Bcl-2 expression as a predictor of chemosensitivities and survival in small cell lung cancer

The bcl-2 gene belongs to a new category of oncogene that inhibits programmed cell death (apoptosis). No data are available on the frequency or clinical importance of its expression in patients with small cell lung cancer (SCLC), although its expression is reported in SCLC cell lines. We investigated the correlation between bcl-2 expression and prognosis, including response to chemotherapy, in SCLC patients and report our findings here.

Tumor specimens biopsied bronchoscopically in 38 SCLC patients were used for immunohistochemical study. Bcl-2 oncoprotein was detected by obtaining an immunostain using a specific monoclonal antibody, DAKO-bcl-2, 124. All patients received more than two courses of chemotherapy with 3- to 4-week intervals.

We detected bcl-2 expression in 21 of the 38 SCLC patients (55%). In 17 patients with bcl-2-negative tumors, the objective response to chemotherapy was 76% with 12% complete response and in 21 patients with bcl-2-positive tumors it was 62% with 8% complete response. The difference in response rate was not significant. In patients with bcl-2-positive tumors, survival time tended to be shorter than in those with bcl-2-negative tumors. There was no significant correlation between bcl-2 expression and clinical factors (gender, age, smoking, performance score, staging).

In 21 of the 38 SCLC patients bcl-2 oncoprotein was abnormally expressed and its expression may be associated with shorter survival times and poor response to chemotherapy.