乙醛脱氢酶1蛋白在乳腺癌中的表达及临床意义

目的:探讨肿瘤干细胞标志物乙醛脱氢酶1(aldehyde dehydrogenase 1,ALDH1)在乳腺癌中的表达及其临床意义.方法:采用免疫组织化学染色法检测92例乳腺癌患者肿瘤组织中ALDH1蛋白的表达,并结合临床病理特征进行相关性分析和无病生存期分析.结果:ALDH1蛋白在乳腺癌组织中的阳性表达与孕激素受体(progesterone receptor, PR)和cerb-B2有关(P<0.05),与患者年龄、肿瘤大小、临床分期以及是否有淋巴结转移无关(P>0.05).ALDH1阳性患者2年无病生存率显著低于ALDH1阴性患者(P<0.05),接受CEF方案化疗和内分泌治疗的ALDH1阳性患者2年无病生存率显著低于ALDH1阴性患者(P<0.05).结论:ALDH1蛋白表达阳性的乳腺癌患者其无病生存率降低与耐药有关,ALDH1可作为乳腺癌预后判断的指标.     

Tumor endothelial cells with high aldehyde dehydrogenase activity show drug resistance

Tumor blood vessels play an important role in tumor progression and metastasis. We previously reported that tumor endothelial cells (TEC) exhibit several altered phenotypes compared with normal endothelial cells (NEC). For example, TEC have chromosomal abnormalities and are resistant to several anticancer drugs. Furthermore, TEC contain stem cell‐like populations with high aldehyde dehydrogenase (ALDH) activity (ALDH^high TEC). ALDH^high TEC have proangiogenic properties compared with ALDH^low TEC. However, the association between ALDH^high TEC and drug resistance remains unclear. In the present study, we found that ALDH mRNA expression and activity were higher in both human and mouse TEC than in NEC. Human NEC:human microvascular endothelial cells (HMVEC) were treated with tumor‐conditioned medium (tumor CM). The ALDH^high population increased along with upregulation of stem‐related genes such as multidrug resistance 1, CD90, ALP, and Oct‐4. Tumor CM also induced sphere‐forming ability in HMVEC. Platelet‐derived growth factor (PDGF)‐A in tumor CM was shown to induce ALDH expression in HMVEC. Finally, ALDH^high TEC were resistant to fluorouracil (5‐FU) in vitro and in vivo. ALDH^high TEC showed a higher grade of aneuploidy compared with that in ALDH^low TEC. These results suggested that tumor‐secreting factor increases ALDH^high TEC populations that are resistant to 5‐FU. Therefore, ALDH^high TEC in tumor blood vessels might be an important target to overcome or prevent drug resistance.     

Polymorphism of aldehyde dehydrogenase and ethanol elimination

The influence of polymorphism of aldehyde dehydrogenase (ALDH) on ethanol elimination was investigated. Japanese healthy male volunteers were divided into two groups, i.e., a normal ALDH group of 52 subjects with the low Km isozyme of ALDH, and a deficient group of 48 subjects without it. The subjects of the normal group were given 0.4, 0.8, 1.2, 1.6 or 2.0 g/kg of ethanol, while those in the deficient group ingested 0.4, 0.8 or 1.2 g/kg of ethanol. Widmark's factors (beta 60, Co and r) and ethanol elimination rate (ER) were compared between the two groups. In the deficient group, beta 60 and ER were not clearly elevated with the increase of ethanol dose, while those in the normal ALDH group increased depending on the blood ethanol level. Blood acetaldehyde level was elevated with the increase of the ethanol dose in the deficient group, but not in the normal group. In the experiment of the repeated ingestion of ethanol in the deficient group, the second peak of blood acetaldehyde level was lower than that of the first one.     

Aldehyde dehydrogenase and aldehyde reductase in isolated bovine brain microvessels

The activities of aldehyde dehydrogenase and aldehyde reductase were measured in microvessel fractions isolated from bovine brain. Aldehyde dehydrogenase specific activity in microvessels was enriched 1.5-fold over that measured in grey matter. The specific activity of aldehyde reductase was significantly lower in parenchymal vessles and microvessels than in grey matter. The presence of aldehyde dehydrogenase and aldehyde reductase in cerebral microvasculature is consistent with previous reports of enrichment of other enzymes involved in synthesis and degradation of monoamines. The enrichment of aldehyde dehydrogenase in cerebral microvasculature provides additional evidence for an enzymatic blood-brain barrier for biogenic aldehydes or ethanol-derived acetaldehyde.     

