Parenchyma-stromal interactions induce fibrosis by secreting CCN2 and promote osteoclastogenesis by stimulating RANKL and CD68 through activated TGF-[beta]/BMP4 in ameloblastoma

• Published in: Journal of oral pathology & medicine Vol. 46; no. 1; pp. 67 - 75
• Main Authors: Takebe, Yuichiro, Tsujigiwa, Hidetsugu, Katase, Naoki, Siar, Chong Huat, Takabatake, Kiyofumi, Fujii, Masae, Tamamura, Ryo, Nakano, Keisuke, Nagatsuka, Hitoshi
• Format: Journal Article
• Language: English
• Published: Copenhagen Wiley Subscription Services, Inc 01.01.2017
• Subjects: Ameloblastoma; Bone growth; Bone morphogenetic protein 4; Bone resorption; Connective tissue growth factor; Fibroblasts; Fibrosis; Frizzled protein; Growth factors; Growth rate; Immunohistochemistry; Osteoclastogenesis; Osteogenesis; Paraffin; Parenchyma; Polymerase chain reaction; TRANCE protein; Tumors; Western blotting
• ISSN: 0904-2512; 1600-0714
• DOI: 10.1111/jop.12467

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-[beta], and BMP4 on stromal tissues in ameloblastoma remain unclear. Materials and 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-[beta] 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-[beta] signaling. Absence of CCN2 expression is associated with a phenotypic switch to a myxoid-type microenvironment that is conducive for TGF-[beta]/BMP4 signaling to promote osteoclastogenesis.