Leveraging the GTP Biosynthetic Pathway for Anti-Tumor Therapies

侵袭是所有癌症（包括乳腺癌）最有害的特征之一，因为它允许细胞 逃离原发部位并在远处器官形成转移。尽管在预防和早期干预方面取得了进展， 尽管转移性乳腺癌的发病率很高，但与转移性乳腺癌相关的死亡率仍然很高。这是 尤其是对于表现为三阴性乳腺癌（TNBC，其特征在于缺乏 ER、PR和Her 2的表达），其是乳腺癌的最具侵袭性和最致命的亚型， 迄今为止缺乏治疗干预的具体目标。了解这些机制， 促进肿瘤细胞的侵袭将使我们能够设计更有效的治疗策略， 减少转移。 我们小组已经建立了GTP代谢和肿瘤细胞侵袭性之间的基本联系; 我们已经揭示了GTP及其代谢酶（GME）作为肿瘤进展和转移的关键参与者， 潜力我们已经开发了独特的荧光报告细胞内GTP，使我们能够 确定了在活细胞中，GTP在细胞内的分布是不均匀的，并提出了假设 GTP的局部浓度可以影响GTP依赖性过程。特别是，我们以前 表明GTP代谢途径的遗传或药理学调节深深地影响了 RHO家族的小GTP酶的激活状态，以及肿瘤细胞的侵袭能力。因此在 目的1基于GME亚细胞定位，探索G蛋白激活的新机制。 我们的初步结果表明，GTP从头产生的限速酶肌醇 一磷酸脱氢酶2（IMPDH 2）在细胞膜位点富集，这些位点对于细胞迁移至关重要 和侵袭（即粘着斑、FA和侵袭足）。IMPDH 2在这些场所的作用实际上是 没有特征的因此，在目标2中，我们将评估IMPDH 2在FA中的催化和结构作用， 侵袭伪足的形成，以及粘着斑激酶（FAK）指导的致癌运动。 对GTP代谢酶转录调控的理解还远未完成。鉴定 GTP生物合成途径的转录主调节因子， 将提供一种更有效的抑制这种途径的方法。我们的初步结果表明，Kruppel样 因子9（KLF 9）和芳香烃受体（AHR）在转录调控中起拮抗作用， GTP代谢酶，KLF 9抑制，而AHR诱导GTP产生。因此，在目标3中，我们 将阐明这种调节，并探索药物治疗，以调节这些活动， 转录因子

Invasion is one of the most detrimental features of all cancers, including breast cancer, as it allows cells to escape the primary site and form metastases at distant organs. Despite progress in prevention and early lesions detection, the mortality associated with metastatic breast cancer is still extremely high. This is especially true for patients presenting with triple negative breast cancer (TNBC, characterized by lack of expression of ER, PR, and Her2 ), which is the most aggressive and deadliest subtype of breast cancer and the one that so far lack specific targets for therapeutic intervention. Understanding the mechanisms that facilitate the invasion of tumor cells will enable us to design more efficient therapeutic strategies to prevent or reduce metastasis. Our group has established a fundamental connection between GTP metabolism and tumor cell invasiveness; we have unveiled GTP and its metabolic enzymes (GME) as key players in tumor progression and metastatic potential. We have developed unique fluorescent reporters for intracellular GTP that have allowed us to determine that, in live cells, the intracellular GTP distribution is not uniform, and brought forward the hypothesis that local concentration of GTP can influence GTP-dependent processes. In particular, we have previously shown that genetic or pharmacological modulation of the GTP metabolic pathway deeply affected the activation status of small GTPases of the RHO-family and, with it, the tumor cells' invasive capability. Thus, in Aim 1 we will explore a novel mechanism of G-proteins activation based on GME subcellular localization. Our preliminary results showed that the rate-limiting enzyme for GTP de novo production, inositol monophosphate dehydrogenase 2 (IMPDH2) enriches at cell membrane sites that are critical for cell migration and invasion (namely focal adhesion, FA, and invadopodia). The role of IMPDH2 at these sites is virtually uncharacterized. Thus, in Aim 2 we will assess the catalytic and structural role of IMPDH2 in FA and invadopodia formation, as well as in focal adhesion kinase (FAK)-directed oncogenic motility. The understanding of GTP metabolic enzymes transcriptional regulation is far from complete. Identification of transcriptional master regulators of the GTP biosynthetic pathway that could be pharmacologically targeted would offer a more efficient way of suppressing this pathway. Our preliminary results suggest that Kruppel-like factor 9 (KLF9) and aryl hydrocarbon receptor (AHR) play antagonistic roles in the transcriptional regulation of GTP metabolic enzymes, with KLF9 suppressing, whereas AHR inducing GTP production. Thus, in Aim 3 we will elucidate this regulation and explore pharmacological treatments to regulate the activity of these transcription factors.