Guangdong and Shenzhen Key Laboratory of Male Reproductive Medicine and Genetics, Institute of Urology, Peking University Shenzhen Hospital, Shenzhen-Peking University-the Hong Kong University of Science and Technology Medical Center, Shenzhen, 518000, China.
Anhui Medical University, Hefei, 230000, Anhui Province, China.
Mol Cancer. 2020 Jun 5;19(1):103. doi: 10.1186/s12943-020-01225-2.
Circular RNAs (circRNAs), a novel type of noncoding RNA (ncRNA), are covalently linked circular configurations that form via a loop structure. Accumulating evidence indicates that circRNAs are potential biomarkers and key regulators of tumor development and progression. However, the precise roles of circRNAs in renal cell carcinoma (RCC) remain unknown.
Through circRNA high-throughput sequencing of RCC cell lines, we identified the circRNA TLK1 (circTLK1) as a novel candidate circRNA derived from the TLK1 gene. qRT-PCR detected the mRNA, circRNA and miRNA expression levels in RCC tissues and cells. Loss-of function experiments were executed to detect the biological roles of circTLK1 in the RCC cell phenotypes in vitro and in vivo. RNA-FISH, RNA pull-down, dual-luciferase reporter, western blot and immunohistochemistry assays were used to investigate the molecular mechanisms underlying the functions of circTLK1.
circTLK1 is overexpressed in RCC, and expression is positively correlated with distant metastasis and unfavorable prognosis. Silencing circTLK1 significantly inhibited RCC cell proliferation, migration and invasion in vitro and in vivo. circTLK1 was mainly distributed in the cytoplasm and positively regulated CBX4 expression by sponging miR-136-5p. Forced CBX4 expression reversed the circTLK1 suppression-induced phenotypic inhibition of RCC cells. Moreover, CBX4 expression was positively correlated with VEGFA expression in RCC tissues. CBX4 knockdown significantly inhibited VEGFA expression in RCC cells.
Collectively, our findings demonstrate that circTLK1 plays a critical role in RCC progression by sponging miR-136-5p to increase CBX4 expression. circTLK1 may act as a diagnostic biomarker and therapeutic target for RCC.
环状 RNA（circRNAs）是一种新型的非编码 RNA（ncRNA），通过环结构形成共价连接的环状构型。越来越多的证据表明，circRNAs 是肿瘤发生和发展的潜在生物标志物和关键调节因子。然而，circRNAs 在肾细胞癌（RCC）中的确切作用尚不清楚。
通过 RCC 细胞系的 circRNA 高通量测序，我们鉴定出 TLK1 基因衍生的新型候选环状 RNA TLK1（circTLK1）。qRT-PCR 检测了 RCC 组织和细胞中的 mRNA、circRNA 和 miRNA 表达水平。进行功能丧失实验以检测 circTLK1 在体外和体内 RCC 细胞表型中的生物学作用。RNA-FISH、RNA 下拉、双荧光素酶报告、western blot 和免疫组织化学检测用于研究 circTLK1 功能的分子机制。
circTLK1 在 RCC 中过表达，表达水平与远处转移和不良预后呈正相关。沉默 circTLK1 显著抑制 RCC 细胞在体外和体内的增殖、迁移和侵袭。circTLK1 主要分布在细胞质中，通过海绵吸附 miR-136-5p 正向调节 CBX4 表达。强制表达 CBX4 逆转了 circTLK1 抑制诱导的 RCC 细胞表型抑制。此外，CBX4 表达与 RCC 组织中的 VEGFA 表达呈正相关。CBX4 敲低显著抑制 RCC 细胞中 VEGFA 的表达。
总之，我们的研究结果表明，circTLK1 通过海绵吸附 miR-136-5p 增加 CBX4 表达，在 RCC 进展中发挥关键作用。circTLK1 可作为 RCC 的诊断生物标志物和治疗靶点。
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