Functional Interactions between Cancer Cells and Sensory Neurons

描述(申请人提供)：癌症引起的疼痛，特别是转移到骨骼的癌症，通常是严重的，难以管理，并对患者的生活质量造成很大影响。尽管阿片类药物仍然是控制严重癌症疼痛的主要治疗方法，但癌症疼痛对阿片类药物的相对抵抗力需要增加剂量，这限制了阿片类药物的使用，因为与中枢神经系统的作用相关的许多不良副作用。了解阿片类药物在治疗癌症疼痛时变得不那么有效的机制是很重要的。驱动癌症疼痛的机制是多因素的，包括骨重建、炎症反应、神经退变和癌细胞释放的痛觉物质，这些物质刺激或敏化初级传入纤维上的伤害性感受器。三磷酸腺苷是已知的一种肿瘤细胞在肿瘤生长过程中含有和释放的止痛物质。ATP激活位于伤害性神经末梢的外周P2X受体。我们小组以前的行为研究表明，在骨癌小鼠模型中，三磷酸腺苷参与了痛觉过敏的发展。此外，阿片类药物还调节了P2X受体上的信号。阿片类药物，如吗啡，减少通过P2X受体发生的ATP诱发电流。我们推测，这种通过P2X受体调节信号的阿片类药物被癌细胞减弱，这可能是阿片类药物在癌症疼痛中作用减弱的原因之一。在拟议的项目中，我们将使用体内和体外共培养的新方法来确定癌细胞对背根神经节(DRG)神经元ATP诱发反应的影响，5-和4-阿片受体激动剂如何调节这些反应，以及癌细胞是否促进DRG神经元阿片受体表达的变化。我们将确定纤维肉瘤细胞对小鼠DRG神经元P2X依赖的激活的影响，癌细胞产生的P2X电流的阿片类药物调制的变化，以及5-和4-阿片受体表达的变化。此外，我们还将比较在体内(在荷瘤小鼠中)发生的变化与在体外共培养模型中发生的变化。这项拟议的研究将在乌克兰(基辅)的Bogomoletz生理学研究所与膜片钳电生理学和P2X受体功能专家奥列格·A·克里什塔尔博士合作完成。这项研究是我们正在进行的项目NIH Grant CA091007的扩展，在该项目中，我们正在研究外周P2X和TRPV1受体在癌症疼痛中的作用，这些研究的伤害性感受器敏化结果将提供关于ATP促进癌症疼痛的机制以及阿片类药物如何在肿瘤生长过程中调节ATP诱发反应的新信息。了解阿片类药物如何调节感觉神经元对癌症相关反应的变化，可能会导致开发新的癌症疼痛管理方法。 与公共卫生相关：据美国国家癌症研究所估计，2007年美国新确诊的癌症病例超过140万例，世界卫生组织估计，2020年全球新确诊的癌症病例可能高达1500万例。大约85%的晚期癌症成人患者报告无法忍受的疼痛，高达75%的癌症儿童患者经历疼痛。了解癌症疼痛的驱动机制，以便开发新的和改进的疼痛管理治疗方法，是一个相关的公共卫生问题。

DESCRIPTION (provided by applicant): Pain from cancer, particularly cancer that metastasizes to bone, is often severe, difficult to manage, and contributes significantly to the patients' poor quality of life. Although opioids remain the primary treatment for managing severe cancer pain, the relative resistance of cancer pain to opioids requires increased doses, which limit their use because of the many undesirable side effects associated with actions in the central nervous system. It is important to understand the mechanisms by which opioids become less effective in treating cancer pain. The mechanisms that drive cancer pain are multi-factorial and include bone remodeling, inflammatory responses, neurodegeneration, and release of algesic substances from the cancer cells that excite or sensitize nociceptors on primary afferent fibers. ATP is one of the known algesic substances that cancer cells contain and release during tumor growth. ATP activates peripheral P2X receptors which are located on nociceptive nerve endings. Previous behavioral studies from our group indicated that ATP contributes to the development of hyperalgesia in a murine model of bone cancer. Moreover, opioids modulate signaling at P2X receptors. Opioids such as morphine decrease ATP-evoked currents that occur through P2X receptors. We hypothesize that this opioid modulation of signaling through the P2X receptor is diminished by cancer cells, and that this may contribute to the decreased effect of opioids in cancer pain. In the proposed project, we will use an in vivo and a new in vitro co-culture method to determine the effect of cancer cells on ATP-evoked responses of dorsal root ganglion (DRG) neurons, how those responses are modulated by 5- and 4-opioid receptor agonists, and whether cancer cells promote a change in the expression of opioid receptors in DRG neurons. We will determine the effect of fibrosarcoma cells on P2X- dependent activation of mouse DRG neurons, changes in opioid modulation of P2X currents produced by cancer cells, and alterations in expression of 5- and 4-opioid receptors. Also, we will compare changes that occur in vivo (in tumor-bearing mice) to changes that occur in our co-culture model in vitro. The proposed studies will be done in Ukraine (Kiev) at the Bogomoletz Institute of Physiology in collaboration with Dr. Oleg A. Krishtal, who is an expert in patch clamp electrophysiology and P2X receptor function. This study is an extension of our ongoing project, NIH Grant CA091007, in which we are examining the contribution of peripheral P2X and TRPV1 receptors in cancer pain and nociceptor sensitization Results from these studies will provide new information on the mechanisms by which ATP contributes to cancer pain, and how opioids modulate ATP-evoked responses during tumor growth. Understanding how opioids can modulate cancer-related changes in responses of sensory neurons may lead to the development of novel approaches for managing cancer pain. PUBLIC HEALTH RELEVANCE: It is estimated by the National Cancer Institute that more than 1.4 million new cases of cancer were diagnosed in the United States in 2007, and the World Health Organization estimates that up to 15 million new cases of cancer may be diagnosed world-wide in 2020. Approximately 85% of adult patients with terminal cancer report intolerable pain and up to 75% of children with cancer experience pain. Understanding the mechanisms that drive cancer pain so that new and improved therapeutic approaches for pain management can be developed is a relevant public health issue.