L ALANOSINE THERAPY FOR MTAP DEFICIENT LUNG CANCER

描述：(申请人摘要)5‘-脱氧-5’-甲硫基腺苷 (MTA)是在多胺合成过程中按化学计量产生的 哺乳动物细胞，并被迅速切割成腺嘌呤和 甲硫柳糖-1-P由一种普遍存在的MTA磷酸化酶(MTAP)催化。MTAP 活性是细胞内源性腺嘌呤的唯一来源，这是 回收到AMP到ATP池。发现MTAP缺乏症 某些肿瘤导致肿瘤抑制基因的鉴定 CDKn2/pl6与染色体9p21上的MTAP连锁。纯合子缺失的 9P见于淋巴细胞性白血病、胶质瘤和非小细胞肺 癌症(NSCLC)。由于MTAP靠近CDKN2/PL6，MTAP 这些含有9P缺失的癌症中存在缺陷：30%的原发癌 NSCLC样本中发现MTAP缺陷。包含MTAP的单元格 如果MTA可用，尽管有抑制ATP合成的药物，但仍会增殖 作为一种嘌呤来源。相反，MTAP缺陷的细胞不能产生 腺嘌呤用于挽救，并选择性地被从头开始的抑制剂杀死 尽管有MTA，但仍有ATP合成。L-丙氨酸是一种天冬氨酸类似物， 抑制腺苷琥珀酸合成酶(ASS)，该酶是脑组织中的分支酶 从头合成AMP。L-丙氨酸甘氨酸二乙酯缩合产物 氨基咪唑羧酸盐核糖核苷酸对ASS的抑制作用 临床可耐受剂量。然而，过去的临床试验未能成功 显示L-丙氨酸团注治疗有显著疗效。回想起来， L-丙氨酸氨基转移酶检测的恶性肿瘤中没有一例表现出 除极少数外，CDKN2纯合缺失，且对 MTAP缺陷的肿瘤是可以预料到的。因此，L-丙氨酸氨基 从未在MTAP缺陷的癌症中进行过测试。初步数据显示， MTAP缺陷的恶性细胞系本质上对 L-丙氨酸比组织学匹配的MTAP阳性品系。供应 MTA仅选择性地恢复丙氨酸处理的细胞的增殖 含有MTAP的病毒。这些数据支持了L的新假设-- 丙氨酸氨基转移酶对MTAP缺陷型肿瘤可能有选择性毒性 对正常组织无毒，能够挽救MTA衍生腺嘌呤。这 假设在裸鼠NSCLC异种移植中被成功证实 每日或连续给予L-丙氨酸氨基葡萄糖苷引起的模型 仅对MTAP缺乏的肿瘤进行消退。建议的目标是 研究是通过L的II期临床试验来验证这一假说- 患有可测量疾病的非小细胞肺癌患者的丙氨酸氨基转移酶 通过遗传或免疫化学分析证明MTAP缺乏(目标1)。 ~(31)P磁共振波谱用于肿瘤ATP耗竭的研究 在治疗期间也是有计划的。L-丙氨酸苷的进一步确证 对MTAP缺陷肿瘤的选择性将使用裸体进行 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).