Nature weighs heavily: why do cancer cells grow like bacteria? It could be caused by this DNA

Today, nature, a leading academic journal, published an important discovery about cancer online A joint team at Stanford University and the University of California, San Diego, points out that a strange kind of DNA may be the key to cancer's treatment I believe our readers and friends all know the name of DNA As the carrier of genetic information, DNA encodes the blueprint of life In a typical human cell, there are 23 pairs of chromosomes composed of DNA and protein Although their average size is only 6 microns, they can only be seen under the microscope But if we straighten the DNA in a cell and connect the head and tail, the total length can be close to 2 meters! And if all the cells in the human body are spliced together, the total length is twice the diameter of the solar system! The subtlety of life is that although there is such a vast amount of genetic information in DNA, the expression of each gene is precisely regulated In humans and other eukaryotes, DNA is usually tightly bound to a structure called a histone octamer Until genetic information about a piece of DNA needs to be used, the tightly wound DNA will not release To some extent, it is similar to our ancient bamboo slips Usually it is folded up and only unfolded when it is read Source: vlasta2, bluefootbaby on flickr.com [CC by 2.0 (https://creativecommons.org/licenses/by/2.0)] But scientists have found that DNA in cancer cells looks a little different In 2014, a paper published in the journal Science found that there was a special DNA called "extrachromosomal DNA" (ecdna) in cancer cells As the name suggests, it's not compressed into chromosomes like traditional DNA Moreover, this kind of DNA can make cancer cells mutate rapidly, which is related to the drug resistance of cancer treatment In 2017, in the journal Nature, researchers found that ecdna with carcinogenic genes appears much more frequently than expected! They are almost invisible in healthy human cells In nearly half of human cancers, ecdna can be observed In this study, scientists have a further understanding of ecdna by using super structure imaging technology, optical mapping, and whole genome sequencing analysis ▲ using scanning electron microscope, we can see chromosomal DNA (blue arrow) and ecdna (orange arrow) in cancer cells Specifically, scientists point out that ecdna is a special ring structure, which looks a bit like plasmid DNA in bacteria However, structural analysis shows that this kind of circular DNA, which is independent of chromosome, is not limited in expression, but it is easy to start the transcription and expression process Unfortunately, in these DNA, there are often some carcinogenic genes Therefore, cancer cells can skillfully use ecdna, activate a large number of carcinogenic genes, help them grow rapidly, and react to the environment quickly to produce drug resistance What's more, when cancer cells divide, these ecdna are not evenly distributed like chromosomes On the contrary, a large number of ecdna may be obtained in a daughter cell, and it may be full of carcinogenic genes Such cells are also more dangerous In 2017, a study in the top medical journal New England Journal of medicine also confirmed that in patients with non-small cell lung cancer, the number of mutations in cancer cells is more or less, which does not affect the prognosis of patients In contrast, the more copies of the gene change in patients, the more difficult the cancer is to treat, the worse their prognosis Source: reference [4] "It's a disruptive discovery The shape of ecdna of cancer cells is different from that of ordinary DNA This discovery has a very important potential value It can not only help us understand the biology of cancer, but also affect the clinic, "said Professor Paul S Mischel, co-author of this study." by showing that ecdna is a circular structure and exposing its epigenetic structure, we have found very important information It gives us a better understanding of the damaged genome and epigenetic groups in cancer cells and brings new insights into their 3D structure On the basis of structure, we can understand why some specific cancer cells are so aggressive " In summary, scientists in the past have tended to focus on which genes are associated with cancer Now we know that the location of these genes is equally important It's worth mentioning that just two months ago, a biotech company named boundless bio received $46 million in financing to inhibit the production and metabolism of ecdna in cancer cells Its co-founder, Professor Howard y Chang, was also one of the co authors of the nature study In their financing press release, they confidently pointed out that innovative therapies targeting ecdna would be the fourth revolution of cancer treatment after chemotherapy, targeted therapy and immunotherapy Can they keep their promise? Let's see reference material: [1] Wu, S., Turner, K.M., Nguyen, N et al Circular ecDNA promotes accessible chromatin and high oncogene expression Nature (2019) doi:10.1038/s41586-019-1763-5 [2] Vicious circles: Ring-shaped DNA provides cancer cells with a malignant twist, Retrieved November 20, 2019, from https:// [3] After cancer immunotherapy is it, where does this company come from? Retrieved November 20, 2019, from https://mp.weixin.qq.com/s?__biz=MzIzMTU0NTM5MA==&mid=2247492875&idx=1&sn=97ce76ee5da3856df8509d8073d5077d