朝鲜族、鄂伦春族醇代谢酶基因多态性与酒依赖的研究

目的了解醇脱氢酶（ＡＤＨ）和醛脱氢酶（ＡＬＤＨ）基因多态性与朝鲜族和鄂伦春族酒依赖发病的相互关系。方法采用耳血聚合酶链反应及等位基因特异性寡核苷酸杂交方法，检测ＡＤＨ和ＡＬＤＨ基因型在酒依赖患者（朝鲜族５５例，鄂伦春族３１例）与正常对照者（朝鲜族５０名，鄂伦春族３７名）人群中的分布频率。结果在酒依赖组与正常对照组之间，朝鲜族仅ＡＬＤＨ２基因频率的分布差异有非常显著性（Ｐ＜０．０１），而鄂伦春族的ＡＤＨ３基因频率分布和ＡＬＤＨ２基因频率分布的差异有非常显著性和显著性（Ｐ＜０．０１，Ｐ＜０．０５），两个民族的ＡＤＨ２基因频率分布差异均无显著性。结论提示朝鲜族酒依赖的发生与ＡＬＤＨ２基因有关，鄂伦春族则为ＡＬＤＨ２和ＡＤＨ３基因共同影响酒依赖的发生。     

Oxidative metabolism and pharmacokinetics of the EGFR inhibitor BIBX1382 in chimeric NOG-TKm30 mice transplanted with human hepatocytes

The epidermal growth factor receptor inhibitor BIBX1382 has failed in drug development because of poor oral exposure and low bioavailability associated with its extensive metabolism by aldehyde oxidase (AOX) in humans. In this study, we investigated the metabolic profiles and pharmacokinetics of BIBX1382 in chimeric NOG-TKm30 mice with humanized liver (humanized liver mice). After intravenous and oral BIBX1382 administration, increased plasma clearance and decreased oral exposure together with high production of the predominant oxidative metabolite (M1, BIBU1476) and secondary oxidized metabolite (M2) were observed in humanized liver mice. Extensive oxidation rates of BIBX1382 were observed in hepatocytes from humanized liver mice and were suppressed by the typical human AOX1 inhibitors raloxifene and hydralazine. Liver cytosolic fractions from humans, humanized liver mice, cynomolgus monkeys, minipigs, and guinea pigs, but not fractions from dogs, rabbits, rats, and mice, displayed high BIBX1382 clearance and resulted in oxidative metabolite production. These results indicate that humanized liver mice have human-type AOX activity based on the transplanted human liver AOX1 function. Humanized liver mice can be considered an important animal model for understanding the metabolism and pharmacokinetics of AOX drug substrates.     

Monoamine oxidase B oxidizes a novel multikinase inhibitor KW-2449 to its iminium ion and aldehyde oxidase further converts it to the oxo-piperazine form in human

(E)-1-{4-[2-(1H-Indazol-3-yl)vinyl]benzoyl}piperazine (KW-2449) is a novel multikinase inhibitor. During our clinical study, we found that KW-2449 is mainly metabolized to its oxo-piperazine form (M1). An inhibition study suggested that monoamine oxidase-B (MAO-B) oxidizes KW-2449 to an iminium (intermediate) and aldehyde oxidase (AO) then metabolizes the intermediate to M1. The conversion of KW-2449 to the iminium (intermediate) by MAO-B was confirmed by the formation of its cyanide adduct. This cooperative metabolic pathway by MAO-B and AO was newly identified in the metabolism of piperazine. The clearance of KW-2449 by MAO-B and AO in human was estimated based on the kinetic analysis with in vitro-in vivo extrapolation. The systemic clearance in human was similar to the calculated value, indicating that the extrapolation approach was applicable to KW-2449 metabolism. Finally, we found that (E)-3-amino-1-{4-[2-(1H-Indazol-3-yl)vinyl]benzoyl}-pyrrolidine (Compound A) as a stable compound against MAO-B and AO. The total body clearance of Compound A was reduced to one tenth of KW-2449, demonstrating that preventing the metabolism of MAO and AO led to more preferable pharmacokinetic profiles. As piperazine is often introduced to drug candidates to improve lipophilicity of the compound to get more hydrophilic nature, the results of this study provide useful information for future drug development.     

An overview of aldehyde oxidase: an enzyme of emerging importance in novel drug discovery

Introduction: Given the rising trend in medicinal chemistry strategy to reduce cytochrome P450-dependent metabolism, aldehyde oxidase (AOX) has recently gained increased attention in drug discovery programs and the number of drug candidates that are metabolized by AOX is steadily growing.

Areas covered: Despite the emerging importance of AOX in drug discovery, there are certain major recognized problems associated with AOX-mediated metabolism of drugs. Intra- and inter-species variations in AOX activity, the lack of reliable and predictive animal models using the common experimental animals, and failure in the predictions of in vivo metabolic activity of AOX using traditional in vitro methods are among these issues that are covered in this article. A comprehensive review of computational human AOX (hAOX) related studies are also provided.

Expert opinion: Following the recent progress in the stem cell field, the authors recommend the application of organoids technology as an effective tool to solve the fundamental problems associated with the evaluation of AOX in drug discovery. The recent success in resolving the hAOX crystal structure can too be another valuable data source for the study of AOX-catalyzed metabolism of new drug candidates, using computer-aided drug discovery methods.