Roles of VEGF-Flt-1 signaling in malignant behaviors of oral squamous cell carcinoma
Nguyen, Phuong Thao
Ayuningtyas, Nurina Febriyanti
Fujita, Minoru 大学院医歯薬保健学研究科（歯）
Background: Vascular endothelial growth factor (VEGF) is a highly specific signaling protein for vascular endothelial cells that plays a critical role in tumor growth and invasion through angiogenesis, and may contribute to cell migration and activation of pre-osteoclasts, osteoclasts and some tumor cells.
Objectives: We aimed to clarify the detailed roles of VEGF-Flt-1 signaling in bone invasion of oral squamous cell carcinoma (OSCC) cells.
Results: Forty-two (42) of 54 cases with gingival SCC (77.8%) strongly expressed VEGF, and had a significantly increased number of Flt-1+ osteoclasts (p<0.01) and more aggressive bone invasion (p<0.05). PlGF, a ligand of Flt-1, induced osteoclastogenesis in single culture of bone marrow cells (BMCs), and inhibition of Flt-1-signaling by VEGF tyrosine kinase inhibitor and It’s down stream (Akt and ERK1/2) inhibitos reduced osteoclastogenesis in PlGF-stimulated BMCs (p<0.01). In molecular level, PlGF stimulation significantly upregulated RANKL expression in Flt-1-expressing HSC2 cells via phosphorylation of Akt and ERK1/2. In the co-culture of VEGF-producing HSC2 cells and BMCs, number of TRAP-positive osteoclasts markedly increased (p<0.01). The osteoclastogenesis was significantly inhibited by RANKL-neutralizing antibody (p<0.01) as well as by VEGF tyrosine kinase inhibitor (p<0.01) and it’s downstream (Akt and ERK1/2) inhibitors (p<0.01, p<0.05, respectively).
Conclusion: VEGF-Flt-1 signaling induces osteoclastogenesis in OSCC through two possible ways: 1) VEGF produced from OSCC cells can directly stimulate the Flt-1 pathway in preosteoclasts to induce migration to future bone resorbing area and differentiation into osteoclasts, and 2) VEGF-Flt-1 signaling upregulates RANKL expression in OSCC cells, which indirectly leads to osteoclast differentiation. Therefore, blocking of the VEGF-Flt-1 signaling may help inhibit bone invasion of OSCC.
This work was supported by Grants-in-Aid for scientific research (A) from the Ministry of Education, Science and Culture (#21249088 [T.T.]).
Public Library of Science
2017 Subarnbhesaj et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.