L ALANOSINE THERAPY FOR MTAP DEFICIENT LUNG CANCER

说明：（申请人摘要）5 ′-脱氧-5 ′-甲硫基腺苷 (MTA)在多胺合成过程中按化学计量产生， 哺乳动物细胞，并迅速裂解为腺嘌呤， 甲基硫代核糖-1-P通过普遍存在的MTA磷酸化酶（MTAP）。MTAP 活性是细胞中内源性腺嘌呤的唯一来源， 从AMP回收到ATP池。发现MTAP缺陷， 某些肿瘤导致了肿瘤抑制基因的鉴定 在染色体9 p21上与MTAP连锁的CDKN 2/p16。纯合性缺失 9 p发生于淋巴母细胞白血病、胶质瘤和非小细胞肺癌 癌症（NSCLC）。由于MTAP与CDKN 2/pl 6的接近性，MTAP 在这些携带9 p缺失的癌症中存在缺陷：30%的原发性 发现NSCLC样本为MTAP缺陷型。含MTAP细胞 尽管有抑制ATP合成的药物，如果MTA是可用的， 作为嘌呤来源。相比之下，MTAP缺陷细胞不能产生 腺嘌呤的补救，并选择性地杀死抑制剂的从头 ATP合成尽管MTA。L-丙氨酸核苷是天冬氨酸类似物， 抑制腺苷酸琥珀酸合成酶（ASS），这是一种分支点酶， AMP从头合成。L-丙氨酸核苷与 氨基咪唑羧酸核糖核苷酸有效地抑制ASS， 临床耐受剂量。然而，过去的临床试验未能 显示L-丙氨酸核苷推注疗法显著活性。回想起来， L-丙氨酸核苷所测试的恶性肿瘤中没有一个表现出 纯合子CDKN 2缺失，除了罕见的，没有选择性影响， MTAP缺陷型肿瘤是可以预期的。因此，L-丙氨酸核苷具有 从未在缺乏MTAP的癌症中进行过测试。初步数据显示， MTAP缺陷型恶性细胞系本质上对 L-丙氨酸核苷比组织学上匹配的MTAP阳性细胞系高。供应 MTA仅在丙氨酸核苷处理的细胞中选择性地恢复增殖 包含MTAP的文件。这些数据支持了新的假设，即L- 在一定剂量下，丙氨酸核苷可能对MTAP缺陷型肿瘤具有选择性毒性， 对正常组织无毒，能够挽救MTA衍生的腺嘌呤。这 在裸鼠NSCLC异种移植物中成功证实了这一假设 模型，其中每日或连续给药L-丙氨酸核苷引起 只有MTAP缺陷型肿瘤的消退。建议的目标 研究是通过L- 丙氨酸氨基转移酶在具有可测量疾病的NSCLC患者中的应用， 通过遗传学或免疫化学测定证明MTAP缺陷（目的1）。 31 P磁共振波谱用于记录肿瘤ATP耗竭 治疗期间也是如此。L-丙氨酸核苷的进一步确认 MTAP缺陷型肿瘤的选择性将使用裸 小鼠异种移植模型（Aim 2）。

DESCRIPTION: (Applicant's Abstract) 5'-Deoxy-5'-methylthioadenosine (MTA) is produced stoichiometrically during polyamine synthesis in mammalian cells, and is rapidly cleaved to adenine and methylthioribose-1-P by a ubiquitous MTA phosphorylase (MTAP). MTAP activity is the only source of endogenous adenine in cells, which is salvaged back to AMP to ATP pools. Discovery of MTAP deficiency in certain neoplasms led to the identification of the tumor suppressor gene CDKN2/pl6 linked to MTAP on chromosome 9p2l. Homozygous deletions of 9p occur in lymphoblastic leukemia, glioma, and non-small cell lung cancer (NSCLC). Due to the proximity of MTAP to CDKN2/pl6, MTAP deficiency occurs in these cancers harboring 9p deletions: 30% of primary NSCLC samples were found to be MTAP-deficient. MTAP-containing cells proliferate despite drugs that inhibit ATP synthesis, if MTA is available as a purine source. In contrast, MTAP-deficient cells cannot produce adenine for salvage, and are selectively killed by inhibitors of de novo ATP synthesis despite MTA. L-alanosine is an aspartate analogue that inhibits adenylosuccinate synthetase (ASS), the branch point enzyme in de novo AMP synthesis. The condensation product of L-alanosine and aminoimidazolecarboxylate ribonucleotide potently inhibits ASS at clinically tolerated dosages. However, past clinical trials failed to show significant activity of L-alanosine bolus therapy. In retrospect, none of the malignancies in which L-alanosine was tested exhibit homozygous CDKN2 deletions except rarely, and no selective effect on MTAP-deficient tumors could have been expected. Thus, L-alanosine has never been tested in MTAP-deficient cancer. Preliminary data show that MTAP-deficient malignant cell lines are intrinsically more sensitive to L-alanosine than histologically matched MTAP-positive lines. Supplying MTA selectively restores proliferation only in alanosine-treated cells that contain MTAP. These data support the novel hypothesis that L- alanosine may be selectively toxic to MTAP-deficient tumors, at doses not toxic to normal tissues able to salvage MTA-derived adenine. This hypothesis is successfully confirmed in a nude mouse NSCLC xenograft model, in which daily or continuous dosing of L-alanosine caused regression only of MTAP-deficient tumors. The goal of the proposed research is to test this hypothesis by Phase II clinical trial of L- alanosine in NSCLC patients with measurable disease, whose tumors are documented MTAP-deficient by genetic or immunochemical assays (Aim 1). 31P magnetic resonance spectroscopy to document tumor ATP depletion during therapy is also planned. Further confirmation of L-alanosine selectivity for MTAP-deficient tumors will be performed using nude mouse xenograft models (Aim 2).