Li Chengxin, Chi Sumin, He Nonggao, Zhang Xiaoli, Guicherit Oivin, Wagner Richard, Tyring Stephen, Xie Jingwu
Sealy Center for Cancer Cell Biology, Department of Pharmacology and Toxicology, University of Texas Medical Branch at Galveston, TX 77555, USA.
Oncogene. 2004 Feb 26;23(8):1608-17. doi: 10.1038/sj.onc.1207273.
Basal cell carcinoma (BCC), the most common form of human cancer, is understood to be associated with activation of the sonic hedgehog pathway, through loss-of-function mutations of tumor suppressor PTCH1 or gain-of-function mutations of smoothened. Interferon (IFN)-based therapy is quite effective in BCC treatment, but the molecular basis is not well understood. Here we report a novel mechanism by which IFNalpha mediates apoptosis in BCCs. In the presence of IFNalpha, we observed increased apoptosis in a BCC cell line ASZ001, in which PTC is null, and therefore with constitutive activation of the sonic hedgehog pathway. We demonstrate that SMO agonist Ag-1.4 mediates activation of extracellular signal-regulated kinase (Erk) phosphorylation, which is abrogated by IFNalpha in sonic hedgehog responsive C3H10T1/2 cells. In transient transfection experiments, we demonstrate that IFNalpha inhibits Erk phosphorylation and serum response element activation induced by expression of SMO, Gli1, PDGFRalpha and activated Raf, but not activated mitogen-activated Erk-regulating kinase (Mek), suggesting that IFNalpha targets mainly on Mek function. We further show that IFNalpha induces expression of Fas in BCC cells through interfering with Mek function. The role of the Fas-L/Fas signaling axis in IFNalpha-mediated apoptosis is demonstrated by the fact that addition of Fas-L neutralizing antibodies, just as caspase-8 inhibitor Z-IETD-FMK, effectively prevents IFNalpha-mediated apoptosis. Thus, our data indicate that IFNalpha-based BCC therapy induces Fas expression and apoptosis through interfering with Mek function.
基底细胞癌（BCC）是人类最常见的癌症形式，已知其与音猬因子信号通路的激活有关，这是通过肿瘤抑制因子PTCH1的功能丧失突变或 smoothened 的功能获得性突变实现的。基于干扰素（IFN）的疗法在BCC治疗中相当有效，但其分子基础尚不清楚。在此我们报告一种新机制，通过该机制IFNα介导BCC细胞凋亡。在IFNα存在的情况下，我们观察到BCC细胞系ASZ001中的凋亡增加，该细胞系中PTC缺失，因此音猬因子信号通路持续激活。我们证明SMO激动剂Ag-1.4介导细胞外信号调节激酶（Erk）磷酸化的激活，在音猬因子反应性C3H10T1/2细胞中，IFNα可消除这种激活。在瞬时转染实验中，我们证明IFNα抑制由SMO、Gli1、PDGFRα和活化的Raf表达诱导的Erk磷酸化和血清反应元件激活，但不抑制活化的丝裂原活化Erk调节激酶（Mek），这表明IFNα主要靶向Mek功能。我们进一步表明，IFNα通过干扰Mek功能诱导BCC细胞中Fas的表达。Fas-L/Fas信号轴在IFNα介导的细胞凋亡中的作用通过以下事实得到证明：添加Fas-L中和抗体，就像半胱天冬酶-8抑制剂Z-IETD-FMK一样，可有效防止IFNα介导的细胞凋亡。因此，我们的数据表明，基于IFNα的BCC治疗通过干扰Mek功能诱导Fas表达和细胞凋亡。
