Periostin蛋白在结直肠癌发生发展中的功能及作用机理研究

Tissue microenvironment is one of the key limiting factors of tumorigenesis and metastasis. Our previous studies have demonstrated that extracellular protein periostin can significantly augment liver metastasis of colon cancer and promote the formation of lung premetastatic niche and cancer stem cell niche in the progression of breast cancer, and can also promote the development of hepatic inflammation, fibrosis and liver cancer. Our preliminary data reveal that knockout of periostin significantly inhibits the development of inflammation-associated colorectal cancer in AOM/DSS-treated mice and intestinal adenomas in APCmin/+ colorectal precancerous lesion mice. However, it is not clear how periostin contributes to regulating the development of colorectal cancer especially colitis-associated colorectal cancer. This project will use AOM/DSS-induced inflammation-associated colorectal cancer mouse model and colorectal precancerous lesion APCmin/+ mouse model, together with periostin-knockout mouse model, overexpression of periostin in liver by adenovirus injection mouse model and CCl4-induced hepatic fibrosis mouse model, to investigate the functions and molecular mechanisms of periostin in the development and progression of colorectal cancer and in the remodeling of liver fibrotic microenvironment for colorectal tumor metastasis. This study will help us learn more about the novel function of periostin in the tumorigenesis and metastasis of colorectal cancer from the perspective of colitis-associated colorectal cancer and liver fibrotic microenvironment remodeling, and will provide clues and a novel molecular target for the clinical prevention and therapeutic intervention against colorectal cancer.

组织微环境是肿瘤发生发展的关键调控因素之一。我们之前的研究已发现，细胞外基质蛋白Periostin促进结肠癌肝转移以及乳腺癌肺转移前微环境和肿瘤干细胞微环境的形成，并可促进肝脏炎症、纤维化和肝癌发生。我们的初步研究表明，Periostin敲除可显著抑制AOM/DSS诱导的小鼠炎症相关肠癌和APCmin/+小鼠肠腺瘤的发生，但对Periostin在结直肠癌尤其是肠炎相关肠癌发生发展中的作用机制并不清楚。本项目将应用AOM/DSS诱导的肠炎相关肠癌模型和APCmin/+结直肠癌癌前病变小鼠腺瘤模型，结合Periostin敲除小鼠模型和腺病毒肝脏特异性过表达模型以及肝纤维化模型，研究Periostin在结直肠癌发生发展和肝纤维化转移微环境重塑中的功能及分子机理，从炎症相关癌症和肝纤维化微环境重塑角度阐明Periostin促进结直肠癌发生和肝转移的新机制，为结直肠癌防治提供理论依据和新的分子靶点。

我们之前已发现，Periostin促进结直肠癌肝转移，但对Periostin在结直肠癌尤其是肠炎相关肠癌发生发展以及结直肠癌肝转移微环境中的功能和作用机制并不清楚。本项目发现：（1）Periostin在AOM/DSS联合诱导的小鼠肠炎相关肠癌肿瘤组织、APCmin/+小鼠肠腺瘤肿瘤组织以及临床肠炎相关肠癌组织中高表达，敲除Periostin可显著抑制小鼠结直肠肿瘤的发生。（2）结直肠原位癌肿瘤组织中的Periostin主要来自于肿瘤相关成纤维细胞，结直肠癌肝转移组织中的Periostin主要来自于活化的肝星形细胞，而非肿瘤细胞或巨噬细胞。（3）结直肠癌肿瘤微环境中的肿瘤相关成纤维细胞来源的Periostin可通过Integrin-FAK-Src信号通路活化YAP来促进肿瘤细胞增殖并上调肿瘤细胞IL-6的分泌，IL-6则可通过磷酸化STAT3刺激肿瘤相关成纤维细胞活化并分泌Periostin。因此肿瘤相关成纤维细胞来源的Periostin和结直肠癌肿瘤细胞来源的IL-6形成一个正反馈环路，共同促进结直肠肿瘤的发生。（4）敲除Periostin可显著减少AOM/DSS诱导的小鼠肠炎相关肠癌肿瘤组织PD-1表达水平以及PD-1阳性巨噬细胞的浸润；临床结直肠癌肿瘤组织中Periostin的表达与巨噬细胞浸润以及PD-1表达呈正相关；联合敲低Periostin和敲低PD-1可显著抑制结直肠癌细胞的皮下成瘤能力，且显著高于单独敲低Periostin或敲低PD-1的抑制效果，表明联合抑制Periostin和PD-1对结直肠癌具有很好的肿瘤抑制作用。（5）Periostin在结直肠癌肝转移组织和肝纤维化微环境中高表达，敲除Periostin显著抑制结直肠癌细胞肝转移和肝纤维化微环境的形成。（6）结直肠癌肿瘤细胞来源的TGF-β可通过Smad3介导的转录激活促进肝星形细胞Periostin蛋白的表达，而肝星形细胞来源的Periostin则可通过STAT3通路来促进结直肠癌肿瘤细胞增殖并分泌TGF-β。因此Periostin和TGF-β通过形成一个正反馈环路来持续促进肝纤维化微环境的形成以及结直肠癌肿瘤细胞的肝定植性生长。综上所述，该研究首次阐明了Periostin在结直肠癌原位癌发生发展和肝转移纤维化微环境形成中的功能及分子机理，为结直肠癌联合免疫治疗提供了新的理论依据和分子靶点。

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