BIOCHEMICAL MODULATION OF DRUG RESISTANCE IN TUMOR CELLS

我们最初应用程序中提出的假设是基于 肿瘤细胞对DNA导向的化疗药物的耐药性 作为氯乙基亚硝脲(CENU)和铂络合物(顺铂和 CBDCA)源于DNA修复系统，该系统保护肿瘤细胞免受 细胞毒性DNA损伤。压倒性的证据表明，0比6 甲基鸟嘌呤DNA甲基转移酶(MGMT)是 CENU抵抗运动。在上一个资助期内，我们已经展示了 这种DNA修复酶可以被临床使用的药物抑制 链佐菌素(STZ)。当高度耐药的肿瘤细胞被预处理时 在BCNU暴露前使用STZ，对MGMT的有效完全抑制 获得，并观察到高度协同的细胞杀伤。目标1 目前的应用将继续对肿瘤细胞进行生化调节 通过含有STZ的MGMT耗竭方案对CENU的耐药性，以及 一种新型MGMT耗尽剂0-6-苯基鸟嘌呤(BG)。这些研究 靶向耐药细胞中的MGMT修复蛋白。目标2将 肿瘤细胞对CENU耐药性的分子调控尝试 从可诱导载体转录的反义核酶，以破坏或 从功能上抑制长寿的MGMT基因。这些研究将针对 长寿的MGMT基因可能与CENU的重新获得有关 人类肿瘤细胞中的耐药性。 在之前的资助期间，我们证明了DNA切除 修复抑制剂(阿糖胞苷，阿糖胞苷和羟基脲，HU) 可以抑制铂引起的DNA损伤的修复，并产生 协同作用杀死细胞。当前应用程序的目标3将尝试 肿瘤细胞对铂类化合物耐药性的生化调控 以2‘，2’-二氟脱氧胞苷(DFDC)和氟达拉滨(F-Ara-A)为原料 DNA切除修复的新型抑制剂。这些研究将包括 令人兴奋的新化合物与铂类似物相结合抑制 白金损伤修复。目标4将说明ERCC的作用 切除修复交叉互补基因在肿瘤细胞中的表达 对铂化合物敏感和耐受。所有人的最终目标 这些研究的目的是增加我们对心力衰竭发病机制的理解。 对这些药物的耐药性，并开发新的治疗方案 在试图逆转耐药性的临床试验中进行了测试 在病人身上。

The hypothesis posed in our original application was predicated on the concept that tumor cell resistance to DNA-directed chemotherapeutics such as the chloroethylnitrosoureas (CENU), and platinum complexes (cis-Pt and CBDCA) results from DNA repair systems which protect the tumor cell from the cytotoxic DNA lesions. Overwhelming evidence indicated that 0-6 methylguanine DNA methyltransferase (MGMT) was the major contributor to CENU resistance. During the previous funding period we have demonstrated that this DNA repair enzyme can be inhibited by the clinically used agent Streptozotocin (STZ). When highly resistant tumor cells were pretreated with STZ prior to BCNU exposure, virtual complete inhibition of MGMT was obtained, and highly synergistic cell kills were observed. Aim 1 of the current application will continue biochemical modulation of tumor cell resistance to the CENU with MGMT-depleting regimens containing STZ, and the novel MGMT-depleting agent 0-6 Benzylguanine (BG). These studies target the MGMT repair protein in drug resistant cells. Aim 2 will attempt molecular modulation of tumor cell resistance to the CENU using antisense ribozymes transcribed from inducible vectors, to destroy or functionally inhibit long-lived MGMT mRNA. These studies will target long lived MGMT mRNA which may be responsible for reacquisition of CENU resistance in human tumor cells. During the previous funding period we demonstrated that DNA excision repair inhibitors (cytosine arabinoside, Ara-C, and Hydroxyurea, HU) could inhibit the repair of platinum-induced DNA damage, and produce synergistic cell kills. Aim 3 of the current application will attempt biochemical modulation of tumor cell resistance to the platinum compounds using 2',2'Difluorodeoxycytidine (dFdC) and Fludarabine (F-Ara-A) as novel inhibitors of DNA excision repair. These studies will incorporate exciting new compounds in combination with platinum analogs to inhibit platinum damage repair. Aim 4 will characterize the role of ERCC (Excision Repair Cross Complementation) gene expression in tumor cells sensitive and resistant to platinum compounds. The ultimate goal of all of these studies is to increase our understanding of the mechanisms of drug resistance to these agents, and to develop novel regimens to be tested in clinical trials which will attempt to reverse drug resistance in patients.