Functional Interactions between Cancer Cells and Sensory Neurons

描述（由申请人提供）：癌症引起的疼痛，特别是转移到骨骼的癌症，通常是严重的，难以控制的，并且显著影响患者的生活质量。尽管阿片类药物仍然是治疗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抗性需要增加剂量，这限制了它们的使用，因为与中枢神经系统的作用相关的许多不良副作用。重要的是要了解阿片类药物在治疗癌症疼痛方面变得不那么有效的机制。驱动癌痛的机制是多因素的，包括骨重塑、炎症反应、神经退行性变和从癌细胞释放痛觉物质，这些物质刺激或敏感初级传入纤维上的伤害感受器。ATP是一种已知的止痛物质，癌细胞在肿瘤生长过程中含有并释放。ATP激活位于痛觉神经末梢的外周P2X受体。我们小组先前的行为研究表明，ATP有助于骨癌小鼠模型中痛觉过敏的发展。此外，阿片样物质调节P2X受体的信号传导。吗啡等阿片类药物可减少atp诱发的P2X受体电流。我们假设这种通过P2X受体的阿片调节信号被癌细胞减弱，这可能有助于阿片在癌症疼痛中的作用减弱。在本项目中，我们将采用一种新的体内和体外共培养方法来确定癌细胞对atp诱发的背根神经节（DRG）神经元反应的影响，这些反应如何被5-和4-阿片受体激动剂调节，以及癌细胞是否促进DRG神经元中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依赖性激活的影响，癌细胞产生的P2X电流的阿片调节的变化，以及5-和4-阿片受体表达的变化。此外，我们将比较体内（荷瘤小鼠）发生的变化与体外共培养模型中发生的变化。拟议的研究将在乌克兰（基辅）的Bogomoletz生理学研究所与Oleg A. Krishtal博士合作进行，Oleg A. Krishtal博士是片钳电生理学和P2X受体功能方面的专家。本研究是我们正在进行的NIH Grant CA091007项目的延伸，在该项目中，我们正在研究外周P2X和TRPV1受体在癌症疼痛和伤害感受器致敏中的作用，这些研究的结果将为ATP促进癌症疼痛的机制以及阿片类药物如何调节肿瘤生长过程中ATP引起的反应提供新的信息。了解阿片类药物如何调节感觉神经元的癌症相关变化，可能会导致治疗癌症疼痛的新方法的发展。

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.