The Switch That Turns on Immortality

The most commonly used human cell line in biological research was derived from a poor, black tobacco farmer named Henrietta Lacks in 1951. Hers are the most studied human cells in history, and they have helped to save untold lives. The story about these cervical cancer cells and the bioethics of the case are told in The Immortal Life of Henrietta Lacks by Rebecca Skloot.

It’s astonishing that this cell line lives on 64 years after the person it came from died. What’s even more amazing, however, is that the cell line could live on for another 563 years, because cancer cell lines are effectively immortal. Ordinary human cells can divide a limited number of times before becoming so senescent that our bodies kill them off.

The key difference appears to be in the cells’ DNA. When a human cell divides, the “tips” of the DNA strands, called telomeres, get a little bit shorter. The older we get, the shorter they become. Once we enter old age, the average length of our telomeres becomes so short that their ability to regenerate and repair our bodies is much reduced. Cancer cells, however, can rebuild telomeres when they divide.

Researchers at the Salk Institute for Biological Studies published a paper that hones in on the biological “switches” that turn on an enzyme called telomerase, which rebuilds telomere tips on the ends of DNA.

In a different paper, researchers from the University of Pennsylvania described a process by which cancer cells hijack the normal function of the human telomerase gene in order to gain biological immortality.

The studies could have huge applications. First, if we can find out how to shut down the ability of a cancer cell to keep reproducing, we can stop it cold. Second, if we could slow down telomere shortening as we age, it could lead to new ways to treat diseases of aging such a heart disease and cancer.

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