Cellular Immortality

When you think about it, cancer is a paradox. On one hand, it is usually fatal, being responsible for around 13% of all deaths. Cancer will touch three out of four people at some time in their lives. On the other hand, cancer is actually a form of immortality. It is caused by cells that refuse to die. With complex, multi-cellular life forms, cell reproduction has limits; eventually cells stop dividing. Consider what happens when a photocopy is made of a photocopy, which was made from an earlier photocopy, and so on. With each “generation,” there is degradation; each copy is of poorer quality than the one before it. In essence, this is what normally happens with normal, living cells. Each time cells divide, protective pieces of DNA on the end of chromosomes become shorter. Eventually, they disappear altogether, leaving the chromosome exposed; at this point, the cell can no longer divide. At this stage, cells are “senescent”; unable to reproduce, they deteriorate and die. This process, called apoptosis, is what causes aging. In healthy humans, this senescent stage, known as the “Hayflick Limit,” occurs after 52 generations. Cancer cells never reach this limit.

Because of the presence of a chemically reactive protein called telomerase, the DNA is continually rebuilt, causing the cells to reproduce indefinitely. These cells are the body’s own material. This is why the immune system does not respond to cancer. Antibodies are activated in the presence of what is known as an exogenous pathogen, or “foreign” (from outside the body) invader, in short, viruses and bacteria. Donor organs received by transplant patients are also technically exogenous pathogens, which is why such patients must take anti-rejection drugs throughout their lives. Since cancer cells are not exogenous, the immune system does not attack them. Why then are cancer victims not immortal? The fact is that people do not die of cancer directly. Cancer victims die because the uncontrolled, unregulated growth of cells interferes with biologically necessary functions, breathing, digestion, circulation, etc. While some research is focused on somehow “fooling” the immune system into attacking cancer cells, such approaches are risky, because the immune system may wind up attacking healthy cells as well. The most promising therapies are those that attack the problem at the root, in other words, “sterilize” cancer cells in such a way that they are unable to divide and reproduce.