Expression of bcl-2 and p53 Protein in Primary Gastric Lymphomas

ABSTRACT

The bcl-2 gene is a proto-oncogene which extends cell survival by blocking apoptosis. Bcl-2 expression has been detected in many types of nodal and MALT lymphoma. The p53 gene is a tumor suppressor gene and p53 mutation is the most common genetic alteration in human malignancies. The relationship between the expression of bcl-2 and p53 protein in primary gastric lymphoma has been rarely reported. The authors investigated the expression of bcl-2 and p53 protein in 37 cases of primary gastric lymphoma by immunohistochemical method using bcl-2 and p53 monoclonal antibodies. There were five cases of low grade B-cell MALT lymphomas and thirty two cases of high grade B-cell lymphomas. Fifteen of 37 cases (41%) showed bcl-2 protein expression in the cytoplasm of tumor cells and 26 cases (70%) showed p53 protein expression in the nucleus of tumor cells. Bcl-2 protein was detected in 4 of 5 (80%) low grade MALT lymphomas, and in 11 of 32 (34%) high grade lymphomas. There was no significant correlation between bcl-2 expression and histologic grade of primary gastric lymphomas (p>0.05). p53 protein was positive in 25 of 32 (78%) high grade lymphomas, and in 1 of 5 (20%) low grade MALT lymphomas. The expression of p53 protein is significantly higher in high grade lymphoma than in low grade MALT lymphoma (p<0.05). The p53 expression in the bcl-2 negative cases (86%) was significantly higher than in the bcl-2 positive cases (47%). There was an inverse relationship between bcl-2 and p53 expression in primary gastric lymphoma. These results suggest that bcl-2 and p53 expression in primary gastric lymphoma may be involved in the transition from low grade MALT lymphoma to high grade lymphoma.