BACKGROUND & AIMS Treatment of liver cancer remains challenging because of a paucity of drugs that target critical dependencies. Sorafenib is a multikinase inhibitor that is approved as the standard therapy for patients with advanced hepatocellular carcinoma, but it only provides limited survival benefit. In this study we aimed to identify potential combination therapies to improve the clinical response to sorafenib. METHODS To investigate the cause of the limited therapeutic effect of sorafenib, we performed a CRISPR-Cas9 based synthetic lethality screen to search for kinases whose knockout synergizes with sorafenib. Synergistic effects of sorafenib and selumetinib on cell apoptosis and phospho-ERK (p-ERK) were analyzed by caspase-3/7 apoptosis assay and western blot, respectively. p-ERK was measured by immunochemical analysis using a tissue microarray containing 78 liver cancer specimens. The in vivo effects of the combination were also measured in two xenograft models. RESULT We found that suppression of ERK2 (MAPK1) sensitizes several liver cancer cell lines to sorafenib. Drugs inhibiting the MEK (MEK1/2 [MAP2K1/2]) or ERK (ERK1/2 [MAPK1/3]) kinases reverse unresponsiveness to sorafenib in vitro and in vivo in a subset of liver cancer cell lines characterized by high levels of active p-ERK, through synergistic inhibition of ERK kinase activity. CONCLUSION Our data provide a combination strategy for treating liver cancer and suggest that tumors with high basal p-ERK levels, which are seen in approximately 30% of liver cancers, are most likely to benefit from such combinatorial treatment. LAY SUMMARY Sorafenib is approved as the standard therapy for patients with advanced hepatocellular carcinoma, but only provides limited survival benefit. Herein, we found that inhibition of the kinase ERK2 increases the response to sorafenib in liver cancer. Our data indicate that a combination of sorafenib and a MEK inhibitor is most likely to be effective in tumors with high basal phospho-ERK levels.

中文翻译：

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磷酸化 ERK 是对肝癌中索拉非尼和 MEK 抑制的合成致死药物组合反应的生物标志物

背景和目的 由于缺乏针对关键依赖性的药物，肝癌的治疗仍然具有挑战性。索拉非尼是一种多激酶抑制剂，被批准作为晚期肝细胞癌患者的标准疗法，但它只能提供有限的生存益处。在这项研究中，我们旨在确定潜在的联合疗法，以改善对索拉非尼的临床反应。方法为了调查索拉非尼治疗效果有限的原因，我们进行了基于 CRISPR-Cas9 的合成致死筛选，以寻找与索拉非尼敲除具有协同作用的激酶。分别通过 caspase-3/7 细胞凋亡测定和蛋白质印迹分析索拉非尼和司美替尼对细胞凋亡和磷酸化 ERK (p-ERK) 的协同作用。p-ERK 是通过免疫化学分析使用含有 78 个肝癌标本的组织微阵列测量的。还在两个异种移植模型中测量了该组合的体内效应。结果 我们发现 ERK2 (MAPK1) 的抑制使几种肝癌细胞系对索拉非尼敏感。抑制 MEK (MEK1/2 [MAP2K1/2]) 或 ERK (ERK1/2 [MAPK1/3]) 激酶的药物在体外和体内逆转以高水平活性为特征的肝癌细胞系对索拉非尼的无反应p-ERK，通过协同抑制 ERK 激酶活性。结论 我们的数据提供了治疗肝癌的联合策略，并表明在大约 30% 的肝癌中观察到的具有高基础 p-ERK 水平的肿瘤最有可能受益于这种联合治疗。概述 索拉非尼被批准作为晚期肝细胞癌患者的标准疗法，但仅提供有限的生存获益。在此，我们发现激酶 ERK2 的抑制增加了肝癌中对索拉非尼的反应。我们的数据表明，索拉非尼和 MEK 抑制剂的组合最有可能对基础磷酸化 ERK 水平高的肿瘤有效。