Head and neck squamous cell carcinoma (HNSCC) clearly involves activation of the Akt mammalian target of rapamycin (mTOR) signalling pathway. However, the effectiveness of treatment with the mTOR inhibitor rapamycin is often limited by chemoresistance. Melatonin suppresses neoplastic growth via different mechanisms in a variety of tumours. In this study, we aimed to elucidate the effects of melatonin on rapamycin‐induced HNSCC cell death and to identify potential cross‐talk pathways. We analysed the dose‐dependent effects of melatonin in rapamycin‐treated HNSCC cell lines (Cal‐27 and SCC‐9). These cells were treated with 0.1, 0.5 or 1 mmol/L melatonin combined with 20 nM rapamycin. We further examined the potential synergistic effects of melatonin with rapamycin in Cal‐27 xenograft mice. Relationships between inhibition of the mTOR pathway, reactive oxygen species (ROS), and apoptosis and mitophagy reportedly increased the cytotoxic effects of rapamycin in HNSCC. Our results demonstrated that combined treatment with rapamycin and melatonin blocked the negative feedback loop from the specific downstream effector of mTOR activation S6K1 to Akt signalling, which decreased cell viability, proliferation and clonogenic capacity. Interestingly, combined treatment with rapamycin and melatonin‐induced changes in mitochondrial function, which were associated with increased ROS production, increasing apoptosis and mitophagy. This led to increase cell death and cellular differentiation. Our data further indicated that melatonin administration reduced rapamycin‐associated toxicity to healthy cells. Overall, our findings suggested that melatonin could be used as an adjuvant agent with rapamycin, improving effectiveness while minimizing its side effects.

中文翻译：

---

褪黑素和雷帕霉素联合用于头颈癌治疗：抑制AKT / mTOR途径活化，并通过线粒体功能调节活化线粒体和细胞凋亡

头颈部鳞状细胞癌（HNSCC）显然涉及激活雷帕霉素（mTOR）信号转导通路的Akt哺乳动物靶标。但是，用mTOR抑制剂雷帕霉素治疗的有效性通常受到化学耐药性的限制。褪黑素通过各种肿瘤中的不同机制抑制肿瘤生长。在这项研究中，我们旨在阐明褪黑素对雷帕霉素诱导的HNSCC细胞死亡的影响，并确定潜在的串扰途径。我们分析了褪黑素在雷帕霉素治疗的HNSCC细胞系（Cal- 27和SCC-9）中的剂量依赖性作用。这些细胞用0.1、0.5或1 mmol / L褪黑素与20 nM雷帕霉素结合处理。我们进一步检查了褪黑素与雷帕霉素在Cal-27异种移植小鼠中的潜在协同作用。抑制mTOR途径之间的关系，活性氧（ROS），细胞凋亡和线粒体吞噬据说增加了雷帕霉素在HNSCC中的细胞毒性作用。我们的结果表明，雷帕霉素和褪黑激素的联合治疗可阻断从mTOR激活S6K1的特定下游效应子到Akt信号传导的负反馈回路，从而降低细胞活力，增殖和克隆形成能力。有趣的是，雷帕霉素和褪黑素联合治疗可引起线粒体功能改变，这与ROS产生增加，细胞凋亡和线粒体增多有关。这导致细胞死亡和细胞分化增加。我们的数据进一步表明，褪黑激素给药可降低雷帕霉素对健康细胞的毒性。总体而言，我们的发现表明褪黑激素可以与雷帕霉素一起用作佐剂，