1] Department of Urology, Los Angeles, CA, USA [2] Program in Genetic, Molecular, and Cellular Biology, Los Angeles, CA, USA.
Oncogene. 2013 Sep 26;32(39):4694-701. doi: 10.1038/onc.2012.483. Epub 2012 Oct 22.
GRP78, a major endoplasmic reticulum chaperone and signaling regulator, is commonly overexpressed in cancer. Moreover, induction of GRP78 by a variety of anti-cancer drugs, including histone deacetylase inhibitors, confers chemoresistance to cancer, thereby contributing to tumorigenesis. Thus, therapies aimed at decreasing GRP78 levels, which results in the inhibition of tumor cell proliferation and resensitization of tumor cells to chemotherapeutic drugs may hold promise for cancer treatment. Despite advances in our understanding of GRP78 actions, little is known about endogenous inhibitors controlling its expression. As endogenous regulators, microRNAs (miRNAs) play important roles in modulating gene expression; therefore, we sought to identify miRNA(s) that target GRP78, under the hypothesis that these miRNAs may serve as therapeutic agents. Here, we report that three miRNAs (miR-30d, miR-181a, miR-199a-5p) predicted to target GRP78 are down-regulated in prostate, colon and bladder tumors, and human cancer cell lines. We show that in C42B prostate cancer cells, these miRNAs down-regulate GRP78 and induce apoptosis by directly targeting its 3' untranslated region. Importantly, we demonstrate that the three miRNAs act cooperatively to decrease GRP78 levels, suggesting that multiple miRNAs may be required to efficiently control the expression of some genes. In addition, delivery of multiple miRNAs by either transient transfection or lentivirus transduction increased the sensitivity of cancer cells to the histone deacetylase inhibitor, trichostatin A, in C42B, HCT116 and HL-60 cells. Together, our results indicate that the delivery of co-transcribed miRNAs can efficiently suppress GRP78 levels and GRP78-mediated chemoresistance, and suggest that this strategy holds therapeutic potential.
GRP78 是内质网的主要伴侣蛋白和信号调节剂，在癌症中普遍过表达。此外，包括组蛋白去乙酰化酶抑制剂在内的多种抗癌药物诱导的 GRP78 表达可赋予癌细胞耐药性，从而促进肿瘤发生。因此，旨在降低 GRP78 水平的治疗方法可能对癌症治疗有一定的前景，因为这会抑制肿瘤细胞增殖并使肿瘤细胞对化疗药物重新敏感。尽管我们对 GRP78 作用的理解取得了进展，但对控制其表达的内源性抑制剂知之甚少。作为内源性调节剂，microRNAs（miRNAs）在调节基因表达方面发挥着重要作用；因此，我们假设这些 miRNAs 可能作为治疗剂，试图确定靶向 GRP78 的 miRNA。在这里，我们报告了三种被预测靶向 GRP78 的 miRNA（miR-30d、miR-181a、miR-199a-5p）在前列腺癌、结肠癌和膀胱癌以及人类癌细胞系中下调。我们表明，在 C42B 前列腺癌细胞中，这些 miRNA 通过直接靶向其 3'非翻译区而下调 GRP78 并诱导细胞凋亡。重要的是，我们证明这三种 miRNA 协同作用降低 GRP78 水平，这表明可能需要多种 miRNA 才能有效地控制某些基因的表达。此外，通过瞬时转染或慢病毒转导递送多种 miRNA 可增加 C42B、HCT116 和 HL-60 细胞对组蛋白去乙酰化酶抑制剂曲古抑菌素 A 的敏感性。总之，我们的研究结果表明，共转录 miRNA 的递送可以有效地抑制 GRP78 水平和 GRP78 介导的化疗耐药性，并表明该策略具有治疗潜力。
