[Mechanisms of lung oncogenesis].

Precancerous lesions of the bronchial epithelium are dysplasias and in situ carcinomas. Squamous metaplasia has not yet been considered as a true malignant state. Epithelial cells, which are able to proliferate (non terminally differentiated) in bronchial tree and alveoli, are the candidates for malignant proliferation (basal cells, mucus cells, Clara cells and type II pneumonocytes). Their initial growth is probably promoted by deregulated autocrine growth factors (EGF, GRP, IGF1), or their receptors (EGF-R). Under continuous carcinogens exposition these proliferating cells accumulate multiple genetic abnormalities affecting dominant oncogenes such as myc and ras, and recessive tumor suppressor genes such as Rb and p53. Neither the order of intervention of these genetic factors nor their correlation with premalignant states have been demonstrated.