Oncogenic Kras drives stromal adipogenesis to promote colorectal cancer (CRC) progression

项目摘要 而结直肠癌（CRC）患者的5年生存率与局限期疾病（定义为 根据SEER）为90%，对于诊断为转移性CRC的患者，该存活率下降至14%。因此， 迫切需要确定控制进展为晚期疾病及其维持的机制。 在KRAS癌基因中携带致癌突变的人CRC（以下称为KRAS*）是 发生转移的可能性增加25%。类似地，我们的CRC小鼠模型，用诱导型KRAS* APC和p53等位基因的转基因和条件无效等位基因（iKAP），揭示了KRAS* 在驱动细胞凋亡中的作用。 癌症进展和转移。从机制上讲，KRAS* 驱动的癌症转移部分通过以下方式发挥作用： 通过IRF 2-CXCL 3轴激活癌细胞内在TGFβ信号传导并抑制抗肿瘤免疫 其招募骨髓来源的抑制细胞。不幸的是，靶向KRAS* 或 TGFβ通路在临床上显示出有限的疗效，促使我们识别和验证其他的TGF β通路。 KRAS* 驱动的癌症进展机制，目标是扩大治疗靶点库 转移性CRC利用iKAP模型，功能基因集富集和组织学分析， 表达KRAS* 的CRC转移显示了强烈的脂肪生成特征和 肿瘤微环境中的脂肪成纤维细胞和血管生成。相应地，小鼠的共培养 用来自iKAP原代细胞系的条件培养基刺激胚胎成纤维细胞分化为 具有脂肪细胞和成纤维细胞特征的细胞，即，“脂肪成纤维细胞”在本提案的F99阶段，我试图定义 表达KRAS* 的癌细胞驱动脂肪纤维形成的分子机制， 脂肪成纤维细胞在KRAS* 驱动的CRC进展中的肿瘤生物学作用。 由于只有少数人或小鼠KRAS* CRC病例进展为转移性疾病，因此明显遗传 KRAS激活以外的事件驱动转移。例如，具有或不具有KRAS* 突变的患者， 淋巴结转移率约为40%。对这种促转移事件的研究将是非常重要的 通过将诱导型端粒酶逆转录酶（LSL-mTERT）整合到我们现有的iAP中， 模型，从而建模端粒为基础的危机和基因组的不稳定性，然后端粒酶再激活。在我们 端粒酶诱导的前列腺癌小鼠模型，危机-端粒酶序列产生癌症相关的 基因组畸变并增加转移潜力。虽然将基因组不稳定性纳入 iAP模型不会创建更像人类模型，它将提供一个平台来识别扩增， 与转移过程相关的缺失。在这个计划的K 00阶段，我试图设计人类- 像iAP模型中的端粒动力学，以评估端粒危机和端粒酶的影响 重新激活驱动转移，并调查基因组改变，可能是转移过程的基础。 这些努力可能有助于发现晚期CRC疾病的新治疗靶点。

Project Summary While the 5-year survival rate for colorectal cancer (CRC) patients with localized stage disease (as defined by SEER) is 90%, this survival rate drops to 14% for patients diagnosed with metastatic CRC. Thus, there is an urgent need to define the mechanisms governing progression to advanced disease and its maintenance. Human CRCs harboring oncogenic mutations in the KRAS oncogene (designated hereafter as KRAS*) are 25% more likely to develop metastases. Similarly, our CRC mouse model, engineered with an inducible KRAS* transgene and conditional null alleles of APC and p53 alleles (iKAP), has revealed a role for KRAS* in driving cancer progression and metastasis. Mechanistically, KRAS*-driven cancer metastasis functions in part by activating cancer cell-intrinsic TGFβ signaling and suppressing anti-tumoral immunity via the IRF2-CXCL3 axis which recruits myeloid derived suppressor cells. Unfortunately, emerging therapies targeting either KRAS* or TGFβ pathways have shown limited efficacy in the clinic, motivating us to identify and validate additional KRAS*-driven cancer progression mechanisms with the goal of expanding the repertoire of therapeutic targets for metastatic CRC. Utilizing the iKAP model, functional gene set enrichment and histological analyses of KRAS*-expressing CRC metastases revealed a strong adipogenesis signature and preponderance of lipofibroblasts and angiogenesis in the tumor microenvironment. Correspondingly, co-culture of mouse embryonic fibroblasts with conditioned media from iKAP primary cell lines stimulated their differentiation into cells with adipocyte and fibroblast traits, i.e., “lipofibroblasts.” In the F99 phase of this proposal, I seek to define the molecular mechanisms by which KRAS*-expressing cancer cells drive lipofibrogenesis and to understand the tumor biological role of lipofibroblasts in KRAS*-driven CRC progression. As only a minority of human or mouse KRAS* CRC cases progress to metastatic disease, clearly genetic events beyond KRAS activation drive metastases. For example, patients with or without KRAS* mutation both show around a 40% lymph node metastatic rate. The study of such pro-metastasis events would be greatly facilitated by incorporating an inducible telomerase reverse transcriptase (LSL-mTERT) into our existing iAP model, thus modeling telomere-based crisis and genome instability followed by telomerase reactivation. In our telomerase-inducible mouse models of prostate cancer, crisis-telomerase sequence generates cancer-relevant genomic aberrations and increases metastatic potential. Although incorporation of genomic instability into the iAP model would not create a more human-like model, it would provide a platform to identify amplifications and deletions associated with the metastatic process. In the K00 phase of this proposal, I seek to engineer human- like telomere dynamics in the iAP model to assess the impact of telomere-based crisis and telomerase reactivation in driving metastasis and to survey the genomic alterations that may underlie the metastatic process. Such efforts may facilitate the discovery of new therapeutic targets for advanced CRC disease.