How Cancer Cells Grow and Divide

Resource for Grades 6-12

WGBH: Nova
How Cancer Cells Grow and Divide

Media Type:
Video

Running Time: 1m 37s
Size: 2.2 MB

or


Source: NOVA: "Battle in the War on Cancer: Breast Cancer"


Resource Produced by:

WGBH Educational Foundation

Collection Developed by:

WGBH Educational Foundation

Collection Credits

Collection Funded by:

National Science Foundation

This video segment from NOVA: "Battle in the War on Cancer: Breast Cancer" describes the role of oncogenes in uncontrolled cancerous growth and depicts the journey of cancer cells from where they originate, into the circulatory system, and then on to other parts of the body.

Alternate Media Available:

How Cancer Cells Grow and Divide (Audio Description) (Video)

open Background Essay

Cancer is defined as any of a group of diseases in which particular cells in a body cease to respond to normal growth controls. The cells multiply unchecked, crowding out, invading, and destroying other tissues. One of the most important discoveries in cancer research in recent years are the genes that scientists think promote this unrestricted growth, called oncogenes. Experts believe that oncogenes alter receptor molecules located on the surface of cells that are responsible for signaling the cell to divide. These receptors somehow get stuck in the "on" position, sending signals to the cells to replicate at a rate that far exceeds cell loss.

Oncogenes and faulty receptors are certainly critical to the formation of cancerous tumors. Studies show, however, that the blood vessels that feed a growing tumor are just as important. Without a steady supply of oxygen and nutrients, cancerous tissues grow extremely slowly, are unable to spread throughout the body, or die out altogether.

The circulatory system must extend to all living tissues within the body. Therefore, wherever the body is undergoing development, growth, or repair, it must also grow a network of new blood vessels in a process called angiogenesis. Cancerous tissues are no different, although they promote angiogenesis somewhat indirectly. Tumor cells send chemical signals, called activator molecules, to the host's healthy cells. These chemical signals activate genes in the healthy tissue that, in turn, encourage the growth of new blood vessels into and around the cancerous tissue.

Medical researchers are now using this knowledge in their search for a cure for cancer. In one study, injections of a protein called endostatin, known to inhibit angiogenesis, greatly reduced the number of cancer cells and the size of tumors in a group of laboratory mice. Whether or not similar drugs can safely prevent the growth and spread of cancer cells in humans has been the focus of dozens of ongoing clinical trials since the late 1990s. While cancer researchers are cautious with their predictions, they say that results of these trials may lead to successful treatments of some forms of cancer.

open Discussion Questions

  • What other kinds of signals do you think cells would respond to that would make them grow and divide appropriately?
  • Why do you think the oncogene acts as though it is stuck in the "on" position?

  • open Transcript

    NARRATOR: How does a gene that causes cancer, known as an oncogene, work? Cells have genes that direct the formation of receptor molecules. Receptor molecules are like antennae sitting on the cell's surface. When they receive growth signals from the outside, they send a message to the cell nucleus that it's time to divide.

    The oncogene causes a slight difference in the receptor molecule. Like an accelerator pedal stuck permanently to the floor, the receptor keeps signaling the cell to divide, whether or not the receptor is getting that message. The more oncogenes there are, the more receptors present that are sending a stream of signals for the cell to reproduce.

    But how does cancer spread? How do cells escape into a person's blood stream and attach themselves in other parts of the body? First, the cells fasten to the membrane around the blood vessel. Then, they use a strong chemical to work their way through the tough membrane into the circulatory system, which carries them to new tissues and organs.

    Scientists understand the molecules that accompany each of these steps, and are trying to develop drugs to stop them. Other therapies are aimed at shutting down the receptor molecules to stop the cancer from growing.


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