IL-33 activates tumor stroma to promote intestinal polyposis

Tumor epithelial cells develop within a microenvironment consisting of extracellular matrix, growth factors, and cytokines produced by non-epithelial stromal cells. In response to paracrine signals from tumor epithelia, stromal cells modify the microenvironment to promote tumor growth and metastasis. Here, we identify interleukin (IL)-33 as an epithelial cell-derived regulator of stromal cell activation and mediator of intestinal polyposis. IL-33 expression was elevated in the tumors and serum of colorectal cancer patients and induced in the adenomatous polyps of ApcMin/+ mutant mice. Genetic and antibody suppression of IL-33 signaling in ApcMin/+ mice inhibited proliferation, induced apoptosis, and suppressed angiogenesis in polyps, which reduced both tumor number and size. In ApcMin/+ polyps, IL-33 expression localized to tumor epithelial cells and expression of the IL-33 receptor, IL1RL1, associated with two stromal cell types, namely subepithelial myofibroblasts (SEMFs) and mast cells, whose activation was previously associated with polyposis. In vitro IL-33 stimulation of human SEMFs induced the expression of extracellular matrix components and growth factors associated with intestinal tumor progression. IL-33 deficiency reduced mast cell accumulation in ApcMin/+ polyps and expression of mast cell-derived proteases and cytokines known to promote polyposis. Together, our results suggest that IL-33 is a tumor epithelial cell-derived paracrine signal that promotes polyposis through the coordinated activation of stromal cells and the formation of a reactive stroma microenvironment. Six T-75 flasks of CCD-18Co cells were grown to 80% confluency; three were treated with rhIL-33, three were given vehicle control; cells were trypsinized and split in two--half of each flask used for sequencing and half for qPCR validation post-sequencing

肿瘤上皮细胞于由非上皮基质细胞分泌的细胞外基质（extracellular matrix）、生长因子与细胞因子构成的微环境中生长发育。肿瘤上皮细胞释放的旁分泌信号（paracrine signal）可促使基质细胞重塑微环境，进而促进肿瘤生长与转移。本研究鉴定出白细胞介素-33（interleukin, IL-33）是上皮细胞来源的基质细胞活化调节因子，亦是肠息肉病（intestinal polyposis）的介导分子。结直肠癌（colorectal cancer）患者的肿瘤组织与血清中IL-33表达水平显著升高，而ApcMin/+突变小鼠的腺瘤性息肉（adenomatous polyps）中也可诱导IL-33表达。在ApcMin/+小鼠中，通过基因干预与抗体阻断抑制IL-33信号通路，可抑制息肉内细胞增殖（proliferation）、诱导细胞凋亡（apoptosis）并抑制血管生成（angiogenesis），进而降低肿瘤的数量与体积。在ApcMin/+小鼠的息肉中，IL-33表达定位于肿瘤上皮细胞；而IL-33受体IL1RL1的表达则与两类基质细胞相关，即上皮下肌成纤维细胞（subepithelial myofibroblasts, SEMFs）与肥大细胞（mast cells），此前已有研究证实这两类细胞的活化与肠息肉病密切相关。体外实验（in vitro）中，重组人IL-33（recombinant human IL-33, rhIL-33）刺激人SEMFs可诱导其表达与肠肿瘤进展相关的细胞外基质成分与生长因子。IL-33缺失可减少ApcMin/+小鼠息肉内肥大细胞的浸润，并降低已知可促进肠息肉病的肥大细胞源性蛋白酶与细胞因子的表达水平。综上，本研究结果表明，IL-33是一类由肿瘤上皮细胞分泌的旁分泌信号分子，可通过协同活化基质细胞并构建反应性基质微环境（reactive stroma microenvironment）来促进肠息肉病的发生发展。将6瓶CCD-18Co细胞接种于T-75培养瓶中，培养至细胞汇合度达80%；其中3瓶经rhIL-33处理，剩余3瓶以溶剂作为对照；随后用胰酶消化细胞并将每瓶细胞均分为两份——一半用于测序，另一半用于测序后的qPCR验证。