title: Immunohistochemical study of p53 and proliferating cell nuclear antigen expression in odontogenic keratocyst and periapical cyst.
abstract: BACKGROUND
  p53 protein is a product of p53 gene, which is now classified as a tumor suppressor gene. The gene is a frequent target for mutation, being seen as a common step in the pathogenesis of many human cancers. Proliferating cell nuclear antigen (PCNA) is an auxiliary protein of DNA polymerase delta and plays a critical role in initiation of cell proliferation.
  
  
  OBJECTIVE
  The aim of this study is to assess and compare the expression of p53 and PCNA in lining epithelium of odontogenic keratocyst (OKC) and periapical cyst (PA).
  
  
  METHODS
  A total of 20 cases comprising 10 OKC and 10 PA were included in retrospective study. Three paraffin section of 4 μm were cut, one was used for routine hematoxylin and eosin stain, while the other two were used for immunohistochemistry. Statistical analysis was performed using Chi-square test.
  
  
  RESULTS
  The level of staining and intensity were assessed in all these cases. OKC showed PCNA expression in all cases (100%), whereas in perapical cyst only 60% of cases exhibited PCNA staining. (1) OKC showed p53 expression in 6 cases (60%) whereas in PA only 10% of the cases exhibited p53 staining. Chi-square test showed PCNA staining intensity was more significant than p53 in OKC. (2) The staining intensity of PA using p53, PCNA revealed that PCNA stating intensity was more significant than p53.
  
  
  CONCLUSIONS
  OKC shows significant proliferative activity than PA using PCNA and p53. PCNA staining was more intense when compared with p53 in both OKC and PA.
authors.affiliation: Department of Oral Pathology and Microbiology, Mar Baselios Dental College, Kothamangalam, Kerala, India.
authors.forename: Thara Purath
authors.initials: TP
authors.lastname: Sajeevan
authors.affiliation: Raagas Dental College, Chennai, Tamil Nadu, India.
authors.forename: Tillai Rajasekaran
authors.initials: TR
authors.lastname: Saraswathi
authors.affiliation: Raagas Dental College, Chennai, Tamil Nadu, India.
authors.forename: Kannan
authors.initials: K
authors.lastname: Ranganathan
authors.affiliation: Raagas Dental College, Chennai, Tamil Nadu, India.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Joshua
authors.affiliation: Raagas Dental College, Chennai, Tamil Nadu, India.
authors.forename: Uma Devi K
authors.initials: UD
authors.lastname: Rao
keywords: Odontogenic keratocyst; p53; periapical cyst; proliferating cell nuclear antigen