Molecular mechanisms driving mesenchymal colorectal cancer

总结 肿瘤上皮细胞的干-间充质表型及其相关的免疫抑制和 结缔组织间质，是最具侵略性和生存能力差的类型的基本特征， 结直肠癌然而，驱动这一过程的分子和细胞机制还远远没有实现。 清楚这一提议源于我实验室最近发表和未发表的一系列观察结果 确定了两种非典型PKC（aPKC; PKC β和PKC β/β）作为新的肿瘤抑制因子， 防止这种侵略性形式的CRC。因此，肠上皮中两种aPKC的同时丢失（在 一种新的DKOIEC小鼠系）导致高度间充质腺癌， 免疫抑制基质。两种aPKC在间充质/基质/细胞中均显著下调。 免疫抑制性CRC人类患者具有最不利的预后。我们未发表 初步数据表明，缺乏PKC β/β（或两种aPKC）的肠上皮细胞（IEC） 上调干细胞受体CD 44，同时下调Lgr 5+肠干细胞， 提示出现了一种新型的肿瘤起始细胞（TIC）。抑制肿瘤类器官中的CD 44 + 证明其对生长的需求并支持其生理病理学相关性。一致性，抑制 一种关键的CD 44基质配体（透明质酸）在体内消除了DKOIEC的间充质表型 肿瘤抑制免疫抑制反应并恢复免疫监视。我们假设 PKC β/β的缺失导致新型CD 44 +/Lgr 5-TIC的上调是发生TICs的核心。 侵袭型CRC。MAP激酶级联的上调，连同鉴定，在 一系列无偏的方法，转录因子KLF 4作为一个潜在的关键中介之间的 PKC β 1/β 2和CD 44表达的变化，使我们推测PKC β 1/β 2缺乏对ERK/JNK的激活可能是一个重要的机制。 触发AP 1，同时诱导KLF 4降解;两种作用共同驱动CD 44 表达和间充质表型非常积极的CRC。因此，在本提案中，我们将 确定CD 44在侵袭性/间质型CRC中的作用（目的1），以及分子生物学作用。 PKC α/β在此过程中调节CD 44表达和功能的机制（目的2）。成功 完成拟议的研究将创造一个具有重要意义和影响的新范例， 更全面地了解导致预后不良的间充质型肺癌的机制， CRC，这将是设计这种侵袭性肿瘤新治疗靶点的关键。

SUMMARY A stem-mesenchymal phenotype of the tumor epithelium, and its associated immunosuppressive and desmoplastic stroma, are fundamental characteristics of the most aggressive and poor survival type of colorectal cancer CRC. However, the molecular and cellular mechanisms driving this process are still far from clear. This proposal stems from a series of recently published and unpublished observations in my laboratory that identify the two atypical PKCs (aPKC; PKC and PKC/) as novel tumor suppressors acting in concert to prevent this aggressive form of CRC. Thus, the simultaneous loss of both aPKCs in the intestinal epithelium (in a new DKOIEC mouse line) results in highly mesenchymal adenocarcinomas with a reactive and strongly immunosuppressed stroma. Both aPKCs are significantly downregulated in mesenchymal/stromal/ immunosuppressive CRC human patients who have the most unfavorable prognosis. Our unpublished preliminary data demonstrate that intestinal epithelial cells (IECs) deficient in PKC/ (or both aPKCs) upregulate the stem cell receptor CD44, concomitant with the downregulation of Lgr5+ intestinal stem cells, suggesting the appearance of a new type of tumor initiating cells (TICs). Inhibition of CD44+ in tumor organoids demonstrate its requirement for growth and supports its physiopathological relevance. Consistently, inhibition of one of the key CD44 stromal ligands (hyaluronan) in vivo abrogates the mesenchymal phenotype of DKOIEC tumors inhibiting the immunosuppressive response and restoring immunosurveillance. We hypothesize that the upregulation of a new type of CD44+/Lgr5- TICs by the loss of PKC/ is central in the development of the aggressive type of CRC. The upregulation of the MAP kinase cascades, together with the identification, in a series of unbiassed approaches, of the transcription factor KLF4 as a potential critical intermediary between PKC/ and CD44 expression, led us to hypothesize that the activation of ERK/JNK by PKC/ deficiency triggers AP1 and, concurrently, induces the degradation of KLF4; both actions cooperate to drive CD44 expression and the mesenchymal phenotype of very aggressive CRC. Therefore, in this proposal, we will determine the role of CD44 in the aggressive/mesenchymal type of CRC (Aim 1), as well as the molecular mechanisms whereby PKC/ regulates CD44 expression and function in this process (Aim 2). The successful completion of the proposed studies will create a new paradigm of significance and impact that will contribute to a more comprehensive understanding of the mechanisms driving the poor prognosis mesenchymal type of CRC, which will be key for the design of new therapeutic targets for this type of aggressive neoplasia.