The growth and metastasis of tumors are assisted by microRNAs

A previously unknown mechanism providing tumor growth is described
and the spread of tumor tissue throughout the body

Alexander Shuster, BNB based on ScienceDaily: New Mechanism Might Promote Cancer's Growth and Spread in the BodyTiny vesicles that break away from the tumor and are picked up by healthy immune cells lead to the release of substances that favor the development and spread of tumor tissue.

This conclusion was reached by the staff of the Cancer Research Center of the Ohio State University and the Children's Hospital of Los Angeles.

During the study, the authors used lung cancer cells. These cells contain regulatory molecules called microRNAs and when the microRNAs of cancer cells are captured by immune cells, the behavior of immune cells changes. In the human body, the TLR8 receptor (Toll-like receptor 8) is involved in this process.

The results of the study suggest the possibility of creating a new strategy for the treatment of oncological diseases and immune disorders and describe the previously unknown role of microRNA molecules.

"The study shows a previously unknown function of microRNAs, which, as we have shown, bind to special receptors. The results obtained give reason to believe that some microRNAs of tumor cells can bind to receptors and activate them like hormones. This fact has not been observed before," says Dr. Carlo Croce, the main author of the study.

microRNAs help control the type and number of protein molecules synthesized by the cell. As a rule, the regulatory activity of microRNAs is carried out through their binding to mRNA.

"As a result of the study, we discovered a previously unknown mechanism that is used by tumor tissue for spreading and growth. Now we can develop cancer drugs based on the results of the study," says Dr. Muller Fabbri, one of the authors of the study, professor of the Department of Pediatrics, Molecular Biology and Immunology at the University of Southern California School of Medicine. According to him, it turned out to be no less interesting that the TLR8 receptor participates in the identified mechanism. The participation of this receptor allows us to think about the expanded practical application of the results of the study, extrapolating them to autoimmune and inflammatory diseases.

The key findings of the study were the following:

• lung tumor cells secrete microRNA-21 and microRNA-29a into vesicles called exosomes, these exosomes are captured by immune system cells (macrophages) located in those places where the tumor tissue borders with normal tissue;
• in human macrophages, microRNA-21 and microRNA-29a bind to TLR8, causing macrophages to secrete tumor necrosis factor alpha and interleukin-6;
• increased levels of these cytokines are associated with an increase in the number of tumors in the lungs in an animal experiment, while a decrease in the level of their content in an animal model experiment was associated with a decrease in the number of tumors in the lungs.

A more detailed description of the results of the study can be found in the Proceedings of the National Academy of Sciences (Fabbri et al., microRNAs bind to Toll-like receptors to induce prometastatic inflammatory response, in open access – VM).

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