Next time you’re asked what animal you could be and why… you should say you would want to be an elephant. Not only are they big, majestic, and powerful, but research is showing that the elephant genes are effective in the fight against cancer.
About 17% of humans worldwide die from cancer, but about 5% of elephants in human captivity die from the disease (1). This statistic had researchers from the University of Chicago and University of Utah thinking of why elephants, who have more potential cancer cells than humans due to their large size, die way less from cancer. The answer has been uncovered, and it’s in their blood–literally.
Cancer occurs when normal cells have undergone a mutation and multiply at an alarming, uncontrollable rate. Mutations can occur due to a dangerous amount of UV radiation, smoking tobacco, and/or having genes that increase the risk for cancer (2). The human body has its own defense mechanisms to prevent normal cells from turning into cancer cells. A normal cell regulates when it divides, when it stops dividing, and when to repair or kill itself in case it is damaged. There are two main types of genes that regulate this cell cycle: proto-oncogenes and tumor suppressor genes. Proto-oncogenes are like the gas pedal of the cell, in which they tell cells when to divide, while tumor suppressor genes are the brake, telling cells to stop cell division (3). One of the tumor suppressor genes, known as the TP53 gene, produces a protein known as p53. When cells are damaged and no longer divide properly, this protein signals the cell to repair its DNA or induce apoptosis, also known as cell suicide, when the cell cannot be repaired (4). This system of genes ensure that cancer cannot be formed.
However, when a mutation to the cell’s DNA occurs, proto-oncogenes and tumor suppressor genes do not function properly. Proto-oncogenes become oncogenes, which tell the cell to constantly divide and reproduce (3). The tumor suppressor genes are inactivated, and p53 can no longer regulate cell division or tell the cell to undergo apoptosis. Since none of the genes can function properly, the cell cycle has gone wack and the cell divides at a extremely fast rate with no stop, causing the formation of a tumor.
We only have one copy of the tumor suppressor gene that creates p53, whereas elephants have 20 copies of the gene (1). This incredible amount of p53 allows cells to be more sensitive to damage and therefore quicker to induce apoptosis. The researchers also found another gene with extra copies in elephants: the Leukemia Inhibitory Factor, or LIF. Elephants have about 7 to 11 copies of LIF, but only one of them–LIF6– actually works (5).
LIF6 has been called a zombie gene. 59 million years back, LIF6 was useless and really had no function. It is estimated that 25 to 30 million years ago, this gene became functional and allowed for elephants to grow to their modern size. The LIF6 gene now carries out whatever p53 signals the cell to do. For example, the researchers caused damage to African elephant cells in the lab and found that when the p53 told the cell to kill itself, the LIF6 gene was turned on and killed the damaged cell (5). LIF6 kills by producing a protein that pokes holes in the mitochondria, the power supply of the cell (1).
The researchers have noticed a trend in larger animals having higher risks for cancer since they have more cells and live longer, giving their cells more chances to become cancerous. Long-lived animals like elephants have developed defenses against cancer, but this trend is noticed even within humans: shorter people tend to have a smaller risk of developing certain cancers, whereas taller people have higher risks of developing certain cancer.
When August 12th rolls around next year, do not forget to celebrate World Elephant Day. These elephants pack way more than their two ivory tusks: 20 TP53 genes and a working LIF6 gene.
- “Zombie Gene Protects against Cancer — in Elephants.” ScienceDaily, ScienceDaily, 14 Aug. 2018, http://www.sciencedaily.com/releases/2018/08/180814173643.htm.
- “How Cancer Starts.” Cancer Research UK, Dangoor Education, 28 Nov. 2017, http://www.cancerresearchuk.org/about-cancer/what-is-cancer/how-cancer-starts.
- “Oncogenes and Tumor Suppressor Genes.” American Cancer Society, American Cancer Society, 25 June 2014, http://www.cancer.org/cancer/cancer-causes/genetics/genes-and-cancer/oncogenes-tumor-suppressor-genes.html.
- “TP53 Gene.” U.S. National Library of Medicine, National Institutes of Health, ghr.nlm.nih.gov/gene/TP53.
- Wei-Haas, Maya. “Cancer Rarely Strikes Elephants. New Clues Suggest Why.” National Geographic, National Geographic Society, 14 Aug. 2018, http://www.nationalgeographic.com/science/2018/08/news-cancer-elephants-genes-dna-new-research/.