Objective: To investigate the effects of apoptosis and its regulating genes in different stages of malignant transformation of large intestine epithelium in colorectal adenoma and adenocarcinoma.
Methods: The density and distribution of the apoptotic cells and the positive expression of p53 and bcl-2 oncoprotein were observed in situ in 32 villous adenomas and 33 papillary adenocarcinomas of the large intestine, using DNA nick end labelling technique and immunohistochemical staining for p53 and bcl-2 oncoprotein. 15 nontumor mucosa were used as controls.
Results: The density of apoptotic cells in adenoma and adenocarcinoma was significantly higher than that in nontumor mucosa (P < 0.01), and their density in adenoma was higher than in adenocarcinoma (P < 0.01). The positive rate and staining intensity of p53 and bcl-2 oncoprotein in adenoma and adenocarcinoma were significantly higher than in non tumor mucosa (P < 0.01), their staining intensity in adenocarcinoma was higher than that in adenoma (P < 0.01). In adenoma, the density of apoptotic cells in the bcl-2 oncoprotein positive group was higher than that in the bcl-2 oncoprotein negative group (P < 0.01).
Conclusion: The abnormal regulation of apoptosis may play an important role in the pathogenesis of large intestine carcinoma. The bcl-2 oncoprotein can inhibit apoptosis in adenoma and adenocarcinoma. However, mutational p53 oncoprotein may likely block apoptosis in adenocarcinoma.