The miR-20/c-Myc/E2F Regulatory Axis is Critical for the Tumor Promoting Activity of Inflammatory Fibroblasts in Colitis-Associated Cancer

总结 炎症是几种癌症的危险因素。例如，在溃疡性结肠炎（UC）中， 结肠慢性炎症，发展结肠炎相关结肠癌（CAC）的风险为3至5- 比一般人群患散发性结直肠癌（CRC）的风险高一倍。更糟的是， 对于UC患者来说，没有治愈性CAC预防或CAC逆转的选择，CAC的发病机制是 不清楚在这种复杂的环境中，精确的致癌触发因素仍然是个谜，因此很难解释 目标鉴于这种情况，我们的长期目标是了解结肠炎和CAC的发病机制， 制定预防性干预措施变得更加可行。我们最近报道了结肠炎相关的 来自UC患者的成纤维细胞和癌症相关的成纤维细胞分泌升高水平的CXCL8（一种免疫调节剂）。 炎症介质），CXCL8水平受miRNA，miR-20 a负调控，并且miR-20 a， 至少部分负责调节间质成纤维细胞中的CXCL 8分泌。已知miR-20a 通过与E2F家族转录因子的相互作用被c-Myc调节。然而，与 我们的数据表明，结肠炎成纤维细胞中的低miR-20 a和低c-Myc水平增加了结肠上皮细胞中miR-20 a和c-Myc的表达。 致瘤性为了解决这个难题，本申请的总体目标是确定 成纤维细胞miR-20（miR-17家族成员）对CAC发病机制的贡献。我们的中央 假设是miR-20 a/c-Myc/E2F轴下调对于miR-20 a/c-Myc/E2F的肿瘤促进活性是关键的。 结肠间质成纤维细胞。为了检验这些关系，我们将追求三个目标：1）定义贡献 miR-20在结肠间质成纤维细胞中的表达与肿瘤发生的关系; 2）探讨成纤维细胞c-Myc和miR-20在结肠间质成纤维细胞中的作用。 E2F7/8对miR-20和肿瘤促进的影响，以及3）为了鉴定与E2F7/8相关的基质成纤维细胞群， 疾病进展，并确定其作为预后工具的用途。这种方法是创新的，因为它使用 专门的人类组织分离物，专注于miR-20 a，c-Myc和E2F7/8的机制研究 关系，并在单细胞水平上协调成纤维细胞亚群对细胞增殖的贡献。 CAC的发病机制。该研究为肿瘤促进活性提供了分子基础，具有重要意义 这将使100万有CAC风险的美国结肠炎患者受益。此外，我们的研究结果将 适用于基质提供额外途径的任何慢性炎症过程， 干预

SUMMARY Inflammation is a risk factor for several types of cancer. For example, in ulcerative colitis (UC), a disease of chronic inflammation of the colon, the risk of developing colitis-associated cancer of the colon (CAC) is 3 to 5- fold higher than the risk in the general population of developing sporadic colorectal cancer (CRC). Worse, there are no curative CAC-preventing or CAC-reversing options for UC patients, and the pathogenesis of CAC is unclear. The precise oncogenic triggers in this complex milieu remain mysterious and are therefore difficult to target. Given this situation, our long-term goal is to understand the pathogenesis of colitis and CAC such that development of preventive interventions becomes more feasible. We recently reported that colitis-associated fibroblasts and cancer-associated fibroblasts from UC patients secrete elevated levels of CXCL8 (an inflammatory mediator), that CXCL8 levels are negatively regulated by a miRNA, miR-20a, and that miR-20a is, at least in part, responsible for the modulation of CXCL8 secretion in interstitial fibroblasts. miR-20a is known to be modulated by c-Myc via interaction with the E2F family of transcription factors. However, in contrast to the colon epithelia our data indicate that low miR-20a and low c-Myc levels in colitic fibroblasts increase tumorigenicity. To resolve this conundrum, the overall objective of this application, is to determine the contribution of fibroblast miR-20, a member of the miR-17 family, to the pathogenesis of CAC. Our central hypothesis is that downregulation of the miR-20a/c-Myc/E2F axis is critical for the tumor-promoting activity of colon interstitial fibroblasts. To test these relationships, we will pursue three Aims: 1) To define the contribution of miR-20 in the colitic stromal fibroblasts to tumorigenesis, 2) To delineate the roles of fibroblast c-Myc and E2F7/8 on miR-20 and tumor-promotion, and 3) To identify the stromal fibroblast populations associated with disease progression and to determine their use as prognostic tools. The approach is innovative as it uses exclusively human tissue isolates, focuses on mechanistic investigation of the miR-20a, c-Myc, and E2F7/8 relationships, and reconciles fibroblast subpopulations at the single cell level for their contributions to the pathogenesis of CAC. The research is significant as it provides a molecular basis for the tumor-promoting activity of the stroma, which will benefit the one million US colitis patients at risk for CAC. In addition, our findings will be applicable for any chronic inflammatory process for which the stroma provides additional avenues for intervention.