Expression of Bax and Bcl2 proteins in small cell lung cancer (SCLC)

Abstract

18189 Background: Bax and Bcl2 proteins are members of Bcl-2 family which plays a critical role in the regulation of apoptosis. There are few data on the occurrence and clinical relevance of these proteins in SCLC. Methods: We have analyzed expression of Bax and Bcl2 in 86 SCLC patients. All patients had limited disease and were treated with surgery followed by chemotherapy between 1982 and 2001 (median follow up 2 years). In all cases the diagnosis of SCLC was established only after the examination of surgical specimen. This series included 59 males and 22 females, 11 T1, 46 T2, 13 T3 and 11 T4 tumors, 41 N0, 15 N1, 24 N2 and 1 N3. Expression of both proteins was evaluated by immunohistochemistry and scored, taking into account proportion of cells with positive staining and staining intensity. H-score was calculated as a proportion of positive cells times staining intensity. Continues data on H-score were used to assess relationships with clinical data. Results: Median H-scores for Bax and Bcl2 were 70 (range 0–300) and 90 (range 0–300) respectively. The positive immunostaining rates (cut-off point of 10%) for Bax and Bcl-2 in the entire group were 81% and 79% respectively. Bax and Bcl-2 expression did not correlate with any clinicopathological parameters such as age, tumor size, lymph node involvement and stage of the disease. Survival was not influenced by expression of Bax (p=0.6) or Bcl2 (p=0.86). There was a significant positive correlation between Bax and Bcl2 expression rates (p=0.018, regression coefficient 0.23). Conclusions: Bax an Bcl2 proteins are commonly overexpressed in SCLC, with tendency for co-expression. Clinical relevance of these markers is questionable in this patient cohort. No significant financial relationships to disclose.