JUNE 2003 IN

How Do Genetic Diseases Move?

As scientists learn the details of genes, it is providing a better understanding of genetic diseases, especially cancer, retro viruses, and DNA viruses. One thing we are finding is that there seem to be links and similarities between these diseases and ordinary viruses.

Following up on these recent discoveries, pharmaceutical researchers are testing new kinds of vaccines that might cure some kinds of cancer in the same way that existing vaccines prevent viral infections. One vaccine, for example, is said to be at least somewhat effective in 95 percent of cases of one particular kind of cancer. The vaccine works like chemo or radiation treatments to weaken tumors. It is hoped that the vaccine might cure some early-stage cancer cases and improve the effectiveness of existing treatments for cancer patients. Similar vaccines might someday prevent some cancer, especially the forms of breast cancer that are linked to inherited genetic defects.

The purpose of a vaccine is to get the body’s immune system to recognize specific protein shapes as foreign objects. Then, the immune system can attack and destroy those proteins, including any disease that contains the proteins. This is the body’s usual way of fighting off both infections and cancer, and vaccines make it possible for the body to have a more rapid and effective immune response.

The new discoveries, though, raise new questions. For example, even when vaccines are effective in creating an immune system recognition of something like cancer cells, it doesn’t necessarily lead the immune system to attack and destroy the problem cells. Another link is involved, and researchers have not yet discovered what that link is.

I believe another question that must be considered is the mechanism by which genetic material spreads around the body. Skin cancer, for example, is little more than a nuisance as long as it stays in one spot. It poses little danger then and can simply be scraped or shaved off. It becames acutely dangerous only when it starts to spread — only when, somehow, the same cancerous DNA starts to show up in other places. Similarly, breast cancer only kills people after the cancer has started to show up at other places in the body. But how is it possible for cancer DNA to move from one place to another?

Possibly, the same mechanism that spreads cancer might also be involved in DNA viruses and retro viruses. Herpes, the most common family of DNA viruses, is dormant most of the time and is completely undetectable during that time. As far as we can tell, it has no effect on the body and cannot be transmitted while it’s dormant. But then, from time to time, something changes to allow the herpes virus to travel the short distance to the skin and sometimes other areas where it causes its symptoms. It is a similar thing with the retro virus HIV. In most people who have HIV, the virus is hidden away somewhere in the body — scientists don’t know where — and is not present in the bloodstream. That’s why HIV tests have to look for HIV antibodies and not for the virus itself. AIDS develops from HIV only after something allows the virus to spread.

Scientists don’t know what the mechanism is that allows these genetic diseases to spread around the body, but epidemiological data gives reason to suspect that it might be the same mechanism in each case. The connections between cancer, herpes, and AIDS are well documented, and in patients who have more than one of these diseases, the more active episodes of the diseases can tend to happen at the same time. One possible explanation is that cancer, or some component of it, is a necessary condition for AIDS and for an active herpes infection. Perhaps it is not that AIDS causes tumors but that those tumors cause AIDS. And perhaps a tumor or something similar is the real cause of a herpes episode, with the symptoms going away after the immune system has destroyed the tumor.

If it turns out that these diseases have some of the same patterns of genetic movement, the current research into the genetic nature of cancer might also be bringing us closer to cures for herpes and AIDS.

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