Objective Despite the recent advances in treatment of colon cancer, the prognosis is unfavourable for patients with distant metastases. The aim of this study was to identify targets for prevention and/or therapy of colon cancer metastasis. Design CMT93 cells, a murine rectal cancer cell line with poor metastasising activity, were transduced with lentiviral shRNA library and transplanted into the rectum of syngeneic C57BL/6 mice. Genomic DNA was collected from metastatic lesions, and the integrated shRNA were retrieved by PCR for sequencing, followed by identification of the candidate genes targeted by the shRNA. Results The genome-wide shRNA library screen identified Hnrnpll (heterogeneous nuclear ribonucleoprotein L-like) encoding a pre-mRNA splicing factor as a candidate metastasis suppressor gene. Knockdown of Hnrnpll enhanced matrigel invasion activity of colon cancer cells in vitro, as well as their metastatic ability in vivo. An RNA-immunoprecipitation analysis showed Hnrnpll-binding to Cd44 pre-mRNAs, and the level of Cd44 variable exon 6 (Cd44v6), a poor prognosis marker of colorectal cancer, was increased by knocking down Hnrnpll. A neutralising Cd44v6 antibody suppressed the matrigel invasion ability induced by Hnrnpll knockdown. HNRNPLL expression was downregulated when colon cancer cells were induced to undergo epithelial-mesenchymal transition (EMT). Immunohistochemistry of clinical samples indicated that colorectal cancer cells with low E-cadherin expression at the invasion front exhibited decreased HNRNPLL expression. Conclusions HNRNPLL is a novel metastasis suppressor of colorectal cancer, and modulates alternative splicing of CD44 during EMT.

中文翻译：

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HNRNPLL，一种新发现的结直肠癌转移抑制因子，在上皮间质转化过程中调节 CD44 的选择性剪接

目的尽管最近结肠癌的治疗取得了进展，但远处转移患者的预后不佳。本研究的目的是确定预防和/或治疗结肠癌转移的靶点。设计 CMT93 细胞是一种转移活性较差的鼠直肠癌细胞系，用慢病毒 shRNA 文库转导并移植到同源 C57BL/6 小鼠的直肠中。从转移病灶中收集基因组 DNA，通过 PCR 检索整合的 shRNA 进行测序，然后鉴定 shRNA 靶向的候选基因。结果全基因组shRNA文库筛选鉴定了编码前mRNA剪接因子的Hnrnpll（异质核核糖核蛋白L样）作为候选转移抑制基因。Hnrnpll 的敲低增强了体外结肠癌细胞的基质胶侵袭活性，以及​​它们的体内转移能力。RNA 免疫沉淀分析显示 Hnrnpll 与 Cd44 前体 mRNA 结合，并且 Cd44 可变外显子 6（Cd44v6）（结直肠癌预后不良的标志物）的水平通过敲低 Hnrnpll 增加。中和 Cd44v6 抗体抑制了由 Hnrnpll 敲低诱导的基质胶侵袭能力。当结肠癌细胞被诱导进行上皮间质转化 (EMT) 时，HNRNPLL 的表达被下调。临床样本的免疫组织化学表明，在侵袭前沿具有低 E-钙粘蛋白表达的结直肠癌细胞表现出降低的 HNRNPLL 表达。结论 HNRNPLL 是一种新型的结直肠癌转移抑制因子，