On the road to human longevity, disease has become the biggest stumbling block, and cancer is undoubtedly one of the most human-headache diseases. Theoretically, if the cancer problem can be effectively solved, the average human life expectancy will be greatly improved. As a result, scientists have been looking for ways to treat cancer and extend lifespan in the longest-lived and most immune animals.
So, are there animals in the world that are immune to cancer? Can they benefit humanity?
Longevity and cancer
At one time, scientists once believed that the larger the animal, the more cells it had, the more likely it was to mutate during the division process, resulting in cancer. Later we found that in the animal kingdom, it is often the larger the animals that live longer. For example, the Greenland sleeping shark, the world's longest-lived vertebrate, can live to 500 years old; great white sharks and elephants also live to be more than 70 years old.
We know that the longer a person lives, the more cells divide, the greater the probability of cancer. The same is true for animals, but elephants and sharks have lived so long, why have they rarely heard of them dying of cancer? Are sharks and elephants immune to cancer?
Rumors that sharks and elephants are immune to cancer date back to the 1970s. Thanks to two professors at the Johns Hopkins School of Medicine in the United States, it was found that cartilage can organize "angiogenesis" and is an effective means of resisting malignant tumors. Later, researchers based on this, transplanted shark cartilage into the tumor tissue of other animals, and found that the tumor was effectively suppressed.
The researcher felt that the shark's whole body was cartilage and had high medical value, so he and another researcher made oral shark chondroitin and claimed to be able to treat cancer. In fact, their "business" is just a marketing scam, because many animal cartilage has such a function. Sharks are also immune to cancer, and in 2004, a Ph.D. from the University of Hawaii in The Dominican Republic published a List of Cancers in Lower Animals, documenting 42 tumors found in cartilaginous fish, including two sharks.
Later, the protagonist changes from a shark to an elephant. American scientists have found that there is a "TP53 gene" that inhibits cancer in elephants, and the number is as high as 20, compared with only one in humans and other animals. Still, 5% of elephants die of cancer, so elephants are not fully immune to cancer. Just when the scientists were disappointed, another creature that could "immunize against cancer" popped up.
The only creature immune to cancer?
This ugly little creature with crumpled skin and a bare body is called the naked mole rat. Don't look at them like a "clown", but in their small bodies there are many secrets hidden, the biggest feature of which is the ability to fight cancer.
Naked mole rats are found in East Africa and are the only species currently classified in the genus Naked Mole Rats. Although they are very similar to mice, they have more powerful abilities than mice, they can eat some poisonous food without poisoning, and their metabolism and growth rate are so slow that under natural conditions, no cancer cells are found in their bodies.
According to the study of Gorbunova, a professor at the University of Rochester in the United States, the secret of the naked mole rat's "cancer-free" lies in a sugar secreted in its cells - hyaluronic acid (necrotic acid). This high concentration of hyaluronic acid inhibits rapid cell division, thereby inhibiting the growth and spread of cancer cells. This is also the reason why cancer has not been found in naked mole rats.
However, naked mole rats, despite their high degree of cancer resistance, have observed two cases of cancer infection in captivity. The scientists were taken aback, and until then they had assumed that naked mole rats were completely immune to cancer. This discovery almost shows that no animal can be completely immune to cancer, and can only prevent and inhibit cancer cells through some special means.
Dr. Walid Khaled of the Department of Pharmacology at the University of Cambridge in the United Kingdom was not disappointed, "although this discovery surprised us and completely changed our understanding of the naked mole rat's fight against cancer." But if we can understand what makes these animals' immune systems special, and how that immune system protects them from cancer, we may be able to develop interventions to prevent cancer in humans. ”
Can naked mole rats help humans live longer?
In addition to having a strong anti-cancer ability, the second major feature of naked mole rats is longevity. The naked mole rat is the longest-lived of its kind. The average lifespan of rats is only two years, but the average lifespan of naked mole rats is as high as 30 years, and the longest can live to 37 years old, which is more than 10 times that of similar species.
Creatures like naked mole rats and rats, which have a huge difference in lifespan, may only be great white sharks and Greenland sleeping sharks. As the overlord of the ocean, the great white shark has a very long lifespan, reaching 70 years old. The Greenland sleep shark is even more striking, with an average lifespan of more than 400 years, while the longest-lived one is already 517 years old.
However, because the longevity of Greenland sleeping sharks is mainly related to the cold environment and "lazy" habits, coupled with the reasons why sharks prey on mammals, their research is of little significance.
Instead, the human body has about 90% of the same genes as naked mole rats, so scientists hope to explain the mystery of naked mole rats from a scientific point of view, so that humans can benefit from it. Professor Jonathan Flint said: "Physical aging is not eternal, how we humans extend life is not insurmountable, in real life many elderly people have reached 80 or 90 years old. ”
Is there a limit to human natural lifespan? At least from the currently accepted theory, the limit of human cell division is 50 times, and the cycle of a normal cell division is about 2.4 years, which means that the limit of human lifespan is 120 years. But because of illness and accidents, very few people can reach it.
But naked mole rats have inspired scientists, and they exhibit amazing anti-aging abilities. In general, the risk of death of organisms increases with age, and aging means closer to death, which is a natural common sense. But naked mole rats disagree, because their risk of death doesn't change much in their lifetime:
The mortality rate at birth is 0.01% in humans and 0.01% in naked mole rats;
0.5% in humans aged 5 and 0.01% in naked mole rats;
By the time humans reach old age, the risk of death has broken through the sky, naked mole rats are still 0.01%, and even declined...
Scientists at the Wellcome Trust Centre at the University of Oxford in the United Kingdom said: "Their metabolic rate is unusually slow, their physical functions hardly change, they never deteriorate, and their appearance and brain tissue do not age." One day, the genes of naked mole rats will enable humans to achieve a longer lifespan and ensure vigorous reproductive ability. If we understand the development of biological evolution and can change it to some extent, then theoretically humans can live to the age of 200. ”
Naked mole rats that don't age, can eat toxic food, can fight cancer, can adapt to anaerobic and hot environments, so how do they die?
Naked mole rats are more likely to die outdoors from predator attacks, lack of food and infections. But in the lab, naked mole rats mostly die of mouth ulcers, suffering from difficulty eating, drinking, and infection.
It is conceivable that if scientists can further study the "secrets" of mole longevity and immune cancer, they will serve humans. Then, it may not be impossible for human beings to reach the limit of 200 years.