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Cancer affects numerous lives around the world today, including mine. I have lost my two sisters from leukemia and my mother from breast cancer. For this reason, I have become interested in learning more about cancer cells and how they develop. In concept 12.3 of our textbook it discusses how the cell cycle is regulated by a molecular control system and also how cancer cells do not respond normally to the body’s control mechanisms. Cancer cells divide excessively and they also invade other tissues in the organism, which can lead to death. I want to find out why these cancer cells do not follow the normal signals that regulate the cell cycle.
Cancer cells do not exhibit density-dependent inhibition or anchorage dependence, like normal cells do. Density-dependent inhibition is observed in animal cells, which causes them to stop dividing when they come into contact with one another. When a cell population reaches a certain density, the availability of nutrients becomes insufficient to allow cell growth and division to continue. Along with density-dependent inhibition, cells exhibit anchorage dependence, the requirement that to divide, a cell must be attached to the substratum. However, cancer cells do not stop dividing when growth factors are used up. A growth factor is a protein released by certain cells that stimulates other cells to divide.
A reasonable hypothesis to explain this manner is that cancer cells do not need growth factors to divide and grow. They may happen to make a growth factor on their own, or they may have an abnormality in the signaling pathway that communicates the growth factor’s signal to the cell cycle control system, even if that factor is not present. An additional possibility is that there is an abnormal cell cycle control system. These are all conditions that may lead to cancer.
Other important differences between cancer cells and normal cells include that if cancer cells decide to stop dividing, they will do so at any random point in the cycle, rather than at the normal checkpoints. Also, cancer cells are said to be “immortal” because if they are given a continual supply of nutrients, they will go on dividing for an indefinite period of time.
The abnormal behavior of cancer cells can be lethal when occurring in the body. The trouble begins when a single cell in a tissue goes through transformation, the process that changes a normal cell to a cancer cell. The immune system of the body usually recognizes the transformed cell as bad and destroys it, but if the cell does not get destroyed it may grow and form a tumor. If the abnormal cells remain at the original site, the lump is referred to as a benign tumor, which normally does not cause serious problems and can be removed by surgery. On the other hand, a tumor can be malignant when it becomes invasive enough to harm the functions of one or more organs. A person with a malignant tumor is said to have cancer. Cells in malignant tumors lose or destroy their attachments to other nearby cells and the extracellular matrix, and can spread into other close tissues. They may also spread their cancerous cells to other distant locations in the body, called metastasis.