DNA Damage: Roles in Toxicity and Mutagenicity

描述(申请人提供)：DNA损伤在致癌物和许多临床使用的抗肿瘤药物引起的细胞毒性和诱变性中起着关键作用。虽然突变和细胞死亡不一定在机制上重叠，但许多DNA损伤可以诱导这两个生物终点。这一点在临床环境中被戏剧性地暴露出来，在那里，继发性癌症的显著发生率被归因于患者对其原发癌使用抗肿瘤药物的治疗。由于DNA仍然是抗癌药物极具吸引力的靶点，因此必须识别和消除诱变损伤的形成，同时保持那些选择性地诱导细胞毒性的损伤。我们的假设是，N3-甲基腺嘌呤(3-MeA)病变的选择性形成提供了一种杀死细胞的方法，同时将与继发性癌症相关的突变降至最低。为了研究这一问题，我们合成了[1-甲基-4-[1-甲基-4-(3-甲氧基磺酰基)-(propanamido)pyrrole-2-carboxamido]pyrrole-2-carboxamido]propane(Me-Lex)]，这是一种选择性地提供3-MeA的甲基化二肽。具体目标是：(1)设计具有更高活性和生物利用度的新型小槽烷基化剂(Me-Lex类似物)。(2)了解目标1中制备的化合物对小沟DNA损伤的细胞毒性和致突变性，并确定DNA修复背景对DNA损伤的影响。(3)利用含有3-MeA的模板和稳定的3-MeA类似物，研究3-MeA通过旁路聚合酶诱导复制DNA聚合酶停滞和跨损伤合成的机制。DNA序列对这些过程的影响也将被研究。(4)在人脑胶质瘤细胞系中检测Me-Lex及其类似物对Me-Lex的细胞毒作用，以验证对双(2-氯乙基)亚硝脲(BCNU)或替莫唑胺(TMZ)耐药的人脑胶质瘤不会对Me-Lex及其类似物产生交叉耐药性的假设。将评估立体定向瘤内注射Me-Lex及其类似物对无瘤鼠脑内人脑胶质瘤存活的影响，并与BCNU和TMZ的类似治疗进行比较。上述目的的结果将为3-MeA和相关DNA损伤的毒性和致瘤性提供有用的信息，以及如何避免致瘤性以提供改进的和更安全的癌症化疗。

DESCRIPTION (provided by applicant): DNA damage plays a critical role in the cytotoxicity and mutagenicity elicited by carcinogens and many clinically used antineoplastic agents. While mutagenesis and cell death do not necessarily overlap mechanistically, many DNA lesions can induce both biological endpoints. This point is dramatically exposed in the clinical setting where a significant incidence of secondary cancers is attributed to the treatment of patients with antineoplastic agents for their primary cancer. Since DNA remains an extremely attractive target for anticancer agents, it is imperative to identify and eliminate the formation of promutagenic lesions while maintaining those that selectively induce cytotoxicity. Our hypothesis is that the selective formation of N3- methyladenine (3-MeA) lesions presents an approach to kill cells while minimizing mutations associated with secondary cancers. To study this issue, we have synthesized [1-methyl-4-[1-methyl 4-(3-(methoxysulfonyl)- (propanamido)pyrrole-2-carboxamido]pyrrole-2-carboxamido]propane (Me-lex), a methylating dipeptide that selectively affords 3-MeA. The Specific Aims are: (1) To design new minor groove alkylating agents (analogues of Me-lex) with improved activity and bioavailabililty. (2) To understand the cytotoxicity and mutagenicity of specific minor groove DNA lesions induced by the compounds prepared in Aim 1, and to determine the impact of the DNA repair background. (3) To determine the mechanisms responsible for 3- MeA induced stalling of replicative DNA polymerases and translesion synthesis via by-pass polymerases using templates with 3-MeA and a stable analogue of 3-MeA. The effect of DNA sequence on these processes will also be investigated. (4) The cytotoxicity of Me-lex and the analogues synthesized in Aim 1 will be assayed in human glioma cell lines to test the hypothesis that human gliomas resistant to the cytotoxic effects of bis(2-chloroethyl)nitrosourea (BCNU) or temozolomide (TMZ) will not be cross-resistant to Me-lex and its analogs. The effects of stereotactic intratumoral delivery of Me-lex and the analogs on survival of athymic rats with intracerebral human gliomas will be evaluated and compared to similar treatments with BCNU and TMZ. The results of the above aims should provide useful information on the toxicity and tumorigenicity of 3-MeA and related DNA lesions, as well as how tumorigenicity can be avoided to afford improved and safer cancer chemotherapies.