威罗菲尼（Plx4032）作为治疗BRAFV600E型黑色素瘤的一线药物，应答期只有6-9个月之后会出现耐药。Nras过表达引起MAPK通路重激活是导致Plx4032耐药的主因，而关于Nras转录调控机制仍不清楚，Nras自身功能特点也使其靶向药物研发困难。项目组首次发现核转录因子Nrf2是Nras潜在转录因子，前期结果显示Nrf2与Nras表达在Plx4032耐药株中显著上调，Nrf2正调控Nras mRNA表达与细胞耐药性，双荧光素酶报告基因实验证实Nrf2结合于Nras全长启动子区。由此本项目提出科学假说：Nrf2作为Nras转录因子，通过促进Nras转录，激活MAPK通路，增强细胞耐药能力。本项目拟阐明Nrf2在Nras启动子区的转录结合位点序列，并从细胞、动物与临床样本多角度证实Nrf2-Nras信号轴异常可影响MM的Plx4032耐药性，为MM的靶向治疗与耐药评估提供新靶标。

Treating advanced or unresectable malignant melanoma has been a prominent issue for many decades because of melanoma’s resistance to various therapeutic regimens. Current treatment of metastatic melanoma that uses mutant BRAFV600E-specific inhibitor-Vemurafenib (Plx4032) have produced high response rates but with rapid relapse; the addition of a MEK1/2 inhibitor has led to a modest increase in survival. Nevertheless, the majority of tumors progress in most patients. Therefore, Revealing novel resistance associated-target genes are urgently needed. The acquired resistance involves Nras overexpression-mediated reactivation of MAPK pathway. However, the underlying mechanisms responsible for up-regulation of Nras in acquired resistance are not clear. More importantly, decades of work have not yet yielded any efficient way to block the expression and activity of Nras. Our preliminary data suggest that Nrf2 (nuclear factor erythroid 2-related factor 2) is a potential transcriptional activator for Nras. Our established Plx4032-resistant cell lines showed increased mRNA and protein expression levels of Nras and Nrf2. Nrf2 knockdown decreased the mRNA expression of Nras, sensitized melanoma cells to Plx4032 treatment while Nrf2 over-expression led to increased mRNA expression of Nras and cell resistance. Particularly, exogenous Nrf2 expression was able to enhance NRAS promoter activity in a concentration dependent manner, using a dual luciferase reporter assay. Therefore, we hypothesize that ectopic expression of Nrf2 play a key role in the Plx4032-resistant progression of melanoma via the transcriptional up-regulation of Nras and reactivation of MAPK pathway. We propose that Nrf2 is a novel therapeutic target instead of Nras to overcome the Plx4032 resistance.