Differential processing of let-7a precursors influences RRM2 expression and chemosensitivity in pancreatic cancer: role of LIN-28 and SET oncoprotein.
Differential processing of let-7a precursors influences RRM2 expression and chemosensitivity in pancreatic cancer: role of LIN-28 and SET oncoprotein.
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DOI：
10.1371/journal.pone.0053436
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Govindarajan R
中科院分区：
文献类型：
--
作者：
Bhutia YD;Hung SW;Krentz M;Patel D;Lovin D;Manoharan R;Thomson JM;Govindarajan R
参与脱氧核糖核苷酸合成的核糖核苷酸还原酶亚基M2 （RRM2）的过表达导致胰腺癌对核苷类似物（如吉西他滨）产生化学耐药。虽然通过合成手段沉默RRM2已显示出减少化疗耐药的希望，但针对内源性分子，特别是microRNAs (miRNAs)，促进化疗结果的探索很少。基于计算预测，我们假设let-7肿瘤抑制mirna将抑制rrm2介导的胰腺癌吉西他滨化疗耐药。在先天性吉西他滨耐药胰腺癌细胞系中，大多数let-7 mirna的表达降低，与RRM2表达呈负相关。将let-7 mirna直接结合到RRM2转录物的3 ' UTR上，鉴定出RRM2的转录后调控影响吉西他滨的化学敏感性。有趣的是，在低分化的胰腺癌细胞系MIA PaCa-2中，人类前体let-7 mirna的过表达导致了RRM2的差异表达和化学敏感性反应。成熟形式的let-7a前体加工缺陷部分解释了let-7a表达结果的差异。同样，在吉西他滨敏感的L3.6pl和Capan-1细胞系中，成熟细胞与前体细胞let-7a的比例逐渐降低，诱导获得吉西他滨抗性。除了已知的let-7生物发生调节因子（如LIN-28）外，短发夹RNA文库筛选发现了几种新的RNA结合蛋白，包括SET癌蛋白，对吉西他滨敏感与耐药的胰腺癌细胞的let-7生物发生和化学敏感性有不同的影响。此外，细胞中LIN-28和SET的敲低导致细胞增殖和集落形成能力的显著降低。最后，在患者源性胰腺导管腺癌（PDAC）组织中发现了与RRM2过表达呈正相关的let-7a前体加工缺陷。这些数据证明了let-7a对RRM2和化疗敏感性的复杂转录后调控，并且参与let-7a转录/加工的调控蛋白的操纵可能为改善胰腺癌的化疗和/或肿瘤生长控制反应提供了一种机制。
Overexpression of ribonucleotide reductase subunit M2 (RRM2), involved in deoxyribonucleotide synthesis, drives the chemoresistance of pancreatic cancer to nucleoside analogs (e.g., gemcitabine). While silencing RRM2 by synthetic means has shown promise in reducing chemoresistance, targeting endogenous molecules, especially microRNAs (miRNAs), to advance chemotherapeutic outcomes has been poorly explored. Based on computational predictions, we hypothesized that the let-7 tumor suppressor miRNAs will inhibit RRM2-mediated gemcitabine chemoresistance in pancreatic cancer. Reduced expression of the majority of let-7 miRNAs with an inverse relationship to RRM2 expression was identified in innately gemcitabine-resistant pancreatic cancer cell lines. Direct binding of let-7 miRNAs to the 3′ UTR of RRM2 transcripts identified post-transcriptional regulation of RRM2 influencing gemcitabine chemosensitivity. Intriguingly, overexpression of human precursor-let-7 miRNAs led to differential RRM2 expression and chemosensitivity responses in a poorly differentiated pancreatic cancer cell line, MIA PaCa-2. Defective processing of let-7a precursors to mature forms, in part, explained the discrepancies observed with let-7a expressional outcomes. Consistently, the ratios of mature to precursor let-7a were progressively reduced in gemcitabine-sensitive L3.6pl and Capan-1 cell lines induced to acquire gemcitabine resistance. Besides known regulators of let-7 biogenesis (e.g., LIN-28), short hairpin RNA library screening identified several novel RNA binding proteins, including the SET oncoprotein, to differentially impact let-7 biogenesis and chemosensitivity in gemcitabine-sensitive versus -resistant pancreatic cancer cells. Further, LIN-28 and SET knockdown in the cells led to profound reductions in cellular proliferation and colony-formation capacities. Finally, defective processing of let-7a precursors with a positive correlation to RRM2 overexpression was identified in patient-derived pancreatic ductal adenocarcinoma (PDAC) tissues. These data demonstrate an intricate post-transcriptional regulation of RRM2 and chemosensitivity by let-7a and that the manipulation of regulatory proteins involved in let-7a transcription/processing may provide a mechanism for improving chemotherapeutic and/or tumor growth control responses in pancreatic cancer.
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影响因子：
64.8
作者：
Lu, J;Getz, G;Golub, TR
通讯作者：
Golub, TR
影响因子：
16.8
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8
作者：
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4.3
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Rocha-Lima, Caio Max