreatic cancer cell lines compared with normal pancreas. In a larger panel of 75 pancreatic adenocarcinomas, these 7 MICPs (ppENK, Cyclin G, ZBP, MICP25, 27, 36, and 38) were methylated in 93, 3, 9, 15, 48, 19, and 41% of cancers, respectively, by methylation-specific PCR but not in any of 15 normal pancreata. In pancreatic cancer cell lines, methylation of ppENK, a gene with known growth suppressive properties, was associated with transcriptional silencing that was reversible with 5-aza-2'-deoxycytidine treatment. Relationships between the methylation patterns of pancreatic adenocarcinomas and their clinicopathological features were also determined. Larger pancreatic cancers and those from older patients (P = 0.017) harbored more methylated loci than smaller tumors and those from younger patients (P = 0.017). ppENK, MICP25, and 27 were variably methylated in normal gastric, duodenal, and colonic mucosae. These data indicate that aberrant methylation of ppENK and its transcriptional repression is a common event in pancreatic carcinogenesis.

Topics: Adenocarcinoma; Adult; Aged; Aged, 80 and over; Antimetabolites, Antineoplastic; Azacitidine; CpG Islands; Cyclin G; Cyclin G1; Cyclins; DNA Methylation; Enkephalins; Humans; Microsatellite Repeats; Middle Aged; Pancreatic Neoplasms; Protein Precursors; Reverse Transcriptase Polymerase Chain Reaction