Table_2_Downregulation of DUSP9 Promotes Tumor Progression and Contributes to Poor Prognosis in Human Colorectal Cancer.DOCX

BackgroundDual-specificity phosphatase 9 (DUSP9) belongs to the dual-specificity protein phosphatase subfamily. Recently, increasing attention has been paid on the role of DUSP9 in a variety of cancers. However, its functional role in tumor development is still unclear, especially in colorectal cancer (CRC).
MethodsThe functional role of DUSP9 in inhibiting the progression of CRC was verified using colony formation assay, wound healing assay, nude mice xenograft model, etc. RNA-seq was performed to assess the gene expression profiling in SW480 cells with DUSP9 stable knockdown and shControl cells. Bisulfite sequencing (BSE) was performed to reveal the methylation status of CpG island in the promoter of DUSP9.
ResultsDUSP9 was significantly downregulated in tumor tissues compared with peritumor tissues. Mechanistically, the high methylation status of CpG island in the promoter of DUSP9 may lead to the downregulation of DUSP9 in CRC. Clinically, low DUSP9 expression in CRC was closely associated with depth of invasion, metastasis (TNM) stage, and poor survival, indicating that DUSP9 may be involved in the progression of CRC. Functional study revealed that DUSP9 inhibited proliferation, migration, invasion, and epithelial–mesenchymal transition of CRC cells both in vitro and in vivo. Transcriptome profiling studies revealed that Erk signaling was involved in the tumor progression mediated by DUSP9 silencing, which is confirmed by cell experiments and clinical tissue sample staining analysis.
ConclusionOur findings demonstrate that DUSP9 plays a critical role in the progression of CRC, and therapeutic intervention to increase the expression or activity of DUSP9 may be a potential target for CRC treatment in the future.

【背景】双特异性磷酸酶9（dual-specificity phosphatase 9, DUSP9）隶属于双特异性蛋白磷酸酶亚家族。近年来，DUSP9在多种癌症中的作用愈发受到关注。然而，其在肿瘤发生发展中的功能角色仍不明确，在结直肠癌（colorectal cancer, CRC）中更是如此。
【方法】本研究通过克隆形成实验、划痕实验、裸鼠异种移植模型等手段，验证了DUSP9抑制结直肠癌进展的功能作用。对稳定敲低DUSP9的SW480细胞及对照小发夹RNA（shControl）细胞进行RNA测序（RNA-seq），以分析其基因表达谱；采用亚硫酸氢盐测序（bisulfite sequencing, BSE），以揭示DUSP9启动子区域CpG岛的甲基化状态。
【结果】与癌旁组织相比，DUSP9在结直肠癌肿瘤组织中显著低表达。机制层面，DUSP9启动子区域CpG岛的高甲基化状态，可能是结直肠癌中DUSP9表达下调的原因。临床数据分析显示，结直肠癌组织中DUSP9低表达与肿瘤浸润深度、转移（TNM）分期及不良预后密切相关，提示DUSP9可能参与了结直肠癌的进展过程。功能实验证实，DUSP9可在体内外抑制结直肠癌细胞的增殖、迁移、侵袭及上皮间质转化（epithelial–mesenchymal transition）。转录组分析显示，ERK信号通路参与了DUSP9沉默介导的肿瘤进展过程，该结论得到了细胞实验及临床组织样本染色分析的验证。
【结论】本研究结果证实，DUSP9在结直肠癌进展中发挥关键作用；通过治疗手段提升DUSP9的表达或活性，有望成为未来结直肠癌治疗的潜在靶点。