Zhang Mingpeng, Wang Xin, Tan Jin, Zhao Minghui, Lian Linjuan, Zhang Weisan
Department of Geriatrics, Tianjin Medical University General Hospital, Tianjin Geriatrics Institute Tianjin 300052, China.
Am J Transl Res. 2016 Aug 15;8(8):3567-73. eCollection 2016.
Poly r(C) binding protein (PCBP) 1 or heterogeneous ribonucleoprotein (hnRNP) E1 is a RNA binding protein functional in multiple biological processes. PCBP1 has been shown to function as a tumor suppressor by negatively regulating translation of EMT inducer proteins in different cancers. Loss of PCBP1 expression or its Akt2-mediated phosphorylation at serine residue 43 has both been indicated to de-repress its regulation of EMT inducer proteins. However, its role in thyroid carcinoma has not been elucidated. Here we report that PCBP1 expression is significantly downregulated in thyroid carcinoma patients. In vitro kinase assay revealed that immunoprecipitated PCBP1 from transient or stably transfected thyroid carcinoma cells can be phosphorylated by recombinant Akt2 kinase. In situ analysis revealed that PCBP1 is a putative target of miR-490-3p, which was further confirmed by PCBP1 3'UTR-based reporter assays using the wild-type or a miR-490 seed mutant 3'UTR. The endogenous regulation of the PCBP1 3'UTR reporter by miR-490-3p could be rescued by transfection of miR-490 antagomir in WRO and BCPAP cells. Stably overexpressing PCBP1 BCPAP cells attenuated tumor formation completely as compared to empty vector overexpressing cells in xenograft assay. Cumulatively, our results indicate that PCBP1 functions as a tumor suppressor in thyroid carcinoma and that its expression is down regulated by high expression of the miR-490-3p observed in thyroid carcinoma patients.
多聚胞嘧啶结合蛋白（PCBP）1或不均一核糖核蛋白（hnRNP）E1是一种在多种生物学过程中发挥作用的RNA结合蛋白。PCBP1已被证明通过负向调节不同癌症中上皮-间质转化（EMT）诱导蛋白的翻译而发挥肿瘤抑制作用。PCBP1表达缺失或其丝氨酸残基43处的Akt2介导的磷酸化均已表明会解除其对EMT诱导蛋白的调节。然而，其在甲状腺癌中的作用尚未阐明。在此我们报告，甲状腺癌患者中PCBP1表达显著下调。体外激酶分析显示，从瞬时或稳定转染的甲状腺癌细胞中免疫沉淀的PCBP1可被重组Akt2激酶磷酸化。原位分析显示，PCBP1是miR-490-3p的假定靶标，使用野生型或miR-490种子突变体3'UTR的基于PCBP1 3'UTR的报告基因分析进一步证实了这一点。在WRO和BCPAP细胞中，通过转染miR-490拮抗剂可挽救miR-490-3p对PCBP1 3'UTR报告基因的内源性调节。在异种移植实验中，与空载体过表达细胞相比，稳定过表达PCBP1的BCPAP细胞完全减弱了肿瘤形成。总的来说，我们的结果表明PCBP1在甲状腺癌中发挥肿瘤抑制作用，并且其表达在甲状腺癌患者中因miR-490-3p的高表达而下调。
