Lack Contact Inhibition

Lack Contact Inhibition - metabolic reactions to occur....

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Lack Contact Inhibition Normal cells stop dividing when they become crowded because mitosis is inhibited when cells contact nearby cells. Cancer cells continue to divide and produce a mass of cells called a tumor . In a laboratory culture dish, normal cells grow in a single layer on the bottom but cancer cells continue to grow and produce a thick mass of cells. Lack Anchorage Dependence Normal cells cling to neighboring cells, cancer cells do not. Metastasis occurs when cells break away and travel through the body via the circulatory and lymphatic systems. These cells form secondary tumors at other sites in the body. Malignancy refers to the ability of a tumor to metastasize, that is, to produce a new tumor at a different location. A malignant tumor is dangerous because it can metastasize (spread). A benign tumor does not spread. Have a Reduced Need for Growth Factors Growth factors are chemicals that stimulate cell division in normal cells by causing certain
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Unformatted text preview: metabolic reactions to occur. Normally, cyclin combines with kinase only in the presence of growth factors. In cancer cells, cyclin may combine with kinase in the absence of growth factors. Some genetic mutations (called oncogenes , discussed below) allow these reactions to occur with reduced amounts of growth factors. The reduced need for growth factors may be responsible for the lack of contact inhibition and anchorage dependence discussed above. Ability to Penetrate the Lamina The lamina is a noncellular barrier that is attached to cells that line the surfaces, internal cavities, and organs (epithelial tissue). Normally, cells cannot penetrate this barrier and therefore cannot invade neighboring tissues and organs. Cancer cells have the ability to penetrate the lamina. The cells are able to invade and destroy neighboring tissue. A benign tumor does not invade neighboring tissue....
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