A quiescent G0-like cell state as a barrier to eradication oral cancer stem cells

描述(申请人提供)：尽管癌症干细胞(CSCs)是口腔鳞状细胞癌(OSCCs)的一个有吸引力的治疗靶点，但此类口腔CSCs的分子图谱尚未形成共识。越来越多的证据表明，一些非CSC的表型可塑性使它们能够回到CSC池中，这进一步阻碍了CSC的根除。准确定义口腔口腔鳞状细胞癌以及在靶向衰竭后恢复它们的机制将为有效的口腔鳞状细胞癌治疗建立一个新的概念框架。我们的初步工作已经分离出耐药的慢周期JARID1B-HI细胞亚群，作为口腔鳞癌的候选CSC群体。JARID1B是一种组蛋白去甲基酶，其表达通过功能标准在其他癌症类型中识别CSC，基于其介导进入干细胞样表观遗传状态的能力，它有望成为一种可推广的CSC标记物。在JARID1B-hi细胞中，PI3K通路的过度激活使其对PI3K靶向药物的耗竭敏感。我们的工作假设是，一个耗尽的JARID1B-hi CSC池可以由一群静止的“G0样”细胞来补充，这些细胞既有高的生长潜力，又有耐药性。虽然缺乏JARID1B-HI细胞中的干细胞标志物和PI3K途径活性，但G0样细胞确实显示出显著的Notch途径激活，这与CSC群体扩张和PI3K/AKT信号增加有关。为了解释这些发现，我们的总体假设是，增殖的口腔鳞状细胞进入静止的G0样状态，通过为JARID1B-HI细胞提供直接前体，创建了一个防止永久性CSC耗竭的储备库。为了验证这一假设，我们将首先使用传统的CSC标准(目标1)测试JARID1B-Hi和G0-like亚集在口腔鳞癌生长中的作用。我们将专门测试JARID1B-hi细胞是否具有独立的CSC功能，而G0样细胞的肿瘤形成可能取决于JARID1B-hi组分。其他研究将确定G0样细胞在维持口腔鳞状细胞癌JARID1B-HI群体中的确切作用(目标2)。在这里，我们测试了Notch介导的非CSCs进入静止的G0样状态是否形成了JARID1B-hi细胞的直接前体，从而为CSC的再繁殖提供了储备库。这些概念在这里的验证将建立新的模型系统，以剖析潜在的细胞状态转换机制，防止治疗期间持久的口腔CSC耗尽。这样，我们的工作也将促进翻译研究，共同针对两种不同的肿瘤细胞表型，通过Notch和PI3K途径协同维持口腔鳞状细胞癌的生长。

DESCRIPTION (provided by applicant): Although cancer stem cells (CSCs) present an appealing therapeutic target in oral squamous cells carcinomas (OSCCs), a consensus molecular profile for such oral CSCs has not emerged. CSC eradication is further hampered by growing evidence of phenotypic plasticity in some non-CSCs allowing them to return to the CSC pool. Accurately defining oral CSCs together with mechanisms for restoring them after targeted depletion would establish a novel conceptual framework for effective OSCC therapy. Our preliminary work has isolated a drug-resistant subset of slow-cycling JARID1B-hi cells as a candidate CSC population in OSCC. JARID1B, a histone demethylase whose expression identifies CSCs by functional criteria in other cancer types, shows promise as a generalizable CSC marker based on its ability to mediate entry into a stem cell-like epigenetic state. Hyper-activation of the PI3-kinase (PI3K) pathway in JARID1B-hi cells renders them sensitive to depletion by PI3K-targeted drugs. Our working hypothesis is that a depleted JARID1B-hi CSC pool can be replenished by a population of quiescent "G0-like" cells, which have both high growth potential and drug resistance. While lacking the stem cell markers and PI3K pathway activity seen in JARID1B-hi cells, G0-like cells do show prominent Notch pathway activation, which has been linked to CSC population expansion and increased PI3K/AKT signaling. To explain these findings, our overall hypothesis is that entry of proliferative OSCC cells into a quiescent, G0-like state creates a reservoir to prevent permanent CSC depletion by providing a direct precursor to JARID1B-hi cells. To test this hypothesis, we will first test the roles of JARID1B- hi and G0-like subsets in OSCC growth using conventional CSC criteria (aim 1). We will specifically test whether JARID1B-hi cells have independent CSC functions, while tumor formation by G0-like cells may depend upon the JARID1B-hi fraction. Additional studies will define the precise role of G0-like cells in sustaining the JARID1B-hi population in OSCC (aim 2). Here we test whether Notch-mediated entry of non-CSCs into a quiescent G0-like state forms a direct precursor for JARID1B-hi cells, thus providing a reservoir for CSC repopulation. Validation of these concepts here would establish new model systems to dissect mechanisms underlying the cell state transitions that prevent durable oral CSC depletion during treatment. In doing so, our work will also facilitate translational studies to jointly target two distinct tumor cell phenotypes that cooperatively sustain OSCC growth via the Notch and PI3K pathways.