Endocrine Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.
PLoS One. 2014 May 23;9(5):e96103. doi: 10.1371/journal.pone.0096103. eCollection 2014.
There have been conflicting reports regarding the function of miR-20a in a variety of cancer types and we previously found it to be dysregulated in sporadic versus familial papillary thyroid cancer. In this study, we studied the expression of miR-20a in normal, benign and malignant thyroid samples, and its effect on thyroid cancer cells in vitro and in vivo.
METHODOLOGY/PRINCIPAL FINDINGS: The expression of miR-20a in normal, benign and malignant thyroid tissue was determined by quantitative RT-PCR. Thyroid cancer cells were transfected with miR-20a and the effect on cellular proliferation, tumor spheroid formation, and invasion was evaluated. Target genes of miR-20 were determined by genome-wide mRNA expression analysis with miR-20a overexpression in thyroid cancer cells and target prediction database. Target genes were validated by quantitative PCR and immunoblotting, and luciferase assays. MiR-20a expression was significantly higher in anaplastic thyroid cancer than in differentiated thyroid cancer, and benign and normal thyroid tissues. MiR-20a significantly inhibited thyroid cancer cell proliferation in vitro (p<0.01) and in vivo (p<0.01), tumor spheroid formation (p<0.05) and invasion (p<0.05) in multiple thyroid cancer cell lines. We found that LIMK1 was a target of miR-20a in thyroid cancer cell lines and direct knockdown of LIMK1 recapitulated the effect of miR-20a in thyroid cancer cells.
CONCLUSIONS/SIGNIFICANCE: To our knowledge, this is the first study to demonstrate that miR-20a plays a role as a tumor suppressor in thyroid cancer cells and targets LIMK1. Our findings suggest the upregulated expression of miR-20a in anaplastic thyroid cancer counteracts thyroid cancer progression and may have therapeutic potential.
miR-20a 在多种癌症类型中的功能存在相互矛盾的报告，我们之前发现其在散发型与家族性甲状腺乳头状癌中存在失调。在这项研究中，我们研究了 miR-20a 在正常、良性和恶性甲状腺样本中的表达及其对甲状腺癌细胞的体外和体内作用。
方法/主要发现：通过定量 RT-PCR 确定正常、良性和恶性甲状腺组织中 miR-20a 的表达。将 miR-20a 转染入甲状腺癌细胞，并评估其对细胞增殖、肿瘤球体形成和侵袭的影响。通过在甲状腺癌细胞中过表达 miR-20a 和靶基因预测数据库进行全基因组 mRNA 表达分析，确定 miR-20a 的靶基因。通过定量 PCR 和免疫印迹以及荧光素酶测定验证靶基因。间变性甲状腺癌中 miR-20a 的表达明显高于分化型甲状腺癌、良性和正常甲状腺组织。miR-20a 显著抑制甲状腺癌细胞的体外增殖（p<0.01）和体内增殖（p<0.01）、肿瘤球体形成（p<0.05）和侵袭（p<0.05）在多种甲状腺癌细胞系中。我们发现 LIMK1 是甲状腺癌细胞系中 miR-20a 的靶基因，直接敲低 LIMK1 可再现 miR-20a 在甲状腺癌细胞中的作用。
结论/意义：据我们所知，这是第一项证明 miR-20a 在甲状腺癌细胞中作为肿瘤抑制因子发挥作用并靶向 LIMK1 的研究。我们的研究结果表明，间变性甲状腺癌中 miR-20a 的上调表达可抑制甲状腺癌的进展，可能具有治疗潜力。
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