13- Immunohistochemical Analysis of P53 Protein in Colorectal Carcinoma and Its Relationship to Clinicopathologic Features

Abstract

Colorectal cancer regarded as one of the most widespread malignant tumor in the world. It is considered the second leading death factor among people in some developed countries. Colorectal cancer comprises several distinct histological types including adenocarcinoma which forms 85%-95% of all colorectal cancer cases. Pathogenesis of colorectal cancer is a multistep process characterized by involvement of many genetic alterations, including p53. The aim of this study is to detect the expression of p53 protein in colorectal carcinoma and to show its relationship with some clinicopathological features including age, gender, histological types, histological grades and staging. Forty paraffin-embedded tissue blocks of colectomy specimens were used in this retrospective study. They were collected from the Department of Pathology in Sulaimania Teaching Hospital, Shorsh Hospital and Shehid Saifeddin Private Clinic from January 2007 to July 2008. Two sections of 4 micrometer thickness were taken from each paraffin embedded tissue block. First section was taken for hematoxylin and eosin stain and the other one for immunohistochemistry [anti-p53 monoclonal antibody] by using DakoCytomation Envision + Dual Link System-HRP (DAB+). The relationship between p53 over expression and the dependent variable (age, gender, histological types, histological grades, and staging) were evaluated statistically using an analysis of variance (ANOVA) with STATA 8 soft ware (College station, Tx). A positive reaction for p53 was scored on a semiquantitative base as score 0 (no staining), score 1+ (weak staining), score 2+ (moderate staining), and score 3+ (strong staining). Staining was negative for p53 (score 0) in 16 cases (40%). Positive cases were scored as (1+) in 4 cases (10.0%); (2+) in 8 cases (20.0%); and (3+), in 12 cases (30.0%). There were no significant relationships between p53 over expression and age (p=0.682), gender (p=0.924), histological types (p=0.30), histological grades (p=0.516), and the stage of the disease (p=0.281). Conclusions: Considering the p53 protein over expression in a relatively high percentage of patients, it seems that p53 mutation may play an important role in the development of colorectal carcinoma. There were no significant relationships between p53 protein expression and some clinicopathologic variables such as age, gender, histological types, histological grades, and the stage of the disease.