DNA Damage: Roles in Toxicity and Mutagenicity

描述（由申请方提供）：DNA损伤在致癌物和许多临床使用的致癌剂引起的细胞毒性和致突变性中起关键作用。虽然诱变和细胞死亡不一定在机制上重叠，但许多DNA损伤可诱导两种生物学终点。这一点在临床环境中显著暴露，其中继发性癌症的显著发生率归因于用抗癌剂治疗原发性癌症的患者。由于DNA仍然是一个非常有吸引力的抗癌药物的目标，它是必要的，以确定和消除的前致突变病变的形成，同时保持那些选择性诱导细胞毒性。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，同时最大限度地减少与继发性癌症相关的突变。为了研究这个问题，我们合成了[1-甲基-4-[1-甲基4-（3-（甲氧磺酰基）-（丙酰胺基）吡咯-2-甲酰氨基]吡咯-2-甲酰氨基]丙烷（Me-lex），其是一种选择性地提供3-MeA的甲基化二肽。具体目的是：（1）设计新的小沟烷化剂（Me-lex类似物），提高活性和生物利用度。(2)了解目标1中制备的化合物诱导的特定小沟DNA损伤的细胞毒性和致突变性，并确定DNA修复背景的影响。(3)确定3- MeA诱导的复制型DNA聚合酶停滞的机制，以及使用3-MeA和3-MeA稳定类似物的模板通过旁路聚合酶的跨损伤合成。DNA序列对这些过程的影响也将被研究。(4)将在人类神经胶质瘤细胞系中测定Me-lex和在Aim 1中合成的类似物的细胞毒性，以检验对双（2-氯乙基）亚硝基脲（BCNU）或替莫唑胺（TMZ）的细胞毒性作用具有抗性的人类神经胶质瘤不会对Me-lex及其类似物具有交叉抗性的假设。将评价Me-lex和类似物的立体定向瘤内递送对患有脑内人类神经胶质瘤的无胸腺大鼠的存活率的影响，并与BCNU和TMZ的类似治疗进行比较。上述目标的结果应该提供有用的信息的毒性和致瘤性的3-MeA和相关的DNA病变，以及如何避免致瘤性，以提供更好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.