Cannabinoid CB2 Agonists for Treatment of Breast Cancer-Induced Bone Pain

描述(申请人提供)：统计数据显示，在美国，每7名女性中就有1人会在一生中患上乳腺癌，75%-95%的晚期乳腺癌患者有与癌症骨转移相关的慢性剧痛。转移性乳腺癌的疼痛似乎同时受到炎症、神经病理和肿瘤形成机制的驱动。这种疼痛极难治疗，导致这些患者的生活质量受到严重影响。如果能够更全面地控制骨癌疼痛，而没有现有止痛药的副作用，将显著改善乳腺癌骨转移患者的功能状态和生活质量，同时降低医疗费用。设计治疗乳腺癌骨痛的新疗法的一个主要问题是缺乏一个可用的模型来定义乳腺癌骨痛的产生和维持机制。这项建议的主要目的是使用我们最近开发的一种小鼠模型，该模型密切反映了乳腺癌引起的骨痛患者经常观察到的骨骼重塑和慢性疼痛。将稳定转染绿色荧光蛋白的小鼠66.1乳腺癌细胞注射到非免疫缺陷小鼠的股骨髓内间隙。在21天的时间里，这些肿瘤细胞在骨髓腔内增殖，并诱导骨重塑、骨癌相关的疼痛行为，最终导致骨折。最近的数据表明，大麻素类CB2激动剂可以在各种临床前疼痛模型中提供显著的镇痛作用，副作用最小。有趣的是，来自骨质疏松症研究的数据表明，CB2受体的激活是促进成骨(骨形成)的，我们实验室的初步数据表明，CB2激动剂在小鼠和人类乳腺癌细胞中都具有直接的抗肿瘤作用。在本提案中，我们将探索CB2激动剂具有多种有益作用的假说，在体内外都可以减轻乳腺癌引起的骨痛，减少肿瘤引起的骨破坏和骨折，以及减少乳腺癌细胞的生长。要测试的具体假设是：CB2受体激活将导致乳腺癌引起的骨癌疼痛小鼠模型的抗过敏反应，同时没有目前止痛治疗中看到的不想要的副作用。在本申请中提出的实验研究将有助于我们理解CB2受体在乳腺癌诱导的骨癌中的疼痛缓解作用，2)确定CB2激动剂是否会在使用乳腺癌细胞的骨癌小鼠模型中促进骨重塑和减少骨折，3)确定CB2激动剂是否在体外和体内都抑制乳腺癌细胞的增殖，4)确定CB2受体激活是否导致包括IL-12、IL-6和TNF1在内的促痛因子的减少，5)确定在骨癌小鼠模型中长期给予CB2激动剂是否会导致不想要的副作用，以及6)最重要的是，为乳腺癌转移性骨癌患者的新型创新治疗提供新的靶点。迫切需要新的治疗方法，在不产生现有药物的中枢神经系统副作用的情况下，充分缓解疼痛，抑制骨降解，避免因转移而导致的疼痛骨折，并导致疾病的改善。这些研究可能为开发治疗乳房到骨转移引起的疼痛的策略提供新的机会，并可能应用于其他骨癌。 公共卫生相关性：乳腺癌是北美女性最常见的恶性肿瘤。在美国，每年有近20万名妇女被确诊为乳腺癌患者，因此迫切需要新的治疗干预措施来治疗疼痛的乳腺癌患者。乳腺癌通常转移到骨骼，导致极度疼痛、骨骼重塑和最终骨折，导致丧失能力的疼痛和有限或完全丧失活动能力。美国国立卫生研究院估计，2006年美国癌症的总成本为2063亿美元，其中直接医疗成本为782亿美元(箭头出版社，2008年)。不幸的是，目前的治疗方法会导致不想要的副作用，甚至会导致骨骼进一步恶化和过敏。这项建议涉及CB2激动剂是否将减轻乳腺癌引起的骨痛，而不会导致当前止痛治疗中出现的不希望看到的副作用。CB2受体存在于免疫细胞和调节骨量的细胞上，但不存在于中枢神经系统的神经元上。激动剂激活CB2受体可抑制几种促进疼痛的炎症因子，显著减轻骨癌引起的自发性疼痛，抑制骨骼的降解，并减少乳腺癌细胞在骨内的增殖。然而，CB2激动剂不会导致不必要的副作用，如便秘、嗜睡、呼吸抑制、止痛耐受性或奖励性“成瘾”效应。

DESCRIPTION (provided by applicant): Statistics show that 1 out of every 7 females in the US will develop breast cancer in their lifetime, with 75-95% of patients with advanced breast cancer having chronic, excruciating pain associated with metastasis of the cancer to bone. Pain from metastatic breast cancer appears to be simultaneously driven by inflammatory, neuropathic and tumorigenic mechanisms. Such pain is extremely difficult to treat causing quality of life in these patients to be severely compromised. Being able to more fully control bone cancer pain, without the side effects of currently available analgesics, would significantly improve the functional status, quality of life while reducing health care costs in breast cancer patients with skeletal metastases. A major problem in designing new therapies to treat breast cancer-induced bone pain has been the lack of a model available to define the mechanisms that generate and maintain breast cancer induced bone pain. The major thrust of this proposal is to use a mouse model we have recently developed that closely mirrors the bone remodeling and chronic pain often observed in patients with breast cancer- induced bone pain. Mouse 66.1 breast cancer cells, stably transfected with green fluorescent protein, are injected and confined to the intramedullary space of the femur of the non-immunocompromised mice. Over a twenty-one day period, these tumor cells proliferate in the marrow space and induce bone remodeling, bone cancer related pain behaviors and ultimately fracture of the bone. Recent data has suggested that cannabinoid CB2 agonists can provide significant analgesia in a variety of preclinical pain models with a minimal side effect profile. Intriguingly, data from osteoporosis studies have suggested that activation of CB2 receptors is pro-osteogenic (bone-building) and preliminary data from our lab suggests CB2 