by Sylvain Comeau

No one lives forever, and while the thought of their eventual demise does not thrill many people, much DNA and cancer research suggests that the limits on our life span is a defensive mechanism, according to Chantal Autexier, a Science College graduate who returned to Concordia for a recent lecture on “The Ends of DNA: Links to Cancer and Aging.”

The ends of DNA (or chromosomes), are called telomeres, and were first identified in the late 1980s. Telomeres prevent chromosones from coming into contact with one another and interfering with each other’s normal functioning. Most cancer cells have short telomeres, so that genetic mutations result from chromosomes coming into contact with each other.

“Telomere length acts as a kind of cell division clock,” said Autexier, who teaches medicine at McGill and heads a research team at the Jewish General Hospital. “Human cells have a finite life span; they can only keep doubling so long before they die.”

The clock starts to spin into infinity in the case of cancer cells. “Cells can start to double infinitely when there are genetic alterations. In fact, a cancer cell is in a sense an immortal cell. That is one of the definitions of cancer.”

Ironically, that is one of the reasons we can probably never aspire to immortality, or even anything close to it. “Researchers have theorized that the limits on human cell division are defensive. It is a tumour-suppressing mechanism. Otherwise, cancer would be inevitable,” Autexier pointed out in an interview following her lecture for the Science College on September 28.

More irony: Advances in cancer research have failed to outpace the increase in tumours that are an eventual result of aging.

“There will always be limits to how far we can stretch the human life span. Seventy years ago, people didn’t die of cancer as often as they do now because they died much earlier, before they could develop tumours. Now people live longer, because we have eradicated some deadly diseases, and because of better hygiene and medical treatment. But as people age, genetic mutations at the DNA level - and therefore cancer - becomes increasingly likely.”

This only makes Autexier’s work on telomeres more important. She conducts fundamental research, but she says that future gene therapy applications could, for example, focus on allowing the telomeres in cancer cells to disappear.

“Even though the telomeres in cancer cells are shorter, they are somehow maintained indefinitely. That’s probably the key point. If telomeres are eroded completely, the cancer cell will die. It will no longer be immortal.”