Parenchyma-stromal interactions induce fibrosis by secreting CCN2 and promote osteoclastogenesis by stimulating RANKL and CD68 through activated TGF-β/BMP4 in ameloblastoma.
BACKGROUND
Tumor parenchyma-stromal interactions affect the properties of tumors and their dynamics. Our group previously showed that secreted frizzled related protein (sFRP)-2 impairs bone formation and promotes bone invasion in ameloblastoma. However, the effects of the secreted growth factors CCN2, TGF-β, and BMP4 on stromal tissues in ameloblastoma remain unclear.


RESULTS
Thirty-five paraffin-embedded ameloblastoma cases, ameloblastoma-derived cell lines (AM-1), and primary cultures of ameloblastoma stromal fibroblasts (ASF) were used. Immunohistochemistry, MTT assay, Western blotting, and RT-PCR were performed on these samples. Parenchyma-stromal CCN2 overexpression correlated significantly with fibrous-type stroma, but not with myxoid-type stroma, suggesting a role of CCN2 in fibrosis (P < 0.05). Recombinant CCN2 induction of enhanced ASF proliferation in AM-1 medium supports this view. Conversely, BMP4 and TGF-β were expressed in myxoid-type fibroblasts, but little expression was found in parenchyma. RANKL-positive and CD68-positive stromal cell populations were significantly greater in myxoid-type tumor areas than in fibrous-type tumor areas, while a higher Ki-67 labeling index was recorded in ameloblastoma with fibrous-type stroma. These data suggest that stromal properties influence bone resorption-related activities and growth rates, respectively.


CONCLUSIONS
These results suggest that the effects of secreted growth factors are governed by ameloblastoma parenchyma-stromal interactions. CCN2 promotes fibrogenesis independent of TGF-β signaling. Absence of CCN2 expression is associated with a phenotypic switch to a myxoid-type microenvironment that is conducive for TGF-β/BMP4 signaling to promote osteoclastogenesis.
Department of Oral Pathology and Medicine, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Yuichiro
Y
Takebe
Department of Life Science, Faculty of Science, Okayama University of Science, Okayama, Japan.
Hidetsugu
H
Tsujigiwa
Department of Molecular and Developmental Biology, Kawasaki Medical School, Okayama, Japan.
Naoki
N
Katase
Department of Oral and Maxillofacial Clinical Sciences, Faculty of Dentistry, University of Malaya, Kuala Lumpur, Malaysia.
Chong Huat
CH
Siar
Department of Oral Pathology and Medicine, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Kiyofumi
K
Takabatake
Department of Oral Pathology and Medicine, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Masae
M
Fujii
Department of Histology, Nihon University School of Dentistry, Matsudo, Japan.
Ryo
R
Tamamura
Department of Oral Pathology and Medicine, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Keisuke
K
Nakano
Department of Oral Pathology and Medicine, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Hitoshi
H
Nagatsuka
D000293:Adolescent; D000328:Adult; D000368:Aged; D000564:Ameloblastoma / Q000378:metabolism* / Q000473:pathology; D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D055415:Bone Morphogenetic Protein 4 / Q000378:metabolism; D001862:Bone Resorption / Q000378:metabolism; D049109:Cell Proliferation; D055513:Connective Tissue Growth Factor / Q000378:metabolism*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005355:Fibrosis; D006801:Humans; D007150:Immunohistochemistry; D007573:Jaw Neoplasms / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010012:Osteogenesis / Q000502:physiology*; D053245:RANK Ligand / Q000378:metabolism; D017154:Stromal Cells / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014407:Tumor Cells, Cultured; D055815:Young Adult; D000097382:CD68 Molecule
D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D055415:Bone Morphogenetic Protein 4; D055513:Connective Tissue Growth Factor; D053245:RANK Ligand; D016212:Transforming Growth Factor beta; C525809:BMP4 protein, human; C526317:CCN2 protein, human; C067980:CD68 antigen, human; D000097382:CD68 Molecule
ameloblastoma; ameloblastoma-derived cell lines cells; bone morphogenetic protein-4; connective tissue growth factor; transforming growth factor-beta