CCNU in NSCLC Patients with Methylation of the MGMT Gene

在美国，每年约有三分之一的癌症相关死亡是由肺癌造成的。研究新的范例，包括新的治疗方法，已经成为肿瘤学界的当务之急。异常CpG岛甲基化已被确定为一种使关键调控基因失活的机制，也可能对指导治疗有用。肿瘤细胞在体外和体内对甲基化和单氯乙基化药物的抗性与DNA修复蛋白o6 -甲基鸟嘌呤-DNA甲基转移酶（MGMT）的表达有关。我们已经开发了一种甲基化特异性PCR检测（MS-PCR），它具有很高的特异性和敏感性，并且已经证明大约1/3的非小细胞肺癌（NSCLC）具有异常甲基化的MGMT基因。本研究的目的是验证MGMT甲基化异常的晚期NSCLC患者对亚硝基脲CCNU敏感的假设。为了验证这一假设，我们将在IIIB和IV期疾病患者中进行CCNU的II期试验，这些患者的肿瘤已经发现MGMT基因的CpG岛甲基化异常。该试验的具体目的是：(1)确定MGMT甲基化异常的晚期NSCLC患者对CCNU的应答率；次要目标将评估进展时间和总生存期。(2)免疫组化（IHC）中MGMT水平与临床预后的相关性。(3) MGMT蛋白的免疫组化染色与MS-PCR的相关性。这项资助可以确定一种新的治疗策略，利用在某些肿瘤中负责保护细胞免受CCNU细胞毒性作用的MGMT基因失活的事实。如果通过提高应答率来证明有效性，这些研究将导致更大规模的多机构临床试验。此外，这种方法可以促进未来的研究，在这些研究中，患者接受更个性化的联合治疗方案，以利用失活或重新激活诱导细胞周期停滞和凋亡所需的基因的途径。

Lung cancer is responsible for approximately 1/3 of all cancer related deaths in the US each year. Investigation of new paradigms, including novel therapeutic approaches, has become an urgent priority for the oncology community. Aberrant CpG island methylation has been identified as a mechanism of inactivating critical regulatory genes, and may also be useful for directing therapy. Resistance of tumor cells to methylating and monocloroethylating agents in vitro and in vivo has been linked to expression of the DNA repair protein, O6-methylguanine-DNA methyltransferase (MGMT). We have developed a methylation- specific PCR assay (MS-PCR) which has given us high specificity and sensitivity, and have demonstrated that about 1/3 of non- small cell lung cancers (NSCLC) have aberrantly methylated MGMT genes. The objective of this proposal is to test the hypothesis that patients with advanced NSCLC and aberrant MGMT methylation will be sensitive to the nitrosourea CCNU. To test this hypothesis, we will conduct a Phase II trial of CCNU in patients with Stage IIIB and IV disease whose tumors have been found to have aberrant CpG island methylation of the MGMT gene. The specific aims of the trial are to: (1) Determine the response rate of patients with advanced NSCLC with aberrant MGMT methylation to CCNU; secondary objectives will assess time to progression and overall survival. (2) Correlate MGMT levels on immunohistochemistry (IHC) with clinical outcome. (3) Correlate IHC staining of the MGMT protein and the MS-PCR. This grant could identify a novel treatment strategy that exploits the fact that the MGMT gene responsible for protecting cells from the cytotoxic effects of CCNU is inactivated in some tumors. If efficacy is demonstrated by enhanced response rates, these studies would lead to larger scale, multi-institutional clinical trials. Moreover, this approach could facilitate future studies in which patients receive more individualized combination treatment regimens to exploit pathways that are either inactivated or to reactivate genes needed to induce cell cycle arrest and apoptosis.