Ceramide kinase (CerK) phosphorylates ceramide to ceramide-1-phosphate (C1P), a bioactive sphingolipid. Since the mechanisms responsible for regulating the proliferation and migration/metastasis of cancer cells by the CerK/C1P pathway remain unclear, we conducted the present study. The knockdown of CerK in A549 lung and MCF-7 breast cancer cells (shCerK cells) increased the formation of lamellipodia, which are membrane protrusions coupled with cell migration. Mouse embryonic fibroblasts prepared from CerK-null mice also showed an enhanced formation of lamellipodia. The overexpression of CerK inhibited lamellipodium formation in A549 cells. The knockdown of CerK increased the number of cells having lamellipodia with Rac1 and the levels of active Rac1-GTP form, whereas the overexpression of CerK decreased them. CerK was located in lamellipodia after the epidermal growth factor treatment, indicating that CerK functioned there to inhibit Rac1. The migration of A549 cells was negatively regulated by CerK. An intravenous injection of A549-shCerK cells into nude mice resulted in markedly stronger metastatic responses in the lungs than an injection of control cells. The in vitro growth of A549 cells and in vivo expansion after the injection into mouse flanks were not affected by the CerK knockdown. These results suggest that the activation of CerK/C1P pathway has inhibitory roles on lamellipodium formation, migration, and metastasis of A549 lung cancer cells.

中文翻译：

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神经酰胺激酶对A549肺癌细胞的Rac1活化，层状脂蛋白形成，细胞迁移和转移的抑制作用。

神经酰胺激酶（CerK）将神经酰胺磷酸化为具有生物活性的鞘脂神经酰胺-1-磷酸（C1P）。由于尚不清楚通过CerK / C1P途径调控癌细胞增殖和迁移/转移的机制，我们进行了本研究。在A549肺癌和MCF-7乳腺癌细胞（shCerK细胞）中CerK的敲低增加了lamellipodia的形成，后者是与细胞迁移结合的膜突起。从无CerK小鼠制备的小鼠胚胎成纤维细胞还显示出片状脂膜形成的增强。CerK的过表达抑制了A549细胞中片状脂质体的形成。CerK的敲除增加了带有Rac1的片状脂溢的细胞数量和活性Rac1-GTP形式的水平，而CerK的过表达降低了它们的数量。在表皮生长因子处理后，CerK位于层状脂瘤中，表明CerK在此处起到抑制Rac1的作用。A549细胞的迁移受CerK负调控。向裸鼠静脉注射A549-shCerK细胞比注射对照细胞导致肺部转移反应明显增强。注射到小鼠侧腹后，A549细胞的体外生长和体内扩增不受CerK敲除的影响。这些结果表明，CerK / C1P途径的激活对A549肺癌细胞的层状脂质体形成，迁移和转移具有抑制作用。向裸鼠静脉注射A549-shCerK细胞比注射对照细胞导致肺部转移反应明显增强。注射到小鼠侧腹后，A549细胞的体外生长和体内扩增不受CerK敲除的影响。这些结果表明，CerK / C1P途径的激活对A549肺癌细胞的层状脂质体形成，迁移和转移具有抑制作用。向裸鼠静脉注射A549-shCerK细胞比注射对照细胞导致肺部转移反应明显增强。注射到小鼠侧腹后，A549细胞的体外生长和体内扩增不受CerK敲除的影响。这些结果表明，CerK / C1P途径的激活对A549肺癌细胞的层状脂质体形成，迁移和转移具有抑制作用。