1. Cancer Uncontrolled cell growth

2. Cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Occurs during the development of multicellular organism as the organism changes from a single simple cell to a complex system of cell types, in adults during tissue repair and during normal cell turnover. Differentiation is due to highly controlled modifications in gene expression and almost never involves a change in the DNA itself. Thus, different cells can have very different physical characteristics despite having the same DNA. Unlike normal cells that differentiate into muscle or nerves cells, cancer cells have an abnormal form and are nonspecialized. Normal cells enter the cell cycle only about 50 times; cancer cells can enter the cell cycle repeatedly. Cancer cells lack differentiation

3. Apoptosis is programmed cell death and involves a sequence of cellular events Apoptosis is caused by enzymes called caspases. Normal cells normally control caspases with internal or external signals. Apoptosis and cell division are balancing processes that maintain the normal level of somatic (body) cells. Cell death is a normal and necessary part of development: frogs, for example, must destroy tail tissue they used as tadpoles, and the human embryo must eliminate webbing found between fingers and toes. Death by apoptosis prevents a tumor from developing.

4. A neoplasm is an abnormal growth of cells. A benign neoplasm is not cancerous; a malignant neoplasm is cancerous. Cancer is a cellular growth disorder that results from the mutation of genes that regulate the cell cycle; i.e., cancer results from the loss of control and a disruption of the cell cycle. Carcinogenesis, the development of cancer is gradual — it may take decades before a cell has the characteristics of a cancer cell. The Cell Cycle and Cancer

6. Characteristics of Cancer Cells Cancer cells lack differentiation. Cancer cells have abnormal nuclei. Cancer cells form tumors. Cancer cells undergo metastasis and angiogenesis. The Cell Cycle and Cancer

7. The nuclei may be enlarged and may have an abnormal number of chromosomes. The chromosomes have mutated; some chromosomes may be duplicated or deleted. Gene amplification, extra copies of genes, is more frequent in cancerous cells. Whereas ordinary cells with DNA damage undergo apoptosis, cancer cells do not. Cancer cells have abnormal nuclei

8. Normal cells are anchored and stop dividing when in contact with other cells; i.e., they exhibit contact inhibition. Cancer cells invade and destroy normal tissue and their growth is not inhibited. Cancer cells pile on top of each other to form a tumor. Cancer cells form tumors

9. A benign tumor is encapsulated and does not invade adjacent tissue. Many types of cancer can undergo metastasis, in which new tumors form which are distant from the primary tumor. Angiogenesis, the formation of new blood vessels, is required to bring nutrients and oxygen to the tumor. A cancer patient’s prognosis depends on whether the tumor has invaded surrounding tissue, whether there is lymph node involvement, and whether there are metastatic tumors elsewhere in the body. There are many forms of cancer. For example some forms of skin cancer are basal cell carcinoma, squamous cell carcinoma, and melanoma. Basal cell carcinoma rarely ever causes death, while 77% of skin cancer deaths are caused by melanoma. Cancer cells undergo metastasis and angiogenesis

11. A DNA repair system corrects mutations during replication; mutations in genes encoding the various repair enzymes can cause cancer. If genes that specify proteins that stimulate the cell cycle or proteins that inhibit the cell cycle are changed (mutated) it can cause cancer. Normal DNA segments have ends that shorten with each replication, eventually signaling the cell to end division; cancer cells have enzymes that keep their DNA segments at a constant length and thus the cells to continue dividing. Origin of Cancer

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