Understanding mechanistic role of SAMHD1 in DNA damage response and therapeutic benefit for malignant glioma

项目摘要/摘要 恶性胶质瘤是成人最常见的中枢神经系统恶性肿瘤，其恶性程度较差。 预后。恶性胶质瘤的传统治疗方法是手术切除，然后进行放射治疗。 (RT)和化疗药物替莫唑胺(TMZ)。尽管有人试图提高这种可能性 在患者存活的这种联合疗法中，只取得了不大的成功。因此，有一个紧迫的问题 需要开发更好的治疗方法来改善患者的预后。TMZ和RT通过诱导癌细胞死亡 DNA损伤；然而，如果DNA修复途径是完整和有效的，很有可能一个细胞 可能对这些治疗产生抗药性。因此，了解治疗耐药的根本原因 可能导致更有效的治疗方法的开发，并最终改善患者的预后。因此， 发现可靶向减轻恶性胶质瘤耐药的新基因将有助于 对正在进行的研究工作意义重大。我们确定了无菌α基序和HD结构域的新角色 含蛋白1在促进DNA末端切除促进DNA双链断裂中的作用 同源重组(HR)修复。SAMHD1是一种脱氧核苷三磷酸(DNTP) 三磷酸水解酶通过耗尽dNTPs在限制未分裂细胞感染HIV-1中的明确作用 反转录所需的。我们的初步数据表明，癌细胞中SAMHD1的耗尽导致 对DNA DSB诱导剂的超敏反应。我们还证明了SAMHD1被招募到DNA DSB中 对DNA损伤的反应。SAMHD1在DNA损伤后与CtIP相互作用并招募CtIP为DNA DSB 以促进DNA末端切除和HR不依赖于其dNTPase活性。SAMHD1是蛋白酶体的靶标 病毒辅助蛋白VPX的降解。我们有数据表明，不同的癌细胞株用 与内源性水平相比，VPX降低了SAMHD1水平，随后又增加了 对DNA损伤诱导的治疗药物的敏感性。值得注意的是，SAMHD1低的恶性胶质瘤患者 水平显示总体存活的可能性明显更高。此外，少突胶质瘤、星形细胞瘤 与正常脑组织相比，胶质母细胞瘤组织中SAMHD1的表达显著增加 组织。有趣的是，GBM是最具侵袭性的胶质瘤形式，表达SAMHD1的水平最高。已被占用 综上所述，我们的初步发现表明SAMHD1可能成为治疗恶性肿瘤的潜在靶点。 神经胶质瘤的治疗。因此，我建议的总体目标是确定通过哪些机制 SAMHD1指导DNA DSB修复介导恶性胶质瘤的治疗耐药，并看看我们如何 利用这些知识来改进胶质瘤的治疗。

Project Summary/Abstract Malignant Glioma is the most commonly diagnosed adult central nervous system malignancy, and carries a poor prognosis. The conventional treatment for malignant glioma is surgical resection followed by radiation therapy (RT) and the chemotherapeutic drug, temozolomide (TMZ). Despite attempts to improve the probability of survival in patients with this combination of therapies, there has been only modest success. Thus, there is urgent need to develop a better therapy to improve patient outcomes. TMZ and RT cause cancer cell death by inducing DNA damage; however, if DNA repair pathways are intact and effective, there is a high probability that a cell may develop resistance to these treatments. Thus, understanding the underlying cause of treatment resistance could lead to the development of more effective therapies and, ultimately, improve patients' prognosis. Therefore, identifying novel genes that can be targeted to alleviate treatment resistance in malignant glioma will contribute significantly to ongoing research efforts. We identified a novel role for sterile alpha motif and HD domain containing-protein 1 (SAMHD1) in promoting DNA end resection to facilitate DNA double-strand break (DSB) repair by homologous recombination (HR). SAMHD1 is a deoxynucleoside triphosphate (dNTP) triphosphohydrolase with a well-defined role in restricting HIV-1 infection in nondividing cells by depleting dNTPs required for reverse transcription. Our preliminary data indicate that SAMHD1 depletion in cancer cells causes hypersensitivity to DNA DSB-inducing agents. We have also shown that SAMHD1 is recruited to DNA DSBs in response to DNA damage. SAMHD1 interacts with CtIP following DNA damage and recruits CtIP to DNA DSBs to facilitate DNA end resection and HR independent of its dNTPase activity. SAMHD1 is targeted for proteasomal degradation by the viral accessory protein, Vpx. We have data showing that various cancer cell lines treated with Vpx have diminished levels of SAMHD1 compared to endogenous levels, and subsequently, have increased sensitivity to DNA damage inducing therapeutic agents. Strikingly, malignant glioma patients with low SAMHD1 levels show a significantly higher probability of overall survival. Furthermore, oligodendroglioma, astrocytoma and glioblastoma tumor samples show significantly higher expression of SAMHD1 as compared to normal brain tissue. Interestingly, GBM, the most aggressive form of glioma, expresses the highest level of SAMHD1. Taken together, our preliminary findings suggest that SAMHD1 could be a potential therapeutic target for malignant glioma treatment. As such, the overall objective of my proposal is to determine the mechanisms by which SAMHD1 directs DNA DSB repair to mediate treatment resistance in malignant glioma and to see how we can utilize this knowledge to improve glioma treatment.