Science Report – Lung Cancer
Lung cancer is the uncontrolled growth of abnormal cells that form in one or both lungs, usually in the cells of air passages. The abnormal cells do not develop into healthy lung tissue, but instead divide rapidly and form tumours, which undermine the lung’s ability to provide the bloodstream with oxygen. Cancerous tumours are called malignant tumours, which spread to other parts of the body through the bloodstream. This process of the cancer spreading beyond its site of origin to other parts of the body is called metastasis, which causes lung cancer to be much harder to treat successfully. Primary lung cancer originates in the lungs, while secondary lung cancer starts elsewhere in the body, metastasises and reaches the lungs. They are considered different and are treated differently.
Cancer is ultimately the result of cells that uncontrollably grow and do not die. Normal cells in the body follow an orderly path of growth, division, and death. Programmed cell death is called apoptosis, and when this process breaks down, cancer begins to form. The diagram illustrates the process of apoptosis, and highlights the process of regular cell deaths. However, unlike regular cells, cancer cells do not experience programmatic death and instead continue to grow and divide. This leads to a mass of abnormal cells that grows out of control. Lung cancer occurs when a lung cell's gene mutation makes the cell unable to correct DNA damage and unable to die. Mutations can occur for a variety of reasons. Most lung cancers are the result of inhaling carcinogenic substances.
Carcinogens are a type of substances that are directly responsible for damaging DNA, and causing lung cancer. Tobacco, asbestos, arsenic, radiation such as gamma and x-rays, the sun, air pollution and compounds in car exhaust fumes are all examples of carcinogens. When our bodies are exposed to carcinogens, highly reactive atoms called free radicals are formed that try to steal electrons from other molecules in the body. These free radicals damage cells and affect their ability to function and divide normally, eventually possibly forming tumours and lung cancer. Approximately 87% of lung cancers are directly related to smoking and inhaling the carcinogens in cigarettes and tobacco smoke. Even exposure to smoke from cigarettes by non smokers (second-hand smoke) can damage cells, thus forming cancer. The picture above compares healthy lungs to tar filled smoker’s lungs, with cancerous tumours already forming.