Pathological Reprogramming of DNA Damage Signaling in Neoplastic Cells

摘要 在我们对肿瘤细胞如何耐受致癌压力和 在肿瘤发生过程中产生的固有DNA损伤，同时积累突变以 癌症。不幸的是，在癌变过程中获得的DNA损伤耐受性和可变性也允许 癌细胞抵抗治疗。填补目前我们对DNA损伤耐受性知识的空白将使我们能够 利用固有的和治疗诱导的DNA损伤来杀死癌细胞。我们的长期目标是解决 癌细胞如何承受致癌压力和DNA损伤的问题。我们最近发现，癌症 细胞通常依赖于两条主要基因组维持途径(反式损伤)的异常激活 合成或TLS，以及同源重组或HR)以耐DNA损伤。这种对 病理激活的DNA修复是癌细胞的一种新的分子脆弱性，并提供了机会 进行高度选择性的靶向治疗。这里的目标是定义癌症通过哪些信号机制 细胞激活TLS和HR。我们的中心假设是病理性DNA修复活动支持癌细胞 生长并对治疗产生抵抗力。其基本原理是，定义病理机制-- 激活的DNA修复将揭示针对癌细胞特定脆弱性的治疗策略。我们 将测试我们的中心假设，并使用以下特定目标(SA)实现我们的目标：SA1 阐明MAGE-A4激活RAD18的结构基础。SA2定义病理上的贡献- 激活的跨损伤合成(TLS)在体内对致癌应激耐受和致癌作用。 SA3定义了同源重组(HR)通过以下途径病理激活的新机制 癌症中的HORMAD1基因。SA1将使用生物物理方法和新的多肽探针来阐明其机制 MAGE-A4通过它与RAD18相互作用。在缺乏Rad18(TLS的顶端介体)或 过量表达MAGE-A4(一种TLS的癌症特异性激活剂)的小鼠将被用来确定TLS如何影响 肿瘤发生和体内癌基因驱动的癌症的基因组图谱。对于SA3，我们将使用CELL 培养模型以确定癌症/睾丸抗原HORMAD1(在 癌细胞)激活DSB修复、癌基因应激耐受和辐射抗性。我们建议 对如何产生致癌压力耐受性和突变性等重要问题的创新的新解决方案， 导致癌变，并导致治疗抵抗。拟议的工作意义重大，因为我们将提供 基因组维护的新范例，与环境暴露、突变、 人类的肿瘤发生和癌症治疗。这项工作将导致新的治疗策略，以 对癌细胞的DNA损伤耐受性，从而增强现有药物的有效性和选择性 抗癌药物。

SUMMARY There are fundamental gaps in our understanding of how neoplastic cells tolerate the oncogenic stress and intrinsic DNA damage that arises during tumorigenesis, while simultaneously accumulating mutations that fuel cancer. Unfortunately, the DNA damage tolerance and mutability acquired during carcinogenesis also allow cancer cells to resist therapy. Filling the current gaps in our knowledge of DNA damage tolerance will allow us to harness intrinsic and therapy-induced DNA damage to kill cancer cells. Our long-term goal is to solve the problem of how cancer cells endure oncogenic stress and DNA damage. We recently discovered that cancer cells commonly depend on aberrant activation of two major genome maintenance pathways (Trans-Lesion Synthesis or TLS, and Homologous Recombination or HR) for DNA damage tolerance. This reliance on 'pathologically-activated' DNA repair is a new molecular vulnerability of cancer cells and provides opportunities for highly selective targeted therapies. The objective here is to define signaling mechanisms by which cancer cells activate TLS and HR. Our central hypothesis is that pathological DNA repair activity sustains cancer cell growth and confers resistance to therapy. The rationale is that defining the mechanisms of pathologically- activated DNA repair will reveal therapeutic strategies that target specific vulnerabilities of cancer cells. We will test our central hypothesis and attain our objectives using the following Specific Aims (SAs): SA1 Elucidate structural basis for RAD18 activation by MAGE-A4. SA2 Define contribution of pathologically- activated Trans-Lesion Synthesis (TLS) to oncogenic stress tolerance and carcinogenesis in vivo. SA3 Define novel mechanism by which Homologous Recombination (HR) is pathologically activated via HORMAD1 in cancer. SA1 will use biophysical methods and new peptide probes to elucidate the mechanism by which MAGE-A4 interacts with RAD18. In SA2 mutant mice lacking Rad18 (the apical mediator of TLS) or mice overexpressing MAGE-A4 (a cancer-specific activator of TLS) will be used to determine how TLS impacts tumorigenesis and the genomic landscape of oncogene-driven cancers in vivo. For SA3 we will use cell culture models to determine how the cancer/testes antigen HORMAD1 (which is aberrantly over-expressed in cancer cells) signals activation of DSB repair, oncogenic stress tolerance and radioresistance. We propose innovative new solutions to the important problems of how oncogenic stress tolerance and mutability arise, drive carcinogenesis, and lead to therapy resistance. The proposed work is significant because we will provide new paradigms for genome maintenance that are relevant to environmental exposures, mutagenesis, tumorigenesis and cancer therapy in humans. This work will lead to novel therapeutic strategies that target DNA damage tolerance specifically in cancer cells, thereby enhancing the efficacy and selectivity of existing anti-cancer agents.