A Canadian study reveals that the speed with which a cell is divided could make all the difference in the outbreak of cancer.
Millions of cells in our body have mutations associated with cancer, yet very few of them end up forming tumors. Recall that a tumor becomes cancer when its abnormal cells invade neighboring tissues, and that they can then spread in the body. A new study published in Nature By researchers from the Lunenfeld-Tanenbaum Research Institute in Toronto (Canada) shows that the duration of the cell cycle (that is to say the time that a cell to divide) is a key factor to predict whether a mutated cell will become cancerous or not. “”It has never been demonstrated at this level on so many different cancers», Insists Rod Bremner, co -author of the study and researcher in oncology.
It is now established that cancer results from mutations in so -called “oncogenic” genes, ie “tumor suppressant” genes. If these genes are mutated and no longer work, the cell can become cancerous (that is, a tumor cell that has become aggressive and problematic). However, recent studies have shown that many healthy cells carry these mutations, without ever forming tumors. The question raised by the researchers is therefore the following: what distinguishes cells that trigger cancer from those that remain harmless, despite the mutations (s)?
Cell cycle under the magnifying glass
The hypothesis of the impact of time of the division of the cells in question quickly came to the table. The cells are divided cyclically, passing through several stages, growth, duplication of DNA and division. “”We know that when a cell specializes (that is, it loses the ability to transform into another type of cell, as stem cells do), its cycle becomes longer“Comments the researcher. To confirm this hypothesis and observe if there is a link between the cell cycle and the development of cancer cells, the researchers have genetically modified mice to be able to manually activate or deactivate certain genes “in order to create a carcinogen mutation“, Deciphers Rod Bremner.
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The researchers then observed what was going on in different tissues after genetic modification: eye, lung and pituitary gland (in the brain). To measure the duration of the cell cycle, they used a double marking technique which makes it possible to visualize under the microscope the moment when the mother cell is divided, in order to form two girl cells. In this way, they were able to calculate the duration of the cell cycle, and then analyze the future of these cells. “For example, in the case of small cell lung cancer (a type of cancer marked by the inactivation of the RB and P53 genes), we have induced these mutations both in the embryo and in adult mice, in different cell types, and in both cases, when the cell cycle was shorter, it caused rapid growth of the tumor in these cells.”
The result observed on the majority of mice and the majority of tissues is that the cell which turns into a cancer cell after division is always that which is divided as quickly. In the eye, for example, it was the lovers of lovers (retina cells) that have become cancerous. Their cell cycle lasted only 26 hours, compared to 77 to 143 hours for other neighboring cells, however also carrying mutations, but which did not cause cancer. “”This study is very interesting, but it still raises many questions: it is unknown what precise step of the cell cycle is involved in the development of a cancer cell», Temperates Renata Basto, head of the Biology of Centrosomes and genetic instability at the Institut Curie.
One solution: slow down cell cycles?
The researchers then modified certain genes which slow down the cell cycle (notably blocking proteins which allow rapid division). And the result obtained is stun: no tumor has formed, despite the carcinogenic mutations still induced by researchers. “”We believed a little bit to an error, at the beginningtestifies Rod Bremner. It is incredible that fabric can contain cells with mutation typically caused cancer, without forming a tumor. I think it’s revealing. ”
The next step will be “to test this hypothesis on human cells in vitro“Announces the researcher. The cell cycle is not the only reason for the appearance of cancer cells, “There are other common causes such as inflammation“Specifies Renata Basto. According to the researcher, it would be complicated to imagine artificial controlling the cell cycle of certain cells of an organ if you suspect cancer. “”It should be very well controlled, and certain organs such as the skin or the intestine requires having a rapid cell renewal to function properly“, She concludes.
