Guo B, Cao S, Tóth K, Azrak R G, Rustum Y M
Department of Pharmacology and Experimental Therapeutics, Grace Cancer Drug Center, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
Clin Cancer Res. 2000 Feb;6(2):718-24.
Overexpression of the Bax protein in human head and neck squamous cell carcinoma A253 cells was reported to result in an increased sensitivity to various chemotherapeutic agents in vitro (Guo et al., Oncol. Res., 11: 91-99, 1999). In the present study, the relationship between Bax expression and response to chemotherapy was further investigated in vitro and in vivo model systems. For in vitro study, A253, A253/Vec (pcDNA3 vector transfectant), and A253/Bax (pcDNA3/Bax transfectant, expressing 50-fold higher Bax protein than A253 and A253/Vec) cells were exposed to various concentrations of raltitrexed (a specific thymidylate synthase inhibitor) and SN-38 (a topoisomerase I inhibitor) for 2 h, and cell growth inhibition was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide clonogenic assay. Compared to A253/Vec, A253/Bax cells exhibited 9.5- and 13.5-fold increases in sensitivity to raltitrexed and SN-38, respectively. For in vivo study, A253/Vec and A253/Bax tumor xenografts were established by s.c. injection of tumor cells into nude mice. The antitumor activity and toxicity of raltitrexed (i.v. push daily for 5 days) and irinotecan (a prodrug of SN-38; i.v. push daily for 3 days) were evaluated. The maximum tolerated doses of raltitrexed and irinotecan were 30 and 100 mg/kg/day, respectively. At the maximum tolerated doses, minimal antitumor activity was observed with raltitrexed, although irinotecan was more active than raltitrexed against A253 or A253/Vec tumors. In contrast, both raltitrexed and irinotecan were significantly more active against A253/Bax xenografts than against A253/Vec xenografts; the yield for complete tumor regression (cure) was 40% and 100% with raltitrexed and irinotecan, respectively, with no significant toxicity. Furthermore, the observed increase of antitumor activity in A253/Bax tumors was associated with an enhanced induction of apoptosis in vivo. The in vivo results demonstrated a proof of the principal concept that selecting up-regulation of the proapoptosis gene Bax can provide the basis for a greater therapeutic efficacy to a variety of chemotherapeutic agents with different structures and mechanisms of action.
据报道，人头颈鳞状细胞癌A253细胞中Bax蛋白的过表达导致其在体外对多种化疗药物的敏感性增加（Guo等人，《肿瘤研究》，11: 91 - 99, 1999）。在本研究中，在体外和体内模型系统中进一步研究了Bax表达与化疗反应之间的关系。对于体外研究，将A253、A253/Vec（pcDNA3载体转染细胞）和A253/Bax（pcDNA3/Bax转染细胞，表达的Bax蛋白比A253和A253/Vec高50倍）细胞暴露于不同浓度的雷替曲塞（一种特异性胸苷酸合成酶抑制剂）和SN - 38（一种拓扑异构酶I抑制剂）中2小时，并通过3 -（4,5 - 二甲基噻唑 - 2 - 基）- 2,5 - 二苯基四氮唑溴盐克隆形成试验评估细胞生长抑制情况。与A253/Vec相比，A253/Bax细胞对雷替曲塞和SN - 38的敏感性分别增加了9.5倍和13.5倍。对于体内研究，通过将肿瘤细胞皮下注射到裸鼠体内建立A253/Vec和A253/Bax肿瘤异种移植模型。评估了雷替曲塞（静脉推注，每日1次，共5天）和伊立替康（SN - 38的前体药物；静脉推注，每日1次，共3天）的抗肿瘤活性和毒性。雷替曲塞和伊立替康的最大耐受剂量分别为30和100 mg/kg/天。在最大耐受剂量下，雷替曲塞观察到最小的抗肿瘤活性，尽管伊立替康对A253或A253/Vec肿瘤比雷替曲塞更具活性。相比之下，雷替曲塞和伊立替康对A253/Bax异种移植瘤的活性均显著高于对A253/Vec异种移植瘤的活性；雷替曲塞和伊立替康使肿瘤完全消退（治愈）的发生率分别为40%和100%，且无明显毒性。此外，在A253/Bax肿瘤中观察到的抗肿瘤活性增加与体内凋亡诱导增强有关。体内结果证明了一个主要概念，即选择上调促凋亡基因Bax可为对具有不同结构和作用机制的多种化疗药物产生更大的治疗效果提供基础。
