New molecular strategies for early lung cancer detection

Identification and validation of differences in protein levels in normal, premalignant, and malignant lung cells and tissues using high-throughput Western Array and immunohistochemistry

The identification of proteins, which exhibit different levels in normal, premalignant, and malignant lung cells, could improve early diagnosis and intervention. We compared the levels of proteins in normal human bronchial epithelial (NHBE) and tumorigenic HBE cells (1170-I) by high-throughput immunoblotting (PowerBlot Western Array) using 800 monoclonal antibodies. This analysis revealed that 87 proteins increased by >2-fold, and 45 proteins decreased by >2-fold, in 1170-I compared with NHBE cells. These proteins are involved in DNA synthesis and repair, cell cycle regulation, RNA transcription and degradation, translation, differentiation, angiogenesis, apoptosis, cell adhesion, cytoskeleton and cell motility, and the phosphatidylinositol 3-kinase signaling pathway. Conventional Western blotting using lysates of normal, immortalized, transformed, and tumorigenic HBEs and non-small cell lung cancer cell lines confirmed some of these changes. The expression of several of these proteins has been then analyzed by immunohistochemistry in tissue microarrays containing 323 samples, including normal bronchial epithelium, hyperplasia, squamous metaplasia, dysplasias, squamous cell carcinomas, atypical adenomatous hyperplasia, and adenocarcinomas from 144 patients. The results of the immunohistochemical studies correlated with the Western blotting findings and showed gradual increases (caspase-8, signal transducers and activators of transcription 5, and p70s6K) or decrease (E-cadherin) in levels with tumor progression. These results indicate that the changes in proteins detected in this study may occur early in lung carcinogenesis and persist in lung cancer. In addition, some of the proteins detected by this approach may be novel biomarkers for early detection of lung cancer and novel targets for chemoprevention or therapy.

Molecular approaches to lung cancer evaluation

The stagnation of therapeutic results in lung cancer over the last decade(s) is a matter of great concern, also due to the constantly increasing incidence of the disease. Among the reasons for this failing therapeutic progress is the lack of understanding of the molecular mechanisms underlying the disease. Presently molecular biology techniques contribute to the deciphering of these mechanisms. This review article gives an overview of the actual situation. The genetic changes leading to malignancy are successively considered at the DNA, RNA and protein levels. Alterations at the DNA level represent the bulk of the available data, being related to p53 mutations, alterations in the beta-tubulin gene, microsatellite alterations, methods for identifying individual and isolated aberrant cells, identification of epigenetic mechanisms such as methylation of the promoter region of tumor suppressor genes; alterations in pre-neoplastic lesions are also evoked. In all cases, the techniques are described and results presented. RNA based methods are critically considered, and the yeast functional assay described. Protein based methods are also considered. The use of cDNA microarrays opens new perspectives and brings the simultaneous identification of numerous DNA alterations at a grip, with hopefully significant improvements in treatment results and increased efficiency for early detection and prevention.

Molecular genetic abnormalities in premalignant lung lesions: biological and clinical implications

Lung cancer is a leading cause of cancer death worldwide; however, despite major advances in cancer treatment during the past two decades, the prognostic outcome of lung cancer patients has improved only minimally. This is largely due to the inadequacy of the traditional screening approach, which detects only well-established overt cancers and fails to identify precursor lesions in premalignant conditions of the bronchial tree. In recent years this situation has fundamentally changed with the identification of molecular abnormalities characteristic of premalignant changes; these concern tumour suppressor genes, loss of heterozygosity at crucial sites and activation of oncogenes. After considering the morphological modifications that occur in premalignant lesions of the bronchial tree, we analyse the alterations occurring in a series of relevant genes: p53 and its functional regulation by MDM2 and p14ARF, p16INK4, p15INK4b, FHIT, as well as LOH at important sites such as 3p, 8p, 9p and 5q. Activation of oncogenes is considered for K-ras, the cyclin D1, the heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2/B1), and finally the c-myc oncogene. The expression of c-myc is influenced strongly by the presence of growth factors (GFs), among which EGF is of prime importance, as well as its receptor coded for by the c-erbB-2 oncogene. Basic knowledge at the molecular level has extremely important clinical implications with regard to early diagnosis, risk assessment and prevention, and therapeutic targets. The novel techniques for early diagnosis and screening of premalignant lung lesions, such as fluorescence bronchoscopy, endobronchial ultrasound, spiral computed tomography combined with precise spatial localization techniques, should basically change the approach to the problems raised by this disease and allow for an increased discovery rate of incipient lesions. Sequential applications will lead to the identification of individuals/populations at high risk, while the availability of accurate 'intermediate end points' will enable the effects of preventive trials to be monitored. Finally, the same molecular abnormalities may serve as 'starting points' for innovative treatments designed to restore the altered functions to normality. Recent developments in our knowledge and understanding of the molecular genetic abnormalities in premalignant lung lesions open an era of hope.