The lungs have a highly complex branching structure made up of a number of specialized cell types, which work together to allow oxygen to enter and carbon dioxide to exit the blood. According to Cedars Sinai, lung cancer accounts for a third of cancer-related deaths in the United States. Lung cancer develops from cells within the lung that acquire genetic mutations, causing them to divide uncontrollably and form a tumor. A number of factors contribute to the development of lung cancer, which are both extrinsic and intrinsic in nature.
Smoking
Smoking is the leading cause of lung cancer. Cedars Sinai reports that 90 percent of lung cancer cases are linked to smoking, and the chance of developing lung cancer is 30 times greater in smokers than non-smokers. This is because the chemicals released from burning cigarettes are often mutagenic, which means they cause genetic mutations or disrupt normal processes in the cell that correct mutations. Second-hand smoke also severely increases the risk of lung cancer--it is thought to cause 5,000 to 10,000 new cases of lung cancer each year.
The risk of lung cancer increases the more smoke a person inhales. Alternatively, quitting smoking can significantly lower an individual's risk of developing lung cancer in the future.
Asbestos
Asbestos is a mineral made up of extremely small fibers. It was used for decades as insulation and fire-proofing material in buildings and cars. Since asbestos fibers are extremely small, airborne fibers can be inhaled and lead to lung problems, including lung cancer. Over time, asbestos fibers accumulate within the lungs, leading to inflammation of the tissue, causing lung disease.
The National Cancer Institute reports that asbestos can lead to benign tumors within the lungs, which are precursors to lung cancer. Asbestos also causes inflammatory disorders within the lung, which increase an individual's risk of developing lung cancer in the future.
Genetic Factors
Genetics also play a role in the development of lung cancer, since mutations to specific genes can promote uncontrolled proliferation, or inactivate natural safeguards that protect against cancer. One gene that is known to be mutated in several cases of lung cancer is EGFR, a protein found on the surface of the cell that promotes cell division. In normal cells, specific factors must be present to activate EGFR signalling, but in cancer EGFR may be constantly active, so the cell always receives a signal to divide.
The Harvard Cancer Center reports that characteristic genetic mutations in the EGFR gene contribute to lung cancer. Lung cancers with EGFR may be treated by a number of therapeutics, such as imatinib, which functions to prevent EGFR signalling to the cell, therefore halting tumor development.
