MiR-509-5p improves the proliferative and invasive abilities of papillary thyroid carcinoma cells by inhibiting SFRP1

Hypoxic papillary thyroid carcinoma cells-secreted exosomes deliver miR-221-3p to normoxic tumor cells to elicit a pro-tumoral effect by regulating the ZFAND5

Papillary thyroid cancer (PTC) has seen a worldwide expansion in incidence in the past three decades. Tumor-derived exosomes have been associated with the metastasis of cancer cells and are present within the local hypoxic tumor microenvironment, where they mediate intercellular communication by transferring molecules including microRNAs (miRNAs) between cells. Although miRNAs have been shown to serve as non-invasive biomarkers for cancer diagnosis, the role of hypoxia-induced tumor-derived exosomes in PTC progression remains unclear. Herein, we investigated the differentially expressed miRNA expression profiles from GEO datasets (GSE191117 and GSE151180) by using the DESeq package in R and identified a novel role for miR-221-3p as an oncogene in PTC development. In vivo and in vitro loss and gain assays were used to clarify the mechanism of hypoxic PTC cells derived exosomal-miR-221-3p in PTC. miR-221-3p was upregulated in human PTC plasma exosomes, tissues and cell lines. We found that hypoxic PTC cells derived exosomal-miR-221-3p promoted normoxic PTC cells proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) in vitro, while inhibition of miR-221-3p limited PTC tumor growth in our PTC xenograft model in nude mice. We finally identified ZFAND5, to be a miR-221-3p target. Mechanistically, hypoxic PTC cell lines-derived exosomes carrying miR-221-3p promoted PTC tumorigenesis by regulating ZFAND5. Our findings further the understanding of the underlying mechanisms associated with PTC progression and identify exosomal-miR-221-3p as a potential biomarker for the diagnosis and prognosis of PTC patients. Our study also suggests that miR-221-3p inhibitors could be a potential treatment strategy for PTC.

Human pulmonary artery smooth muscle cell dysfunction is regulated by miR-509-5p in hypoxic environment

Reportedly, dysfunction of human pulmonary arterial smooth muscle cells (PASMCs) is associated with the pathogenesis of pulmonary arterial hypertension (PAH). Herein, the role of miR-509-5p in hypoxia-induced PASMCs and the underlying mechanism were explored. PASMCs were cultured under both normoxia and hypoxia conditions. Quantitative real-time polymerase-chain reaction (qPCR) was employed for quantifying the expressions of miR-509-5p and DNMT1 mRNA in the serum of PAH patients and PASMCs. MiR-509-5p mimics and inhibitors were then, respectively, transfected into PAMSCs, and CCK-8 and Transwell assays were utilized to detect PASMCs' proliferation and migration. Flow cytometry was executed for evaluating PASMCs' apoptosis. Interrelation between miR-509-5p and DNMT1 was determined utilizing bioinformatics analysis and dual-luciferase reporter assay. Western blot assay was used to detect the expression of DNMT1 or SOD2. MiR-509-5p in serum samples of patients with PAH as well as hypoxia-induced PASMCs was significantly down-regulated, whereas DNMT1 was markedly up-regulated. MiR-509-5p mimics reduces the proliferation and migration of PASMCs, but promotes the apoptosis; conversely, miR-509-5p inhibitors exerted opposite effects. DNMT1 was identified as a target gene of miR-509-5p, and overexpression of DNMT1 reversed the biological functions of miR-509-5p in regulating the phenotypes of PAMSCs. MiR-509-5p up-regulated the expression of SOD2 by down-regulating DNMT1. MiR-509-5p regulates the proliferation, migration and apoptosis of PASMCs, and restoration of miR-509-5p may be a promising strategy to treat PAH.

ChrXq27.3 miRNA cluster functions in cancer development

MicroRNAs (miRNAs) regulate the expression of their target genes post-transcriptionally; thus, they are deeply involved in fundamental biological processes. miRNA clusters contain two or more miRNA-encoding genes, and these miRNAs are usually coexpressed due to common expression mechanisms. Therefore, miRNA clusters are effective modulators of biological pathways by the members coordinately regulating their multiple target genes, and an miRNA cluster located on the X chromosome q27.3 region has received much attention in cancer research recently. In this review, we discuss the novel findings of the chrXq27.3 miRNA cluster in various types of cancer.

The chrXq27.3 miRNA cluster contains 30 mature miRNAs synthesized from 22 miRNA-encoding genes in an ~ 1.3-Mb region. The expressions of these miRNAs are usually negligible in many normal tissues, with the male reproductive system being an exception. In cancer tissues, each miRNA is dysregulated, compared with in adjacent normal tissues. The miRNA-encoding genes are not uniformly distributed in the region, and they are further divided into two groups (the miR-506-514 and miR-888-892 groups) according to their location on the genome. Most of the miRNAs in the former group are tumor-suppressive miRNAs that are further downregulated in various cancers compared with normal tissues. miR-506-3p in particular is the most well-known miRNA in this cluster, and it has various tumor-suppressive functions associated with the epithelial–mesenchymal transition, proliferation, and drug resistance. Moreover, other miRNAs, such as miR-508-3p and miR-509-3p, have similar tumor-suppressive effects. Hence, the expression of these miRNAs is clinically favorable as prognostic factors in various cancers. However, the functions of the latter group are less understood. In the latter group, miR-888-5p displays oncogenic functions, whereas miR-892b is tumor suppressive. Therefore, the functions of the miR-888–892 group are considered to be cell type- or tissue-specific.

In conclusion, the chrXq27.3 miRNA cluster is a critical regulator of cancer progression, and the miRNAs themselves, their regulatory mechanisms, and their target genes might be promising therapeutic targets.