{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nmiR-520h has emerged as a multifunctional regulator in several cancers, where its aberrant expression contributes to chemoresistance and tumor progression. In breast cancer cells, elevated miR-520h levels promote resistance to agents such as paclitaxel and doxorubicin by inhibiting pro‐apoptotic molecules (e.g., DAPK2, HDAC1, and OTUD3–PTEN) and thereby reducing drug‐induced apoptosis. In parallel, increased miR-520h expression in epithelial ovarian cancer enhances cell proliferation, migration, invasion, and epithelial-to-mesenchymal transition (EMT) through downregulation of Smad7 and subsequent activation of the TGF‑β pathway—a process further amplified by c-Myb induction. Moreover, in relapsed acute lymphoblastic leukemia, miR-520h appears to modulate key cell cycle regulators (including POLD1 and MCM2) via E2F1, while in colorectal cancer, its sequestration by the long noncoding RNA PART1 helps upregulate CTNNB1 and activate Wnt/β-catenin signaling. In hepatocellular carcinoma, miR-520h is sponged by IGF2-AS, which results in restoration of CDKN1A levels and suppression of tumor aggressiveness, and in non-small cell lung cancer, reduced miR-520h permits enhanced expression of YAP1—contributing to gefitinib resistance; restoration of miR-520h in these cells represses YAP1 and diminishes chemoresistance."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "8"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nIn addition to its oncogenic roles, miR-520h is involved in the translational regulation of key proteins under normal conditions. For example, in human embryonic stem cells, the full-length ABCG2 mRNA is expressed but its protein product is tightly regulated by miR-520h (in conjunction with miR-519c), which prevents ABCG2 translation under specific conditions. Furthermore, in the context of diabetic nephropathy, the noncoding RNA NORAD sequesters miR-520h to modulate TLR4 expression; this NORAD/miR-520h/TLR4 loop promotes the proliferative capacity and survival of glomerular mesangial cells, thereby exacerbating disease progression."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "9"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nBeyond cancer and stem cell regulation, miR-520h also plays significant roles in metabolic and reproductive disorders. In gestational diabetes mellitus, miR-520h is upregulated in both patient serum and high-glucose–treated trophoblast cells, where it targets mTOR; this suppression of mTOR leads to decreased cell viability and increased apoptosis, correlating with elevated fasting blood glucose levels. Similarly, in unexplained recurrent spontaneous abortion, elevated serum levels of miR-520h suggest its potential utility as a diagnostic biomarker. In polycystic ovary syndrome, miR-520h directly targets IL6R, thereby inhibiting cell proliferation and promoting apoptosis—effects that are at least in part mediated through inhibition of the JAK/STAT pathway."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "11", "end_ref": "13"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Qi Shen, Qinghua Yao, Jie Sun, et al. 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"}, {"type": "b", "children": [{"type": "t", "text": "miR-520h is crucial for DAPK2 regulation and breast cancer progression."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Oncogene (2016)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1038/onc.2015.168"}], "href": "https://doi.org/10.1038/onc.2015.168"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "25982274"}], "href": "https://pubmed.ncbi.nlm.nih.gov/25982274"}]}, {"type": "r", "ref": 3, "children": [{"type": "t", "text": "Sheng Li, Chengzhong Wang, Weikai Wang, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Abnormally high expression of POLD1, MCM2, and PLK4 promotes relapse of acute lymphoblastic leukemia."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Medicine (Baltimore) (2018)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1097/MD.0000000000010734"}], "href": "https://doi.org/10.1097/MD.0000000000010734"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "29768346"}], "href": "https://pubmed.ncbi.nlm.nih.gov/29768346"}]}, {"type": "r", "ref": 4, "children": [{"type": "t", "text": "Jing Zhang, Wenxue Liu, Fangqian Shen, et al. 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