BCL-2 ONCOPROTEIN EXPRESSION IS INCREASED ESPECIALLY IN THE PORTION OF SMALL-CELL CARCINOMA WITHIN THE COMBINED TYPE OF SMALL-CELL LUNG-CANCER

Immunohistochemical analysis of Bcl-2 oncoprotein, one of the oncogene s associated with the regulation of programmed cell death, was perform ed on 12 surgically resected tumors of the combined type of small-cell lung cancer. Ten cases (83%) expressed Bcl-2 oncoprotein within the t umor tissues. Two of them showed its expression in both the small cell carcinoma and non-small cell carcinoma types, and 7 cases exhibited B cl-2 expression only in the portion of the small cell carcinoma. Consi dering previous reports indicating a high prevalence of Bcl-2 oncoprot ein expression in small cell lung cancer, it is suggested that Bcl-2 o ncoprotein even in the combined type of lung cancer may play an import ant role in tumorigenesis and tumor development and ensuing histologic al alterations between small cell carcinoma and non-small cell carcino ma types.