Istanbul Kultur University, Faculty of Science and Letters, Department of Molecular Biology and Genetics, Istanbul, Turkey.
Curr Pharm Des. 2014;20(2):180-8. doi: 10.2174/13816128113199990029.
Androgen signaling is critical in prostate cancer development and progression. The co-existence of hormone responsive and irresponsive cells due to functional androgen receptor (AR) in prostate gland is the major obstacle in prostate cancer therapy models. Targeting aberrant cell cycle by novel cell cycle blocking agents is a promising strategy to treat various types of malignancies. Purvalanol and roscovitine are cyclin dependent kinase (CDK) inhibitors able to activate apoptotic cell death by inducing cell cycle arrest at G1/S and G2/M phases in cancer cells. Polyamines are unique cationic amine derivatives involved in the regulation of cell proliferation. Although the elevated intracellular level of polyamines (putrescine, spermidine and spermine) is typical for prostate gland, abnormal regulation of polyamine metabolism might result in rapid cell proliferation and, thus in prostate cancer progression. Therefore, treatment with drug-induced depletion of intracellular polyamine levels through the activated polyamine catabolism is critical to achieve successful strategies for prostate cancer. In this study we aimed to investigate the apoptotic efficiency of CDK inhibitors in three prostate cancer cell lines (LNCaP, DU145 and PC3), showing different AR expression profile. We found that both purvalanol and roscovitine were able to induce apoptosis at moderate cytotoxic concentrations by decreasing mitochondria membrane potential. The apoptotic effect of both CDK inhibitors was due to activation of caspases by modulating Bcl-2 family members. The efficiency of drugs was quite similar on the three prostate cell lines used in this study. However, DU145 cells were found the least sensitive against CDK inhibitors while purvalanol was more potent than roscovitine. Similarly to classical chemotherapeutic agents, both drugs could up-regulate polyamine catabolic enzymes (SSAT, SMO and PAO) in cell type dependent manner. Transient silencing of SSAT and/or inhibition of PAO/ SMO with MDL72527 prevented CDK inhibitors- induced apoptotic cell death in DU145 and PC3 cells. Although roscovitine was less effective in DU145 cells, pre-treatment with α-difluoromethylornithine (DFMO), an inhibitor of ODC, enhanced the roscovitine-induced apoptotic cell death through the cleavage of caspase-9 and caspase-3. Therefore, we conclude that polyamine catabolism might have essential role in the cellular responses against CDK inhibitors in different androgen-responsive or irresponsive prostate cancer cells.
雄激素信号在前列腺癌的发展和进展中至关重要。由于前列腺中功能性雄激素受体 (AR) 的存在，激素反应性和非反应性细胞共存是前列腺癌治疗模型的主要障碍。通过新型细胞周期阻断剂靶向异常细胞周期是治疗各种类型恶性肿瘤的有前途的策略。Purvalanol 和 roscovitine 是细胞周期蛋白依赖性激酶 (CDK) 抑制剂，能够通过诱导癌细胞在 G1/S 和 G2/M 期的细胞周期停滞来激活细胞凋亡。多胺是参与细胞增殖调节的独特阳离子胺衍生物。尽管多胺（腐胺、精脒和精胺）的细胞内水平升高是前列腺的典型特征，但多胺代谢的异常调节可能导致细胞快速增殖，从而导致前列腺癌的进展。因此，通过激活多胺分解代谢使细胞内多胺水平降低的药物治疗对于实现前列腺癌的成功治疗策略至关重要。在这项研究中，我们旨在研究 CDK 抑制剂在三种具有不同 AR 表达谱的前列腺癌细胞系 (LNCaP、DU145 和 PC3) 中的凋亡效率。我们发现，Purvalanol 和 roscovitine 都能够通过降低线粒体膜电位在中等细胞毒性浓度下诱导凋亡。两种 CDK 抑制剂的凋亡作用是通过调节 Bcl-2 家族成员来激活半胱天冬酶引起的。这两种药物在本研究中使用的三种前列腺细胞系上的效率相当相似。然而，DU145 细胞对 CDK 抑制剂的敏感性最低，而 Purvalanol 比 roscovitine 更有效。与经典化疗药物一样，两种药物都能够以细胞类型依赖的方式上调多胺分解代谢酶（SSAT、SMO 和 PAO）。用 MDL72527 瞬时沉默 SSAT 和/或抑制 PAO/ SMO 可防止 DU145 和 PC3 细胞中 CDK 抑制剂诱导的凋亡细胞死亡。尽管 roscovitine 在 DU145 细胞中效果较差，但用 ODC 抑制剂α-二氟甲基鸟氨酸 (DFMO) 预处理增强了 roscovitine 诱导的凋亡细胞死亡，通过裂解 caspase-9 和 caspase-3。因此，我们得出结论，多胺分解代谢可能在不同雄激素反应性或非反应性前列腺癌细胞对 CDK 抑制剂的细胞反应中发挥重要作用。
