PKB/AKT and ERK regulation of caspase-mediated apoptosis by methylseleninic acid in LNCaP prostate cancer cells
PKB/AKT and ERK regulation of caspase-mediated apoptosis by methylseleninic acid in LNCaP prostate cancer cells
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DOI：
10.1093/carcin/bgi094
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发表时间：
2005-08-01
期刊：
影响因子：
4.7
通讯作者：
Lü, JX
中科院分区：
文献类型：
--
作者：
Hu, HB;Jiang, C;Lü, JX
甲基硒醇被认为是硒的抗癌作用的活性代谢产物，部分是通过诱导癌细胞凋亡来实现的。由于AKT/蛋白激酶B负调控基因PTEN(10号染色体上缺失的磷酸酶和张力蛋白同源物)失活在前列腺癌(Pca)中很常见，我们比较了PTEN野生型DU145细胞(低基础AKT活性)和PTEN突变体LNCaP PCa细胞(高基础AKT活性)对甲基硒前体甲基亚硒酸(MSEA)和无机盐亚硒酸钠的凋亡反应。我们的结果表明，LNCaP细胞耐受的MSEA剂量比DU145细胞高4倍，尽管它们对亚硒酸钠诱导的细胞凋亡略有敏感。MSEA可轻度抑制LNCaP细胞AKT的磷酸化，增加ERK1/2的磷酸化水平。亚硒处理增加了P53、Ser15和两种蛋白激酶的磷酸化，但亚硒酸钠诱导的细胞凋亡不受这两种蛋白的化学抑制剂的影响。相反，PI3K/AKT抑制剂使LNCaP细胞对MSEA诱导的细胞凋亡增敏，并伴有细胞色素c线粒体释放增加和多个caspase激活，而不改变P53 Ser15的磷酸化。细胞外信号调节激酶1和2(ERK1/2)的抑制进一步加剧了细胞的凋亡，但没有进一步增加细胞色素c的释放。Caspase抑制剂z-VAD-fmk可完全阻断MSEA诱导的细胞凋亡，但caspase-8抑制剂的保护作用强于caspase-9抑制剂。将活性AKT基因导入DU145细胞，可增强其对MSEA诱导的细胞凋亡的抵抗力。综上所述，AKT在调节LNCaP和DU145细胞对MSEA的凋亡敏感性中起重要作用。MSEA诱导的LNCaP细胞ERK1/2的激活也有助于抵抗细胞凋亡。然而，这些酶并不能显著地调节Caspase介导的亚硒酸盐诱导的LNCaP细胞的凋亡。这些发现支持这些蛋白激酶通路在调节不同形式的硒诱导的细胞凋亡中的不同参与。
Methylselenol has been implicated as an active metabolite for the anticancer effect of selenium in part through the induction of cancer cell apoptosis. Since inactivation of the AKT/protein kinase B negative regulator gene PTEN (phosphatase and tensin homologue deleted on chromosome 10) is common in prostate cancer (PCa), we compared PTEN wild-type DU145 PCa cells (low basal AKT activity) with PTEN-mutant LNCaP PCa cells (high basal AKT activity) for their apoptosis responses to the methylselenol precursor methylseleninic acid (MSeA) and sodium selenite, an inorganic salt. Our results show that LNCaP cells withstood similar to 4 times higher doses of MSeA than DU145 cells, although they were slightly more sensitive than the latter to selenite-induced apoptosis. Treatment by MSeA modestly attenuated AKT phosphorylation and increased phospho-ERK1/2 in LNCaP cells. Selenite treatment increased the phosphorylation of p53 Ser15 and both kinases, but the selenite-induced apoptosis was not influenced by chemical inhibitors of either kinase. In contrast, PI3K/AKT inhibitors greatly sensitized LNCaP cells to apoptosis induced by MSeA, accompanied by increased mitochondrial release of cytochrome c and multiple caspase activation without changing p53 Ser15 phosphorylation. The apoptosis was further accentuated by extracellular signal regulated kinases 1 and 2 (ERK1/2) inhibition without further increase in cytochrome c release. The general caspase inhibitor z-VAD-fmk completely blocked MSeA-induced apoptosis when both kinases were inhibited, whereas a caspase-8 inhibitor exerted a greater protection than did a caspase-9 inhibitor. Transfection of DU145 cells with a constitutively active AKT increased their resistance to MSeA-induced apoptosis. In summary, AKT played an important role in regulating apoptosis sensitivity of LNCaP and DU145 cells to MSeA. An MSeA-induced activation of ERK1/2 in LNCaP cells also contributed to resistance to apoptosis. However, these kinases did not significantly regulate caspase-mediated apoptosis induced by selenite in LNCaP cells. These findings support the differential involvement of these protein kinase pathways in regulating apoptosis induction by different forms of selenium.