Cx32 通过表皮生长因子受体通路在肝癌中发挥抗细胞凋亡和促肿瘤作用。
Cx32 exerts anti-apoptotic and pro-tumor effects via the epidermal growth factor receptor pathway in hepatocellular carcinoma.
机构信息
Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, 510080, People's Republic of China.
Tumor Research Institute, Xinjiang Medical University Affiliated Tumor Hospital and State Key Laboratory, Urumqi, 830000, People's Republic of China.
出版信息
J Exp Clin Cancer Res. 2019 Apr 4;38(1):145. doi: 10.1186/s13046-019-1142-y.
BACKGROUND
Abnormal expression or distribution of connexin 32 (Cx32) is associated with hepatocarcinogenesis, but the role of Cx32 and the underlying mechanisms are still unclear.
METHODS
The expression level of Cx32 in 96 hepatocellular carcinoma (HCC) specimens was determined using western blotting and immunohistochemistry. The correlation between Cx32 expression and clinicopathological parameters was analyzed. The cell apoptosis rate was examined using flow cytometry and western blotting. The role of Cx32 in the Src kinase and epidermal growth factor receptor (EGFR) signaling pathways was measured by quantitative real-time PCR, western blotting and coimmunoprecipitation (CO-IP). The effect of Cx32 overexpression on the streptonigrin (SN)-induced tumor growth suppression and apoptosis was assessed in nude mice.
RESULTS
Our study showed that overexpressed Cx32 accumulated in the cytoplasm and that Cx32-containing gap junctions (GJs) were nearly absent in HCC specimens. Upregulated Cx32 expression was highly correlated with advanced tumor-node-metastasis (TNM) stage and poor tumor differentiation and was an independent predictive marker for poor prognosis in HCC. Overexpression of Cx32 significantly inhibited SN-induced apoptosis by activating the EGFR signaling pathway in vitro and in vivo. Moreover, the expression levels of Cx32 and EGFR were positively correlated in HCC specimens. The CO-IP experiments demonstrated that Cx32 could bind to Src kinase, and the western blotting results revealed that Cx32 increased the levels of EGFR and p-EGFR by upregulating Src expression.
CONCLUSION
The present study demonstrated that overexpressed and internalized Cx32 was associated with advanced TNM stage and poor tumor differentiation and predicted poor prognosis in HCC. Cx32 facilitated HCC progression by blocking chemotherapy-induced apoptosis in vitro and in vivo via interacting with Src and thus promoting the phosphorylation of EGFR, subsequently activating the EGFR signaling pathway. Cx32 may be a potential biomarker and a new therapeutic target for HCC.
背景
连接蛋白 32（Cx32）的异常表达或分布与肝癌的发生有关，但 Cx32 的作用及其潜在机制仍不清楚。
方法
采用 Western blot 和免疫组织化学法检测 96 例肝癌（HCC）标本中 Cx32 的表达水平，分析 Cx32 表达与临床病理参数的相关性。采用流式细胞术和 Western blot 检测细胞凋亡率。采用实时定量 PCR、Western blot 和免疫共沉淀（CO-IP）检测 Cx32 在Src 激酶和表皮生长因子受体（EGFR）信号通路中的作用。在裸鼠中评估 Cx32 过表达对链黑菌素（SN）诱导的肿瘤生长抑制和凋亡的影响。
结果
本研究表明，过表达的 Cx32 在内质网中积累，而 HCC 标本中 Cx32 包含的间隙连接（GJ）几乎不存在。上调的 Cx32 表达与晚期肿瘤-淋巴结-转移（TNM）分期和肿瘤分化不良高度相关，是 HCC 预后不良的独立预测标志物。过表达 Cx32 可通过体外和体内激活 EGFR 信号通路，显著抑制 SN 诱导的凋亡。此外，在 HCC 标本中，Cx32 和 EGFR 的表达水平呈正相关。CO-IP 实验表明，Cx32 可以与 Src 激酶结合，Western blot 结果显示，Cx32 通过上调 Src 的表达增加 EGFR 和 p-EGFR 的水平。
结论
本研究表明，过表达和内化的 Cx32 与 HCC 的晚期 TNM 分期和肿瘤分化不良有关，并预测 HCC 的预后不良。Cx32 通过与Src 相互作用阻断体外和体内化疗诱导的凋亡，从而促进 HCC 的进展，进而激活 EGFR 信号通路。Cx32 可能是 HCC 的一个潜在的生物标志物和新的治疗靶点。
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