Overcoming Resistance to RAF Inhibition in BRAF-Mutant Colorectal Cancer

BRAF癌基因突变是结直肠癌(CRC)的常见事件。这些突变是 与不良结局和对基于表皮生长因子受体(EGFR)的不敏感相关 心理治疗。鉴于RAF抑制剂在治疗BRAF突变的恶性肿瘤方面取得了成功 对于黑色素瘤，BRAF突变的CRC的应答率令人惊讶地低。这些完全不同的基础 治疗结果仍未完全了解。我们小组的初步研究发现， 在结直肠癌细胞系中，PLX4720对MAPK通路的抑制是不完全的。在某些情况下，这可能是由于 以增强EGFR依赖的信号转导，但这不能解释这种情况下的所有耐药性。我们的 目的是确定在BRAF突变的结直肠癌中产生新的耐药性的作用机制。 RAF抑制剂，希望能够实现更有效的治疗。第一，差异表达基因 与BRAF相关联的突变CRC将通过分析TCGA数据集进行鉴定；这些基因将被 与那些根据正在进行的系统性研究修改对MAPK途径抑制剂的反应的药物进行整合 功能屏幕。顶级基因将接受机制研究，以阐明分子 同时，正在进行的功能筛查将扩大以识别 在BRAF突变的大肠细胞中具有RAF抑制的合成致死基因。在这里，验证 领先的候选人将优先考虑可能会被下药的基因--几名候选人已经 已经被提名了。靶向药物与RAF抑制剂的合理组合将在细胞中探索 在培养和异种移植模型中。最后，将进行RAF和MEK联合抑制剂的临床试验。 通过增强对MAPK通路的抑制，并可能 防止出现耐药现象。肿瘤活检将在治疗前、治疗中和 进程后，以及整个外显子组和转录组测序将被用来识别基因组 可能导致抵抗的变化。总而言之，这项工作应该提供对 MAPK抑制剂和克服它们的新的治疗方法。

Mutation of the BRAF oncogene is a common event in colorectal cancer (CRC). These mutations are associated with adverse outcome and insensitivity to epidermal growth factor receptor (EGFR) based therapy. Whereas RAF inhibitors have been succesful in the treatment of BRAF-mutant malignant melanoma, response rates in BRAF-mutant CRC are surprisingly low. The basis for these disparate treatment outcomes remains incompletely understod. Preliminary studies from our groups found that suppression of the MAPK pathway by PLX4720 is incomplete in CRC lines. In some cases, this may be due to augmented EGFR-dependent signaling, but this does not explain all resistance in this setting. Our objective is to identify mechanisms operant in BRAF-mutant colorectal cancer that confer de novo resistance to RAF inhibitors, in hopes of enabling more efficacious therapeutics. First, differentially expressed genes linked to BRAF-mutant CRC will be identified by analysis of the TCGA dataset; these genes will be Integrated with those that modify response to MAPK pathway inhibitors based on ongoing systematic functional screens. Top-ranking genes will be subjected to mechanistic studies to elucidate the molecular basis by which they confer resistance, in parallel, ongoing functional screens will be expanded to Identify genes that are synthetic lethal with RAF inhibition in BRAF-mutant colorectal cells. Here, validation of leading candidates will be prioritized for genes that are potentially druggable-several candidates have already been nominated. Rational combinations of targeted agents with RAF inhibitors will be explored in cell culture and in xenograft models. Finally, clinical trials of combined RAF and MEK inhibitors will be performed at DF/HCC in an attempt to improve efficacy by enhancing suppression of the MAPK pathway and possibly prevent the emergence of drug-resistance. Tumor biopsies will be collected pre-treatment, on-treatment and post-progression, and whole exome and transcriptome sequencing will be used to identify genomic alterations that may drive resistance. Altogether, this work should provide a rigorous analysis of resistance to MAPK inhibitors and new therapeutic approaches to overcome them.