Chen C-H, Fong L W R, Yu E, Wu R, Trott J F, Weiss R H
Division of Nephrology, Department of Internal Medicine, University of California Davis, Davis, CA, USA.
Comprehensive Cancer Center, University of California Davis, Davis, CA, USA.
Oncogene. 2017 Jun 22;36(25):3588-3598. doi: 10.1038/onc.2016.510. Epub 2017 Feb 6.
Targeted therapeutics, such as those abrogating hypoxia inducible factor (HIF)/vascular endothelial growth factor signaling, are initially effective against kidney cancer (or renal cell carcinoma, RCC); however, drug resistance frequently occurs via subsequent activation of alternative pathways. Through genome-scale integrated analysis of the HIF-α network, we identified the major protein kinase C substrate MARCKS (myristoylated alanine-rich C kinase substrate) as a potential target molecule for kidney cancer. In a screen of nephrectomy samples from 56 patients with RCC, we found that MARCKS expression and its phosphorylation are increased and positively correlate with tumor grade. Genetic and pharmacologic suppression of MARCKS in high-grade RCC cell lines in vitro led to a decrease in cell proliferation and migration. We further demonstrated that higher MARCKS expression promotes growth and angiogenesis in vivo in an RCC xenograft tumor. MARCKS acted upstream of the AKT/mTOR pathway, activating HIF-target genes, notably vascular endothelial growth factor-A. Following knockdown of MARCKS in RCC cells, the IC50 of the multikinase inhibitor regorafenib was reduced. Surprisingly, attenuation of MARCKS using the MPS (MARCKS phosphorylation site domain) peptide synergistically interacted with regorafenib treatment and decreased survival of kidney cancer cells through inactivation of AKT and mTOR. Our data suggest a major contribution of MARCKS to kidney cancer growth and provide an alternative therapeutic strategy of improving the efficacy of multikinase inhibitors.
靶向治疗药物，如那些阻断缺氧诱导因子（HIF）/血管内皮生长因子信号传导的药物，最初对肾癌（或肾细胞癌，RCC）有效；然而，耐药性常常通过随后激活替代途径而发生。通过对HIF-α网络进行全基因组规模的综合分析，我们确定主要蛋白激酶C底物MARCKS（富含肉豆蔻酰化丙氨酸的C激酶底物）是肾癌的一个潜在靶分子。在对56例RCC患者的肾切除样本进行的筛查中，我们发现MARCKS的表达及其磷酸化增加，且与肿瘤分级呈正相关。在体外对高级别RCC细胞系中MARCKS进行基因和药理学抑制导致细胞增殖和迁移减少。我们进一步证明，在RCC异种移植瘤中，较高的MARCKS表达在体内促进生长和血管生成。MARCKS在AKT/mTOR途径上游起作用，激活HIF靶基因,尤其是血管内皮生长因子-A。在RCC细胞中敲低MARCKS后，多激酶抑制剂瑞戈非尼的IC50降低。令人惊讶的是，使用MPS（MARCKS磷酸化位点结构域）肽减弱MARCKS与瑞戈非尼治疗协同作用，并通过使AKT和mTOR失活降低肾癌细胞的存活率。我们的数据表明MARCKS对肾癌生长有重要作用，并提供了一种提高多激酶抑制剂疗效的替代治疗策略。
