Chemical Probes of Endogenous Mutation: Small Molecule APOBEC3B Inhibitors

描述（由申请人提供）：获得性基因组突变是驱动癌症发展、繁殖和对化疗药物耐药性的燃料。虽然许多基因组突变的起源仍然未知，但已经发现了一种新的致癌突变源，其中APOBEC 3B（A3 B），先天免疫系统的DNA胞嘧啶脱氨酶，催化内源性突变。DNA胞嘧啶脱氨作用通过产生尿嘧啶破坏沃森-克里克碱基配对，尿嘧啶在随后的DNA复制过程中模板化补充胸腺嘧啶的腺嘌呤插入（G到A超突变）。A3 B信使RNA（mRNA）在65%的患者来源的原发性乳腺癌标本和90%的乳腺癌细胞系中上调。过表达A3 B的肿瘤具有两倍于低A3 B表达肿瘤的总体突变，并且更可能在TP 53（众所周知的肿瘤抑制基因）中具有突变。这项奖学金提案将测试创新假设，即A3 B的小分子抑制将降低乳腺癌细胞的总体突变率。方法包括合成A3 B的小分子抑制性探针（Aim 1），并在突变报告细胞系中测试这些抑制剂，从而能够直接定量A3 B催化的诱变（Aim 2）。这项拟议的工作将有助于实现以下长期目标：（i）证明A3 B催化的基因组突变驱动癌症进展;（ii）开发基于A3 B小分子抑制剂的新型癌症治疗方法。A3 B是一个近乎完美的药物靶点，因为它是人类的非必需酶。这里的目标是向现场递送A3 B的第一化学调节剂，这是一种可以被各种生物技术利用的工具。 实验室在药物相关浓度下探测A3 B传播的癌症。这一目标与NCI的使命一致，即支持旨在开发最先进癌症治疗方法的研究。

DESCRIPTION (provided by applicant): Acquired genomic mutation is the fuel that drives cancer development, propagation, and resistance to chemotherapeutic drugs. Although the origin of much genomic mutation remains unknown, a new source of cancer-causing mutation has been uncovered in which APOBEC3B (A3B), a DNA cytosine deaminase of the innate immune system, catalyzes endogenous mutation. DNA cytosine deamination destroys Watson-Crick base pairing by producing uracils which template the insertion of adenines that complement thymines (G-to-A hypermutation) during subsequent rounds of DNA replication. A3B messenger RNA (mRNA) is upregulated in 65% of patient-derived primary breast cancer specimens and 90% of breast cancer cell lines. Tumors that over-express A3B have twice as many overall mutations as low A3B expressing tumors and are more likely to have mutations in TP53, the well-known tumor suppressor gene. This fellowship proposal will test the innovative hypothesis that small molecule inhibition of A3B will decrease the overall mutation rate in breast cancer cells. Methods include synthesizing small molecule inhibitory probes of A3B (Aim 1) and testing these inhibitors in mutation-reporting cell lines that enable the direct quantification of A3B-catalyzed mutagenesis (Aim 2). This proposed work will help to achieve the long-term goals of (i) demonstrating that A3B-catalyzed genomic mutation drives cancer progression and (ii) developing novel cancer therapeutics based on small molecule inhibitors of A3B. A3B is a near-perfect drug target because it is a non-essential enzyme in humans. The objective here is to deliver to the field the first chemical modulator of A3B, a tool that can be utilized by various laboratories to probe A3B-propagated cancers at pharmaceutically relevant concentrations. This goal is aligned with the mission of the NCI to support research aimed at developing state-of-the-art treatments for cancer.