FGF19/FGFR4 signaling axis confines and switches the role of melatonin in head and neck cancer metastasis.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

[Identification of two small molecule inhibitors of hypoxia-inducible factor 1 with different cell-based screening model].

OBJECTIVE: To investigate the inhibitory activity of HIF-1 by triptolide and manasaantin A, two cell-based models with luciferase report gene assay were established. METHOD: Two cell-based models of HIF-1 were used to evaluate HIF-1 inhibition activity of triptolide and manasaantin A. Secreted VEGF expression induced by hypoxia was detected by ELISA with two compounds. The growth inhibition of different solid tumor cell lines was measured by the MTT assay. RESULT: The expression of firefly luciferase was induced by hypoxia in U251-HRE and T47D-HRE cells. U251-HRE model was suitable for the detection of HIF-1 inhibition activity of triptolide. The IC50 of triptolide on HIF-1 activity was (3.4 +/- 0.5) x 10(-8) mol x L(-1). The report gene assay using T47D cells co-transfected with pGL2-TK-HRE and pRL-CMV showed more sensitive inhibition activity of HIF-1 on manassantin A than that of detected by U251-HRE model. The IC50 of manassantin A on HIF-1 activity was (2.4 +/- 0.6) x 10(-8) mol x L(-1). HIF-1 target gene VEGF was also inhibited by test compounds on protein level in T47D cells. Manasaantin A showed selective inhibition on the growth of human solid cancer cell lines, especially on breast cancer and pancreatic cancer cells. Meanwhile, triplotide showed strong proliferation inhibition activity on all tested cell lines. CONCLUSION: It is very important to select a suitable cell-based report gene assay of HIF-1 for screening of different kinds of inhibitor.