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Cancer

A Disease of Mitosis

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Cancer: a Disease of Mitosis

• Cancer is a disease of mitosis – resulting in uncontrollable mitotic division.

• Cells do not live forever, and they will reach a point where they will either divide through mitosis or die through a process called apoptosis.

• Cancer cells are the exception, these cells do not die and divide uncontrollably as they crowd out healthy, productive cells.

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Cancerous Transformation of Cells

• Cancer can have many causes, but most are thought to be related to carcinogens in the environment. – Carcinogens are chemicals that can damage DNA

and interfere with a cell's normal cycle - disrupting the cells ability to control when and how often it divides.

• Cancerous transformation results from DNA mutations to the genes that control the cell cycle.

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Cancerous Transformation of Cells

• Two types of genes normally control the cell cycle: proto-oncogenes ), which start cell division and tumor-suppressor genes which turn off cell division.

• These two gene-types work together, one turning on cell division when the body needs to repair or replace tissue, and the other turning off cell division when the repairs have been made.

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Cancerous Transformation of Cells

• If the proto-oncogenes become mutated (changes to DNA), they can become oncogenes, genes that lead to uncontrolled mitosis.

• Mutations in the tumor-suppressor genes result in the cell not having the ability to turn off mitosis.

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Normal Vs. Cancer Cell Structure

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Tumor Formation

• Dividing cancer cells accumulate forming a mass that is called a malignant tumor. – As the tumor grows larger, cancer cells release

growth proteins that promote the development of new blood vessels.

– The growth of blood vessels at the tumor site provides the cancer cells with nutrients and oxygen and takes nutrients away from normal cells.

– The normal cells are “starved” and their functions are not carried out.

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Metastasis

– The blood vessels at the tumor site provide a manner by which cancer cells can “escape” from the tumor site and travel to other parts of the body.

– We say that the cancer has metastasized when cancer cells spread from the original tumor site to other parts of the body.

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Example: Leukemia

• In the case of leukemia, white blood cells grow uncontrollably and crowd out red blood cells.– An individual's ability to deliver nutrients to the

body is significantly reduced. – The blood’s ability to clot is severely

compromised.

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Leukemia Symptoms

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Questions

1. How does a cancer cell differ from a normal cell?

2. What is a cancerous tumor?3. How do cancer cells promote the development

of blood vessels at the tumor site? 4. How are normal cells affected by the presence

of cancer cells?5. What is metastasis? How does it take place?