Defining the role of mitochondrial injury in MEK inhibitor cardiotoxicity

项目总结/摘要 Ras-Raf-MEK-ERK通路的持续过度激活导致超过30%的人类肿瘤的发生。 癌的曲美替尼（Trm）是一种高度选择性的MEK 1抑制剂，MEK 1是多功能性前列腺素的唯一上游激活剂。 促生存激酶ERK 1/2。Trm通常与dabrafenib联合使用，以延长患者的生命 与黑色素瘤;其在其他常见肿瘤类型，包括三阴性乳腺癌（TNBC）的疗效正在研究中。 广泛探索。Trm通常耐受性良好，但它可能导致心肌病， 失败（HF）高达11%。Trm相关心脏毒性的潜在机制尚不清楚。我们 初步数据显示，14天的Trm处理废除了小鼠心肌ERK 1/2活化，并诱导了 可逆性心脏收缩功能障碍，特征为线粒体丰度降低和受损 体内氧化磷酸化。Trm处理的小鼠心脏的RNAseq分析显示， 线粒体转录物和免疫反应途径的增加在分子上不同于其他 HF病因。在体外原代心肌细胞暴露于Trm引起线粒体损伤和激活 典型的炎症通路。这些令人惊讶的影响是我们目前对生物多样性的理解所无法预测的。 MEK-ERK心肌细胞生物学或通过我们对MEK抑制剂的抗癌机制的理解 (MEKi的）。在这里，我们将使用3个具体的目标来测试中心假设，MEK-ERK抑制损害 OXPHOS诱导线粒体损伤，导致先天性免疫激活，这些效应共同 有助于Trm的心脏毒性和抗癌功效。在机械目标1中，我们将发现如果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。目的2 将确定MEK功能的遗传或药理学丧失是否足以诱导心肌细胞 使用心肌细胞MEK 1缺陷的新型小鼠模型和FDA批准的其他线粒体损伤 药理学MEKi。目的3将测试Trm诱导的线粒体毒性是否激活先天免疫 使用经验证的TNBC小鼠模型和临床相关的 联合靶向治疗这些研究将确定模式识别受体的激活是否 线粒体损伤相关的分子模式有助于Trm心脏毒性或抗癌功效， 并将确定在免疫检查点抑制剂中加入Trm是否会增加心脏毒性风险。的 提出的实验有可能影响心肌生物学和癌症治疗领域， 相关但不同的方式：（1）扩大我们对心肌细胞线粒体MEK-ERK调节的理解 功能;（2）确定有助于Trm心脏毒性的分子过程;（3）确定是否 线粒体毒性和先天免疫激活有助于Trm和其它MEKi的抗癌功效。

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.