agonists have direct anti-tumor effects in both mouse and human breast cancer cells. In the present proposal, we will explore the hypothesis that CB2 agonists can have multiple beneficial actions to reduce breast cancer-induced bone pain, reduce tumor induced bone destruction and fracture and reduce the growth of breast cancer cells both in vitro and in vivo. The specific hypotheses to be tested are: CB2 receptor activation will result in antihypersensitivity in a murine model of breast-induced bone cancer pain while lacking the unwanted side effects seen with current analgesic therapies. Experimental studies proposed in this application will: 1) aid in our understanding of the pain relieving effects of the CB2 receptors in breast-induced bone cancer, 2) identify whether CB2 agonists will enhance bone remodeling and reduce bone fracture in a murine model of bone cancer using breast cancer cells, 3) identify whether CB2 agonists inhibit the proliferation of breast cancer cells both in vitro and in vivo, 4) identify whether CB2 receptor activation results in a decrease in pronociceptive factors including IL-12, IL-6, and TNF1, 5) identify whether chronic administration of CB2 agonists in a murine model of bone cancer results in unwanted side effects, and 6) most importantly, offer a novel target for new and innovative therapy for patients suffering from bone cancer due to breast metastases. New treatments are urgently needed that would result in adequate pain relief without the debilitating CNS side effects of current agents, as well as inhibit bone degradation, avoiding painful bone fractures induced by the metastases and result in disease modification. These studies are likely to offer new opportunities for the development of strategies to treat pain resulting from metastasis of breast to bone as well as possible applications to other bone cancers. PUBLIC HEALTH RELEVANCE: Breast cancer is the most frequent malignant tumor in women in North America. With nearly 200,000 women diagnosed each year in the U.S., there is a great need for novel therapeutic intervention in treating breast cancer patients in pain. Breast cancer commonly metastasizes to the bone resulting in excruciating pain, bone remodeling and eventual bone fracture contributing to incapacitating pain and limited or total loss of mobility. The U.S. National Institutes of Health estimate overall costs of cancer in the U.S. in 2006 to be $206.3 billion with $78.2 billion in direct medical costs (Arrowhead Publishers, 2008). Unfortunately, current therapies result in unwanted side effects and even promote further deterioration of the bone and hypersensitivities. This proposal addresses whether CB2 agonist will attenuate breast cancer-induced bone pain without resulting in unwanted side effects seen with current analgesic therapies. CB2 receptors are found on immune cells and on cells that regulate bone mass but not on neurons of the central nervous system. The activation of CB2 receptors with agonists inhibits several inflammatory factors that promote pain, significantly attenuate spontaneous pain due to bone cancer, inhibit the degradation of bone, and reduce breast cancer cell proliferation within the bone. Yet, CB2 agonists do not result in the unwanted side effects such as constipation, somnolence, respiratory depression, analgesic tolerance or rewarding "addiction" effects.