Defining the role of mitochondrial injury in MEK inhibitor cardiotoxicity

项目摘要/摘要 Ras-Raf-MEK-ERK通路的持续高激活在30%以上的人类肿瘤发生中起作用 癌症。曲美替尼(Trametinib，Trm)是MEK1的一种高度选择性的抑制剂，MEK1是多功能的唯一上游激活剂 促生存激酶ERK1/2。TRM常与达普拉非尼联合用来延长患者的生命 对于黑色素瘤；它对包括三阴性乳腺癌(TNBC)在内的其他常见肿瘤类型的疗效正在 被广泛探索。TRM一般耐受性良好，尽管它可引起心肌病，从而可能导致心脏 高达11%的病例出现故障(HF)。Trm相关心脏毒性的机制尚不清楚。我们的 初步数据显示，14天的Trm处理可抑制小鼠心肌ERK1/2的激活并诱导 以线粒体丰度减少和受损为特征的可逆性心脏收缩功能障碍 体内氧化磷酸化。对Trm处理的小鼠心脏的RNAseq分析显示， 线粒体转录本和免疫反应途径的增加在分子上与其他 心衰病因。Trm对原代培养心肌细胞线粒体的损伤和激活作用 典型的炎症途径。这些令人惊讶的影响是我们目前对 MEK-ERK心肌细胞生物学或我们对MEK抑制剂抗癌机制的了解 (梅基的)。在这里，我们将使用3个特定的目标来检验MEK-ERK抑制损害的中心假设 OXPHOS诱导线粒体损伤导致先天性免疫激活，这些作用共同作用 有助于Trm的心脏毒性和抗癌效果。在机械目标1中，我们会发现如果Trm 通过损害氧化磷酸化和诱导氧化应激来诱导线粒体损伤。目标2 将确定MEK功能的遗传或药物丧失是否足以诱导心肌细胞 利用新的小鼠心肌细胞MEK1缺乏模型和FDA批准的其他模型造成线粒体损伤 药理学Meki的Aim 3将测试Trm诱导的线粒体毒性是否激活先天免疫 应用经验证的TNBC小鼠模型和临床相关的TBC在心肌细胞和癌细胞中的反应 联合靶向治疗。这些研究将确定模式识别受体的激活 通过线粒体损伤相关的分子模式有助于Trm的心脏毒性或抗癌效果， 并将确定将Trm添加到免疫检查点抑制剂是否会增加心脏毒性风险。这个 拟议中的实验有可能影响心肌生物学和癌症治疗领域 相关但不同的方法：(1)扩大我们对MEK-ERK对心肌细胞线粒体调控的理解 功能；(2)确定导致Trm心脏毒性的分子过程；(3)确定 线粒体毒性和先天免疫激活有助于Trm和其他Meki的抗癌效果。

PROJECT SUMMARY/ABSTRACT Persistent hyperactivation of the Ras-Raf-MEK-ERK pathway contributes to oncogenesis in over 30% of human cancers. Trametinib (Trm) is a highly selective inhibitor of MEK1, the sole upstream activator of multifunctional pro-survival kinases ERK1/2. Trm commonly is used in combination with dabrafenib to prolong life in patients with melanoma; its efficacy in other common tumor types including triple negative breast cancer (TNBC) is being widely explored. Trm generally is well tolerated, though it can cause cardiomyopathy that may lead to heart failure (HF) in up to 11% of cases. The mechanisms underlying Trm-associated cardiotoxicity are unclear. Our preliminary data show that 14-day Trm treatment abrogated mouse myocardial ERK1/2 activation and induced reversible cardiac contractile dysfunction characterized by reduced mitochondrial abundance and compromised oxidative phosphorylation in vivo. RNAseq analysis of Trm-treated mouse hearts revealed broad decreases in mitochondrial transcripts and increases in immune response pathways that are molecularly distinct from other HF etiologies. In vitro exposure of primary cardiomyocytes to Trm caused mitochondrial injury and activated canonical inflammatory pathways. These surprising effects were not predicted by our current understanding of MEK-ERK cardiomyocyte biology or by our understanding of the anticancer mechanisms of MEK inhibitors (MEKi’s). Here we will use 3 specific aims to test the central hypothesis that MEK-ERK inhibition impairs OXPHOS to induce mitochondrial injury resulting in innate immune activation, and that these effects collectively contribute to both the cardiotoxicity and anticancer efficacy of Trm. In the mechanistic Aim 1 we will find if Trm induces mitochondrial injury by compromising oxidative phosphorylation and inducing oxidative stress. Aim 2 will determine whether genetic or pharmacological loss of MEK function is sufficient to induce cardiomyocyte mitochondrial injury using novel mouse models of cardiomyocyte MEK1 deficiency and other FDA-approved pharmacological MEKi’s. Aim 3 will test whether Trm-induced mitochondrial toxicity activates innate immune responses in cardiomyocytes and cancer cells using a validated mouse model of TNBC and a clinically relevant combination targeted therapy. These studies will establish whether activation of pattern recognition receptors by mitochondrial damage associated molecular patterns contributes to Trm cardiotoxicity or anticancer efficacy, and will define whether the addition of Trm to an immune checkpoint inhibitor enhances cardiotoxic risk. The proposed experiments have the potential to impact the fields of myocardial biology and cancer therapeutics in related but distinct ways: (1) Expand our understanding of MEK-ERK regulation of cardiomyocyte mitochondrial function; (2) Identify the molecular processes that contribute to Trm cardiotoxicity; (3) Determine whether mitochondrial toxicity and innate immune activation contribute to the anticancer efficacy of Trm and other MEKi’s.