Assessment of diagnostic potency of exosomal microRNA in circulating blood of patient with thyroid cancer

Diagnostics of thyroid cancer (TC) remains a challenging issue due to the high incidence of asymptomatic thyroid nodular pathologies and absence of non-invasive methods of their assessment. Thyroid tumors are classified as benign and malignant with incidence ration approximated as 9:1. Correct and timely differential diagnosis is the basis for correctly choosing a treatment policy and hence determines treatment results. Methods for molecular genetic analysis are being recently developed and introduced into clinical practice, enabling the diagnostic process to be optimized. Analysis of the intracellular and secreted (exosomal) fractions of small regulatory RNAs (microRNAs) is one of the most promising methods for the diagnosis of cancers, including TC. The stability of extracellular microRNA is determined by bonds to proteins, lipoproteins, or its encapsulation into the membrane microvesicles – exosomes. There is reason for suggesting that exosomes with the specific composition of microRNA are a result of the process of active and biologically important secretion while release of other microRNA forms accompanies apoptotic or necrotic cell death. This determines the special diagnostic value of the exosomal fraction of circulating microRNAs, which may reflect the presence and clinically relevant properties of a tumor. This paper discusses the state of the problem and presents methods and preliminary results of the studies conducted by the authors to develop a novel method for diagnosing and monitoring TC. Thus, level of plasma exosomal miR-21 was shown to distinguish patients with benign tumor and follicular CT, while miR-31 can help to distinguish patients with benign tumor and papillary TC. Moreover, reciprocal character of miR-21 and miR-181a concentration in plasma exosomes was detected by comparison of patient with papillary and follicular TC.

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