Park Soon Young, Mittal Sandeep, Dong Jianwen, Jeong Kangjin, Martinez-Ledesma Emmanuel, Piao Yuji, Khan Sabbir, Henry Verlene, Verhaak Roel Gw, Majd Nazanin, Balasubramaniyan Veerakumar, de Groot John F
Department of Cell Developmental and Cancer Biology, Oregon Health and Science University Portland, Oregon, USA.
Department of Neuro-Oncology, The University of Texas MD Anderson Cancer Center Houston, Texas, USA.
Am J Cancer Res. 2020 Nov 1;10(11):3765-3783. eCollection 2020.
The Cdc2-like kinases (CLKs) regulate RNA splicing and have been shown to suppress cell growth. Knockdown of CLK2 was found to block glioma stem-like cell (GSC) growth through the AKT/FOXO3a/p27 pathway without activating mTOR and MAPK signaling, suggesting that these pathways mediate resistance to CLK2 inhibition. We identified CLK2 binding partners using immunoprecipitation assays and confirmed their interactions in GSCs. We then tested the cellular viability of several signaling inhibitors in parental and CLK2 knockdown GSCs. Our results demonstrate that CLK2 binds to 14-3-3τ isoform and prevents its ubiquitination in GSCs. Stable CLK2 knockdown increased PP2A activity and activated PI3K signaling. Treatment with a PI3K/mTOR inhibitor in CLK2 knockdown cells led to a modest reduction in cell viability compared to drug treatment alone at a lower dose. However, FGFR inhibitor in CLK2 knockdown cells led to a decrease in cell viability and increased apoptosis. Reduced expression of CLK2 in glioblastoma, in combination with FGFR inhibitors, led to synergistic apoptosis induction and cell cycle arrest compared to blockade or either kinase alone.
细胞周期蛋白依赖性激酶2样激酶（CLKs）调节RNA剪接，并已被证明可抑制细胞生长。研究发现，敲低CLK2可通过AKT/FOXO3a/p27途径阻断胶质瘤干细胞样细胞（GSC）的生长，而不激活mTOR和MAPK信号通路，这表明这些途径介导了对CLK2抑制的抗性。我们使用免疫沉淀试验鉴定了CLK2结合伴侣，并在GSCs中证实了它们的相互作用。然后，我们测试了几种信号抑制剂在亲本和CLK2敲低的GSCs中的细胞活力。我们的结果表明，CLK2与14-3-3τ亚型结合，并阻止其在GSCs中的泛素化。稳定敲低CLK2可增加PP2A活性并激活PI3K信号通路。与单独使用较低剂量的药物治疗相比，在CLK2敲低的细胞中用PI3K/mTOR抑制剂治疗导致细胞活力适度降低。然而，CLK2敲低细胞中的FGFR抑制剂导致细胞活力降低并增加凋亡。与单独阻断或任何一种激酶相比，胶质母细胞瘤中CLK2表达降低与FGFR抑制剂联合使用可导致协同诱导凋亡和细胞周期停滞。
