Tyrosine phosphorylation of p27Kip1 as a biomarker to identify Cdk4/6 inhibitor response

总结 虽然CDK4靶向药物（CDK4i）Palbociclib、Abemaciclib和Ribociclib已显示出临床前景， 在转移性乳腺癌（BC）的治疗中，缺乏伴随诊断来识别反应性乳腺癌， 病人仍然是一个问题。虽然CDK4i治疗在一些患者中增加了无进展生存期（PFS）， 转移性HR+患者中，许多患者表现出对CDK 4/6抑制的原发性耐药性，并且没有产生任何耐药性 从这些药物中获益，在6个月内转为化疗。开发一种生物标志物， 活性CDK4靶标的存在，以及因此CDK4i敏感的患者的存在， 转移性乳腺癌患者在治疗开始时被精确定位。由于CDK4/6是所有 虽然这类药物可能在致癌信号通路中起作用，但这类药物也可能在至少一个亚组中具有疗效。 另外的肿瘤类型，以及CDK4i反应性的生物标志物将加速这种扩展。 肿瘤类型，如转移性Her2+、三阴性乳腺癌或卵巢癌， 几乎没有治疗选择。预测CDK4i有效性的生物标志物将意味着更快的获益， 正确的患者，节省成本和时间，减少对患者的毒性， 在迫切需要新疗法的肿瘤类型中扩展这些疗法的使用。在 本质：生物标记物将有助于将正确的药物提供给正确的患者。该翻译项目将侧重于 一种新的诊断标志物p27Kip1 pY88在识别对目前治疗有反应的患者中的应用 使用CDK4i疗法。在已发表和已发表的工作中，我们已经表明pY88作为替代物， 在细胞系、原代外植体培养中，以及现在在 来自用CDK4i疗法进行临床治疗的患者的活组织检查。本RO1项目的目标是证明 p27 pY是一种诊断性生物标志物，用于鉴定CDK4/6i应答患者， 协调为什么pY可能通过将其与耐药机制联系起来来划分耐药， 这将进一步为CDK4/6i药物的潜在用途提供信息。在目标1和2（翻译目标）中，我们 计划测试基于IHC的测定法，以确定pY88是否可作为生物标志物预测显著的PFS 用CDK4/6i治疗的HR +/HER2-BC患者的改善。在目标3（机制目标）中，我们将 确定pY状态如何与CDK4/6i敏感性和抗性相关。目的1：测试pY的能力 通过比较HR+患者活检材料中的pY88状态，预测显著PFS的生物标志物 用CDK4/6i临床治疗的BC与患者结局数据。目标2.为了测试经验证的pY测试， 临床相关队列，来自两项已完成和正在进行的临床试验。目标3：确定pY 通过使用生物化学研究来检查pY状态与CDK4/6i敏感性和抗性相关， CDK4/6i抗性的体外和体内模型。

SUMMARY While the CDK4 targeting drugs (CDK4i), Palbociclib, Abemaciclib, and Ribociclib, have shown clinical promise in the treatment of metastatic breast cancer (BC), lack of a companion diagnostic to identify responsive patients remains a problem. While CDK4i therapy increases progression-free survival (PFS) in some metastatic HR+ patients, many patients exhibit primary resistance to CDK4/6 inhibition and do not derive any benefit from these agents, switching to chemotherapy within 6 months. Development of a biomarker to identify the presence of the active CDK4 target, and therefore CDK4i sensitive patients, would enable responsive metastatic breast cancer patients to be pinpointed at the onset of therapy. As CDK4/6 is downstream of all oncogenic signaling pathways, it is also likely that this class of drugs will have efficacy in at least a subset of additional tumor types, and a biomarker for CDK4i responsiveness would accelerate the expansion of this class of therapy into tumor types, such as metastatic Her2+, Triple negative breast or ovarian cancer, which have few therapeutic options. A biomarker to predict effectiveness of CDK4i would mean more rapid benefit to the correct patients, a cost and time savings and reduced toxicity for patients who would not be benefited and extended use of these therapies across tumor types where novel therapies are desperately needed. In essence: a biomarker would help get the right drug to the right patients. This translational project will focus on the utility of a novel diagnostic marker, p27Kip1 pY88, to identify patients who would respond to the currently used CDK4i therapy. In published and presented work, we have shown that pY88 serves as a surrogate marker for CDK4 activity and in turn CDK4i responsiveness, in cell lines, primary explant culture, and now in biopsies from patients treated clinically with CDK4i therapy. The goal of this RO1 project is to demonstrate that p27 pY is a diagnostic biomarker to identify CDK4/6i-responsive patients and then also to reconcile why pY might demarcate resistance by associating it to mechanisms of resistance, with the idea that this will further inform potential uses of the CDK4/6i drugs. In Aims 1 and 2 (translational aims) we plan to test an IHC based assay to determine if pY88 can serve as a biomarker to predict significant PFS improvement in patients with HR+/HER2- BC treated with CDK4/6i. In Aim 3 (mechanism aim), we will determine how pY status relates to CDK4/6i sensitivity and resistance. Aim 1: To test the ability of the pY biomarker to predict significant PFS, by comparing pY88 status in biopsy material from patients with HR+ BC treated clinically with CDK4/6i with patient outcome data. Aim 2. To test the validated pY test in clinically relevant cohorts, from two completed and ongoing clinical trials. Aim 3: To determine how pY status relates to CDK4/6i sensitivity and resistance, by using biochemical studies to examine pY status in in vitro and in vivo models of CDK4/6i resistance.