OncoLog: M. D. Anderson's report to physicians about advances in cancer care and research.
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From OncoLog, September 2004, Vol. 49, No. 9

House Call: How Cancer Happens and Ways to Lower Your Risk

A handful of genes may hold the secret to cancer’s mysteries. Genes reside within every cell in the human body and are made up of DNA, tiny pieces of code that control every aspect of a cell’s life: how much it can grow, what its primary functions are, how often it can divide to form new cells, and when it should die. Healthy cells turn into cancerous ones when their genes are damaged. This process, called carcinogenesis, occurs in three stages.

Stage 1: INITIATION

Although genes flawlessly control cellular functions in billions of cells throughout the human body, mistakes sometimes occur when DNA is copied from one cell to another, introducing a genetic error into all the cell’s offspring. These mistakes, or mutations, can happen spontaneously or be inherited, but often they result from cellular contact with cancer-causing agents, or carcinogens, such as tobacco, radiation, or viruses. Carcinogens can cause DNA strands to break easily or cause genes to become deleted, lined up in an incorrect order, or copied more times than necessary.

Normally, when DNA becomes damaged, there are genes in charge of repairing it so that the mistake cannot be passed on to new cells. If the DNA cannot be repaired, the cell commits suicide. However, if the genes that watch for and repair DNA damage are themselves damaged or destroyed, the normal defense mechanism is lost.

Stage 2: PROMOTION

One simple mutation by itself does not cause cancer; typically, cancer occurs when one mutation leads to other mutations that work together to defeat the growth regulation of a healthy cell. As new mutations occur, genes that control cell growth may start promoting cell growth when normally they would restrict it. As a result, the abnormal cells begin multiplying, often uncontrollably. In addition, as the genes that control cell death become altered, abnormal cells are able to stay alive when they should have committed suicide because their genetic material was damaged. These damaged cells are thus able to thrive and multiply, passing on their mistakes to future generations of cells.

Cells that acquire additional genetic changes that allow them to grow uncontrollably and avoid death have an advantage over normal cells.

Stage 3: PROGRESSION

Not all cancers form a tumor, but most do, and tumors take on a life of their own. Each tumor needs oxygen and nutrients from blood to survive, so tumors develop their own network of blood vessels that connect them to the rest of the body. This makes it possible for cancer to spread to other parts of the body; cancer cells that break loose from the original tumor can float through the bloodstream to other parts of the body where they attach themselves to healthy tissues. From there, they invade normal tissues, develop new blood vessels, and often overgrow normal tissues. These new cancer cells often have even more mutations than the cells in the original tumor, and as a result, the spreading cancer is usually harder to kill and, therefore, more deadly than the original tumor. Further, these new tumors may acquire more changes that allow them to resist normally effective treatments.

Lowering Your Cancer Risk

Although scientists have learned a great deal about the role of genes in cancer development, they still have more to learn about the process and how to reverse it. In the meantime, you can cut down on your risk of cancer by following these health-smart tips:

  • Avoid tobacco products, including second-hand smoke, which contain many harmful chemicals that have been linked to lung, head and neck, and bladder cancers, among many others.
  • Avoid excessive unprotected exposure to ultraviolet rays from the sun, which are the leading cause of skin cancer.
  • Eat fried or grilled meats in moderation because these high-heat cooking processes can release harmful carcinogens in meats.
  • Consume lots of fruits and vegetables, which supply important vitamins and minerals for healthy cell development.
  • Exercise regularly to promote healthy body functions and control weight (obesity plays a role in many cancers).
  • Get regular medical checkups and screening tests for common cancers such as colon, prostate, breast, cervical, and skin cancers.

For more information on this topic or for questions about M. D. Anderson’s treatments, programs, or services, call askMDAnderson at (877) MDA-6789.

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