PTHrP Modulation of TRPV1 in Pain Associated with Breast Cancer Bone Metastasis

描述（由申请人提供）：乳腺癌是美国女性中最常见的癌症，每年有20万新病例报告。侵袭性乳腺癌最常转移到骨骼，这是高发病率和相关痛苦的关键因素。转移性乳腺肿瘤在骨骼中的生长导致四肢、骨盆和脊柱的慢性疼痛，现有的止痛药物（主要是吗啡衍生物）无法有效控制这种疼痛。由于姑息治疗是乳腺癌骨转移患者的主要治疗目标，因此更好地了解转移性骨肿瘤微环境与邻近感觉神经纤维之间的信号串扰对于开发高效的慢性骨癌疼痛镇痛药物是必要的。转移性乳腺癌细胞分泌高水平的甲状旁腺激素相关肽（PTHrP），其作用于成骨细胞和破骨细胞，诱导骨溶解/破坏，随后释放刺激肿瘤生长的营养物质和细胞信号分子。在这里，我提出了一个新的假设，即PTHrP通过其受体PTH1作用于感觉传入，通过上调瞬时受体电位香草素-1 （TRPV1）通道的活性/表达，诱导构成性伤害感受器致敏，这可能是转移性乳腺癌/骨癌相关慢性疼痛的机制。TRPV1通道通常仅在有害温度（e43℃）下被激活。然而，PTHrP通过PTH1受体作用可诱导TRPV1蛋白磷酸化，并在体温（37℃）下导致构成通道激活，这一机制可能在没有任何明显刺激的情况下导致慢性疼痛。我的研究目标1将确定pthrp对感觉神经元中TRPV1通道活性/表达的调节以及伤害感受器致敏的特定细胞信号事件。我将利用膜片钳电生理学、Ca2+成像和膜蛋白生物化学来确定PTHrP调节TRPV1的分子机制。我的研究目的2将利用人乳腺癌细胞mda - mb231 - bm -1833在小鼠体内移植，通过注射心内转移到骨骼，确定pthrp调节TRPV1在体内慢性骨痛的感觉传入中的作用。我将在这些患有转移性乳腺/骨肿瘤的小鼠中使用一系列非诱发/自发骨相关疼痛行为评估。我还将在这些小鼠中利用PTHrP和TRPV1的药理抑制，进一步证实PTHrP调节TRPV1在转移性乳腺/骨肿瘤生长相关的慢性骨痛中的作用。我提出的研究将促进我们对转移性乳腺/骨肿瘤和感觉神经元如何介导慢性疼痛之间相互作用的理解。这项研究的结果将显著有助于开发有效的药物治疗与转移性骨癌相关的慢性疼痛。

DESCRIPTION (provided by applicant): Breast cancer is the most frequently diagnosed cancer among women in the United States with >200,000 new cases reported every year. Aggressive forms of breast cancers most commonly metastasize to bones, which constitutes the key factor for high morbidity rate and associated suffering. Metastatic breast tumor growth in bones leads to chronic pain in the limbs, pelvis and spines, which is undermanaged with existing pain medications, mainly morphine derivatives. As palliative care is the major therapeutic goal for patients with breast cancer bone metastasis, a better understanding of signaling crosstalk between metastatic bone tumor microenvironment and the adjacent sensory nerve fibers is necessary for the development of highly efficacious analgesics for chronic bone cancer pain. Metastatic breast cancer cells secrete high levels of parathyroid hormone-related peptide (PTHrP), which act on osteoblasts and osteoclasts to induce bone lysis/destruction and subsequent release of nutrients and cell signaling molecules that stimulate tumor growth. Here I propose a novel hypothesis that PTHrP, by acting through its receptor PTH1 on sensory afferents, induce constitutive nociceptor sensitization via upregulation of activity/expression of the transient receptor potential vanilloid-1 (TRPV1) channel, which might underlie a mechanism for chronic pain associated with metastatic breast/bone cancers. The TRPV1 channel is normally activated only at noxious temperatures (e43oC). However, PTHrP acting through the PTH1 receptor could induce phosphorylation of TRPV1 protein and lead to constitutive channel activation at body temperatures (d37oC), a mechanism that could underlie chronic pain in the absence of any overt stimulation. Aim 1 of my study will determine the specific cellular signaling events that underlie PTHrP-modulation of TRPV1 channel activity/expression in sensory neurons, and nociceptor sensitization. I will utilize patch-clamp electrophysiology, Ca2+ imaging, and membrane protein biochemistry to determine the molecular mechanisms underlying TRPV1 modulation by PTHrP. Aim 2 of my study will determine the role of PTHrP-modulation of TRPV1 in sensory afferents on chronic bone pain in vivo using scid mice xenografts of human breast cancer cells, MDA-MB231-BoM-1833, that metastasize to bones when injected intracardialy. I will use a series of un-evoked/spontaneous bone-related pain behavioral assessments in these mice with metastatic breast/bone tumors. I will also utilize pharmacological inhibition of PTHrP and TRPV1 in these mice, to further confirm the contribution of PTHrP-modulation of TRPV1 in chronic bone pain associated with metastatic breast/bone tumor growth. My proposed studies will advance our understanding of how the interplay between metastatic breast/bone tumors and sensory neurons mediate chronic pain. Findings from this study will significantly contribute to the development of effective pharmacotherapies for chronic pain associated with metastatic bone cancers.