title: Surface vacuolar ATPase in ameloblastoma contributes to tumor invasion of the jaw bone.
abstract: Ameloblastoma is the most common benign odontogenic tumor in Japan. It is believed that it expands in the jaw bone through peritumoral activation of osteoclasts by receptor activator of nuclear factor kappa-B ligand (RANKL) released from the ameloblastoma, as in bone metastases of cancer cells. However, the clinical features of ameloblastoma, including its growth rate and patterns of invasion, are quite different from those of bone metastasis of cancer cells, suggesting that different underlying mechanisms are involved. Therefore, in the present study, we examined the possible mechanisms underlying the invasive expansion of ameloblastoma in the jaw bone. Expression levels of RANKL assessed by western blotting were markedly lower in ameloblastoma (AM-1) cells than in highly metastatic oral squamous cell carcinoma (HSC-3) cells. Experiments coculturing mouse macrophages (RAW264.7) with AM-1 demonstrated low osteoclastogenic activity, as assessed by tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cell formation, probably because of low release of RANKL, whereas cocultures of RAW264.7 with HSC-3 cells exhibited very high osteoclastogenic activity. Thus, RANKL release from AM-1 appeared to be too low to generate osteoclasts. However, AM-1 cultured directly on calcium phosphate-coated plates formed resorption pits, and this was inhibited by application of bafilomycin A1. Furthermore, vacuolar-type H+-ATPase (V-ATPase) and H+/Cl- exchange transporter 7 (CLC-7) were detected on the surface of AM-1 cells by plasma membrane biotinylation and immunofluorescence analysis. Immunohistochemical analysis of clinical samples of ameloblastoma also showed plasma membrane-localized V-ATPase and CLC-7 in the epithelium of plexiform, follicular and basal cell types. The demineralization activity of AM-1 was only 1.7% of osteoclasts demineralization activity, and the growth rate was 20% of human normal skin keratinocytes and HSC-3 cells. These results suggest that the slow expansion of several typical types of ameloblastomas in jaw bone is attributable to its slow growth and low demineralization ability.
authors.affiliation: Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812‑8582, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Yoshimoto
authors.affiliation: Department of General Dentistry, Fukuoka Dental College, Fukuoka 814-0193, Japan.
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Morita
authors.affiliation: Section of Oral and Maxillofacial Oncology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Matsubara
authors.affiliation: Section of Oral and Maxillofacial Oncology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Mitsuyasu
authors.affiliation: Special Patient Oral Care Unit, Kyushu University Hospital, Fukuoka 812-8582, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Imai
authors.affiliation: Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Shunichi
authors.initials: S
authors.lastname: Kajioka
authors.affiliation: Department of General Dentistry, Fukuoka Dental College, Fukuoka 814-0193, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yoneda
authors.affiliation: Department of Physiology, School of Medicine, Kurume University, Kurume 830-0011, Japan.
authors.forename: Yushi
authors.initials: Y
authors.lastname: Ito
authors.affiliation: Department of General Dentistry, Fukuoka Dental College, Fukuoka 814-0193, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Hirofuji
authors.affiliation: Section of Oral and Maxillofacial Oncology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Nakamura
authors.affiliation: Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812‑8582, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Hirata
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D000564:Ameloblastoma / Q000201:enzymology* / Q000473:pathology; D000818:Animals; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D007568:Jaw / Q000201:enzymology* / Q000473:pathology; D007573:Jaw Neoplasms / Q000201:enzymology* / Q000473:pathology; D015603:Keratinocytes / Q000166:cytology; D051379:Mice; D009062:Mouth Neoplasms / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D010010:Osteoclasts / Q000378:metabolism; D053245:RANK Ligand / Q000378:metabolism; D000067996:RAW 264.7 Cells; D000071681:Tartrate-Resistant Acid Phosphatase; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism*
chemical_list: D007527:Isoenzymes; D053245:RANK Ligand; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase; D025262:Vacuolar Proton-Translocating ATPases