Liu Zhuo, Yu Miao, Fei Bingyuan, Sun Jing, Wang Dongxin
Department of Gastrointestinal Colorectal and Anal Surgery, China-Japan Union Hospital of Jilin University, Changchun, Jilin 130021, China.
Department of Biochemistry and Molecular Medicine, The George Washington University, Washington, DC 20052, USA.
Onco Targets Ther. 2019 Mar 20;12:2095-2104. doi: 10.2147/OTT.S192923. eCollection 2019.
Colorectal cancer (CRC) is the third commonly diagnosed cancer with a high risk of death. After curative surgery, 40% of patients will have metastases or develop recurrence. Therefore, chemotherapy is significantly responsible as the major therapy method. However, chemoresistance is found in almost all metastatic patients and remains a critical obstacle to curing CRC.
Cell viability is analyzed by sulforhodamine B staining assay. The nonhomologous end joining (NHEJ) repair ability of each cell line was determined by NHEJ reporter assay. mRNA expression levels of NHEJ factors are detected by real-time quantitative polymerase chain reaction. The protein expression levels were observed by western blot assay.
Our study found that 5-florouracil (5-Fu) and oxaliplatin (OXA)-resistant HCT116 and LS174T cells showed upregulated efficiency of DNA double-strand repair pathway NHEJ. We then identified that the NHEJ key factor XLF is responsible for the chemoresistance and XLF deficiency sensitizes CRC cells to 5-Fu and OXA significantly.
Our research first demonstrates that the NHEJ pathway, especially its key factor XLF, significantly contributes to chemoresistance in CRC.
结直肠癌（CRC）是第三大常见诊断癌症，死亡风险高。根治性手术后，40%的患者会发生转移或复发。因此，化疗作为主要治疗方法起着重要作用。然而，几乎所有转移性患者都存在化疗耐药性，这仍然是治愈CRC的关键障碍。
通过磺酰罗丹明B染色法分析细胞活力。通过非同源末端连接（NHEJ）报告基因检测法测定各细胞系的NHEJ修复能力。通过实时定量聚合酶链反应检测NHEJ因子的mRNA表达水平。通过蛋白质印迹法观察蛋白质表达水平。
我们的研究发现，对5-氟尿嘧啶（5-Fu）和奥沙利铂（OXA）耐药的HCT116和LS174T细胞显示出DNA双链修复途径NHEJ的效率上调。然后我们确定NHEJ关键因子XLF是化疗耐药的原因，XLF缺陷使CRC细胞对5-Fu和OXA显著敏感。
我们的研究首次表明，NHEJ途径，尤其是其关键因子XLF，在CRC化疗耐药中起重要作用。
