The P2X7 receptor for ATP as a therapeutic target in the prevention of radiation-induced salivary gland dysfunction

摘要 尽管头颈部鳞状细胞癌(HNSCC)放射治疗方面的技术进步， 电离辐射(IR)后对唾液腺等周围正常组织的附带损害 这对这些患者来说是一个重大问题，并严重降低了他们的生活质量。据估计，95%的 HNSCC患者在放疗后出现口干和唾液腺功能减退，73% 其中一些患者在完成放射治疗后继续遭受数月至数年的痛苦。缺乏治疗 介导慢性IR引起的唾液功能障碍的潜在机制。我们之前的研究 演示细胞外ATP(EATP)的作用，它是受损组织中的一个关键的“警报”分子，它有助于 对于IR引起的唾液功能障碍，可以通过药物或基因阻断eATP的P2X7R来抑制， 从而赋予唾液腺显著的辐射防护。此外，我们的研究表明，辐射防护 与治疗IR引起的慢性口干症和唾液功能障碍相关的研究尚未见报道。 我们的最终目标是使用P2X7R拮抗剂作为放射防护剂来保留头部唾液腺的功能 和接受放射治疗的宫颈癌患者，尽管目前几乎没有关于 P2X7R拮抗剂将干扰放射治疗实现的肿瘤消退，拟议的研究将 解决知识上的这一差距。该提案的总体目标是开发一种使用P2X7R的方法 拮抗剂预防头颈部肿瘤放疗患者IR所致唾液功能障碍 不抑制IR诱导的HNSCC肿瘤消退。这项提案的成功完成将极大地 加速将这一新的药理学方法转化为接受IR治疗的人类患者 头颈癌。将致力于实现以下具体目标： 特异性靶点1将开发一种在照射后的同基因小鼠中使用P2X7R拮抗的放射防护方法 保留唾液腺功能和抗肿瘤反应的HNSCC小鼠模型。 特定目标2将研究P2X7R拮抗剂对人卵巢癌放射防护作用的持久性 开发一种治疗放疗后HNSCC患者发生的慢性唾液功能障碍的方法。 特异性目标3将评估eATP释放和嘌呤组信号在P2X7R下游的作用 小鼠和人唾液腺器官培养中对IR所致唾液腺功能障碍的激活作用 寻找替代的辐射防护目标，并将在老鼠身上的发现转化为人类。

Summary Despite technological advancements in head and neck squamous cell carcinoma (HNSCC) radiotherapies, collateral damage to surrounding normal tissues such as salivary glands following ionizing radiation (IR) remains a significant problem for these patients and severely diminishes their quality of life. It is estimated that >95% of HNSCC patients exhibit xerostomia and salivary gland hypofunction following the irradiation regimen and >73% of these patients continue to suffer for months to years after completion of radiotherapy. The lack of treatment options to prevent IR-induced xerostomia or recover salivary function is compounded by a limited understanding of the underlying mechanisms that mediate chronic IR-induced salivary dysfunction. Our previous studies demonstrate the action of extracellular ATP (eATP), a key “alarmin” molecule in damaged tissue that contributes to IR-induced salivary dysfunction, can be inhibited by pharmacological or genetic blockade of P2X7Rs for eATP, thereby conferring significant radioprotection to salivary glands. In addition, our studies show that radioprotection from P2X7R antagonism maintains normal salivary output through day 30 post-IR, although longer time periods relevant to the treatment of IR-induced chronic xerostomia and salivary dysfunction have not been investigated. Our ultimate goal is to use P2X7R antagonists as radioprotective agents to retain salivary gland function in head and neck cancer patients undergoing radiotherapy, although there is little information available on whether P2X7R antagonists will interfere with tumor regression achieved by radiotherapy, and proposed studies will address this gap in knowledge. The overall goal of this proposal is to develop an approach using P2X7R antagonism to prevent IR-induced salivary dysfunction in head and neck cancer patients receiving radiotherapy without inhibiting the IR-induced regression of HNSCC tumors. Successful completion of this proposal will greatly accelerate translation of this novel pharmacological approach to human patients undergoing IR therapies for head and neck cancer. The following specific aims will be pursued: Specific Aim 1 will develop a radioprotective approach using P2X7R antagonism in an irradiated syngeneic mouse model of HNSCC that preserves salivary gland function and anti-tumor responses. Specific Aim 2 will investigate the durability of the radioprotective effects of P2X7R antagonism towards developing an approach for chronic salivary dysfunction that occurs in HNSCC patients following radiotherapy. Specific Aim 3 will evaluate the contribution of eATP release and purinomic signaling downstream of P2X7R activation to IR-induced salivary gland dysfunction in mouse and human salivary gland organotypic cultures towards identifying alternative radioprotective targets and translating findings in mice to humans.