Co-Targeting IL-6 and CDK4/6 Pathways as a Novel Approach of Preventive Therapy for Triple-Negative Breast Cancer

三阴性乳腺癌（TNBC）具有高度侵袭性，并且与不良临床结局相关。TNBC 是乳腺癌患者死亡的主要原因;并且是乳腺癌的唯一亚型， 缺乏有效的预防和治疗方案。开发新的预防或治疗方法 TNBC是一项重要任务。该研究项目的优先领域是退伍军人的健康， 特别是关于TNBC的女性退伍军人。为了帮助满足这一未得到满足的医疗需求，我们建议 同时靶向白细胞介素6（IL-6）和细胞周期蛋白依赖性激酶（CDK）4/6通路; 因为与其他乳腺癌相比，IL-6和CDK4/6通路的共激活在TNBC中富集 亚型共活化也与发展转移的时间缩短相关。多篇文献 已经报道了IL-6信号可以赋予抗癌药物抗性;一份报告表明， 乳腺癌细胞对CDK4/6抑制剂耐药的机制是IL-6/STAT3通路的激活。 此外，我们的初步结果表明，CDK4/6抑制剂abemaciclib进一步诱导TNBC中的IL-6水平， 细胞，这可能使abemaciclib处理的TNBC细胞对abemaciclib更具抗性。因此，我们认为， TNBC中IL-6与CDK4/6的共活化可能潜在地损害CDK4/6抑制剂的功效， 为共同靶向IL-6和CDK4/6通路以进行有效的TNBC预防性治疗提供了强有力的理论基础。目前， 在临床试验中没有小分子IL-6药物可用。靶向TNBC中的IL-6信号传导， 治疗中，我们重新利用FDA批准的口服生物可利用药物bazedoxifene作为一种新型的IL- 6/GP130信令。巴多昔芬作为DUAVEE（具有缀合雌激素的巴多昔芬）销售， 预防绝经后骨质疏松症。为了靶向TNBC中的CDK4/6，我们建议测试abemaciclib（Trade Verzenio），是最有效的CDK4/6小分子抑制剂之一。Abemaciclib已经 FDA批准用于治疗激素受体阳性，人表皮生长因子 受体2（HER2）阴性晚期或转移性乳腺癌。我们的初步数据显示， 巴多昔芬和abemaciclib组合在体外协同抑制TNBC细胞活力， 抑制体内肿瘤生长。此外，初步结果观察到，巴多昔芬和阿贝西尼 在原位肿瘤模型中，在原发性肿瘤被移除后，组合预防了肝转移。 我们的中心假设是巴多昔芬和阿贝西尼对IL-6和CDK4/6通路的双重抑制， 联合治疗是通过抑制肿瘤生长来防止TNBC进一步进展的有效方法 预防肿瘤转移和复发。我们将通过三个具体的假设来检验中心假设。 目的：（1）评价巴多昔芬和阿贝西尼联合预防TNBC肿瘤生长的活性 和肿瘤复发。(2)评定疗效 使用两种互补的药物预防TNBC肿瘤转移的研究 TNBC实验转移的小鼠模型。(3)阐明苯多昔芬的作用机制 和abemaciclib组合。成功完成拟议的研究有可能推迟 使用巴多昔芬-abemaciclib组合作为一种新的治疗方法， 预防性治疗的方法，并提供了一个独特的机会，以改善病人的护理和生存， 女性退伍军人和积极在军队中服役的女性与TNBC。

Triple-negative breast cancer (TNBC) is highly aggressive and is associated with poor clinical outcomes. TNBC is a major cause of death among breast cancer patients; and is the only subtype of breast cancer that is still lacking effective prevention and therapeutic options. Development of novel preventive or therapeutic approach for TNBC is an important task. The priority area of this research project is on women Veteran’s health, in particular, on women Veterans with TNBC. To assist in this unmet medical need, we propose to pharmacologically target Interleukin 6 (IL-6) and cyclin-dependent kinases (CDK)4/6 pathways simultaneously; because IL-6 and CDK4/6 pathways’ co-activation is enriched in TNBC compared to other breast cancer subtypes. The co-activation is also associated with a shortened time to develop metastasis. Multiple literatures have reported that IL-6 signaling could confer resistance to anti-cancer drugs; and a report suggests that one of the mechanisms of resistance to CDK4/6 inhibitors in breast cancer cells is the activation of IL-6/STAT3 pathway. In addition, our preliminary results show that CDK4/6 inhibitor abemaciclib further induces IL-6 levels in TNBC cells, which could potentially make abemaciclib-treated TNBC cells more resistance to abemaciclib. Therefore, co-activation of IL-6 in TNBC with CDK4/6, could potentially compromise the efficacy of CDK4/6 inhibitors and provide strong rationale to co-target IL-6 and CDK4/6 pathways for effective TNBC preventive therapy. Currently, no small molecule IL-6 drugs are available in clinical trials. To target IL-6 signaling in TNBC for preventive therapy, we repurposed a FDA-approved orally bioavailable drug bazedoxifene as a novel inhibitor of the IL- 6/GP130 signaling. Bazedoxifene is marketed as DUAVEE (bazedoxifene with conjugated estrogens) for preventing postmenopausal osteoporosis. To target CDK4/6 in TNBC, we propose to test abemaciclib (Trade Name: Verzenio), which is one of the most potent CDK4/6 small molecule inhibitors. Abemaciclib has been approved by FDA for the treatments of hormone receptor positive, human epidermal growth factor receptor 2 (HER2)-negative advanced or metastatic breast cancer. Our preliminary data indicate that bazedoxifene and abemaciclib combination synergistically inhibited TNBC cell viability in vitro and significantly suppressed tumor growth in vivo. In addition, preliminary results observed that bazedoxifene and abemaciclib combination prevented liver metastasis in orthotopic tumor model after the primary tumors were removed. Our central hypothesis is that dual inhibition of the IL-6 and CDK4/6 pathways by bazedoxifene and abemaciclib combination is an effective approach to prevent TNBC from further progression by suppressing tumor growth and preventing tumor metastasis and tumor recurrence. We will test the central hypothesis by three specific aims: (1) Evaluate the activity of bazedoxifene and abemaciclib combination in preventing TNBC tumor growth and tumor recurrence using clinically relevant TNBC orthotopic mouse model in vivo. (2) Evaluate the efficacy of bazedoxifene and abemaciclib combination in preventing TNBC tumor metastasis using two complementary mouse models of TNBC experimental metastasis. (3) Elucidate the mechanisms of action of the bazedoxifene and abemaciclib combination in TNBC. Successful completion of proposed studies has a potential to delay the TNBC from further progression and metastasis for years using bazedoxifene-abemaciclib combination as a novel approach for preventive therapy and presents a unique opportunity to improve patient care and survival for women Veterans and women actively serving in the military with TNBC.