Department of Oral Biology and Diagnostic Sciences, Dental College of Georgia, Augusta University, 1120 15th Street, Augusta, GA, 30912, USA.
Present address: Department of Otolaryngology Head and Neck Surgery, First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China.
J Exp Clin Cancer Res. 2021 Mar 10;40(1):93. doi: 10.1186/s13046-021-01888-9.
There is no consensus about the effective dosages of melatonin in cancer management, thus, it is imperative to fully understand the dose-dependent responsiveness of cancer cells to melatonin and the underlying mechanisms.
Head and neck squamous cell carcinoma (HNSCC) cells with or without melatonin treatment were used as a research platform. Gene depletion was achieved by short hairpin RNA, small interfering RNA, and CRISPR/Cas9. Molecular changes and regulations were assessed by Western blotting, quantitative RT-PCR (qRT-PCR), immunohistochemistry, and chromatin Immunoprecipitation coupled with qPCR (ChIP-qPCR). The therapeutic efficacy of FGF19/FGFR4 inhibition in melatonin-mediated tumor growth and metastasis was evaluated in orthotopic tongue tumor mice.
The effect of melatonin on controlling cell motility and metastasis varies in HNSCC cells, which is dose-dependent. Mechanistically, high-dose melatonin facilitates the upregulation of FGF19 expression through activating endoplasmic stress (ER)-associated protein kinase RNA-like endoplasmic reticulum kinase (PERK)-Eukaryotic initiation factor 2 alpha (eIF2α)-activating transcription factor 4 (ATF4) pathway, which in turn promotes FGFR4-Vimentin invasive signaling and attenuates the role of melatonin in repressing metastasis. Intriguingly, following long-term exposure to high-dose melatonin, epithelial HNSCC cells revert the process towards mesenchymal transition and turn more aggressive, which is enabled by FGF19/FGFR4 upregulation and alleviated by genetic depletion of the FGF19 and FGFR4 genes or the treatment of FGFR4 inhibitor H3B-6527.
Our study gains novel mechanistic insights into melatonin-mediated modulation of FGF19/FGFR4 signaling in HNSCC, demonstrating that activating this molecular node confines the role of melatonin in suppressing metastasis and even triggers the switch of its function from anti-metastasis to metastasis promotion. The blockade of FGF19/FGFR4 signaling would have great potential in improving the efficacy of melatonin supplements in cancer treatment.
目前对于褪黑素在癌症管理中的有效剂量尚无共识，因此，充分了解癌细胞对褪黑素的剂量依赖性反应及其潜在机制至关重要。
使用有或无褪黑素处理的头颈部鳞状细胞癌（HNSCC）细胞作为研究平台。通过短发夹 RNA、小干扰 RNA 和 CRISPR/Cas9 实现基因耗竭。通过 Western blot、定量 RT-PCR（qRT-PCR）、免疫组织化学和染色质免疫沉淀结合 qPCR（ChIP-qPCR）评估分子变化和调控。在原位舌肿瘤小鼠中评估 FGF19/FGFR4 抑制在褪黑素介导的肿瘤生长和转移中的治疗效果。
褪黑素对控制 HNSCC 细胞运动和转移的作用因剂量而异，呈剂量依赖性。从机制上讲，高剂量褪黑素通过激活内质网应激（ER）相关蛋白激酶 RNA 样内质网激酶（PERK）-真核起始因子 2α（eIF2α）-激活转录因子 4（ATF4）通路促进 FGF19 表达上调，从而促进 FGFR4-波形蛋白侵袭信号，并削弱褪黑素抑制转移的作用。有趣的是，经过长期暴露于高剂量褪黑素后，上皮性 HNSCC 细胞向间充质转化的过程逆转，并变得更具侵袭性，这是由 FGF19/FGFR4 上调所驱动的，而通过基因敲除 FGF19 和 FGFR4 基因或使用 FGFR4 抑制剂 H3B-6527 可以减轻这种作用。
本研究深入了解了褪黑素介导的 HNSCC 中 FGF19/FGFR4 信号的调节机制，表明激活该分子节点限制了褪黑素抑制转移的作用，甚至引发其功能从抗转移到促进转移的转变。阻断 FGF19/FGFR4 信号可能会极大地提高褪黑素补充剂在癌症治疗中的疗效。
