Molecular Discovery, Biogen Idec, 12 Cambridge Center, Cambridge, MA 02142, United States.
Cytokine. 2013 Jan;61(1):210-7. doi: 10.1016/j.cyto.2012.09.020. Epub 2012 Oct 27.
The TWEAK receptor Fn14 (TNFRSF12), a member of the TNF Receptor superfamily, can mediate many processes, including apoptosis. Fn14 agonists have therefore been the subject of interest as potential cancer therapeutics. In cell culture experiments, interferon gamma (IFNγ) is typically required for induction of apoptotic activity by either TWEAK or Fn14 agonistic antibodies in most cell lines. We have investigated the mechanism of IFNγ signaling and the role of JAK-STAT signaling in TWEAK/Fn14-mediated tumor cell killing. We found that IFNγ-mediated enhancement of tumor cell killing is JAK-STAT dependent, as JAK inhibitors block IFNγ-dependent TWEAK induced apoptosis. Exposure of tumor cells to IFNγ results in an increase in Fn14 expression on the cell surface, which may be a mechanism by which IFNγ induces sensitivity to TWEAK. In a reciprocal fashion, we observed that IFNγ receptor levels increase in response to TWEAK treatment in WiDr cells. Significantly, we found that TWEAK alone can induce STAT1 phosphorylation in WiDr tumor cells. Moreover, TWEAK induction of tumor cell apoptosis in WiDr cells in the absence of IFNγ is mediated by the JAK-STAT pathway. Correspondingly, we show that treatment of tumor bearing mice with mBIIB036, an Fn14 agonistic antibody, results in STAT1 phosphorylation in the tumors. Notably, the level of STAT1 phosphorylation appears to correlate with the degree of tumor growth inhibition by BIIB036 in vivo. Additionally, in WiDr cells, TWEAK induces a soluble factor, which we have identified as IFNβ, capable of independently inducing STAT1 phosphorylation when transferred to naïve cells. Finally, either IFNα or IFNβ can partially substitute for IFNγ in sensitizing tumor cells to Fn14 agonists. In summary, we show that TWEAK/Fn14 can signal through the JAK-STAT pathway to induce IFNβ, and that the ability of TWEAK to induce tumor cell apoptosis is mediated by JAK-STAT signaling. We also demonstrate that IFNγ enhancement of TWEAK/FN14-mediated tumor cell death is JAK-dependent and may occur by IFNγ-dependent upregulation of Fn14 on tumor cells. These findings may have implications for the appropriately targeted clinical development of Fn14 agonists as anti-cancer therapy.
TWEAK 受体 Fn14（TNFRSF12）是 TNF 受体超家族的成员，能够介导包括细胞凋亡在内的多种过程。因此，Fn14 激动剂已成为潜在癌症治疗药物的研究对象。在细胞培养实验中，干扰素 γ（IFNγ）通常是 TWEAK 或 Fn14 激动性抗体在大多数细胞系中诱导细胞凋亡所必需的。我们研究了 IFNγ 信号转导机制以及 JAK-STAT 信号转导在 TWEAK/Fn14 介导的肿瘤细胞杀伤中的作用。我们发现，IFNγ 介导的肿瘤细胞杀伤增强作用依赖于 JAK-STAT，因为 JAK 抑制剂阻断 IFNγ 依赖性 TWEAK 诱导的细胞凋亡。肿瘤细胞暴露于 IFNγ 会导致细胞表面 Fn14 表达增加，这可能是 IFNγ 诱导对 TWEAK 敏感性的一种机制。相反，我们观察到 WiDr 细胞中 TWEAK 处理会导致 IFNγ 受体水平增加。重要的是，我们发现 TWEAK 本身可以在 WiDr 肿瘤细胞中诱导 STAT1 磷酸化。此外，在没有 IFNγ 的情况下，TWEAK 诱导 WiDr 肿瘤细胞凋亡是通过 JAK-STAT 途径介导的。相应地，我们表明，用 Fn14 激动性抗体 mBIIB036 治疗荷瘤小鼠会导致肿瘤中 STAT1 磷酸化。值得注意的是，STAT1 磷酸化的水平似乎与 BIIB036 在体内抑制肿瘤生长的程度相关。此外，在 WiDr 细胞中，TWEAK 诱导一种可溶性因子，我们已将其鉴定为 IFNβ，当转移到幼稚细胞时，它能够独立诱导 STAT1 磷酸化。最后，IFNα 或 IFNβ 可以部分替代 IFNγ 使肿瘤细胞对 Fn14 激动剂敏感。总之，我们表明 TWEAK/Fn14 可以通过 JAK-STAT 途径信号转导诱导 IFNβ，并且 TWEAK 诱导肿瘤细胞凋亡的能力是通过 JAK-STAT 信号转导介导的。我们还证明，IFNγ 增强 TWEAK/FN14 介导的肿瘤细胞死亡依赖于 JAK，并可能通过 IFNγ 依赖性上调肿瘤细胞上的 Fn14 发生。这些发现可能对 Fn14 激动剂作为癌症治疗的适当靶向临床开发具有重要意义。
