Purpose

Chemotherapy based on cisplatin (CDDP) has been established as the treatment of choice for head and neck squamous cell carcinoma (HNSCC). Malignant tumors respond to microenvironmental alterations through a dynamic balance between mitochondrial fission and fusion. HNSCCs are known to exhibit hypoxic conditions, yet the respective effects and underlying mechanisms of hypoxia on chemosensitivity and mitochondrial dynamics remain to be resolved.

Methods

The effect of hypoxia on the chemosensitivity of HNCC cells was determined by flow cytometry. Mitochondrial fission factor (Mff) expression was assessed by RT-PCR and Western blotting in hypoxic HNSCC cells, and further verified in primary CDDP-sensitive and CDDP-resistant HSNCC samples. The biological function of Mff was evaluated by loss of function and gain of function analyses, both in vitro and in vivo.

Results

We found that hypoxia promoted mitochondrial fission and CDDP sensitivity in HNSCC cells. Importantly, Mff was found to be correlated with chemosensitivity in primary clinical samples under hypoxic conditions. Hypoxia-inducible factor 1α (HIF-1α) was found to markedly increase Mff transcription and to directly bind to Mff. Hypoxia enhanced the release of reactive oxygen species (ROS) and upregulated the expression of Mff via HIF-1α in HNSCC cells. ROS depletion in HNSCC cells attenuated HIF-1α expression, Mff expression and mitochondrial fission. Moreover, Mff knockdown led to suppression of hypoxia-induced mitochondrial fission and to decreased CDDP chemosensitivity in vivo and in vitro.

Conclusions

Our findings indicate that hypoxia-induced release of ROS can promote mitochondrial fission and CDDP chemosensitivity via HIF1α/Mff regulation in HNSCC cells, indicating that Mff may serve as a biomarker to predict neoadjuvant chemosensitivity in HNSCC patients and as a target for overcoming chemoresistance.

中文翻译：

---

缺氧诱导的 ROS 通过 HIF-1α/Mff 调节头颈鳞状细胞癌促进线粒体裂变和顺铂化疗敏感性

 目的

基于顺铂（CDDP）的化疗已被确定为头颈鳞状细胞癌（HNSCC）的首选治疗方法。恶性肿瘤通过线粒体裂变和融合之间的动态平衡来响应微环境变化。已知 HNSCC 表现出缺氧状况，但缺氧对化疗敏感性和线粒体动力学的各自影响和潜在机制仍有待解决。

 方法

通过流式细胞术测定缺氧对HNCC细胞化疗敏感性的影响。通过 RT-PCR 和蛋白质印迹法评估缺氧 HNSCC 细胞中线粒体裂变因子 (Mff) 的表达，并在原代 CDDP 敏感和 CDDP 耐药 HSNCC 样本中进一步验证。通过体外和体内功能丧失和功能获得分析来评估 Mff 的生物学功能。

 结果

我们发现缺氧促进了 HNSCC 细胞的线粒体分裂和 CDDP 敏感性。重要的是，在低氧条件下，Mff 被发现与原始临床样本的化疗敏感性相关。缺氧诱导因子 1α (HIF-1α) 被发现可显着增加 Mff 转录并直接与 Mff 结合。缺氧增强了 HNSCC 细胞中活性氧 (ROS) 的释放，并通过 HIF-1α 上调了 Mff 的表达。 HNSCC 细胞中 ROS 的消耗减弱了 HIF-1α 表达、Mff 表达和线粒体裂变。此外，Mff 敲低导致缺氧诱导的线粒体裂变受到抑制，并降低体内和体外 CDDP 化学敏感性。

 结论

我们的研究结果表明，缺氧诱导的 ROS 释放可以通过 HIF1α/Mff 调节 HNSCC 细胞促进线粒体裂变和 CDDP 化疗敏感性，这表明 Mff 可以作为预测 HNSCC 患者新辅助化疗敏感性的生物标志物和克服化疗耐药的靶点。