Department of Infectious Diseases, Beijing You'an Hospital, Capital Medical University, China.
PLoS One. 2012;7(10):e47040. doi: 10.1371/journal.pone.0047040. Epub 2012 Oct 4.
BACKGROUND/OBJECTIVE: IFNs are a group of cytokines that possess potent antiviral and antitumor activities, while β-catenin pathway is a proliferative pathway involved in carcinogenesis. Interaction between these two pathways has not been well elaborated in hepatocellular carcinoma (HCC).
HCC cell lines, HepG2 and Huh7, were used in this study. β-catenin protein levels and corresponding signaling activities were observed by flow cytometry and luciferase assay, respectively. Cell proliferation was quantified by counting viable cells under microscope, and apoptosis by TUNEL assay. DKK1 and GSK3β levels were determined by flow cytometry. Secreted DKK1 was tested by ELISA. FLUD, S3I and aDKK1 were used to inhibit STAT1, STAT3 and DKK1 activities, respectively.
Our findings show that all three types of IFNs, IFNα, IFNγ and IFNλ, are capable of inhibiting β-catenin signaling activity in HepG2 and Huh7 cells, where IFNγ was the strongest (p<0.05). They expressed suppression of cellular proliferation and induced apoptosis. IFNγ expressed greater induction ability when compared to IFNα and IFNλ (p<0.05). All tested IFNs could induce DKK1 activation but not GSK3β in HepG2 and Huh7 cells. IFNs induced STAT1 and STAT3 activation but by using specific inhibitors, we found that only STAT3 is vital for IFN-induced DKK1 activation and apoptosis. In addition, DKK1 inhibitor blocked IFN-induced apoptosis. The pattern of STAT3 activation by different IFNs is found consistent with the levels of apoptosis with the corresponding IFNs (p<0.05).
In hepatocellular carcinoma, all three types of IFNs are found to induce apoptosis by inhibiting β-catenin signaling pathway via a STAT3- and DKK1-dependent pathway. This finding points to a cross-talk between different IFN types and β-catenin signaling pathways which might be carrying a biological effect not only on HCC, but also on processes where the two pathways bridge.
背景/目的：干扰素（IFNs）是一类具有强大抗病毒和抗肿瘤活性的细胞因子，而β-连环蛋白通路是参与肿瘤发生的增殖途径。这两种途径之间的相互作用在肝细胞癌（HCC）中尚未得到充分阐述。
本研究使用 HCC 细胞系 HepG2 和 Huh7。通过流式细胞术和荧光素酶测定分别观察β-连环蛋白蛋白水平和相应的信号转导活性。通过在显微镜下计数活细胞来量化细胞增殖，通过 TUNEL 测定法检测细胞凋亡。通过流式细胞术测定 DKK1 和 GSK3β 水平。通过 ELISA 检测分泌型 DKK1。使用 FLUD、S3I 和 aDKK1 分别抑制 STAT1、STAT3 和 DKK1 活性。
我们的研究结果表明，三种类型的 IFNs（IFNα、IFNγ 和 IFNλ）均能抑制 HepG2 和 Huh7 细胞中的β-连环蛋白信号转导活性，其中 IFNγ 作用最强（p<0.05）。它们表现出抑制细胞增殖和诱导凋亡的作用。与 IFNα 和 IFNλ 相比，IFNγ 表现出更强的诱导能力（p<0.05）。所有测试的 IFNs 均可诱导 HepG2 和 Huh7 细胞中 DKK1 的激活，但不能诱导 GSK3β 的激活。IFNs 诱导 STAT1 和 STAT3 的激活，但使用特异性抑制剂，我们发现只有 STAT3 对 IFN 诱导的 DKK1 激活和凋亡至关重要。此外，DKK1 抑制剂阻断 IFN 诱导的凋亡。不同 IFNs 诱导的 STAT3 激活模式与相应 IFNs 诱导的凋亡水平一致（p<0.05）。
在肝细胞癌中，三种类型的 IFNs 均通过抑制β-连环蛋白信号通路诱导凋亡，该途径依赖于 STAT3 和 DKK1。这一发现表明不同 IFN 类型与β-连环蛋白信号通路之间存在交叉对话，这不仅对 HCC，而且对这两种途径交汇的过程都具有生物学效应。
