Molecular genetics and mechanisms of apoptosis in carcinomas of the lung and pleura: Therapeutic targets

Cancers of the lung and pleura remain a major cause of cancer deaths, both in men and women, with strong causal relationships between cigarette smoking and asbestos fibres, and deaths from lung cancer and mesothelioma, respectively. The poor survival rates for small cell lung cancer and mesotheliomas argue powerfully for greater understanding of mechanisms of carcinogenesis, genetic abnormalities and the role of tumour suppressor genes and proteins in carcinomas of the lung and pleura. Despite progress in the development of newer cytotoxic drugs, lung cancer remains a lethal disease. Chemotherapy and radiotherapy produce only a modest improvement in survival of patients with advanced disease. Increased knowledge of molecular mechanisms of lung cancer and apoptosis are providing opportunities for treating lung cancer with new classes of molecularly targeted drugs. These novel therapies should target the abnormalities in lung cancer by maximizing the effects of anti-tumour molecules, with minimal side effects on normal tissues. Of the several molecular targets, those receiving attention are p53 gene replacement, Bcl-2 downregulation, apoptosis by induced by TNF, the FAS/CD95 receptor system and TRAIL, and inhibition of NF-κB. Although several studies have shown benefits, there is a need for well planned clinical trials of drugs that target the apoptotic cascade. Stem cell therapy and gene replacement offer the prospect of novel approaches that are likely in the near future to play a definitive role in the treatment of advanced lung cancer. Furthermore, with their apparent minimal toxicity to normal tissues, the newer molecular targets represent attractive investigational directions for innovative cancer therapies.