N(6)-methyladenosine-mediated miR-380-3p maturation and upregulation promotes cancer aggressiveness in pancreatic cancer

N(6)-methyladenosine (m6A)-modified microRNAs (miRNAs) are relevant to cancer progression. Also, although the involvement of miR-380-3p in regulating cancer progression in bladder cancer and neuroblastoma has been preliminarily explored, its role in other types of cancer, such as pancreatic cancer (PC), has not been studied. Thus, this study aimed to investigate the role of miR-380-3p in regulating PC progression. Here, through performing Real-Time qPCR, we evidenced that miR-380-3p was significantly upregulated in the clinical pancreatic cancer tissues and cells compared to their normal counterparts. Interestingly, miR-380-3p was enriched with m6A modifications, and elimination of m6A modifications by deleting METTL3 and METTL14 synergistically suppressed miR-380-3p expressions in PC cells. Next, the gain and loss-of-function experiments verified that knockdown of miR-380-3p suppressed cell proliferation, epithelial–mesenchymal transition (EMT), and tumorigenesis in PC cells <i>in vitro</i> and <i>in vivo</i>, whereas miR-380-3p overexpression had opposite effects. Furthermore, the underlying mechanisms were uncovered, and our data suggested that miR-380-3p targeted the 3’ untranslated regions (3ʹUTRs) of PTEN for its inhibition and degradation, resulting in the activation of the downstream Akt signal pathway. Moreover, the rescuing experiments validated that both PTEN overexpression and Akt pathway inhibitor LY294002 abrogated the promoting effects of miR-380-3p overexpression on cancer aggressiveness in PC cells. Collectively, this study firstly investigated the role of the m6A-associated miR-380-3p/PTEN/Akt pathway in regulating PC progression, which provided novel therapeutic and diagnostic biomarkers for this cancer.

N6-甲基腺嘌呤（N(6)-methyladenosine，m6A）修饰的微小RNA（microRNAs，miRNAs）与肿瘤进展密切相关。尽管已有初步研究探索了miR-380-3p在膀胱癌及神经母细胞瘤中调控肿瘤进展的作用，但其在胰腺癌（PC）等其他癌种中的功能尚未得到阐明。因此，本研究旨在探讨miR-380-3p对胰腺癌进展的调控作用。本研究通过实时定量聚合酶链式反应（Real-Time qPCR）证实，相较于正常对照组织与细胞，临床胰腺癌组织及细胞中miR-380-3p的表达水平显著上调。值得注意的是，miR-380-3p存在丰富的m6A修饰，而通过敲除METTL3与METTL14消除m6A修饰，可协同抑制胰腺癌细胞中miR-380-3p的表达。随后，功能获得与功能缺失实验证实，敲低miR-380-3p可在体外及体内抑制胰腺癌细胞的增殖、上皮间质转化（epithelial–mesenchymal transition，EMT）及成瘤能力，而过表达miR-380-3p则产生相反的效应。进一步的机制研究显示，miR-380-3p可靶向结合张力蛋白同源缺失于10号染色体的磷酸酶（PTEN）的3'非翻译区（3' untranslated regions，3ʹUTRs），抑制并降解PTEN，从而激活下游Akt信号通路。此外，拯救实验验证，过表达PTEN或使用Akt通路抑制剂LY294002，均可抵消miR-380-3p过表达对胰腺癌细胞侵袭能力的促进作用。综上，本研究首次揭示了m6A修饰相关的miR-380-3p/PTEN/Akt通路在胰腺癌进展中的调控作用，为该类肿瘤提供了全新的诊疗生物标志物。