Hirata Yukihiro, Murai Noriyuki, Yanaihara Nozomu, Saito Misato, Saito Motoaki, Urashima Mitsuyoshi, Murakami Yasuko, Matsufuji Senya, Okamoto Aikou
Department of Obstetrics and Gynecology, The Jikei University School of Medicine, 3-25-8, Nishi-Shinbashi, Minato-ku, Tokyo 105-8461, Japan.
BMC Cancer. 2014 Nov 3;14:799. doi: 10.1186/1471-2407-14-799.
Epithelial ovarian cancer (EOC) is the most common cause of gynecological malignancy-related mortality. Ovarian clear cell carcinoma (CCC) has unique clinical characteristics and behaviors that differ from other histological types of EOC, including a frequent association with endometriosis and a highly chemoresistant nature, resulting in poor prognosis. However, factors underlying its malignant behavior are still poorly understood. Aberrant expression of microRNAs has been shown to be involved in oncogenesis, and microRNA-21 (miR-21) is frequently overexpressed in many types of cancers. The aim of this study was to investigate the role of miR-21 in 17q23-25 amplification associated with CCC oncogenesis.
We identified 17q23-25 copy number aberrations among 28 primary CCC tumors by using a comparative genomic hybridization method. Next, we measured expression levels of the candidate target genes, miR-21 and PPM1D, for 17q23-25 amplification by real-time RT-PCR analysis and compared those data with copy number status and clinicopathological features. In addition, immunohistochemical analysis of PTEN (a potential target of miR-21) was performed using the same primary CCC cases. We investigated the biological significance of miR-21 overexpression in CCC using a loss-of-function antisense approach.
17q23-25 amplification with both miR-21 overexpression and PTEN protein loss was detected in 4/28 CCC cases (14.2%). The patients with 17q23-25 amplification had significantly shorter progression-free and overall survival than those without 17q23-25 amplification (log-rank test: p = 0.0496; p = 0.0469, respectively). A significant correlation was observed between miR-21 overexpression and endometriosis. Both PTEN mRNA and PTEN protein expression were increased by miR-21 knockdown in CCC cells. We also confirmed that miR-21 directly bound to the 3'-untranslated region of PTEN mRNA using a dual-luciferase reporter assay.
MiR-21 is a possible driver gene other than PPM1D for 17q23-25 amplification in CCC. Aberrant expression of miR-21 by chromosomal amplification might play an important role in CCC carcinogenesis through the regulation of the PTEN tumor suppressor gene.
上皮性卵巢癌（EOC）是妇科恶性肿瘤相关死亡的最常见原因。卵巢透明细胞癌（CCC）具有独特的临床特征和行为，与其他组织学类型的EOC不同，包括常与子宫内膜异位症相关以及具有高度化疗耐药性，导致预后不良。然而，其恶性行为的潜在因素仍知之甚少。微小RNA的异常表达已被证明参与肿瘤发生，并且微小RNA-21（miR-21）在多种癌症中经常过度表达。本研究的目的是探讨miR-21在与CCC发生相关的17q23-25扩增中的作用。
我们使用比较基因组杂交方法在28例原发性CCC肿瘤中鉴定17q23-25拷贝数畸变。接下来，我们通过实时RT-PCR分析测量了17q23-25扩增的候选靶基因miR-21和PPM1D的表达水平，并将这些数据与拷贝数状态和临床病理特征进行比较。此外，使用相同的原发性CCC病例对PTEN（miR-21的潜在靶标）进行免疫组织化学分析。我们使用功能丧失反义方法研究了miR-21在CCC中过表达的生物学意义。
在4/28例CCC病例（14.2%）中检测到17q23-25扩增，同时伴有miR-21过表达和PTEN蛋白缺失。17q23-25扩增的患者无进展生存期和总生存期明显短于无17q23-25扩增的患者（对数秩检验：分别为p = 0.0496；p = 0.0469）。观察到miR-21过表达与子宫内膜异位症之间存在显著相关性。在CCC细胞中，miR-21敲低可增加PTEN mRNA和PTEN蛋白表达。我们还使用双荧光素酶报告基因检测证实miR-21直接与PTEN mRNA的3'非翻译区结合。
MiR-21是CCC中17q23-25扩增除PPM1D之外的一个可能的驱动基因。染色体扩增导致的miR-21异常表达可能通过调节PTEN肿瘤抑制基因在CCC致癌过程中起重要作用。
