Identifying Fundamental Mechanisms that Mediate Resistance to Anti-Cancer Therapies

实现癌症长期缓解的一个主要障碍是一些癌细胞抵抗治疗的能力。令人惊讶的是，人类肿瘤耐药的基本细胞生物学与许多浮游生物物种具有令人难以置信的再生能力的基础细胞生物学非常相似。在这些扁虫物种中，即使是一小块切除的组织也可以重建出一个全新的动物。这种非凡的能力有赖于维持一个与癌症干细胞有许多相似之处的异质脊椎动物干细胞库。例如，这些细胞中的一部分可以耐受高剂量的γ辐射，并恢复整个干细胞种群。然而，人们对这种耐受的机制知之甚少，对它们对化疗的耐药性也几乎一无所知。初步研究显示，浮游生物对药物顺铂表现出抗药性。用80-100μM顺铂治疗浮游生物，诱导了一种与人类癌症化疗耐药发展大致相似的表型：动物表现出最初的组织丢失，然后是再生。基于这些数据和已知的顺铂效应，中心假设是顺铂对茎和祖细胞群体的线粒体功能有不同的影响，从而差异地改变了标记肿瘤抑制基因的保守染色质特征，即广泛的H3赖氨酸4三甲基化(H3K4me3)，增加了细胞异质性，并促进了化疗耐药性。本研究的目的是利用人类肿瘤和脊椎动物干细胞群体之间显著的功能相似性，通过以下具体目标揭示体内化疗耐药发展与代谢和表观遗传调控之间的基本机制：1)使用线粒体探针、高分辨率成像和生化分析来确定干细胞和前体细胞群体中顺铂反应的线粒体功能差异。这项研究使用最先进的方法来确定干细胞在体内的代谢异质性。2)通过干扰代谢物的可获得性并测量其对H3K4me3、转录异质性和化疗耐药性的影响，建立代谢、染色质状态和化疗耐药性之间的机制联系。这项研究将揭示代谢和表观遗传调控在化疗耐药中的关键联系。3)利用已建立的呼吸道器官模型评价肺癌中代谢H3K4me3调节机制的保守性。这项研究将验证耐药肺癌细胞通过减少H3K4me3对顺铂诱导的ROS产生反应的假设。这项拟议的研究将揭示化疗耐药的新机制和靶向基因。

A major obstacle to achieving long-term cancer remission is the ability of some cancer cells to resist therapy. Strikingly, the fundamental cell biology underlying therapy resistance in human tumors is remarkably similar to that which confers incredible regenerative capacity in many planarian species. In these flatworm species, even a small piece of excised tissue can recreate an entirely new animal. This remarkable ability relies on the maintenance of a heterogeneous pool of planarian stem cells that bear many similarities to cancer stem cells. For example, a subset of these cells can tolerate high doses of γ-radiation and restore the entire stem cell population. Yet little is known about the mechanisms that confer this tolerance and almost nothing is known about their resistance to chemotherapies. Preliminary research revealed that planarians show resistance to the drug cisplatin. Treatment of planarians with 80-100μM cisplatin induced a phenotype that broadly mimicked the development of chemoresistance in human cancers: animals exhibited an initial loss of tissue followed by regeneration. Based on these data and known effects of cisplatin, the central hypothesis is that cisplatin differentially affects mitochondrial function across the stem and progenitor populations, which differentially alters a conserved chromatin signature that marks tumor suppressor genes i.e., broad H3 lysine 4 trimethylation (H3K4me3), increases cellular heterogeneity, and promotes chemoresistance. The goal of this study is to leverage the remarkable functional similarities between human tumors and the planarian stem cell population to uncover fundamental mechanisms that link the development of chemoresistance to metabolic and epigenetic regulation in vivo through the following specific aims: 1) To identify cisplatin-responsive differences in mitochondrial function in stem and progenitor cell populations using mitochondrial probes, high resolution imaging, and biochemical assays. This study uses state-of the-art approaches to determine the metabolic heterogeneity of stem cells in vivo. 2) To establish mechanistic links between metabolism, chromatin state, and chemoresistance by perturbing metabolite availability and measuring the impact on H3K4me3, transcriptional heterogeneity, and chemoresistance. This study will reveal critical links between metabolic and epigenetic regulation in chemoresistance. 3) To assess the conservation of metabolic H3K4me3 regulatory mechanisms in lung cancer using established airway organoid models. This study will test the hypothesis that resistant lung cancer cells respond to cisplatin-induced ROS by reducing H3K4me3. The proposed research will uncover novel mechanisms and target genes underlying chemoresistance.