Study on selective cancer chemotherapy targeting the deficiency of a purine metabolic enzyme

这项研究计划的广泛和长期目标是确定甲基硫代腺苷磷酸化酶（MTAP）缺乏症在人类癌症中的患病率和临床特征，并开发和应用MTAP阴性癌症的特异性治疗新方法。在哺乳动物细胞中，甲基硫腺苷（MTA）是在多胺合成过程中产生的。MTA不会在正常组织中积累，但MTAP会迅速裂解成腺嘌呤和5'-甲基硫核糖1-磷酸（MTR-1-P）。腺嘌呤和MTR-1-P被循环生成嘌呤核苷酸和蛋氨酸。分别。由于已知所有正常细胞或组织都含有MTAP，人类癌症中MTAP的缺乏将使我们能够开发肿瘤特异性化疗，在这种化疗中，MTAP阴性的癌细胞将被选择性地杀死，药物会导致嘌呤核苷酸或蛋氨酸的消耗，在这种情况下，MTAP阳性的正常组织可以通过给予MTA作为嘌呤核苷酸或蛋氨酸的来源而获救。为了检测MTAP阴性的原发性癌症，我们采用Taqman化学建立了定量PCR检测MTAP基因纯合缺失的方法。即使在含有30%正常细胞的样品中，该方法也能诊断出MTAP基因缺失。由于MTAP缺陷并不完全是由基因缺失引起的，因此已经成功地产生了单克隆抗体，并准备进行免疫组织化学。为了开发选择性治疗mtap阴性肿瘤的新方法，我们在动物模型中使用l -丙氨酸选择性治疗mtap阴性肿瘤。

The broad, long-term objectives of this research proposal are to determine the prevalence and clinical characteristics of methylthioadenosine phosphorylase (MTAP) deficiency in human cancers and to develop and apply new methods for the specific treatment of MTAP-negative cancers.In mammalian cells, methylthioadenosine (MTA) is produced during the synthesis of the polyamines. MTA does not accumulate in normal tissues but is cleaved rapidly to adenine and 5'-methylthioribose 1-phosphate (MTR-1-P) by MTAP. The adenine and MTR-1-P are recycled to purine nucleotides and methionine. respectively. Since all normal cells or tissues are known to contain MTAP, MTAP deficiency in human cancers will enable us to develop tumor-specific chemotherapy, in which MTAP-negative cancer cells will be selectively killed with drugs causing the depletion of purine nucleotides or methionine, under conditions where MTAP-positive normal tissues can be rescued by giving MTA as the sources of purine nucleotides or methionine.In. order to detect MTAP-negative primary cancers, we have developed quantitative PCR assay to detect homozygous deletion of MTAP gene using Taqman chemistry. This method was able to diagnose MTAP gene deletion even in the samples containing 30 % normal cells. Since MTAP deficiency is not solely attributable to gene deletion, monoclonal antibodies has been generated successfully and are ready for immunohistochemistry. To develop new methods for the selective treatment of MTAP-negative cancers, we used L-alanosine to selectively treat MTAP-negative tumors in animal models.