Inducible PTK6 expression drives oncogenic signaling in breast cancer

 描述(申请人提供)：30%的被诊断为乳腺癌的患者最终发展为转移性疾病并复发，这个过程可能需要几年到几十年的时间。肿瘤进展面对最初有效的治疗是一个重大的临床问题 挑战。肿瘤细胞通过激活适应性和应激诱导的信号通路来逃避治疗。肿瘤转移和耐药的发生是由于多种应激敏感信号通路的激活，这些通路的细胞功能是由氧反应的低氧诱导因子(HIF)调控的。然而，直接靶向HIF是具有挑战性的，因为它们定位于细胞核，并调控数百个基因。大多数“缺氧诱导因子抑制剂”对缺氧诱导因子α的稳定性/活性起间接作用，而不是直接作用。为了提高乳腺癌患者发生转移疾病的治疗效果，必须识别作用于HIF下游的“驱动”基因，并将其作为靶点。我们已经确定蛋白酪氨酸激酶6(PTK6)是乳腺癌致癌信号的主要驱动因素。PTK6，也被称为乳腺肿瘤激酶(BRK)，是一种非受体酪氨酸激酶，在高达86%的乳腺癌中表达，但在正常乳腺组织中表达非常低或缺失。值得注意的是，PTK6的表达增加预示着不良的结局，并介导了抗癌药物的耐药性(例如。抗体)针对细胞表面受体。在体外，强制表达PTK6赋予了癌症的“特征”，包括增加增殖、促进生存和迁移。最近，我们发现PTK6在增加细胞压力和促进肿瘤进展的条件下迅速上调，如氧化应激、低糖、紫外线和缺氧。皮质类固醇、核糖皮质激素受体(GRs)的细胞内配体和宿主应激反应的介体也可以诱导PTK6的强劲表达。值得注意的是，GR的表达与基底型或三阴性(ER-/PR-/Her2-)乳腺癌(TNBC)的不良预后密切相关。TnBC细胞还结构性地高水平表达细胞转录因子HIF1α和HIF2α。 对压力的反应。我们最新的初步数据表明，GR/HIF复合体在包括化疗在内的各种细胞应激反应中诱导PTK6。一旦表达，PTK6就激活了应激相关蛋白激酶p38MAPK和ERK5，这两个新的效应因子与乳腺癌的生存、化疗耐药、EMT和迁移/侵袭行为有关。这些数据共同支持一种模型，在该模型中，皮质醇/GR和/或肿瘤相关应激介导HIF诱导的PTK6表达，然后启动应激激活的信号通路(p38MAPK和ERK5)，导致癌细胞存活增加和获得迁移/侵袭行为。简而言之，我们假设可诱导的PTK6在体内对肿瘤细胞具有化疗耐药性和转移行为。在此，我们建议定义PTK6诱导(目标1)和信号转导(目标2)的要求，并使用患者来源的TNBC异种移植(PDX)模型(目标3)测试PTK6作为体内转移发展和治疗耐药的介导者的作用。

 DESCRIPTION (provided by applicant): Thirty percent of patients diagnosed with breast cancer ultimately develop metastatic disease and relapse in a process that can take years to decades. Tumor progression in the face of initially effective treatment represents a major clinical challenge. Tumor cells circumvent treatment via activation of adaptive and stress-induced signaling pathways. Metastasis and drug resistance occur in response to activation of a variety of stress-sensing signaling pathways whose cellular functions are orchestrated by the oxygen- responsive hypoxia inducible factors (HIFs). Yet, directly targeting HIFs is challenging as they are localized to the nucleus and regulate hundreds of genes. Most "HIF inhibitors" act indirectly rather than directly on HIFα stability/activity. To improve efficacy of treatments for breast cancr patients at risk of developing metastatic disease, "driver" genes acting downstream of HIFs must be identified and targeted. We have identified protein tyrosine kinase 6 (PTK6) as a major driver of oncogenic signaling in breast cancer. PTK6, also known as breast tumor kinase (Brk) is a non-receptor tyrosine kinase that is expressed in up to 86% of breast cancers but is very low or absent from normal breast tissues. Notably, increased PTK6 expression predicts poor outcome and mediates resistance to anti-cancer agents (ex. antibodies) aimed at cell-surface receptors. Forced expression of PTK6 confers "hallmarks" of cancer in vitro, including increased proliferation, pro-survival and migration. Recently, we found that PTK6 is rapidly upregulated in response to conditions that increase cellular stress and facilitate tumor progression, such as oxidative stress, low glucose, UV, and hypoxia. Robust PTK6 expression is also induced by corticosteroids, intracellular ligands for nuclear glucocorticoid receptors (GRs) and mediators of host stress responses. Notably, expression of GR is tightly associated with poor outcome in basal-type or triple-negative (ER-/PR-/Her2-) breast cancer (TNBC). TNBC cells also constitutively express high levels of HIF1α and HIF2α, transcription factor mediators of cellular responses to stress. Our most recent preliminary data suggest that GR/HIF complexes induce PTK6 in response to a variety of cellular stresses that may include chemotherapy. Once expressed, PTK6 activates the stress-associated protein kinases, p38 MAPK and ERK5, two emerging effectors of survival, chemo-resistance, EMT, and migratory/invasive behavior in breast cancer. These data collectively support a model in which cortisol/GR and/or tumor-associated stress mediate HIF-induced PTK6 expression, which then turns on stress-activated signaling pathways (p38 MAPK and ERK5), leading to increased cancer cell survival and the acquisition of migratory/invasive behaviors. In short, we hypothesize that inducible PTK6 confers chemo-resistance and metastatic behavior to tumor cells in vivo. Herein, we propose to define the requirements for PTK6 induction (Aim 1) and signal transduction (Aim 2) and test the role of PTK6 as a mediator of metastasis development and therapy-resistance in vivo using patient-derived xenograft (PDX) models of TNBC (Aim 3).