title: Aberrant promoter methylation of p16 in colorectal adenocarcinoma in North Indian patients.
abstract: OBJECTIVE
  To investigate p16 gene methylation and its expression in 30 patients with sporadic colorectal adenocarcinoma in a North Indian population.
  
  
  METHODS
  Methylation specific polymerase chain reaction was used to detect p16 gene methylation and immunohistochemistry was used to study the p16 expression in 30 sporadic colorectal tumors as well as adjoining and normal tissue specimens.
  
  
  RESULTS
  Aberrant promoter methylation of p16 gene was detected in 12 (40%) tumor specimens, whereas no promoter methylation was observed in adjoining and normal tissue. Immunohistochemistry showed expression of p16 protein in 26 (86.6%) colorectal tumors whereas complete loss of expression was seen in 4 (13.3%) and reduced expression was observed in 12 (40%) tumors. In the adjoining mucosa, expression of p16 was in 11 (36.6%) whereas no clear positivity for p16 protein was seen in normal tissue. There was a significant difference in the expression of p16 protein in tumor tissue and adjoining mucosa (P < 0.001). The methylation of the p16 gene had a significant effect on the expression of p16 protein (P = 0.021). There was a significant association of methylation of p16 gene with the tumor size (P = 0.015) and of the loss/reduced expression of p16 protein with the proximal site of the tumor (P = 0.047). Promoter methylation and expression of p16 had no relation with the survival of the patients (P > 0.05).
  
  
  CONCLUSIONS
  Our study demonstrated that promoter hypermethylation of the p16 gene results in loss/reduced expression of p16 protein and this loss/reduced expression may contribute to tumor enlargement.
authors.affiliation: Pooja Malhotra, Rakesh Kochhar, Department of Gastroenterology, Postgraduate Institute of Medical Education and Research, Chandigarh, 160012, India.
authors.forename: Pooja
authors.initials: P
authors.lastname: Malhotra
authors.forename: Rakesh
authors.initials: R
authors.lastname: Kochhar
authors.forename: Kim
authors.initials: K
authors.lastname: Vaiphei
authors.forename: Jai Dev
authors.initials: JD
authors.lastname: Wig
authors.forename: Safrun
authors.initials: S
authors.lastname: Mahmood