p53 and Bcl-2 expression in pneumoconiosis-related pre-cancerous lesions and lung cancers: Frequent and preferential p53 expression in pneumoconiotic bronchiolar dysplasias

Abstract

To explore the mechanism by which lung cancers excessively arise from pneumoconiosis, we determined the altered expression of p53 and Bcl-2 by immunohistochemistry (IHC) in lung cancers, dysplasias and non-cancerous pulmonary epithelia in pneumoconiotics in comparison with those from non-pneumoconiotic patients. We examined p53 expression in squamous cell carcinomas (SCCs) and dysplasias separately in the central and peripheral zones of bronchial trees, based on observations that SCCs from pneumoconiotic patients occurr more frequently in peripheral epithelia than those from non-pneumoconiotic patients (55 of 72 SCCs with pneumoconiosis vs. 33 of 72 SCCs without pneumoconiosis). Forty-one of 72 patients with pneumoconiosis-related lung cancers had altered p53 expression, which was comparable to the positivity of p53 expression in lung cancers without pneumoconiosis. p53 expression was observed significantly more frequently in bronchiolar dysplasias with pneumoconiosis than in those from non-pneumoconiotic patients (13 of 23 vs. 4 of 22), while p53 expression was found in bronchial dysplasias with pneumoconiosis as frequently as those without pneumoconiosis. Moreover, in patients with pneumoconiosis, bronchiolar dysplasias exhibited p53 expression more frequently than bronchial dysplasias (13 of 23 vs. 4 of 19). When comparison was restricted to bronchiolar dysplasias from patients without lung cancer, p53 expression had a strikingly higher frequency in the dysplasias with pneumoconiosis than in those from non-pneumoconiotic patients (8 of 15 vs. 0 of 14). Bcl-2 occasionally was expressed in squamous metaplasias and basal cell hyperplasias, in contrast to p53, for which immunostaining was negative in these lesions. Altogether, our results show that pre-cancerous and/or cancerous targets in pneumoconiosis may be distributed over a more peripheral zone than those in patients without pneumoconiosis.