Impact of uracil DNA glycosylase on lung cancer cell sensitivity to pemetrexed

描述（由申请人提供）：耐药和剂量限制性毒性是人类癌症治疗的主要障碍。通过将目前的抗癌药物与肿瘤增敏剂相结合，可以改善全身癌症治疗。肿瘤对化疗的敏感性受多种因素的影响，包括对抗癌药物引起的DNA损伤的识别和修复。培美曲塞是一种用于治疗人类肺癌和间皮瘤的抗叶酸药物。培美曲塞方案的成功受到剂量限制性骨髓抑制和获得性耐药的发展的影响。在肿瘤细胞内，培美曲塞通过抑制参与新胸腺嘧啶生物合成的酶导致基因组尿嘧啶掺入。碱基切除修复（BER）是由尿嘧啶DNA糖基化酶（UDG）启动的，它能主动识别并清除基因组中错配的尿嘧啶。该建议将利用肺癌细胞系解决UDG在培美曲塞敏感性中的作用的理解空白。使用该模型，我们将解决一个假设，即通过参与DNA损伤反应信号（AIM1）的转录因子对核UDG启动子的调控，在培美曲塞治疗后诱导UDG表达。在AIM 2中，我们将建立UDG-/-肺癌细胞，以解决UDG表达缺失使肺癌细胞对培美曲塞敏感的假设。最后，在AIM3中，我们将使用候选UDG抑制剂来评估抑制UDG活性可以增强培美曲塞细胞毒性的假设。本文提出的研究将极大地扩展我们对UDG对DNA损伤的调控以及培美曲塞诱导的尿嘧啶积累对癌细胞毒性的影响的认识，并评估UDG靶向提高培美曲塞疗效的潜力。

DESCRIPTION (provided by applicant): Drug resistance and dose-limiting toxicities are major obstacles in the treatment of human cancers. Improved systemic cancer therapy can be achieved by combining current anti-cancer drugs with tumor sensitizing agents. Tumor sensitivity to chemotherapy is influenced by several factors, including recognition and repair of the DNA damage caused by anti-cancer agents. Pemetrexed is an antifolate used in the treatment of human lung cancers and mesothelioma. The success of pemetrexed regimens is influenced by dose-limiting myelosuppression and the development of acquired resistance. Within tumor cells, pemetrexed causes genomic uracil incorporation through inhibition of enzymes involved in de novo thymidine biosynthesis. Base excision repair (BER), initiated by uracil DNA glycosylase (UDG), actively recognizes and removes misincorporated uracil from the genome. This proposal will utilize lung cancer cell lines address gaps in understanding of the role of UDG in pemetrexed sensitivity. Using this model we will address the hypothesis that UDG expression is induced in response to pemetrexed treatment via regulation of the nuclear UDG promoter by transcription factors involved in DNA damage response signaling (AIM1). In AIM 2, we will establish UDG-/- lung cancer cells to address the hypothesis that loss of UDG expression sensitizes lung cancer cells to pemetrexed. Lastly, in AIM3, we will use candidate UDG inhibitors to evaluate the hypothesis that inhibition of UDG activity can potentiate pemetrexed cytotoxicity. The studies proposed herein will greatly expand our knowledge of the regulation of UDG in response to DNA damage and the impact of pemetrexed- induced uracil accumulation on cancer cell toxicity, as well as evaluate the potential for UDG targeting to improve pemetrexed efficacy.