TY - JOUR
T1 - RAF1–MEK/ERK pathway-dependent ARL4C expression promotes ameloblastoma cell proliferation and osteoclast formation
AU - Fujii, Shinsuke
AU - Ishibashi, Takuma
AU - Kokura, Megumi
AU - Fujimoto, Tatsufumi
AU - Matsumoto, Shinji
AU - Shidara, Satsuki
AU - Kurppa, Kari J.
AU - Pape, Judith
AU - Caton, Javier
AU - Morgan, Peter R.
AU - Heikinheimo, Kristiina
AU - Kikuchi, Akira
AU - Jimi, Eijiro
AU - Kiyoshima, Tamotsu
N1 - Funding Information:
We thank Drs K Nagata, T Harada, Y Kami, H Hiura, Y Tajiri, K Hasegawa, R Nagano, S Nakamura, Y Mori, and H Wada for valuable technical support in this research. We also thank the Research Support Center, Graduate School of Medical Sciences, Kyushu University. We appreciate the technical assistance from The Joint Use Laboratories, Faculty of Dental Science, Kyushu University. This work was supported by JSPS KAKENHI grants to SF (2020–2022) (20K09906) and TK (2020–2022) (20K10096), Fukuoka Foundation for Sound Health Cancer Research Fund, Takeda Science Foundation, The Shin‐Nihon Foundation of Advanced Medical Research, and SGH Foundation (to SF), and Maritza ja Reino Salonen Foundation (to KH).
Funding Information:
We thank Drs K Nagata, T Harada, Y Kami, H Hiura, Y Tajiri, K Hasegawa, R Nagano, S Nakamura, Y Mori, and H Wada for valuable technical support in this research. We also thank the Research Support Center, Graduate School of Medical Sciences, Kyushu University. We appreciate the technical assistance from The Joint Use Laboratories, Faculty of Dental Science, Kyushu University. This work was supported by JSPS KAKENHI grants to SF (2020?2022) (20K09906) and TK (2020?2022) (20K10096), Fukuoka Foundation for Sound Health Cancer Research Fund, Takeda Science Foundation, The Shin-Nihon Foundation of Advanced Medical Research, and SGH Foundation (to SF), and Maritza ja Reino Salonen Foundation (to KH).
Publisher Copyright:
© 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
PY - 2022/1
Y1 - 2022/1
N2 - Ameloblastoma is an odontogenic neoplasm characterized by slow intraosseous growth with progressive jaw resorption. Recent reports have revealed that ameloblastoma harbours an oncogenic BRAFV600E mutation with mitogen-activated protein kinase (MAPK) pathway activation and described cases of ameloblastoma harbouring a BRAFV600E mutation in which patients were successfully treated with a BRAF inhibitor. Therefore, the MAPK pathway may be involved in the development of ameloblastoma; however, the precise mechanism by which it induces ameloblastoma is unclear. The expression of ADP-ribosylation factor (ARF)-like 4c (ARL4C), induced by a combination of the EGF–MAPK pathway and Wnt/β-catenin signalling, has been shown to induce epithelial morphogenesis. It was also reported that the overexpression of ARL4C, due to alterations in the EGF/RAS–MAPK pathway and Wnt/β-catenin signalling, promotes tumourigenesis. However, the roles of ARL4C in ameloblastoma are unknown. We investigated the involvement of ARL4C in the development of ameloblastoma. In immunohistochemical analyses of tissue specimens obtained from 38 ameloblastoma patients, ARL4C was hardly detected in non-tumour regions but tumours frequently showed strong expression of ARL4C, along with the expression of both BRAFV600E and RAF1 (also known as C-RAF). Loss-of-function experiments using inhibitors or siRNAs revealed that ARL4C elevation depended on the RAF1–MEK/ERK pathway in ameloblastoma cells. It was also shown that the RAF1–ARL4C and BRAFV600E–MEK/ERK pathways promoted cell proliferation independently. ARL4C-depleted tumour cells (generated by knockdown or knockout) exhibited decreased proliferation and migration capabilities. Finally, when ameloblastoma cells were co-cultured with mouse bone marrow cells and primary osteoblasts, ameloblastoma cells induced osteoclast formation. ARL4C elevation in ameloblastoma further promoted its formation capabilities through the increased RANKL expression of mouse bone marrow cells and/or primary osteoblasts. These results suggest that the RAF1–MEK/ERK–ARL4C axis, which may function in cooperation with the BRAFV600E–MEK/ERK pathway, promotes ameloblastoma development.
AB - Ameloblastoma is an odontogenic neoplasm characterized by slow intraosseous growth with progressive jaw resorption. Recent reports have revealed that ameloblastoma harbours an oncogenic BRAFV600E mutation with mitogen-activated protein kinase (MAPK) pathway activation and described cases of ameloblastoma harbouring a BRAFV600E mutation in which patients were successfully treated with a BRAF inhibitor. Therefore, the MAPK pathway may be involved in the development of ameloblastoma; however, the precise mechanism by which it induces ameloblastoma is unclear. The expression of ADP-ribosylation factor (ARF)-like 4c (ARL4C), induced by a combination of the EGF–MAPK pathway and Wnt/β-catenin signalling, has been shown to induce epithelial morphogenesis. It was also reported that the overexpression of ARL4C, due to alterations in the EGF/RAS–MAPK pathway and Wnt/β-catenin signalling, promotes tumourigenesis. However, the roles of ARL4C in ameloblastoma are unknown. We investigated the involvement of ARL4C in the development of ameloblastoma. In immunohistochemical analyses of tissue specimens obtained from 38 ameloblastoma patients, ARL4C was hardly detected in non-tumour regions but tumours frequently showed strong expression of ARL4C, along with the expression of both BRAFV600E and RAF1 (also known as C-RAF). Loss-of-function experiments using inhibitors or siRNAs revealed that ARL4C elevation depended on the RAF1–MEK/ERK pathway in ameloblastoma cells. It was also shown that the RAF1–ARL4C and BRAFV600E–MEK/ERK pathways promoted cell proliferation independently. ARL4C-depleted tumour cells (generated by knockdown or knockout) exhibited decreased proliferation and migration capabilities. Finally, when ameloblastoma cells were co-cultured with mouse bone marrow cells and primary osteoblasts, ameloblastoma cells induced osteoclast formation. ARL4C elevation in ameloblastoma further promoted its formation capabilities through the increased RANKL expression of mouse bone marrow cells and/or primary osteoblasts. These results suggest that the RAF1–MEK/ERK–ARL4C axis, which may function in cooperation with the BRAFV600E–MEK/ERK pathway, promotes ameloblastoma development.
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U2 - 10.1002/path.5814
DO - 10.1002/path.5814
M3 - Article
C2 - 34622442
AN - SCOPUS:85119065878
VL - 256
SP - 119
EP - 133
JO - Investigative and Cell Pathology
JF - Investigative and Cell Pathology
SN - 0022-3417
IS - 1
ER -