Lung cancer is the leading cause of cancer-related deaths worldwide. Smoking accounts for approximately
70% of the cases of non– small cell lung cancer (NSCLC) and 90% of the cases of small-cell lung cancer
(SCLC), although some patients develop lung cancer without a history of smoking.
Nicotine is the most active addictive component of tobacco smoke. It does not initiate tumorigenesis in humans and
rodents, but it alters the pathophysiology of lung cells by inducing the secretion of growth factors, neurotransmitters
and cytokines, and promotes tumour growth and metastases by inducing cell cycle progression, migration, invasion,
angiogenesis and the evasion of apoptosis. Most of these effects are a result of nicotine binding and activation
of cell-surface neuronal nicotinic acetylcholine receptors (nAChRs) and downstream intracellular signalling
cascades, and many are blocked by nAChR subtype-selective antagonists.
Recent genome-wide association studies have revealed single nucleotide polymorphisms of nAChR subunits that influence nicotine dependence
and lung cancer.
This review describes the molecular basis of nAChR structural and functional diversity in normal and cancer lung cells, and the genetic
alterations facilitating smoking-induced lung cancers. It also summarises current knowledge concerning the intracellular pathways activated
by nicotine and other compounds present in tobacco smoke.