Molecular Therapeutics/Drug Discovery Program, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213, USA.
J Pharmacol Exp Ther. 2010 Dec;335(3):715-27. doi: 10.1124/jpet.110.170555. Epub 2010 Aug 26.
The c-Myc oncoprotein is overexpressed in many tumors and is essential for maintaining the proliferation of transformed cells. To function as a transcription factor, c-Myc must dimerize with Max via the basic helix-loop-helix leucine zipper protein (bHLH-ZIP) domains in each protein. The small molecule 7-nitro-N-(2-phenylphenyl)-2,1,3-benzoxadiazol-4-amine (10074-G5) binds to and distorts the bHLH-ZIP domain of c-Myc, thereby inhibiting c-Myc/Max heterodimer formation and inhibiting its transcriptional activity. We report in vitro cytotoxicity and in vivo efficacy, pharmacodynamics, pharmacokinetics, and metabolism of 10074-G5 in human xenograft-bearing mice. In vitro, 10074-G5 inhibited the growth of Daudi Burkitt's lymphoma cells and disrupted c-Myc/Max dimerization. 10074-G5 had no effect on the growth of Daudi xenografts in C.B-17 SCID mice that were treated with 20 mg/kg 10074-G5 intravenously for 5 consecutive days. Inhibition of c-Myc/Max dimerization in Daudi xenografts was not seen 2 or 24 h after treatment. Concentrations of 10074-G5 in various matrices were determined by high-performance liquid chromatography-UV, and metabolites of 10074-G5 were identified by liquid chromatography/tandem mass spectrometry. The plasma half-life of 10074-G5 in mice treated with 20 mg/kg i.v. was 37 min, and peak plasma concentration was 58 μM, which was 10-fold higher than peak tumor concentration. The lack of antitumor activity probably was caused by the rapid metabolism of 10074-G5 to inactive metabolites, resulting in tumor concentrations of 10074-G5 insufficient to inhibit c-Myc/Max dimerization. Our identification of 10074-G5 metabolites in mice will help design new, more metabolically stable small-molecule inhibitors of c-Myc.
c-Myc 癌蛋白在许多肿瘤中过度表达,是维持转化细胞增殖所必需的。作为转录因子,c-Myc 必须通过每个蛋白中的碱性螺旋-环-螺旋亮氨酸拉链蛋白 (bHLH-ZIP) 结构域与 Max 二聚化。小分子 7-硝基-N-(2-苯苯基)-2,1,3-苯并恶二唑-4-胺 (10074-G5) 结合并扭曲 c-Myc 的 bHLH-ZIP 结构域,从而抑制 c-Myc/Max 异二聚体形成并抑制其转录活性。我们报告了 10074-G5 在人异种移植荷瘤小鼠中的体外细胞毒性和体内疗效、药效学、药代动力学和代谢。在体外,10074-G5 抑制了 Daudi 伯基特淋巴瘤细胞的生长并破坏了 c-Myc/Max 二聚化。当用 20mg/kg 10074-G5 静脉内连续 5 天治疗 C.B-17 SCID 小鼠的 Daudi 异种移植时,10074-G5 对其生长没有影响。在治疗后 2 或 24 小时未观察到 Daudi 异种移植中 c-Myc/Max 二聚化的抑制。用高效液相色谱-紫外法测定了各种基质中 10074-G5 的浓度,并通过液相色谱/串联质谱法鉴定了 10074-G5 的代谢物。用 20mg/kg 静脉内给药的小鼠中 10074-G5 的血浆半衰期为 37 分钟,血浆峰浓度为 58μM,是肿瘤峰浓度的 10 倍。缺乏抗肿瘤活性可能是由于 10074-G5 快速代谢为无活性代谢物,导致肿瘤中 10074-G5 的浓度不足以抑制 c-Myc/Max 二聚化。我们在小鼠中鉴定的 10074-G5 代谢物将有助于设计新的、代谢更稳定的 c-Myc 小分子抑制剂。