Inhibition of the chemokine receptors CXCR1 and CXCR2 synergizes with docetaxel for effective tumor control and remodeling of the immune microenvironment of HPV-negative head and neck cancer models [mouse]

Relapsed head and neck squamous cell carcinoma (HNSCC) unrelated to HPV infection carries a poor prognosis. Novel approaches are needed to improve the clinical outcome and prolong survival in this patient population which has poor long-term responses to immune checkpoint blockade. This study evaluated the chemokine receptors, CXCR1 and CXCR2, as potential novel targets for the treatment of HPV-negative HNSCC. Expression of IL-8, CXCR1, and CXCR2 was investigated in HNSCC tissues and human cell line models. Inhibition of CXCR1/2 with the clinical stage, small molecule inhibitor, SX-682, was evaluated in vitro and in vivo using human xenografts and murine models of HNSCC, both as a monotherapy and in combination with the taxane chemotherapy, docetaxel. High levels of IL-8, CXCR1, and CXCR2 expression were observed in HPV-negative compared to HPV-positive HNSCC tumors or cell lines. Treatment of HPV-negative HNSCC cell lines in vitro with SX-682 sensitized the tumor cells to the cytotoxic activity of docetaxel. In vivo, treatment of HNSCC xenograft models with the combination of SX-682 plus docetaxel led to strong anti-tumor control resulting in tumor cures. This phenomenon was associated with an increase of microRNA-200c and a decreased expression of its target, tubulin beta-3, a protein involved in resistance to microtubule-targeting chemotherapies. In vivo treatment of a murine syngeneic model of HNSCC with SX-682 plus docetaxel led to potent anti-tumor efficacy through a simultaneous decrease in suppressive CXCR2+ polymorphonuclear, myeloid-derived suppressor cells and an increase in cytotoxic CD8+ T cells in the combination therapy treated tumors compared to controls. This study reports, for the first time, mechanistic findings through which the combination of CXCR1/2 inhibition and docetaxel chemotherapy exhibits synergy in models of HPV-negative HNSCC. These findings provide rationale for the use of this novel combination approach to treat HPV-negative HNSCC patients and for future combination studies of CXCR1/2 inhibition, docetaxel, and immune-based therapies. MOC1 - To investigate the effect of docetaxel plus CXCR1/CXCR2 inhibition on the murine MOC1 HNSCC model, control, SX-682, docetaxel, and SX-682 plus docetaxel treated MOC-1 tumors from C57BL/6 mice were collected, RNA was purified from a piece of total tumor tissue, and RNA sequencing was performed.

与人乳头瘤病毒（human papillomavirus, HPV）感染无关的复发型头颈部鳞状细胞癌（head and neck squamous cell carcinoma, HNSCC）预后较差。该类患者群体对免疫检查点阻断治疗的长期应答不佳，亟需全新治疗策略以改善其临床结局、延长生存时间。本研究将趋化因子受体CXCR1与CXCR2作为HPV阴性HNSCC的潜在新型治疗靶点展开评估。本研究检测了HNSCC组织及人类细胞系模型中白细胞介素8（Interleukin 8, IL-8）、CXCR1与CXCR2的表达水平。本研究采用临床阶段小分子抑制剂SX-682抑制CXCR1/2通路，并分别以单药及联合紫杉烷类化疗药物多西他赛（docetaxel）的方案，在HNSCC的人类异种移植瘤模型与小鼠模型中开展体内外药效评价。相较于HPV阳性的HNSCC肿瘤及细胞系，HPV阴性HNSCC组织与细胞系中IL-8、CXCR1与CXCR2的表达水平显著升高。体外实验中，SX-682处理HPV阴性HNSCC细胞系可使肿瘤细胞对多西他赛的细胞毒性作用产生敏感性。体内实验中，联合使用SX-682与多西他赛处理HNSCC异种移植瘤模型可实现强效的肿瘤生长抑制，甚至达到肿瘤根治效果。该联合治疗效应与微小RNA-200c（microRNA-200c）的表达上调及其靶标微管蛋白β3（tubulin beta-3）的表达下调密切相关——微管蛋白β3是介导靶向微管化疗药物耐药的关键蛋白。体内实验中，联合使用SX-682与多西他赛处理HNSCC小鼠同基因移植模型，可通过双重机制实现强效抗肿瘤效应：相较于对照组，联合治疗组肿瘤中具有免疫抑制功能的CXCR2+多形核髓系来源抑制细胞比例显著降低，同时细胞毒性CD8+ T细胞浸润水平显著升高。本研究首次揭示了CXCR1/2抑制联合多西他赛化疗在HPV阴性HNSCC模型中发挥协同抗肿瘤效应的分子机制。本研究结果为采用该新型联合方案治疗HPV阴性HNSCC患者提供了理论依据，同时也为后续开展CXCR1/2抑制、多西他赛与免疫治疗的联合研究奠定了基础。MOC1模型：为探究多西他赛联合CXCR1/2抑制对HNSCC小鼠MOC1模型的治疗效果，本研究收集了C57BL/6小鼠的MOC1肿瘤组织，设置对照组、SX-682单药组、多西他赛单药组以及SX-682联合多西他赛组；随后从肿瘤组织中提取总RNA并进行RNA测序。