BEIJING, Dec. 12 (Xinhua) — A new study has found that the powerful destructive power of cancer cells may be related to its unique “doughnut-shaped” DNA,media reported. The DNA in some cancer cells is not compressed and folded into a linear structure as healthy cells do, but rather into a ring structure, making the cancer more invasive.
In this image taken by a scanning electron microscope, the blue arrow refers to the normal chromosome and the orange arrow refers to ring DNA.
DNA transmits information not only through base sequences, but also through shapes. We’ve been in biology, where most of human DNA is tightly folded into a structure called chromosomes in the nucleus of a cell. Almost all cells contain 23 pairs of chromosomes, and the DNA contained in each chromosome is tightly wrapped around the protein skeleton, expanding up to 1.82 meters in length. In this structure, some genes can be “read” by specific molecules to pass on genetic instructions; This mechanism is precisely regulated to prevent cells from passing the wrong genetic instructions, causing cell replication to get off track.
All the genetic knowledge we know suggests that the rate of change within cells should be slower. But researchers found a few years ago that in a type of brain cancer called glioblastoma, tumors appear to change at an unnatural rate, and when their tumor cells differentiate, they seem to increase the expression of the primary cancer gene, which converts normal cells into cancer cells.
The study found that some of the highly expressed primary cancer genes are removed from chromosomes and then attached to other DNA fragments inside the cell. Nearly half of all human cancers have this “extra-chromosome” DNA fragment, or ecDNA, but they are rarely found in healthy cells.
In this latest study, researchers have found the reason why ecDNA is so strong. Imaging and molecular analysis were used to find that these PIECES of DNA were wrapped in rings on protein skeletons, similar to ring DNA found in bacteria. The structure of cyclic DNA is relatively more open than that of normal DNA, which allows for faster transcription and expression of genetic information, including primary cancer genes. As a result, tumor cells can quickly replicate a large number of primary cancer genes and easily adapt to changing environments.
When healthy cells divide into children, they follow specific DNA distribution patterns. But cancer cells distribute ecDNA quite randomly, and some subcells are even assigned to multiple proto-cancer genes in a single division. (Leaf)