Chandele Anmol, Prasad Vandna, Jagtap Jayashree C, Shukla Ravi, Shastry Padma R
National Centre for Cell Science, NCCS Complex, Ganeshkhind, Pune 411 007, India.
Neoplasia. 2004 Jan-Feb;6(1):29-40. doi: 10.1016/s1476-5586(04)80051-4.
Survivin, a member of the inhibitor of apoptosis (IAP) gene family, plays an important role in both the regulation of cell cycle and the inhibition of apoptosis, and is frequently overexpressed in many tumor types. In neuroblastomas, the expression of survivin correlates with a more aggressive and histologically unfavorable disease. Survivin is predominantly a cytoplasmic protein that is expressed in a cell cycle-dependent manner, increasing in the G2/M phase of the cell cycle followed by a rapid decline in the G1 phase. Recently, the role of survivin in resistance to chemotherapy has become an area of intensive investigation. In this study, we demonstrate a phase-specific resistance due to survivin in staurosporine (STS)-induced apoptosis in the human neuroblastoma cell line SK-N-MC. G2/M-arrested cultures show an upregulation of survivin expression and are more resistant, whereas G1-phase cells that show decreased levels of survivin are more sensitive to apoptosis. Localization studies revealed differences in the distribution of survivin in two synchronized populations, with G1 cells having weakly positive staining confined to the nucleus, in contrast to G2/M cells that depicted a more uniform and intense expression of survivin throughout the cell. In our experimental system, STS induced apoptosis through the mitochondrial-caspase 9-mediated pathway. Retention of survivin in G1 cells by inhibition of the ubiquitin-proteosome pathway or inhibition of caspase 9 protected the cells against apoptosis. Our data suggest that survivin exerts its antiapoptotic effect by inhibiting caspase 9 activity, an important event in STS-mediated apoptosis. In context with cell cycle-dependent responses to chemotherapy, the data from this study suggest the possibility of exploiting the survivin pathway for inducing apoptosis in tumor cells.
生存素是凋亡抑制蛋白（IAP）基因家族的成员之一，在细胞周期调控和凋亡抑制中均发挥重要作用，且在多种肿瘤类型中常过度表达。在神经母细胞瘤中，生存素的表达与更具侵袭性及组织学上预后不良的疾病相关。生存素主要是一种细胞质蛋白，以细胞周期依赖性方式表达，在细胞周期的G2/M期增加，随后在G1期迅速下降。最近，生存素在化疗耐药中的作用已成为深入研究的领域。在本研究中，我们证明了在人神经母细胞瘤细胞系SK-N-MC中，生存素导致了对星形孢菌素（STS）诱导凋亡的阶段特异性耐药。处于G2/M期阻滞的培养物显示生存素表达上调且更具耐药性，而生存素水平降低的G1期细胞对凋亡更敏感。定位研究揭示了生存素在两个同步群体中的分布差异，G1期细胞的阳性染色较弱且局限于细胞核，而G2/M期细胞则在整个细胞中呈现更均匀且强烈的生存素表达。在我们的实验系统中，STS通过线粒体-半胱天冬酶9介导的途径诱导凋亡。通过抑制泛素-蛋白酶体途径或抑制半胱天冬酶9使生存素保留在G1期细胞中可保护细胞免受凋亡。我们的数据表明，生存素通过抑制半胱天冬酶9的活性发挥其抗凋亡作用，这是STS介导凋亡中的一个重要事件。结合细胞周期对化疗的依赖性反应，本研究的数据表明利用生存素途径诱导肿瘤细胞凋亡的可能性。
