In most cases, thyroid cancer can be treated. However, 5% of patients the tumor is resistant to treatment, spreads throughout the body and leads to death.
In a study at the Institute of Biomedical Sciences at the University of Sao Paulo, Brazil, researchers found that increased expression of tumor is accompanied by a decrease in 52 microRNA - small RNA molecules that do not encode proteins but perform a regulatory function in several cellular processes. The results were published in Oncotarget.
"The data obtained so far suggest that these microRNAs can be studied as a tumor suppressor. The idea was to return to normal levels of these molecules in the tumor and see if it will prevent the progression of the disease ", - said M. Geraldo, a professor at the University of Campinas Institute of Biology.
In most experiments, genetically modified mouse model in which the BRAF gene is turned off only in the thyroid gland. The change was similar to that which is found in many patients with thyroid cancer or melanoma. "When this mutation is present, the cancer is more aggressive, - says Geraldo. - The model simulates the processes occurring at 5 percent of the patients that die due to disease progression. "
First, it was necessary to evaluate the expression of microRNAs has changed with the progression of the disease in mice. Then scientists identified a group of molecules with very similar behavior. Scientists have found a region of the genome to which these miRNAs are encoded, and found that this place is known as the long arm of chromosome 14 (chromosome band 14q32).
"In an article published back in 2015, told of the existence of a rare condition called Temple syndrome, which is characterized by partial or complete loss of this genomic region, - says Geraldo. - Our study indicated an increased risk of thyroid cancer in carriers of the syndrome. "
The next step was to evaluate the expression of these microRNAs in patients with thyroid tumors, using the tools of bioinformatics in the public databases that keep the genome data of people with thyroid cancer.
The research team has chosen one of the 52 miRNAs identified in an animal model, miR-654, to check its function in laboratory tests using cell lines of human tumors of the thyroid gland. Tests have confirmed that when the expression of miR-654, which was low in tumor cells was restored to levels equivalent to the levels of the healthy state, the cells multiplied less were less able to migrate and many of them died.
In the new project Geraldo plans to find out which of the 52 microRNAs is most interesting to examine in detail for therapeutic purposes. According to the National Cancer Institute of Brazil, thyroid cancer is the most common form of head and neck cancer. The data show that the incidence of thyroid cancer has tripled in the past decade. Papillary thyroid cancer is the most common subtype of from 75 to 80 percent of cases.