Involvement of sphingosine kinase 2 in p53-independent induction of p21 by the chemotherapeutic drug doxorubicin
Involvement of sphingosine kinase 2 in p53-independent induction of p21 by the chemotherapeutic drug doxorubicin
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DOI：
10.1158/0008-5472.can-07-2090
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发表时间：
2007-11-01
期刊：
影响因子：
11.2
通讯作者：
Spiegel, Sarah
中科院分区：
文献类型：
--
作者：
Sankala, Heidi M.;Hait, Nitai C.;Spiegel, Sarah
1 - 磷酸鞘氨醇是一种强效的脂质介质，由鞘氨醇（鞘脂的一种代谢产物）经两种鞘氨醇激酶（SphK）同工酶SphK1和SphK2催化磷酸化而形成。在MCF7人乳腺癌细胞的细胞核中富集的SphK2的表达可增加细胞周期蛋白依赖性激酶抑制剂p21的表达，但对p53及其磷酸化无影响。已知抗癌药物阿霉素通过p53依赖性和p53非依赖性机制增加p21。用针对独特mRNA序列的小干扰RNA下调内源性SphK2，可降低p21的基础表达以及阿霉素诱导的p21表达，而不影响p53表达的增加。SphK2的下调还可减少G₂ - M期阻滞，并显著增强阿霉素诱导的细胞凋亡。此外，在p53失活的MCF7细胞中，siSphK2可降低阿霉素诱导的p21表达。同样，在表达人野生型p53和p21的HCT116结肠癌细胞以及p53缺失的对应细胞中，SphK2的下调显著降低了阿霉素对p21的诱导。敲低SphK2使HCT116细胞对阿霉素诱导的细胞凋亡敏感，同时伴有多聚（ADP - 核糖）聚合酶的裂解。总之，我们的结果表明，内源性SphK2对于阿霉素以p53非依赖性方式诱导p21表达很重要，并提示SphK2可能影响人类癌细胞的细胞生长抑制和细胞凋亡之间的平衡。
Sphingosine-1-phosphate is a potent lipid mediator formed by phosphorylation of sphingosine, a metabolite of sphingolipids, catalyzed by two sphingosine kinase (SphK) isoenzymes, SphK1 and SphK2. Expression of SphK2, which is enriched in the nucleus of MCF7 human breast cancer cells, increased expression of the cyclin-dependent kinase inhibitor p21 but had no effect on p53 or its phosphorylation. The anticancer drug doxorubicin is known to increase p21 via p53-dependent and p53-independent mechanisms. Down-regulation of endogenous SphK2 with small interfering RNA targeted to unique mRNA sequences decreased basal and doxorubicin-induced expression of p21 without affecting increased expression of p53. Down-regulation of SphK2 also decreased G(2)-M arrest and markedly enhanced apoptosis induced by doxorubicin. Moreover, siSphK2 reduced doxorubicin-induced p21 expression in p53-inactivated MCF7 cells. Likewise, in human wildtype p53- and p21-expressing HCT116 colon carcinoma cells, as well as in p53-null counterparts, down-regulation of SphK2 markedly reduced p21 induction by doxorubicin. Knockdown of SphK2 sensitized HCT116 cells to apoptosis induced by doxorubicin with concomitant cleavage of poly(ADP-ribose) polymerase. Collectively, our results show that endogenous SphK2 is important for p53-independent induction of p21 expression by doxorubicin and suggest that SphK2 may influence the balance between cytostasis and apoptosis of human cancer cells.