Snigdha Kirti, Singh Amit, Kango-Singh Madhuri
Department of Biology, University of Dayton, Dayton, OH, USA.
Center for Tissue Regeneration and Engineering at Dayton (TREND), University of Dayton, Dayton, OH, USA.
Oncogene. 2021 Jun;40(24):4124-4136. doi: 10.1038/s41388-021-01831-4. Epub 2021 May 20.
Presence of inflammatory factors in the tumor microenvironment is well-documented yet their specific role in tumorigenesis is elusive. The core inflammatory pathways like the Toll-Like Receptor (TLR) and the Tumor Necrosis Factor (TNF) pathway are conserved in Drosophila. We induced GFP-marked epithelial tumors by expressing activated oncogenic forms of Ras or Yorkie (Yki, mammalian YAP) in scribble deficient cells (scrib, mammalian SCRIB) to study the role of inflammatory factors in tumorigenesis. Similar to Rasscrib, we found that Ykiscrib form invasive neoplastic lethal tumors that induce a systemic inflammatory response. We identified Cactus (Cact, mammalian IκBα), the negative regulator of TLR, as a key player in tumor growth. Cact accumulates in the cytoplasm in Drosophila tumor models, similar to squamous cell carcinoma in mice models and human patients where cytoplasmic IκBα favors oncogenic transformation. Further, cact is transcriptionally upregulated in tumors, and downregulation of Cact affects tumor growth. We investigated if TLR or TNF pathway affect tumor growth through activation of Jun N-terminal Kinase (JNK) pathway and its target Matrix Metalloprotease1 (MMP1). Genetically manipulating levels of TLR components or TNF receptors showed that Cact acts upstream of JNK signaling and regulates JNK via a non-canonical mechanism during tumorigenesis. Further, Hippo coactivator Yki transcriptionally regulates cact expression, and downregulation of Yki or Cact is sufficient to cause downregulation of JNK-mediated signaling that promotes tumorigenesis. Here, we report a link between Hippo, IκBα and JNK signaling that may induce inflammation and innate immune response in tumorigenesis.
肿瘤微环境中炎症因子的存在已有充分记录,但其在肿瘤发生中的具体作用尚不清楚。像Toll样受体(TLR)和肿瘤坏死因子(TNF)途径这样的核心炎症信号通路在果蝇中是保守的。我们通过在scribble缺陷细胞(scrib,哺乳动物的SCRIB)中表达激活的致癌形式的Ras或Yorkie(Yki,哺乳动物的YAP)来诱导绿色荧光蛋白标记的上皮肿瘤,以研究炎症因子在肿瘤发生中的作用。与Rasscrib相似,我们发现Ykiscrib形成侵袭性肿瘤致死性肿瘤,可诱导全身炎症反应。我们确定了TLR的负调节因子Cactus(Cact,哺乳动物的IκBα)是肿瘤生长的关键参与者。在果蝇肿瘤模型中,Cact在细胞质中积累,类似于小鼠模型和人类患者中的鳞状细胞癌,其中细胞质IκBα有利于致癌转化。此外,cact在肿瘤中被转录上调,Cact的下调影响肿瘤生长。我们研究了TLR或TNF途径是否通过激活Jun N末端激酶(JNK)途径及其靶标基质金属蛋白酶1(MMP1)来影响肿瘤生长。对TLR成分或TNF受体水平进行基因操作表明,Cact在肿瘤发生过程中作用于JNK信号的上游,并通过非经典机制调节JNK。此外,Hippo共激活因子Yki转录调节cact的表达,Yki或Cact的下调足以导致促进肿瘤发生的JNK介导信号的下调。在这里,我们报道了Hippo、IκBα和JNK信号之间的联系,这可能在肿瘤发生中诱导炎症和先天免疫反应。