Breast Tumor Heterogeneity and its Impact on Tumor Progression

虽然几乎所有的人类肿瘤都来源于单一的起源细胞，但肿瘤内的肿瘤细胞由于遗传和表观遗传改变、谱系多样化和基质细胞的影响而随着时间的推移而进化。这些过程在来自个体肿瘤的肿瘤细胞群体内产生相当大的异质性。尽管我们知道肿瘤细胞异质性的存在，但尚不清楚肿瘤细胞的异质亚群是否仅仅共存，或者它们是否彼此交流，互补彼此的表型并产生个体群体不能自己产生的生物学结果。缺乏对tum9r群体之间的这种功能性相互作用的理解在很大程度上是由于无法维持培养中人类肿瘤的异质性以及无法从个体肿瘤中繁殖不同的克隆亚群。我们和我们的合作者已经开发出克服这些障碍的方法，并使培养条形码，荧光标记的肿瘤细胞克隆群体成为可能，然后跟踪由移植克隆混合物产生的肿瘤异种移植物中的单个克隆群体。使用这些方法，我们已经获得了支持肿瘤内克隆亚群相互合作促进肿瘤扩张和转移的假设的证据。在这项提案中，我们描述了在人类乳腺肿瘤中测试这一假设的计划，通过（1）表征来自个体乳腺肿瘤的克隆群体之间的遗传和表型变异程度，并分析每个克隆亚群的肿瘤起始，侵袭和转移活性，（2）生成一个地图，绘制肿瘤内克隆群体的定位及其随时间的动态演变，（3）研究人类乳腺肿瘤细胞群内异质性的功能后果，以及（4）阐明负责肿瘤内串扰产生的表型的机制。这些研究将为了解肿瘤细胞群之间的合作相互作用的性质以及这些相互作用如何影响肿瘤扩张、侵袭或转移提供重要见解。

While virtually all human tumors are derived from a single cell-of-origin, neoplastic cells within a tumor evolve over time due to genetic and epigenetic alterations, lineage diversification, and influences from stromal cells. These processes generate considerable heterogeneity within populations of neoplastic cells from individual tumors. Despite our knowledge of the existence of tumor cell heterogeneity, it is not understood whether the heterogeneous subpopulations of tumor cells merely co-exist, or alternatively whether they communicate with each other, complementing one another's phenotypes and generating biological outcomes that individual populations are incapable of producing on their own. The lack of understanding of such functional interactions between tum9r populations has been due in large part to the inability to maintain the heterogeneity of human tumors in culture and to propagate distinct clonal subpopulations from individual tumors. We and our collaborators have developed approaches that have overcome these barriers and made it feasible to culture bar-coded, fluorescently-tagged, clonal populations of tumor cells and then track individual clonal populations within tumor xenografts generated from mixtures of transplanted clones. Using these approaches, we have obtained evidence the supports the hypothesis that clonal subpopulations within a tumor cooperate with one another to promote tumor expansion and metastasis. In this proposal, we describe plans to test this hypothesis in human breast tumors by (1) characterizing the extent of genetic and phenotypic variation among clonal populations derived from an individual breast tumor and analyzing the tumor-initiating, invasive, and metastatic activity of each clonal subpopulation, (2) generating a map that plots the localization of clonal populations within tumors and their dynamic evolution over time, (3) investigating the functional consequences of heterogeneity within human breast tumor cell populations, and (4) elucidating the mechanisms responsible for phenotypes generated by intratumoral crosstalk. These studies will provide important insights into the nature of cooperative interactions between tumor cell populations and how these affect tumor expansion, invasion, or metastasis.