Role of Bcl-2, Bax, and Bak in spontaneous apoptosis and proliferation in neuroendocrine lung tumors: Immunohistochemical study.

Fifty-six primary neuroendocrine lung tumors were examined morphologically and histologically and their apoptosis level was determined. Malignant carcinomas were characterized by increased apoptotic index and enhanced expression of Bcl-2, Bak, p53, and Ki-67 compared to typical carcinoid. However, apoptosis in these tumors was not completed. Proteins of the Bcl family play an important role in the regulation of spontaneous apoptosis in neuroendocrine lung tumors. Bcl-2 accumulating in the nucleus is a morphological analogue of phosphorylated inactive form of this protein, which does not inhibit apoptosis. Expression of Bcl-2 and Bax decreases in small-cell lung carcinoma (SCLC) with metastases indicating attenuation of apoptosis and development of metastatic clones resistant to apoptosis induces. [ABSTRACT FROM AUTHOR]