Chen Biao, Xu Ximing, Lin Dan-Dan, Chen Xin, Xu Yang-Tao, Liu Xin, Dong Wei-Guo
Cancer Center, Renmin Hospital of Wuhan University, Wuhan, China.
Department of Gastroenterology, Renmin Hospital of Wuhan University, Wuhan, China.
Front Genet. 2021 Jul 5;12:635429. doi: 10.3389/fgene.2021.635429. eCollection 2021.
Keratin 18 (KRT18), one of the most abundant keratins in epithelial and endothelial cells, has been reported to be aberrantly expressed in many malignancies and extensively regarded as a biomarker and important regulator in multiple cancers, including gastric cancer (GC). But the molecular regulatory mechanisms of KRT18 in GC patients and cells are largely unknown. In the present study, we analyzed the expression level of KRT18 in 450 stomach adenocarcinoma tissue samples from TCGA database and found a significantly higher expression level in tumor tissues. We then explored the potential functions of KRT18 in AGS cells (human gastric adenocarcinoma cell line) by KRT18 knockdown using siRNA and whole transcriptome RNA-seq analysis. Notably, KRT18 selectively regulates expression of cell proliferation and apoptotic genes. Beyond this, KRT18 affects the alternative splicing of genes enriched in apoptosis, cell cycle, and other cancer-related pathways, which were then validated by reverse transcription-quantitative polymerase chain reaction approach. We validated KRT18-KD promoted apoptosis and inhibited proliferation in AGS cells. We then used RNA-seq data of GC samples to further demonstrate the modulation of KRT18 on alternative splicing regulation. These results together support the conclusion that KRT18 extensively modulates diverse alternative splicing events of genes enriched in proliferation and apoptosis processes. And the dysregulated splicing factors at transcriptional or posttranscriptional level by KRT18 may contribute to the alternative splicing change of many genes, which expands the functional importance of keratins in apoptotic and cell cycle pathways at the posttranscriptional level in GC.
角蛋白18（KRT18）是上皮细胞和内皮细胞中含量最丰富的角蛋白之一，据报道在许多恶性肿瘤中异常表达，并被广泛视为多种癌症（包括胃癌（GC））的生物标志物和重要调节因子。但KRT18在GC患者和细胞中的分子调控机制在很大程度上尚不清楚。在本研究中，我们分析了来自TCGA数据库的450份胃腺癌组织样本中KRT18的表达水平，发现肿瘤组织中的表达水平显著更高。然后，我们通过使用siRNA敲低KRT18和全转录组RNA测序分析，探索了KRT18在AGS细胞（人胃腺癌细胞系）中的潜在功能。值得注意的是，KRT18选择性调节细胞增殖和凋亡基因的表达。除此之外，KRT18影响富含凋亡、细胞周期和其他癌症相关途径的基因的可变剪接，随后通过逆转录定量聚合酶链反应方法进行了验证。我们验证了KRT18敲低促进了AGS细胞的凋亡并抑制了其增殖。然后，我们使用GC样本的RNA测序数据进一步证明了KRT18对可变剪接调控的调节作用。这些结果共同支持了这样的结论，即KRT18广泛调节富含增殖和凋亡过程的基因的多种可变剪接事件。并且KRT18在转录或转录后水平失调的剪接因子可能导致许多基因的可变剪接变化，这在转录后水平扩展了角蛋白在GC凋亡和细胞周期途径中的功能重要性。
