Role of the mitochondrial ABC protein ABCB6 in drug resistance

描述（由申请人提供）：ABC （atp结合盒）家族包括最著名的抗癌药物耐药介质。特别是，MDR（多药耐药）泵积极地从癌细胞中挤出多种药物，从而赋予这些药物耐药性。亚砷酸盐是一种越来越广泛使用的抗癌药物，而砷的毒性在世界范围内都是一个新兴的问题。我们的初步结果表明，出乎意料的是，ABCB6的表达和功能可能是提供亚砷酸盐抗性的重要细胞机制。尽管ABC转运蛋白在解毒中的作用已经确立，但这一概念仍然具有挑战性。ABCB1-MDR1通过将各种抗癌药物的细胞内水平保持在细胞杀伤阈值以下来提供耐药性。然而，ABCB6是在线粒体膜中表达的，这就提出了一个问题，即它的功能是如何向细胞传递抵抗力的。本提案的总体目标是了解线粒体ABC转运蛋白如何提供耐药性。需要验证的具体假设是，ABCB6在保护细胞免受亚砷酸盐介导的毒性方面发挥作用。这一假设基于以下观察结果：首先，我们发现选择抗亚砷酸盐的细胞比亲本细胞系表达更高水平的ABCB6；其次，ABCB6的过表达赋予了对重金属的广泛抗性；第三，基于NCI60细胞组分析的药物基因组学方法提示ABCB6参与耐药。基于这些观察结果，我们提出了一系列全面的研究来确定ABCB6赋予抗性的生化机制。特别是，提出的研究旨在解决以下关键问题：首先，ABCB6转运什么底物？其次，ABCB6位于细胞的什么位置？第三，ABCB6的功能形式是什么？尽管在过去的十年中，癌症治疗取得了长足的进步，癌症死亡率逐渐下降，但在美国，每年仍有超过50万人死于癌症。大多数转移性癌症的有效治疗需要使用毒性化疗。不幸的是，癌细胞可能会对细胞毒性药物产生抗药性，这通常是通过ABC转运蛋白活性的升高来实现的，而ABC转运蛋白介导了癌细胞中各种药物的能量依赖性外排。本研究的目的是阐明ABCB6这一候选多药转运体的作用机制和生物化学。

DESCRIPTION (provided by applicant): The ABC (ATP-Binding Cassette) family includes the best known mediators of resistance to anticancer drugs. In particular, MDR (multidrug resistance) pumps actively extrude many types of drugs from cancer cells, thereby conferring resistance to those agents. Arsenite is an increasingly used anticancer agent, while arsenic toxicity is an emerging problem all over the world. Our preliminary results indicate that, unexpectedly, the expression and function of ABCB6 may be an important cellular mechanism to provide arsenite resistance. Despite the established role of ABC transporters in detoxification, this concept remains challenging. ABCB1-MDR1 provides resistance by keeping the intracellular levels of various anticancer agents below a cell-killing threshold. ABCB6 is, however, expressed in the mitochondrial membrane, raising the question as to how its function may convey resistance to the cells. The overall goal of this proposal is to understand how mitochondrial ABC transporters provide drug resistance. The specific hypothesis to be tested is that ABCB6 plays a role in protecting the cells against arsenite-mediated toxicity. This hypothesis is based on the following observations: First, we found that cells selected for resistance to arsenite express higher levels of ABCB6 than parental lines; Second, the overexpression of ABCB6 conferred broad resistance to heavy metals; Third, a pharmacogenomic approach based on the analysis of the NCI60 cell panel suggested the involvement of ABCB6 in drug resistance. Based on these observations, a comprehensive series of studies is proposed to determine the biochemical mechanism by which ABCB6 confers resistance. In particular, the studies proposed are designed to address the following critical questions: First, what substrate(s) does ABCB6 transport? Second, where is ABCB6 located in the cell? Third, what is the functional form of ABCB6? Relevance Although considerable progress has been made in treating cancer over the past decade with a gradual decline in cancer death rates, there are still over 500,000 deaths from cancer in the U.S. each year. Effective treatment of most metastatic cancers requires the use of toxic chemotherapy. Unfortunately, cancer cells may become resistant against cytotoxic agents, often through the elevated activity of ABC transporters, which mediate the energy-dependent efflux of various drugs from cancer cells. This proposal's aim is to elucidate the mechanism and biochemistry of ABCB6, a candidate multidrug transporter.