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Cancer - Lesson Summary

Scientists have found that cancer is characterised by the uncontrollable growth of the body’s cells. Normal cells display the property of contact inhibition, this property is completely absent in cancer cells. As a result, cancerous cells divide to form abnormal masses of cells called tumours. Tumours are either benign or malignant. Benign tumours cause little damage, malignant tumours  grow very rapidly and damage surrounding normal tissues. They compete with normal cells for vital nutrients, thereby starving them. Cells cast off such malignant tumours, travel to other parts of the body through the blood and start new tumours elsewhere. This property is known as metastasis.
The physical, chemical and biological agents responsible for transforming normal cells into cancerous  neoplastic cells are known as carcinogens. Different types of ionising radiations such as X-rays and non-ionising radiations such as UV rays and gamma rays damage DNA, causing neoplastic transformation. Chemical carcinogen nicotine present in tobacco causes lung cancer.  Biological carcinogens can be found in viruses, called tumor viruses and have genes called viral oncogenes. Even normal cells have certain genes like cellular oncogenes and proto-oncogenes, which when activated lead to the oncogenic transformation of cells.
Cancer is detected by using a variety of methods such as a biopsy, histopathology of blood as well as tissue and bone marrow tests. Apart from these methods, detection of cancer in internal organs is made possible by techniques such as radiography, that is, the use of X-rays, CT and MRI.
Certain cancers are detected due to antibodies produced by the immune system against cancer-specific antigens. Cancer-specific antigens are protein or other molecules that are unique to cancer cells. These molecules are usually found in the outer plasma membrane and they are thought to be potential targets for immunotherapy or other types of anti-cancer treatment. Molecular biology proves useful in identifying genes in individuals who are prone to inherit susceptibility to certain cancers.
Cancer is usually treated by a combination of surgery, radiation therapy and immunotherapy. In the radiation therapy, tumour cells are irradiated lethally while taking care not to damage normal surrounding cells. Sometimes cancerous cells are killed by chemotherapeutic drugs, which may be specific to particular tumours. In this manner, cancer can be diagnosed and treated with the help of several medical techniques if detected at the early stages. However, it is a killer disease and most often goes undetected by the human immune system.


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