CCL2 Protects Prostate Cancer PC3 Cells from Autophagic Death via Phosphatidylinositol 3-Kinase/AKT-dependent Survivin Up-regulation
CCL2 Protects Prostate Cancer PC3 Cells from Autophagic Death via Phosphatidylinositol 3-Kinase/AKT-dependent Survivin Up-regulation
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DOI：
10.1074/jbc.m801073200
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发表时间：
2008-09-05
影响因子：
4.8
通讯作者：
Pienta, Kenneth J.
中科院分区：
文献类型：
--
作者：
Roca, Hernan;Varsos, Zachary;Pienta, Kenneth J.
抵抗细胞死亡是癌症的一个标志。自噬是一种因营养缺乏而激活的生存机制；然而，过度的自噬最终会以非凋亡的方式诱导细胞死亡。目前的研究表明，CCL2可以保护前列腺癌PC3细胞免于自噬死亡，从而延长无血清条件下的存活时间。血清饥饿后，CCL2诱导PC3、DU 145和C4-2B前列腺癌细胞的survivin上调。当使用磷脂酰肌醇3-激酶抑制剂LY294002 （2 μ M）或akt特异性抑制剂- x （Akti-X; 2.5 μ M）处理ccl2刺激的PC3细胞时，细胞存活和survivin表达均受到抑制。此外，CCL2显著降低血清饥饿PC3的轻链3-II (LC3-II)；相比之下，LY294002或Akti-X治疗逆转了CCL2对LC3-II水平的影响，表明CCL2信号通路限制了这些细胞的自噬。在血清剥夺后，免疫荧光分析LC3定位显示CCL2刺激后LC3点明显减少。通过磷酸化p70s6激酶（Thr(389)）的增加，CCL2治疗也导致更高的持续mTORC1活性。雷帕霉素是一种自噬诱导剂，在血清缺失的情况下，它既能下调survivin，又能降低PC3细胞的活力。然而，用CCL2治疗允许细胞部分抵抗雷帕霉素诱导的死亡，这与survivin蛋白水平相关。在两种稳定的表达由PC3产生的survivin特异性短发夹RNA的转染物中，survivin蛋白水平在CCL2处理下控制细胞活力和LC3定位。综上所述，这些研究结果表明，CCL2通过磷脂酰肌醇3-激酶/Akt/survivin通路保护前列腺癌PC3细胞免于自噬死亡，并揭示了survivin在这一生存机制中的重要作用。
Resistance to cell death is a hallmark of cancer. Autophagy is a survival mechanism activated in response to nutrient deprivation; however, excessive autophagy will ultimately induce cell death in a nonapoptotic manner. The present study demonstrates that CCL2 protects prostate cancer PC3 cells from autophagic death, allowing prolonged survival in serum-free conditions. Upon serum starvation, CCL2 induced survivin up-regulation in PC3, DU 145, and C4-2B prostate cancer cells. Both cell survival and survivin expression were stunted in CCL2-stimulated PC3 cells when treated either with the phosphatidylinositol 3-kinase inhibitor LY294002 (2 mu M) or the Akt-specific inhibitor-X (Akti-X; 2.5 mu M). Furthermore, CCL2 significantly reduced light chain 3-II (LC3-II) in serum-starved PC3; in contrast, treatment with LY294002 or Akti-X reversed the effect of CCL2 on LC3-II levels, suggesting that CCL2 signaling limits autophagy in these cells. Upon serum deprivation, the analysis of LC3 localization by immunofluorescence revealed a remarkable reduction in LC3 punctate after CCL2 stimulation. CCL2 treatment also resulted in a higher sustained mTORC1 activity as measured by an increase in phospho-p70S6 kinase (Thr(389)). Rapamycin, an inducer of autophagy, both down-regulated survivin and decreased PC3 cell viability in serum-deprived conditions. Treatment with CCL2, however, allowed cells to partially resist rapamycin-induced death, which correlated with survivin protein levels. In two stable transfectants expressing survivin-specific short hairpin RNA, generated from PC3, survivin protein levels controlled both cell viability and LC3 localization in response to CCL2 treatment. Altogether, these findings indicate that CCL2 protects prostate cancer PC3 cells from autophagic death via the phosphatidylinositol 3-kinase/Akt/survivin pathway and reveal survivin as a critical molecule in this survival mechanism.