Bcl-2 Expression in Non-Small Cell Lung Cancers: Higher Frequency of Expression in Squamous Cell Carcinomas with Earlier pT Status

Abnormal expression of the bcl-2 gene product (Bcl-2) has been found in a wide variety of tumors, including lung cancer. In the present study, a total of 116 tumor specimens from surgically resected non-small cell lung cancer (NSCLC) patients, that were previously studied for p53 protein expression, were analyzed with immunohistochemistry for Bcl-2 expression. Forty (34%) of 116 tumor specimens showed Bcl-2 expression, which was found to occur more frequently in males than females (p = 0.049) and to be associated with smoking (p = 0.047). Bcl-2 expression was more frequently observed in squamous cell carcinomas (27 of 51, 53%) than in adenocarcinomas (12 of 55, 22%; p = 0.002), and in pT1 tumors (11 of 13, 85%) than in pT2 and pT3 tumors (16 of 38, 42%) in squamous cell carcinomas (p = 0.01). Bcl-2 expression did not correlate either with p53 protein status. We compared Bcl-2 expression in primary tumors and metastatic tumors of regional lymph nodes. Of 11 cases with Bcl-2-negative primary tumors, 10 were Bcl-2-negative in metastatic tumors except 1 case. In contrast, of 10 cases with Bcl-2-positive primary tumors, 6 lost Bcl-2 expression in metastatic tumors, while the remaining 4 cases still showed Bcl-2 expression in metastatic tumors. In the 89 potentially curatively treated patients, those with Bcl-2-positive and Bcl-2-negative tumors did not show a significant difference in survival (5-year survival rates, 56 and 42%, respectively, p = 0.2 by the generalized Wilcoxon test). These data indicate that Bcl-2 expression is frequently observed in squamous cell carcinomas with early pT status, and that it does not predict prognosis of patients with NSCLC.