More than 20 microRNA molecules work together to prevent cancer from growing.
The development process of cancer is actually much more complex than we have estimated so far. This conclusion stems from a study led by scientists from the Weizmann Institute, which focused on one of the "hottest" topics in contemporary research in biology: tiny segments of genetic material called microRNA. The scientists discovered, more than 20 such small molecules work together to prevent the growth of cancer. This means that for a healthy cell to become a cancer cell, it has to overcome this common barrier.
The microRNA molecules, which were discovered in the 90s, play a key role in controlling the formation of proteins. They are a total of 22 "genetic letters", but these molecules can block entire genes by blocking the chemical messengers involved in the production of proteins. "After it became clear how essential the microRNA molecules are to cell life, we need to rethink everything known about the control of processes in the cell," says Prof. Yosef Yordan from the Department of Biological Control.
In a study recently published in the scientific journal Science Signaling, research students Roy Avraham and Aldame Shoshana-Chen from Prof. Yordan's laboratory examined the relationship between the microRNA and a growth factor called EGF, which instructs the cell to divide. EGF is essential for tissue growth during wound healing and during embryonic development, but when something goes wrong in its signaling, it can cause the cell to divide uncontrollably and thus lead to cancer.
Much to their surprise, the scientists discovered that when EGF binds to a normal, non-cancerous cell, it almost immediately causes a decrease in the amount of 23 microRNA molecules, and that immediately after, a number of genes with cancerous potential are activated which cause the cell to divide. In other words, these 23 microRNA molecules are normally involved in cell division: when their levels in the cell drop temporarily, they allow EGF to promote growth.
What is most surprising about these findings is the discovery of a timed action of so many microRNA segments. It seems that instead of one strong "brake" controlling its activity, EGF has more than twenty miniature brakes that work together to prevent the cell from going through too many divisions. Imagine, for example, that instead of one handbrake in a car, it will have over twenty small brakes on the steering wheel and the gas pedal. But what happens during cancer? Maybe the cancer cells start dividing uncontrollably because the microRNA is not blocking the EGF properly? Examining EGF-sensitive malignant tumors taken from the breast and brain, the scientists found that the levels of the same 23 microRNAs were abnormally low.
This study sheds new light on the activity of the microRNA molecules, thereby clarifying various aspects of cancer. The findings may help in the detection or diagnosis of cancer through the decrease in microRNA levels associated with cancerous tumors. Furthermore, measuring microRNA levels may give a measure of the biological aggressiveness of the tumor, or help determine whether a certain chemotherapy treatment succeeds in overcoming the cancer.
