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Cancer

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Cancer

Today there are one in three people worldwide who are affected by cancer, and almost 60% of these people will almost certainly die. 7000 New Zealanders die every year from this disease. It is the second largest killer next to heart disease. Cancer does not just affect certain groups of people, it can affect anybody and it is not just one disease, it refers to more than a hundred diseases. Cancer is caused by carcinogens. At present, hundreds of chemicals are known to induce cancer. Normally, the body’s cells divide in an orderly way, allowing the body to grow and to heal after injury. Damage or mutations that occur to the proto-oncogenes (POG) and tumour suppresser Genes (TSG) in the genetic material (DNA and RNA) by these carcinogens bring about Cancer, which causes cells to have less control of cell division and differentiation. POGs lead to changed cells or transformed cells and cause excessive cell division. Further mutations cause the cells to become immortal. These cells continue to divide and form a ball of cells. These cells require a lot of energy and fluids flowing to maintain the high rate of the cell division. When these balls become too large for fluids to flow through, the middle of the ball dies. TSG’s act as anti-proto-oncogenes, they regulate the rate of cell division. POG’s and TSG’s constantly compete to overpower each other. These TSG’s can be mutated and this brings about a change in the control mechanism of cell division. Cells are stimulated to divide through a growth factor. Growth factor molecules bind to cell membranes of cells and send a chemical message to a receptor in the cell membrane. The receptor sends a message through the cytoplasm to the nucleus to stimulate cell division. Sometimes when these growth factors are absent the receptor in the cell membrane is mutated to send out the message to the nucleus. Cells are also stimulated to divide through the two proteins, cyclins and cyclin-dependent kinases. When these two join together, this stimulates cell division. These proteins act on the growth inhibitor proteins P53 and PRP, which are growth inhibitor proteins. Tumours may be malignant, spreading or benign, non-spreading. Malignant tumours are aggressive, invasive, and mobile. They invade healthy tissue and continue to divide. The original cancer is called the primary tumour. If the tumour is malignant, the disease may develop in other parts of the body where secondary tumours may form.
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