Zombie Genes Protecting Elephants Against Cancer Have Been Discovered

Elephants' very low cancer rate is one of the most intriguing scientific paradoxes. Worldwide, % 17 of humans die of cancer, compared with fewer than % 5 of elephants. Elephants have 100 times more potential cancer cells than humans. However, many mechanisms protect them against cancer. Research in recent years discovered that elephants have copies of the tumor suppressor gene p53 numbering 20 times more, and therefore develop much less cancer. In August 2018, Cell Reportspublished a study discovering another factor protecting elephants from cancer . According to the study, a "dead / zombie" tumor suppressor gene becoming active during evolution protects elephants from cancer.

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• The Role of p53 in Elephants' Lower Cancer Rates

As is known, our genes are continually copied. During copying, errors accumulate in some genes and incorrect versions arise. These genes are called pseudogenes (false genes). In other words, we could call them "dead genes". While studying p53 in elephants, researchers discovered LIF6 (Leukemia Inhibitory Factor 6), a pseudogene. According to the researchers, this gene was previously "dead" and became active again during evolution. LIF6 is controlled by p53. When a cell sustains DNA damage, LIF6 becomes active and enables apoptosis (programmed cell death) to eliminate the cell. These genes are also called zombie genes . A previously inactive gene becomes active and works to prevent cancerous transformation. In elephants, this gene is thought to have come back to "life" 25-30 million years ago.

What Does This Study Mean for Us?

• Another reason underlying low cancer rates in large, long-lived animals such as elephants has been discovered.
• Large animals have many cells and generally live a long time. Over time, in their cells, mutations begin to accumulate, and these mutations can lead to cancerous transformation. During evolution, increases in tumor suppressor gene copy numbers and activation of some "dead" genes substantially reduce cancer risk.
• The importance of pseudogenes in human cancers remains under investigation. Recent studies show high activity of these genes in human cancers.