Assessment of Bcl-2 oncoprotein expression in colorectal epithelial neoplasms An Immunohistochemical study

Colorectal cancer is one of the most frequent cancers in the world. Colorectal cancer is the result of genetic and epigenetic alterations that cause disorders in cell growth, differentiation and apoptosis, resulting in transformation of normal epithelium to adenocarcinoma. Expression of Bcl-2 gene is believed to enhance tumor progression by countering apoptosis triggers, resist DNA damage-induced apoptosis, and undergo growth arrest in G0/G1 or G2/M phases, which promotes tumor cell survival and oncogenic progressions, and may inhibit cell growth and proliferation. To evaluate Bcl-2 oncoprotein expression in colorectal epithelial neoplasms, to correlate the Bcl-2 immunopositivity with certain clinicopathological parameters and to compare the results with other studies. This is a cross sectional study of 50 cases of colorectal adenocarcinoma and 10 samples of colorectal adenomatous polyps. The samples were collected from Mosul Hospitals and some private lab. Patient's age and sex in addition to the site of the tumor was obtained from the archival histological reports. Hematoxylin and Eosin stained section from each case were revised regarding the histological type, grade and stage of the tumor. Immunohistochemical stain for Bcl2 oncoprotein was performed. The staining assessment of Bcl-2 was done by using a semiquantitative immunostaining score (ISS) for Bcl-2, taking both intensity and the percentage of stained cells to obtain an IS score that ranged from 0 to 4.0. The mean age of all cases was 53.8 years The Fifth decade takes the peak incidence, followed by the seventh decade. Male to female ratio was 1.4:1. Microscopically, 45 (90%) of cases were classical adenocarcinoma, 2 (4%) were mucinous adenocarcinoma, 2 (4%) were signet ring carcinoma and 1 (2%) was neuroendocrine carcinoma. Eight (16%) were well differentiated classical adenocarcinoma, 22(44%) were moderately differentiated, and 15(30%) were poorly differentiated tumor. Duke's staging, 1(2%) case was Duke's A, 18(36%) cases were Duke's B, 25(50%) cases were Duke's C and 6(12%) cases were Duke's D. The Bcl-2 Positivity was observed in 38% of colorectal carcinoma. No significant correlation identified between Bcl-2 expression and the patient's age and sex despite the finding of predominance of Bcl-2 immunoreactivity in young age group and in female. Bcl-2 positivity correlates significantly with the macroscopic type of the tumor with highest positivity in a polypoidal tumor. Bcl-2 expression seen only in colorectal adenocarcinoma classical (NOS) type, while it was negative in other types (p=0.045). An inverse significant correlation between Bcl-2 expression and histological grading was reported where Bcl-2 was reported mainly in well and moderately differentiated tumors (42.1 % and 52.7% respectively). No significance correlation identified between Bcl-2 expression and tumor Duke's stage. Conclusion: Bcl-2 expression was found in 38% of cases. It was significantly correlated with tumor macroscopic types, histological types and grade. No correlation found between Bcl-2 and age, sex, site and stage of the tumors.