What's in your thyroid?
Scientists of the NMIC of Oncology named after Petrov identified molecules that will help accurately diagnose follicular thyroid cancer
Press Center of NMIC Oncology
The expansion of knowledge about the role of microRNAs in carcinogenesis allowed scientists of the N.N. Petrov NMIC of Oncology to identify molecules that can serve as markers in the diagnosis of follicular thyroid cancer. The discovery will form the basis for the development of test systems for accurate diagnosis of this disease at the preoperative stage.
The work on the research project lasted three years. During this time, experts have isolated and analyzed hundreds of microRNAs from benign and malignant follicular nodes of the thyroid gland. A combination of experimental and computational approaches made it possible to identify a pair of microRNA molecules ‒ miR-146b and miR-451. Evaluation of the ratio of their activity allows to establish or exclude cancer in the patient. The results of the scientific work are presented in the scientific publication International Journal of Molecular Science 2020 (Knyazeva et al., Reciprocal Dysregulation of MiR-146b and MiR-451 Contributions in Malignant Phenotype of Follicular Thyroid Tumor).
According to WHO, the incidence of thyroid cancer has doubled in recent decades. Thyroid cancer has several biological types, among which follicular carcinoma is one of the most difficult options in terms of diagnosis and treatment.
When a patient has thyroid nodules, the main question that worries both the attending physician and the patient is "What is the nature of the neoplasm – benign or malignant"?
To establish an accurate diagnosis, doctors use ultrasound diagnostics and fine needle aspiration biopsy (TAB) followed by cytological examination of the obtained biomaterial. However, in the case of the follicular nature of the node, cytological examination does not allow to confirm or exclude its malignant nature. Currently, there is no method in clinical practice that would accurately differentiate between truly malignant follicular thyroid cancer and benign follicular adenoma. At the same time, the first disease requires surgical treatment, and the second usually only observation. The risk of "leaving under observation" follicular carcinoma makes doctors in some cases decide to remove the thyroid gland. And as a result – dozens of operations performed on patients with benign neoplasms.
The possibility of solving this problem by analyzing microRNA biomaterial obtained during a fine needle biopsy has been investigated for a long time. But it has not yet been implemented in clinical practice due to technological difficulties. The original solution was proposed by scientists of the N.N. Petrov National Research Center of Oncology. Specialists of the subcellular technologies laboratory with the endocrinology group have found that the number of some microRNA molecules differs in follicular cancer and adenoma cells, and these differences often have a multidirectional character: the activity of one molecule increases in the case of cancer, the other decreases. Some of these reciprocal (multidirectional) changes are repeated from case to case and probably have a biological meaning. From a practical point of view, it is important that they can be evaluated and used as diagnostic criteria.
To identify the very "marker" microRNAs, scientists conducted a large-scale study. For the experiment, they collected tissue samples of thyroid nodes from patients with confirmed diagnoses of "follicular adenoma", "minimally invasive follicular cancer" and "broadly invasive follicular cancer". Then a quantitative analysis of about 200 microRNAs was carried out in order to search for molecules whose activity has a direct or inverse correlation with the invasiveness of the node tissue, that is, to put it another way, the volume of germination into nearby tissues. Based on the results obtained, only 10 micro-RNAs were selected, the diagnostic potential of which was investigated in more detail.
‒ With the assistance of morphologists, we have compiled groups of samples of follicular thyroid nodules with various invasive potentials, that is, with varying degrees of "germination" into nearby tissues. In these samples, we were looking for such micro-RNAs, changes in expression, or "activity", which correspond to the degree of invasion of node cells outside its capsule, ‒ said Anastasia Valeryevna Malek, head of the Laboratory of subcellular Technologies of the N.N. Petrov NMIC of Oncology.
A detailed analysis of ten selected molecules in an expanded sample collection revealed statistically significant concentration differences. But when assessing the parameters of diagnostic significance (specificity, sensitivity), none of the molecules by itself could be offered as a marker for clinical use, i.e. it did not allow to confidently distinguish benign and malignant follicular nodes.
‒ Then we assumed that a diagnosis could be made using a quantitative analysis of two microRNAs by assessing the ratio of their concentrations. We have created a program to perform such calculations for a large number of molecules and samples. This approach made it possible to identify pairs of molecules whose concentration ratio is clearly associated with the diagnosis of follicular cancer.
In particular, the pair "miR-146b / miR-451" showed good diagnostic potential. It was found that in malignant samples with a higher degree of invasion, the amount and activity of the miR-451 molecule decreased, while the amount and activity of the miR-146b molecule increased. The work of other researchers confirmed the participation of these molecules in the development of follicular cancer. Interestingly, the biological activity of one molecule was associated with the "benign" characteristics of cells, while the other was involved in the formation of a "malignant" phenotype.
Thus, there was a clear relationship between the concentration of miR-146b and miR-451 molecules and the invasive potential of follicular node cells. This pair of micro-RNAs turned out to be a marker for accurate diagnosis, it made it possible to distinguish truly malignant follicular thyroid cancer from benign follicular adenoma.
According to scientists, the method of diagnosing follicular thyroid cancer can be introduced into routine clinical practice. Test systems based on PCR analysis of several microRNA pairs may be developed in the next few years.
‒ In general, the following diagnostic algorithm is proposed: a fine needle aspiration biopsy is performed on the patient, then the biopsy material is examined by a cytologist, and if signs of a follicular tumor are detected, the cytological preparation is used to isolate microRNA. It is important that the new method is "organically" integrated into the standard diagnostic algorithm and does not involve additional procedures for the patient. After RNA isolation, the analysis and calculation of the ratios of concentrations of "marker" microRNAs is carried out, ‒ said Anastasia Valeryevna Malek, PhD, Head of the Laboratory of Subcellular Technologies of the N.N. Petrov NMIC of Oncology. – In routine clinical practice, the quantitative determination of micro-RNA is likely to be performed by RT-PCR. However, the technology requires optimization of the main stages: RNA isolation, quantitative analysis of "marker" molecules and algorithms for calculating the data obtained. As a result, we assume that the time and cost of the analysis will be comparable with modern methods of PCR diagnostics, for example, viral infections or point mutations.
The development of new methods for the diagnosis of various types of cancer based on microRNA is one of the leading areas of work of laboratory scientists. Currently, research is being conducted in the field of diagnostics of prostate cancer, breast cancer, cervical cancer and colorectal cancer at the N.N. Petrov Oncology Research Center.
Reference
microRNAs are a class of small regulatory RNA molecules that control the expression of protein-coding genes. microRNAs are involved in all key cell processes, including cell proliferation (reproduction by division), differentiation (realization of a function programmed by genes) and apoptosis (programmed death). microRNAs are also involved in intercellular interaction. Research by scientists around the world shows that microRNAs are involved in the development of various types of cancer.
Follicular cancer is a type of malignant neoplasm of the thyroid gland. It occurs in adults, the peak incidence occurs in 50-55 years. This type of tumor is characterized by slow growth. In the later stages, metastases form in the lymph nodes of the neck, as well as in the bones, liver and lungs. Modern diagnostic technologies do not allow to distinguish follicular cancer from benign thyroid adenoma at the preoperative stage. Therefore, many patients are forced to undergo surgery – removal of the gland (thyroidectomy) and switch to lifelong use of hormone replacement therapy.
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