Xue Haowei, Lu Jinsen, Yuan Renxiang, Liu Jinli, Liu Yehai, Wu Kaile, Wu Jing, Du Juan, Shen Bing
Department of Oral and Maxillofacial Surgery, The First Affiliated Hospital of Anhui Medical University, Hefei, 230022 Anhui China.
Department of Physiology, Anhui Medical University, 81 Meishan Road, Hefei, 230032 Anhui China.
Cell Biosci. 2016 Jan 25;6:5. doi: 10.1186/s13578-016-0070-1. eCollection 2016.
Human head and neck squamous carcinoma is the 6th most prevalent carcinoma worldwide. Although many novel therapies have been developed, the clinical treatment for patients remains non-ideal. Chloride intracellular channel 4 (CLIC4), one of the seven members of the CLIC family, is a newly found Cl(-) channel that participates in various biological processes, including cellular apoptosis and differentiation. Accumulating evidence has revealed the significant role of CLIC4 in regulating the apoptosis of different cancer cells. Here, we investigated the functional role of CLIC4 in the apoptosis of HN4 cells, a human head and neck squamous carcinoma cell line.
In the present study, we used immunohistochemical staining to demonstrate that the expression level of CLIC4 is elevated in the tissue of human oral squamous carcinoma compared with healthy human gingival tissue. Specific CLIC4 small interfering RNA was used to knockdown the expression of CLIC4. The results showed that knockdown of CLIC4 with or without 100 μM adenosine triphosphate (ATP) treatment significantly increased the expression of Bax, active caspase 3, active caspase 4 and CHOP but suppressed Bcl-2 expression in HN4 cells. Moreover, the results from the TdT-mediated dUTP nick end labeling assay indicated that CLIC4 knockdown induced a higher apoptotic rate in HN4 cells under the induction of ATP. In addition, knockdown of CLIC4 dramatically enhanced ATP-induced mitochondrial membrane depolarization in HN4 cells. Moreover, intracellular Ca(2+) measurement revealed that Ca(2+) release induced by ATP and thapsigargin, a Ca(2+)-ATPase inhibitor of the endoplasmic reticulum, was significantly enhanced by the suppression of CLIC4 in HN4 cells.
Knockdown of CLIC4 enhanced ATP-induced apoptosis in HN4 cells. Both the pathways of mitochondria and endoplasmic reticulum stress were involved in CLIC4-mediated cell apoptosis. Based on our finding, CLIC4 may be a potential and valuable target for the clinical treatment of head and neck squamous carcinoma.
人类头颈部鳞状细胞癌是全球第六大常见癌症。尽管已经开发了许多新疗法，但患者的临床治疗仍然不理想。氯离子细胞内通道4（CLIC4）是CLIC家族七个成员之一，是一种新发现的参与各种生物学过程（包括细胞凋亡和分化）的Cl(-)通道。越来越多的证据表明CLIC4在调节不同癌细胞凋亡中起重要作用。在此，我们研究了CLIC4在人源头颈部鳞状癌细胞系HN4细胞凋亡中的功能作用。
在本研究中，我们使用免疫组织化学染色证明，与健康人牙龈组织相比，CLIC4在人口腔鳞状癌组织中的表达水平升高。使用特异性CLIC4小干扰RNA来敲低CLIC4的表达。结果表明，无论是否用100μM三磷酸腺苷（ATP）处理，敲低CLIC4均显著增加HN4细胞中Bax、活化的半胱天冬酶3、活化的半胱天冬酶4和CHOP的表达，但抑制Bcl-2表达。此外，末端脱氧核苷酸转移酶介导的dUTP缺口末端标记试验结果表明，在ATP诱导下，CLIC4敲低诱导HN4细胞凋亡率更高。此外，敲低CLIC4显著增强了ATP诱导的HN4细胞线粒体膜去极化。此外，细胞内Ca(2+)测量显示，ATP和毒胡萝卜素（一种内质网Ca(2+)-ATP酶抑制剂）诱导的Ca(2+)释放，在HN4细胞中通过抑制CLIC4而显著增强。
敲低CLIC4增强了ATP诱导的HN4细胞凋亡。线粒体和内质网应激途径均参与CLIC4介导的细胞凋亡。基于我们的发现，CLIC4可能是头颈部鳞状癌临床治疗的潜在且有价值的靶点。
