The Role of MicroRNAs, tRNA Fragments, and Circular RNAs in Leukemia

Dear Colleagues,

Leukemias constitute a group of hematological malignancies, usually arising from the bone marrow and characterized by very high abundance of abnormal blood cells. Until today, the exact causes of leukemia remain unknown, while a combination of genetic and environmental factors are believed to contribute to leukemia development. Therefore, elucidation of the molecular background of leukemia as well as its clinical aspects, such as effective diagnosis, prognosis, and treatment, constitutes a great challenge in the personalized medicine era.

MicroRNAs (miRNAs) are single-stranded, small non-coding RNA molecules that epigenetically regulate gene expression, mostly through binding to the 3′ untranslated region (3′ UTR) of targeted messenger RNA (mRNA) molecules and, hence, mediating translational repression, usually combined with or followed by mRNA degradation. miRNAs can function either as oncogenes or tumor suppressors by controlling the activity and function of key signaling pathways and cellular processes such as cell proliferation, apoptosis, cell differentiation, and response to hypoxia. From a clinical perspective, particular miRNAs can also serve as molecular biomarkers and therapeutic targets for hematological malignancies, including leukemia.

Transfer RNA (tRNA)-derived RNA fragments are small non-coding RNAs specifically cleaved from transfer RNA (tRNAs), with a length of 14–48 nucleotides. They are classified into three main classes, namely tRNA fragments (tRFs), stress-induced tRNA-derived RNA fragments (tiRNAs), and toxic small tRNA-derived RNA fragments (tsRNAs). The tRNA molecules present a high differentiation in their cleavage sites, thus leading to several tRNA-derived RNA fragments varying in length and having distinct functions. They participate in translation regulation and gene silencing, with a subsequent effect on cell viability and proliferation. Furthermore, they play a pivotal role in stress-induced situations.

Circular RNAs (circRNAs) are a neglected RNA type deriving from back-splicing. The high-throughput analysis revolution uncovered their widespread expression, arousing scientific interest. circRNAs have been designated as crucial modulators in several aspects of cell life, both in physiological and pathological states. Circular RNAs can affect post-transcriptional gene regulation mediated by miRNAs by acting as miRNA sponges. As studies regarding the intricate functions of circRNAs emerged, their association with multiple regulatory networks became evident, proving that these molecules play key roles in leukemia and may have wide clinical applications.

This Special Issue focuses on the information of the readers regarding the potential of miRNAs, tRNA-derived RNA fragments, and circRNAs to regulate protein-coding gene expression at a post-transcriptional level, in leukemia and other hematological malignancies. Authors are encouraged to submit their original research studies concerning this topic. Review articles will also be taken into consideration. We hope that this Special Issue regarding the identity, biological role, and/or clinical utility of miRNAs, tRNA fragments, and circRNAs in leukemia will pique the interest of the readers of this journal.

Dr. Christos K. Kontos
Dr. Paraskevi Karousi
Guest Editors

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• miRNAs
• tRFs
• tiRNAs
• circRNAs
• regulators
• acute lymphoblastic leukemia
• chronic lymphocytic leukemia
• acute myelogenous leukemia
• chronic myelogenous leukemia
• molecular biomarkers