Shingu Takashi, Yamada Kazuo, Hara Nobumasa, Moritake Kouzo, Osago Harumi, Terashima Masaharu, Uemura Takeshi, Yamasaki Toshiki, Tsuchiya Mikako
Department of Biochemistry, Shimane Medical University, Izumo 693-8501, Japan.
Cancer Res. 2003 Jul 15;63(14):4044-7.
Because the aberrantly activated phosphoinositide 3-kinase (PI3K)/Akt pathway renders tumor cells resistant to cytotoxic insults, including those related to anticancer drugs, inhibition of the pathway may possibly restore or augment the effectiveness of chemotherapy. Using the human malignant glioma cell lines U87, A172, LN18, and LN229, we examined effects of the PI3K inhibitor LY294002 on both apoptosis and cytotoxicity induced by chemotherapeutic agents, including antimicrotubule agents vincristine and paclitaxel, an alkylating agent 1,3-bis(2-chloroethyl)-1-nitrosourea, a topoisomerase II inhibitor etoposide, and a DNA cross-linking agent cisplatin (cis-diamminedichloroplatinum), and we compared the LY294002-induced enhancement of effects of those agents. Ten to 20 micro M LY294002 augmented both apoptosis and caspase 3-like activity caused by antimicrotubule agents to a larger extent than induced by 1,3-bis(2-chloroethyl)-1-nitrosourea, etoposide, and cisplatin in all four malignant glioma cell lines examined. The same doses of LY294002 enhanced cytotoxicity more efficiently with antimicrotubule agents than with other chemotherapeutic agents. Quantitative analyses using a modified isobologram and median effect plot method revealed that enhancement by LY294002 of vincristine- or paclitaxel-induced cytotoxicity was synergistic, whereas enhancement by the PI3K inhibitor of the other chemotherapeutic agent-induced cytotoxicity was additive. Our study indicates that the synergistic augmentation of the cytotoxicity by LY294002 occurs specifically with antimicrotubule agents, at least partially through an increase in caspase 3-dependent apoptosis, and we suggest that inhibitors of the PI3K/Akt pathway in combination with antimicrotubule agents may induce cell death effectively and be a potent modality to treat patients with malignant gliomas.
由于异常激活的磷酸肌醇3激酶（PI3K）/Akt信号通路使肿瘤细胞对细胞毒性损伤产生抗性，包括那些与抗癌药物相关的损伤，抑制该信号通路可能会恢复或增强化疗效果。我们使用人恶性胶质瘤细胞系U87、A172、LN18和LN229，研究了PI3K抑制剂LY294002对化疗药物诱导的细胞凋亡和细胞毒性的影响，这些化疗药物包括抗微管药物长春新碱和紫杉醇、烷化剂1,3-双（2-氯乙基）-1-亚硝基脲、拓扑异构酶II抑制剂依托泊苷以及DNA交联剂顺铂（顺二氨二氯铂），并比较了LY294002对这些药物作用的增强效果。在所有检测的四种恶性胶质瘤细胞系中，10至20微摩尔的LY294002增强抗微管药物诱导的细胞凋亡和半胱天冬酶3样活性的程度，大于1,3-双（2-氯乙基）-1-亚硝基脲、依托泊苷和顺铂所诱导的程度。相同剂量的LY294002增强抗微管药物的细胞毒性比增强其他化疗药物的细胞毒性更有效。使用改良的等效线图和中位效应图法进行定量分析表明，LY294002增强长春新碱或紫杉醇诱导的细胞毒性具有协同作用，而PI3K抑制剂增强其他化疗药物诱导的细胞毒性具有相加作用。我们的研究表明，LY294002对细胞毒性的协同增强作用尤其发生在抗微管药物中，至少部分是通过增加半胱天冬酶3依赖性细胞凋亡实现的，并且我们认为PI3K/Akt信号通路抑制剂与抗微管药物联合使用可能有效诱导细胞死亡，是治疗恶性胶质瘤患者的一种有效方式。
