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，临床预后较差。TNBC 是导致乳腺癌患者死亡的主要原因，也是乳腺癌中唯一仍然存在的亚型。 缺乏有效的预防和治疗选择。开发新的预防或治疗方法 对于TNBC来说，这是一项重要的任务。这一研究项目的优先领域是关于女退伍军人的健康， 特别是针对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 同时靶向白介素6(IL-6)和细胞周期蛋白依赖性蛋白激酶(CDK)4/6通路； 因为与其他乳腺癌相比，TNBC中IL-6和CDK4/6通路的共激活更为丰富 子类型。这种共激活也与发生转移的时间缩短有关。多篇文献 有报道称，IL-6信号可能导致抗癌药物产生耐药性；而一份报告表明， 乳腺癌细胞对CDK4/6抑制剂耐药的机制是激活IL-6/STAT3通路。 此外，我们的初步结果表明，CDK4/6抑制剂阿贝西利进一步诱导了TNBC中IL-6的水平 这可能会使阿维西利处理的TNBC细胞对阿维西利产生更大的耐药性。因此， 在TNBC中IL-6与CDK4/6共激活，可能会损害CDK4/6抑制剂的疗效，并 为联合靶向IL-6和CDK4/6通路进行有效的TNBC预防治疗提供了强有力的理论依据。目前， 临床试验中还没有小分子IL-6药物可用。针对TNBC中的IL-6信号进行预防性治疗 在治疗过程中，我们将FDA批准的口服生物利用药Bazedoxifene作为一种新的IL-2抑制剂。 6/gp130信令。Bazedoxifene的市场名称为Duavee(具有结合雌激素的Bazedoxifene)，用于 预防绝经后骨质疏松症。为了在TNBC中瞄准CDK4/6，我们建议测试abemaciclib(Trade 名称：Verzenio)，它是最有效的CDK4/6小分子抑制剂之一。Abemaciclib一直是 FDA批准用于治疗激素受体阳性的人表皮生长因子 受体2(HER2)阴性的晚期或转移性乳腺癌。我们的初步数据显示 Bazedoxifen和Abemaciclib联合应用对体外培养的TNBC细胞活力有明显的协同抑制作用 抑制体内肿瘤生长。此外，初步结果观察到巴多昔芬和阿维菌利 联合应用可预防原发肿瘤切除后原位肿瘤模型的肝转移。 我们的中心假设是bazedoxifene和abemaciclib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防止TNBC进一步发展的有效方法 并防止肿瘤转移和肿瘤复发。我们将通过三个具体的例子来检验中心假说 目的：(1)评价巴多昔芬联合阿贝西利对TNBC肿瘤生长的抑制作用 并利用临床相关的TNBC原位小鼠体内模型进行肿瘤复发。(2)疗效评价 巴多昔芬联合阿贝西利预防TNBC肿瘤转移的临床研究 小鼠实验性肿瘤转移模型的建立。(3)阐明巴多昔芬的作用机制。 阿贝西利联合用药。成功完成拟议的研究可能会推迟 使用巴多昔芬-阿贝米利联合应用作为新的药物治疗多年来进一步进展和转移的TNBC 预防治疗的方法，并提供了一个独特的机会来改善患者的护理和生存 女性退伍军人和在TNBC服役的女性。

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.