基于PDX模型队列“临床替代性试验”的口腔鳞癌西妥昔单抗耐药机制研究

Exploring the mechanisms of resistance to targeted therapies is crucial to the practice of precision medicine. Cetuximab remains the only recommended targeted agent for the first-line treatment of recurrent/metastatic oral squamous cell carcinoma (OSCC) in NCCN guidelines. However, cetuximab resistance significantly limits its clinical use and remains a substantial challenge. Tumor heterogeneity, which fosters clonal evolution, is a key factor contributing to drug resistance. The applicant has conducted a series of studies focusing on patient-derived xenograft (PDX) models. The present study will further explore the mechanisms of cetuximab resistance from the perspective of tumor heterogeneity with the "PDX Trial". We aim to track cancer evolution under anticancer treatment at the single cell level, and to capture driver events in drug-resistant subclones. Additionally, we intend to verify the candidates of driven events and define the underlying mechanisms of de novo and acquired resistance to cetuximab in vitro and in vivo. Finally, we seek to evaluate the therapeutic efficacy of agents targeting the driver event, in combination with cetuximab in designed PDX cohort. In conclusion, this project will provide theoretical basis for the personalized treatment of cetuximab in OSCC patients as well as a novel insight into overcoming resistance to targeted agents in other cancers.

靶向药物的耐药机制探寻是实现癌症精准治疗的关键。西妥昔单抗是NCCN指南中建议用于口腔鳞癌一线治疗的唯一靶向药物， 然而广泛存在的耐药现象限制了它进一步的临床应用。肿瘤异质性克隆进化是产生耐药性的主要原因。课题组前期围绕病人组织源性小鼠移植瘤PDX（Patient-derived xenografts）模型进行了系列研究；在此基础上，本项目将首次借助PDX模型队列充分聚焦肿瘤异质性，来研究口腔鳞癌西妥昔单抗的耐药机制。利用单细胞测序技术通过解析药物作用前后模型中肿瘤亚克隆的演化轨迹，捕获相关细胞亚群并获得其遗传学特征图谱，在单细胞水平探寻肿瘤耐药相关的关键驱动事件，进而通过体内外功能实验明确西妥昔单抗的原发性及获得性耐药机制，并借助PDX模型试验评估西妥昔单抗联合用药方案，为口腔鳞癌精准治疗提供理论依据，也能为其他肿瘤的西妥昔单抗研究或其他靶向药物的耐药机制探讨提供新颖的思路及实践基础。

耐药性是癌症治疗的重大难题，靶向药物的耐药机制探寻是实现癌症精准治疗的关键。西妥昔单抗是一种广泛用于治疗口腔鳞癌的一线药物。然而广泛存在的耐药现象限制了它进一步的临床应用。本研究利用49例PDX模型模拟临床研究组建了PDX模型治疗队列进行了“II期临床试验”，本研究阐明了介导口腔鳞癌西妥昔单抗原发性和获得性耐药机制，获得了潜力的西妥昔单抗“首次用药的药效预测标志物”(例如ANKH的扩增，PARP3的上调)。本研究还随机入组了61例PDX模型组建了西妥昔单抗验证队列，证实了上述耐药生物标志物的准确性。本研究系统绘制了西妥昔单抗获得性耐药的肿瘤克隆演进轨迹，证实了RAS-RAC-MAPK通路异常激活是口腔鳞癌西妥昔单抗获得性耐药的重要驱动因素，并揭示出靶向干预RAC1和RAC3可在体内外克服口腔鳞癌对西妥昔单抗的获得性耐药，延缓肿瘤复发。本研究在靶向药物耐药研究顺利开展的基础上，聚焦了口腔癌免疫治疗耐药频发的难题，分别从增敏免疫治疗效果和逆转免疫抑制性微环境视角开发了口腔癌治疗策略。总之，本研究充分考虑肿瘤异质性特征使用规模性PDX模型组建临床替代性试验，为创新型临床试验制定和逆转获得性耐药的联合用药方案开发提供了依据，也为靶向药物和免疫治疗耐药机制研究提供新颖的思路和实践基础。