DNA Damage: Roles in Toxicity and Mutagenicity

描述（由申请人提供）：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致突变性中起着关键作用。虽然诱变和细胞死亡在机制上不一定重叠，但许多DNA损伤可以诱导这两个生物学终点。这一点在临床环境中被戏剧性地暴露出来，继发性癌症的显著发生率归因于对原发癌症患者使用抗肿瘤药物的治疗。由于DNA仍然是抗癌药物的一个极具吸引力的靶点，因此必须识别和消除致突发性病变的形成，同时保持那些选择性诱导细胞毒性的病变。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，同时最小化与继发性癌症相关的突变。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）-（丙酰胺）吡咯-2-羧酰胺]吡咯-2-羧酰胺]丙烷（Me-lex），这是一种选择性提供3- mea的甲基化二肽。具体目的是：(1)设计新的小槽烷基化剂（Me-lex的类似物），提高活性和生物利用度。(2)了解Aim 1中制备的化合物诱导的特定微小凹槽DNA病变的细胞毒性和诱变性，并确定DNA修复背景的影响。(3)利用含有3-MeA和稳定的3-MeA类似物的模板，确定3-MeA诱导复制DNA聚合酶停滞和通过旁通聚合酶转译合成的机制。DNA序列对这些过程的影响也将被研究。(4)在Aim 1中合成的Me-lex及其类似物的细胞毒性将在人类胶质瘤细胞系中进行检测，以验证对双（2-氯乙基）亚硝基脲（BCNU）或替莫唑胺（TMZ）具有细胞毒性作用的人类胶质瘤不会对Me-lex及其类似物产生交叉抗性的假设。将评价立体定向瘤内给药Me-lex及其类似物对脑胶质瘤胸腺大鼠生存的影响，并与BCNU和TMZ的类似治疗进行比较。上述目的的结果应该为3-MeA和相关DNA病变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.