Chen Tianran, Liu Chuan, Lu Heng, Yin Mingzhen, Shao Changjuan, Hu Xiaoding, Wu Jiaxue, Wang Yajie
1 Department of Oncology, Changhai Hospital, The Second Military Medical University, Shanghai, China.
2 Department of Oncology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Tumour Biol. 2017 Oct;39(10):1010428317713390. doi: 10.1177/1010428317713390.
Triple-negative breast cancer is a kind of breast cancer with poor prognosis and special biological behavior, which lacked endocrine therapy and targeted therapy. We investigate the effect of human APE1 (apurinic/apyrimidyl endonuclease 1), a rate-limiting enzyme of base excision repair, on the prognosis in triple-negative breast cancer and drug sensitivity of olaparib. The expression of APE1 was detected by immunohistochemistry in the triple-negative breast cancer tissues and its effect on survival of triple-negative breast cancer patients was followed. To find whether APE1 effect the drug sensitivity in triple-negative breast cancer cells, the APE1-knockout HCC1937 cell line (triple-negative breast cancer cell line) was established by CRISPR/Cas9 system. Then, we use the wild-type and knockout one to test the drug sensitivity of olaparib. The expression of APE1 in triple-negative breast cancer tissues was significantly higher than that in the adjacent tissues (85.6% vs 14.4%) and its expression was related to tumor size (p < 0.05). We also found that it is an independent prognostic factor in patients with triple-negative breast cancer (overall survival, p = 0.01). In vitro assay, the half maximal inhibitory concentration of olaparib in HCC1937-APE1-KO was significantly increased (17.22 vs 91.85 μM) compared to the wild type. The growth curve showed that olaparib had a stronger lethality on HCC1937 compared to HCC1937- APE1-KO (p < 0.05 on day 3). HCC1937 resulted in more mitotic G2/M arrest and increased apoptosis rate after treatment with 40 μM of olaparib, while HCC1937-APE1-KO did not change significantly. When HCC1937 was treated with different concentrations of olaparib, it was found that APE1 expression decreased more significantly at 15 μM of olaparib was. In HCC1937-APE1-KO, the expression of endogenous poly (ADP-ribose) polymerase 1 was also less than that of HCC1937. These results suggested that the expression of APE1 was an important basis for the maintenance of poly (ADP-ribose) polymerase 1, and the deletion of APE1 may be related to the resistance of olaparib.
三阴性乳腺癌是一种预后较差且具有特殊生物学行为的乳腺癌，缺乏内分泌治疗和靶向治疗。我们研究了碱基切除修复的限速酶人APE1（脱嘌呤/脱嘧啶核酸内切酶1）对三阴性乳腺癌预后及奥拉帕利药物敏感性的影响。通过免疫组织化学检测三阴性乳腺癌组织中APE1的表达，并随访其对三阴性乳腺癌患者生存的影响。为了探究APE1是否影响三阴性乳腺癌细胞的药物敏感性，利用CRISPR/Cas9系统建立了APE1基因敲除的HCC1937细胞系（三阴性乳腺癌细胞系）。然后，我们使用野生型和基因敲除型细胞来检测奥拉帕利的药物敏感性。三阴性乳腺癌组织中APE1的表达显著高于相邻组织（85.6%对14.4%），且其表达与肿瘤大小相关（p<0.05）。我们还发现它是三阴性乳腺癌患者的一个独立预后因素（总生存期，p=0.01）。体外实验中，与野生型相比，HCC1937-APE1-KO中奥拉帕利的半数最大抑制浓度显著增加（17.22对91.85μM）。生长曲线显示，与HCC1937-APE1-KO相比，奥拉帕利对HCC1937的杀伤力更强（第3天p<0.05）。用40μM奥拉帕利处理后，HCC1937导致更多有丝分裂G2/M期阻滞并增加凋亡率，而HCC1937-APE1-KO无明显变化。当用不同浓度的奥拉帕利处理HCC1937时，发现15μM奥拉帕利时APE1表达下降更显著。在HCC1937-APE1-KO中，内源性聚（ADP-核糖）聚合酶1的表达也低于HCC1937。这些结果表明，APE1的表达是维持聚（ADP-核糖）聚合酶1的重要基础，APE1的缺失可能与奥拉帕利耐药有关。
