A research team provided the first empirical data documenting cancer across species. It showed that cancer mortality does not increase with body size or life span because of their sizes or how long they get to live. Actually, they observed that some larger, longer living animals may develop less cancer. They calculated elephant cancer mortality rates at less than 5%, compared to human cancer mortality rates of 11% to 25% which was really astonishing. This beyond belief finding has become known as Peto’s Paradox. Elephants are the largest land animals on Earth. They have characteristic long noses, or trunks; large, floppy ears and wide thick legs. African elephants grow 8.2 to 13 feet (2.5 to 4 meters) from shoulder to toe and weigh 5,000 to 14,000 lbs. (2,268 to 6,350 kilograms), according to the National Geographic.
Cancer on the other hand is a class of diseases characterised by out-of-control cell growth. There are over 100 different types of cancer, and each is classified by the type of cell that is initially affected. It’s not just one disease. Cancer can start in the breast, the blood, the colon, or even in the lungs. Cancers are alike in some ways, but they are different in the ways they grow and spread. Every time a cell divides, there is a chance for a mutation to occur in the DNA. A healthy cell does not turn into a cancer cell overnight. Its behaviour gradually changes, a result of damage to between three and seven of the hundreds of genes that control cell growth, division and life span. Over time, more changes may take place. The cell and its descendants may eventually become immortal, escape destruction by the body’s defences, develop their own blood supply and invade the rest of body hence becoming cancerous.
Research with Elephants
The team looked at the genome of the African elephant for changes in oncogenes and tumour suppressor genes. Oncogenes can cause cells to grow out of control while tumour suppressor genes slow down cell division. The analysis revealed the shocking discovery that elephants express many extra genes derived from the critical tumour suppressor gene TP53. Because p53 is essential for regulating cell division and preventing tumour formation, it has been nicknamed the “guardian of the genome.”The TP53 gene provides instructions for making a protein called tumour protein. This protein acts as a tumour suppressor, which means that it regulates cell division by keeping cells from growing and dividing too fast or in an uncontrolled way. This prevents the propagation of cells with mutations that could lead to cancer.
They learned that elephants were naturally cancer resistant and had 20 times as much TP53 as humans. They measure how elephant cells responded to DNA damage. The blood, were exposed to ionising radiation to induce DNA breakage. Broken DNA was repaired in the elephant lymphocytes quickly compared to human lymphocytes. The elephant cells after being exposed to radiation more elephant cells than human cells underwent programmemed cell death or apoptosis. We showed that elephant TP53 helps elephants to quickly remove pre-cancerous cells with DNA damage. Now, focus is on research to better understand the specific mechanism of how elephant TP53 works. The ultimate goal is to help patients who already have, or could be at risk of getting cancer in the future to have better chances of fighting this disease.
Source: Medical Xpress