Department of Urology, The First Affiliated Hospital of Dalian Medical University, Dalian, Liaoning 116011, P.R. China.
Int J Oncol. 2018 Nov;53(5):2278-2288. doi: 10.3892/ijo.2018.4539. Epub 2018 Aug 23.
Emerging evidence has indicated that long non‑coding RNA (lncRNA) HOXA transcript at the distal tip (HOTTIP) regulates cell growth, differentiation, apoptosis and cancer progression. However, the expression and function of HOTTIP in the progression of renal cell carcinoma (RCC) remain largely unknown. In this study, we investigated the role of the lncRNA HOTTIP in RCC. The expression levels of HOTTIP in RCC tissues and cell lines were determined by RT‑qPCR. The association between HOTTIP expression and clinicopathological characteristics and prognosis was analyzed in patients with RCC from the TCGA database. Loss‑of‑ function assays were designed and conducted to verify the oncogenic function of HOTTIP in RCC progression. Luciferase assay was performed to explore the mechanisms of the miRNA‑lncRNA sponge. The results revealed that HOTTIP expression was upregulated in RCC. An increased HOTTIP expression in RCC was associated with a larger tumor size and a higher clinical stage, lymph node metastasis and vascular invasion. Additionally, patients RCC with a high HOTTIP expression had a significantly shorter overall survival (OS) and disease‑free survival (DFS). HOTTIP knockdown significantly inhibited cell proliferation, migration and invasion, and increased the apoptosis of RCC cells in vitro. Mechanistic analyses revealed that HOTTIP functioned as a competing endogenous RNA (ceRNA) for hsa‑miR‑615‑3p, and led to the derepression of its endogenous target, insulin‑like growth factor-2 (IGF‑2), which is a protein hormone that exerts a stimulatory effect on tumor cell growth. miR‑615 inhibition reversed the suppressive effects of HOTTIP knockdown on RCC cell progression. HOTTIP regulated IGF‑2 expression in a miR‑615‑dependent manner in RCC cells. In addition, IGF‑2 expression was significantly upregulated in the RCC specimens and a positive association between the expression of HOTTIP and IGF‑2 in RCC tissues was detected. The effect of HOTTIP was abolished by the siRNA‑mediated silencing of IGF-2 in RCC cells. On the whole, this study demonstrates, for the first time, at least to the best of our knowledge, that the HOTTIP/miR‑615/IGF‑2 axis plays an important role in RCC progression and potentially contributes to the improvement of RCC diagnosis and therapy.
越来越多的证据表明，长链非编码 RNA（lncRNA）HOXA 转录远端起始（HOTTIP）调节细胞生长、分化、凋亡和癌症进展。然而，HOTTIP 在肾细胞癌（RCC）进展中的表达和功能仍知之甚少。在本研究中，我们研究了 lncRNA HOTTIP 在 RCC 中的作用。通过 RT-qPCR 测定 RCC 组织和细胞系中 HOTTIP 的表达水平。分析了 TCGA 数据库中 RCC 患者 HOTTIP 表达与临床病理特征和预后的关系。设计并进行了缺失功能测定，以验证 HOTTIP 在 RCC 进展中的致癌作用。进行了荧光素酶测定以探讨 miRNA-lncRNA 海绵的机制。结果显示，HOTTIP 在 RCC 中表达上调。RCC 中 HOTTIP 的增加与更大的肿瘤大小和更高的临床分期、淋巴结转移和血管浸润有关。此外，HOTTIP 高表达的 RCC 患者的总生存（OS）和无病生存（DFS）明显缩短。HOTTIP 敲低显著抑制 RCC 细胞的增殖、迁移和侵袭，并增加体外 RCC 细胞的凋亡。机制分析表明，HOTTIP 作为 hsa-miR-615-3p 的竞争性内源性 RNA（ceRNA）发挥作用，并导致其内源性靶标胰岛素样生长因子-2（IGF-2）的去抑制，IGF-2 是一种对肿瘤细胞生长具有刺激作用的蛋白质激素。miR-615 抑制逆转了 HOTTIP 敲低对 RCC 细胞进展的抑制作用。HOTTIP 在 RCC 细胞中以 miR-615 依赖的方式调节 IGF-2 的表达。此外，在 RCC 标本中 IGF-2 的表达明显上调，并且在 RCC 组织中检测到 HOTTIP 和 IGF-2 的表达之间存在正相关。在 RCC 细胞中，IGF-2 的 siRNA 介导的沉默消除了 HOTTIP 的作用。总的来说，这项研究首次表明，至少在我们所知的范围内，HOTTIP/miR-615/IGF-2 轴在 RCC 进展中发挥重要作用，并可能有助于改善 RCC 的诊断和治疗。
