Apoptotic markers p53, Bcl-2 and Bax in primary lung cancer

Apoptosis is the fundamental process necessary for eliminating damaged or unwanted cells. Alterations in the apoptotic pathway appear to be key events in cancer development and progression. The aim of the study was to determine the p53, Bcl-2 and Bax expressions in lung cancer, taking into account histological heterogeneity and the adjacent bronchial resection margin.

Tissue specimens from 60 histopathologically verified lung cancer specimens and 12 bronchial stumps were evaluated. The presence of the studied markers was revealed by immunocytochemistry on paraffin-embedded tissue.

The percentage of p53- and Bax-positive lung cancers was comparable (51.6% for both proteins), while Bcl-2 immunoreactivity was observed in fewer (31.6%) cases. There was no p53 accumulation in bronchial stumps, while Bcl-2 and Bax staining formed a repeatable specific pattern in bronchial epithelium. The differences in apoptotic marker expression between non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) were revealed, especially regarding p53 and Bax expression (60% vs. 10%, p = 0.005 and 58% vs. 20%, p = 0.04, respectively). Taking into account the histological structure of NSCLC, Bax expression appeared to be more frequent in adenocarcinoma than in squamous cell lung cancers (88% vs. 42%, p = 0.004). No interrelationship between the studied proteins in lung cancer tissue was revealed.

The expression of p53, Bcl-2 and Bax was altered in lung cancer tissue compared to histologically normal bronchial epithelium. The difference between apoptotic marker expression in NSCLC and SCLC could reflect the different pathogenesis of these two lung pathologies.