GTP Metabolism Controls Tumor Invasion

 描述（由申请人提供）：恶性黑色素瘤是最具侵袭性的癌症类型之一。它的转移能力和对抗癌化疗的抗性使得黑色素瘤非常难以治愈。此外，没有与黑色素瘤进展相关的可靠分子标志物。侵袭作为转移的先决条件，是黑色素瘤最有害的特征之一。最近，使用培养的细胞，实验动物和分析人类黑色素瘤标本，我们已经确定鸟苷一磷酸还原酶（GMPR）作为黑色素瘤侵袭的抑制剂。我们的初步数据显示，GMPR的功能性拮抗剂，鸟苷一磷酸合酶（GMPS），在人转移性黑色素瘤中过表达，并需要黑色素瘤细胞的侵袭和裸鼠人黑色素瘤异种移植物的生长。此外，我们证明了一个相对研究不足的化学抑制剂GMPS，decoyinine，减少黑色素瘤细胞的侵袭。此外，我们的分析，病理学上可用的数据库确定了其他几个鸟苷酸代谢酶的差异表达在原发性和转移性黑色素瘤标本。C-MYC是一种转录因子，调节参与促进增殖和增强细胞代谢（包括核苷酸生物合成）的多个基因的表达。C-MYC水平的上调是包括转移性黑色素瘤在内的人类恶性肿瘤中最常见的事件之一。我们实验室的初步数据表明，GMPR是一个C-MYC反应基因，长期GMPR抑制是由表观遗传调控介导的。因此，我们的中心假设是，通过在多个点破坏正常的生物合成途径，鸟苷酸池的扭曲促进了转移性黑色素瘤的进展。我们的长期目标是开发新的治疗方法来治疗或预防转移性黑色素瘤，以及确定一组生物标志物用于转移潜能的早期诊断。我们在当前提案中的目标是i）调查 GMPS的药理学抑制的治疗潜力; ii）表征参与鸟苷酸代谢的几种限速酶作为潜在的黑素瘤标志物;和iii）鉴定黑素瘤细胞中GMPR转录抑制的潜在机制。为了实现这些目标，我们提出了以下三个具体目标：1）确定GMPS抑制剂decoyinine对免疫受损小鼠中黑素瘤异种移植物的功效2）确定参与鸟苷酸代谢的酶对原发性黑素瘤患者的总体存活（OS）的预后价值。3）探讨GMPR的调控机制及GMPR在MYC依赖的侵袭上调中的作用。黑色素瘤是一种无法治愈的人类癌症，没有可靠的预后分子标志物。我们提出的研究将描述一个有前途的黑色素瘤治疗的新靶点，发现黑色素瘤侵袭的新机制，并确定黑色素瘤患者的新预后因素。

 DESCRIPTION (provided by applicant): Malignant melanoma is one of the most aggressive types of cancers. Its ability to metastasize and resistance to anticancer chemotherapy makes melanoma extremely difficult to cure. Additionally, there are no reliable molecular markers associated with melanoma progression. Invasion as a prerequisite for metastasis, is one of the most detrimental features of melanoma. Recently, using cultured cells, experimental animals and analysis of human melanoma specimens, we have identified guanosine monophosphate reductase (GMPR) as a suppressor of melanoma invasion. Our preliminary data show that functional antagonist of GMPR, guanosine monophosphate synthase (GMPS), is overexpressed in human metastatic melanomas and is required for melanoma cell invasion and growth of human melanoma xenografts in nude mice. Furthermore, we demonstrated that a relatively understudied chemical inhibitor of GMPS, decoyinine, reduces melanoma cell invasion. Moreover, our analysis of publically available databases identified several other guanylate metabolism enzymes that differentially express in primary and metastatic melanoma specimens. C-MYC is a transcription factor that regulates expression of multiple genes involved in promotion of proliferation, and augmentation of cellular metabolism, including biosynthesis of nucleotides. Up-regulation of C-MYC levels is one of the most frequent events in human malignancies including metastatic melanoma. Preliminary data in our laboratory suggested that GMPR is a C-MYC-responsive gene and that long-term GMPR suppression is mediated by epigenetic regulation. Therefore our central hypothesis is that progression to metastatic melanoma is facilitated by distortion of guanylate pools through disruption of normal biosynthetic pathways at multiple points. Our long term goal is to develop novel therapeutic approaches to treat or prevent metastatic melanoma, as well as to identify a set of biomarkers for early diagnosis of metastatic potential. Our objectives in the current proposal are i) to investigate the therapeutic potential of pharmacological inhibition of GMPS; ii) to characterize several rate- limiting enzymes involved in guanylate metabolism as potential melanoma markers and iii) to identify mechanisms underlying transcriptional suppression of GMPR in melanoma cells. To achieve these goals we propose the following three specific aims: 1) To determine the efficacy of the GMPS inhibitor decoyinine against melanoma xenografts in immunocompromised mice 2) To determine the prognostic value of enzymes involved in guanylate metabolism for overall survival (OS) of primary melanoma patients. 3)To investigate the mechanisms of GMPR regulation and the role of GMPR in MYC-dependent up-regulation of invasion. Melanoma is one of the incurable types of human cancers with no reliable prognostic molecular markers. Our proposed research will characterize a promising new target for melanoma therapy, discover new mechanisms underlying melanoma invasion, and identify new prognostic factors for melanoma patients.