Treatment Resistance Pathways & Targeting Residula Cancers

系统性治疗最初在控制和逆转肿瘤生长方面是有效的。然而，尽管有这种最初的反应，残留的癌症总是会重新生长。从历史上看，对治疗耐药性的研究主要集中在对特定药物或多种药物产生耐药性的块状肿瘤上皮细胞中获得性基因改变的鉴定。但我们最近的数据支持存在一个小的但 在原肿瘤中存在的不同的癌细胞亚群，在常规治疗后的残留癌中大大丰富。这些残留的癌细胞具有相对静止和对治疗的抵抗力的特点，但它们像干细胞一样具有增强的自我更新能力。因此，我们假设，在原始肿瘤中存在的一种独特的癌细胞亚群对传统治疗具有内在的抵抗力，并对肿瘤的启动和癌症的再生长负责。 为了验证我们的假设，我们建议：(1)确定我们的新辅助试验中的耐药乳腺癌是否富含具有自我更新和肿瘤启动能力的细胞亚群。我们将使用细胞表面标志物和荧光活性染料滞留来鉴定这些细胞，并通过流式细胞仪对其进行纯化。自我更新和致瘤性将通过体外乳房(MS)分析和 分别为异种移植。(2)明确乳腺癌常规化疗后耐药和自我更新的调控基因和信号转导途径。这将使用mRNA和BAG甲基化微阵列来确定标记保留的MS启动细胞、CD44+/CD24假定的“乳腺癌干细胞”和耐药残留癌细胞之间的基因表达和表观遗传学相似性，以及与分化的原代浸润性乳腺癌细胞的差异。(3)确定抑制自我更新和治疗耐药通路是否可以改善现有的癌症治疗方法，使用MS-形成分析以及我们在“动物临床试验”中建立的新的原代异种移植小鼠模型，从而直接针对该肿瘤重新启动亚群进行人类试验。 如果我们的假设是正确的，那么在明显成功的治疗后复发是由于这些静止的、耐药的肿瘤细胞持续存在，从而允许肿瘤重新启动。如果是这样的话，抗癌药物开发的方法必须从根本上改变，以针对这些罕见的肿瘤启动细胞，而不是像迄今所做的那样，只针对大块肿瘤的细胞。

Systemic therapies are effective initially in controlling and reversing tumor growth. However, residual cancers will invariably re-grow despite this initial response. Historically, investigation of treatment resistance has focused on the identification of acquired genetic alterations in bulk tumor epithelial cells that confer resistance to specific agents, or to multiple agents. But our recent data supports the existence of a small but distinct subpopulation of cancer cells present in the original tumor that are greatly enriched in residual cancers after conventional therapies. These residual cancer cells are characterized by their relative quiescence and resistance to therapy, yet they possess enhanced self-renewal capacity like that of stem cells. We therefore hypothesize that a unique subpopulation of cancer cells present in the original tumors are intrinsically resistant to conventional therapies, and are responsible for tumor initiation and cancer regrowth. To test our hypothesis, we propose: (1) To determine whether treatment-resistant breast cancers from our neoadjuvant trials are enriched for subpopulations of cells with self-renewal and tumor-initiating capacity. We will use cell surface markers and fluorescent vital dye retention to identify these cells and purify them by FACS. Self-renewal and tumorigenicity will be assessed by in vitro mammosphere (MS) assays and xenograft transplantation, respectively. (2) To define the regulatory genes and signaling pathways responsible for treatment resistance and self-renewal in human breast cancers after conventional chemotherapy. This will be done using mRNA and BAG methylation microarrays to determine gene expression and epigenetic similarities among label-retaining MS-initiating cells, CD44+/CD24- putative "breast cancer stem cells", and chemoresistant residual cancer cells, and differences from differentiated primary invasive breast cancer cells. (3) To determine whether suppression of self-renewal and treatment resistance pathways can improve existing cancer therapies using MS-formation assays as well as our novel primary xenograft mouse models in "animal clinical trials", leading to human trials targeting this tumor re-initiating subpopulation directly. If our hypothesis is correct, then relapse after apparently successful therapy is due to the persistence of these resting, therapy-resistant tumor cells, thereby allowing tumor re-initiation. If so, approaches for anticancer drug development must be changed fundamentally to target these rare tumor-initiating cells, rather than only cells of the bulk tumor as has been done to date.