Colon cancer is among the leading causes of cancer death in North America. CD44, an adhesion and antiapoptotic molecule is overexpressed in colon cancer. Cofilin is involved in the directional motility of cells. In the present study, we looked at how CD44 might modulate cell migration in human colon cancer via cofilin. We used a human colon cancer cell line, HT29, which expresses CD44, HT29 where CD44 expression was knocked down by siRNA, SW620, a human colon cancer cell line which does not express CD44, stably transfected exons of CD44 in SW620 cells and the colon from CD44 knockout and wild-type mouse. Western blot analysis of siRNA CD44 lysates showed increased level of AKT phosphorylation and decreased level of cofilin expression. Similar results were also observed with SW620 cells and CD44 knockout mouse colon lysates. Experiments using the AKT phosphorylation inhibitor LY294002 indicate that AKT phosphorylation downregulates cofilin. Immunoprecipitation studies showed CD44 complex formation with Lyn, providing an essential link between CD44 and AKT phosphorylation. LY294002 also stabilized Lyn from phosphorylated AKT, suggesting an interaction between Lyn and AKT phosphorylation. Immunocytochemistry showed that cofilin and Lyn expression were downregulated in siRNA CD44 cells and CD44 knockout mouse colon. siRNA CD44 cells had significantly less migration compared to HT29 vector. Given the well-defined roles of CD44, phosphorylated AKT in apoptosis and cancer, these results indicate that CD44-induced cell migration is dependent on its complex formation with Lyn and its consequent regulation of AKT phosphorylation and cofilin expression.

译文

结肠癌是北美癌症死亡的主要原因之一。CD44是一种粘附和抗凋亡分子,在结肠癌中过度表达。Cofilin参与细胞的定向运动。在本研究中,我们研究了CD44如何通过cofilin调节人结肠癌中的细胞迁移。我们使用了表达CD44,HT29的人结肠癌细胞系HT29,其中CD44表达被不表达CD44的人结肠癌细胞系siRNA SW620下调,SW620细胞和结肠中CD44的稳定转染外显子来自CD44基因敲除和野生型小鼠。siRNA CD44裂解物的Western印迹分析显示AKT磷酸化水平升高,cofilin表达水平降低。SW620细胞和CD44敲除小鼠结肠裂解物也观察到类似的结果。使用AKT磷酸化抑制剂LY294002的实验表明,AKT磷酸化下调了cofilin。免疫沉淀研究表明,与Lyn形成CD44复合物,在CD44和AKT磷酸化之间提供了重要的联系。LY294002还使Lyn从磷酸化的AKT中稳定下来,表明Lyn和AKT磷酸化之间存在相互作用。免疫细胞化学显示cofilin和Lyn在siRNA CD44细胞和CD44基因敲除小鼠结肠中的表达下调。与HT29载体相比,siRNA CD44细胞的迁移明显减少。鉴于CD44,磷酸化的AKT在细胞凋亡和癌症中的明确定义的作用,这些结果表明CD44-induced细胞迁移取决于其与Lyn的复合物形成及其对AKT磷酸化和cofilin表达的调节。

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