Potent cytotoxicity of the phosphatase inhibitor microcystin LR and microcystin analogues in OATP1B1- and OATP1B3-expressing HeLa cells
Potent cytotoxicity of the phosphatase inhibitor microcystin LR and microcystin analogues in OATP1B1- and OATP1B3-expressing HeLa cells
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DOI：
10.1158/1535-7163.mct-06-0500
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发表时间：
2007-02-01
影响因子：
5.7
通讯作者：
Moscow, Jeffrey A.
中科院分区：
文献类型：
--
作者：
Monks, Noel R.;Liu, Shuqian;Moscow, Jeffrey A.
微囊藻毒素是一类环状多肽，是蛋白磷酸酶家族PP1和PP2A的有效抑制剂。只有三种人类蛋白被认为能够介导肝脏摄取微囊藻毒素(有机阴离子转运多肽OATP1B1、OATP1B3和OATP1A2)，这些转运蛋白的主要肝脏表达解释了微囊藻毒素的肝脏特异性毒性。微囊藻毒素作为抗癌药物研究的一个重要障碍是需要特定的转运蛋白来进行细胞摄取。我们报道，与正常对照组织相比，OATP1B3在非小细胞肺癌肿瘤组织中表达上调。这一发现促使人们探索将微囊藻毒素作为潜在的抗癌药物。我们建立了一个具有OATP1B1和OATP1B3活性的HeLa细胞模型。瞬时转基因的HeLa细胞对微囊藻毒素LR的敏感性是载体转染对照细胞的1000多倍，表明转运蛋白的表达对微囊藻毒素的细胞毒性具有显著的选择性。此外，微囊藻毒素类似物在OATP1B1和OATP1B3转基因细胞中表现出不同的细胞毒性，包括两个IC50值为1nmol/L的类似物。微囊藻毒素类似物的细胞毒性似乎与抑制这些细胞中的PP2A有关，并通过染色质凝聚和细胞碎裂来诱导细胞迅速死亡。这些研究表明，当微囊藻毒素化合物能够进入细胞内时，微囊藻毒素诱导的磷酸酶抑制会导致强大的细胞毒性，是一类表达这些摄取蛋白的新型肿瘤治疗剂。
Microcystins are a family of cyclic peptides that are potent inhibitors of the protein phosphatase families PP1 and PP2A. Only three human proteins are thought to be able to mediate the hepatic uptake of microcystins (the organic anion-transporting polypeptides OATP1B1, OATP1B3, and OATP1A2), and the predominant hepatic expression of these transporters accounts for the liver-specific toxicity of microcystins. A significant obstacle in the study of microcystins as anticancer drugs is the requirement of specific transport proteins for cellular uptake. We report that OATP1B3 mRNA is up-regulated in non-small cell lung cancer tumors in comparison with normal control tissues. This finding led to the exploration of microcystins as potential anticancer agents. We have developed a HeLa cell model with functional OATP1B1 and OATP1B3 activity. Transiently transfected HeLa cells are over 1,000-fold more sensitive to microcystin LR than the vector-transfected control cells, showing that transporter expression imparts marked selectivity for microcystin cytotoxicity. In addition, microcystin analogues showed variable cytotoxicities in the OATP1B1- and OATP1B3-transfected cells, including two analogues with IC50 values < 1 nmol/L. Cytotoxicity of microcystin analogues seems to correlate to the inhibition of PP2A in these cells and induces rapid cell death as seen by chromatin condensation and cell fragmentation. These studies show that microcystin-induced phosphatase inhibition results in potent cytotoxicity when microcystin compounds can gain intracellular access and are a potent novel class of therapeutic agents for tumors expressing these uptake proteins.