| Popis: |
BackgroundDenosumab is a game-changing drug for giant cell tumor of bone (GCTB); however, its clinical biomarker in terms of post-administration ossification of the tumors has not been elucidated. The aims of this study were to investigate the relationship between Wnt/β-catenin signaling and the ossification of GCTB and to evaluate whether endogenous nuclear β-catenin expression predicted denosumab-induced bone formation in GCTB. MethodsWe established cultures of patient-derived primary GCTB stromal cells (pGCTB-SCs) and assessed the osteoblastic characteristics of pGCTB-SCs using cytochemical staining, optical density method (405 nm), and immunocytochemistry. Several mRNA expressions of osteoblastic markers (ALP, collagen type Ⅰ alpha 1 (COL1A1), integrin-binding sialoprotein (IBSP), runt-related transcription factor2 (RUNX2), and bone gamma-carboxyglutamate protein (BGLAP) was also investigated using quantitative real-time PCR (qRT-PCR) analysis. The impact on nuclear β-catenin translocation (NBT) by differentiation-induction was evaluated using Western blotting and immunocytochemistry. Wnt signaling inhibitor, GGTI-286, and selective Rac1 inhibitor, NSC23766, were added with OGM to evaluate the essential role of NBT. Furthermore, the distribution of endogenous NBT and the relationship with the tumoral ossification were assessed. Its predictability for the ossification in GCTB was also evaluated using a nuclear β-catenin labeling index (NBLI) of clinical samples (n = 86) and quantitative analyses of CT images.ResultspGCTB-SCs significantly expressed the osteoblastic markers with osteogenic medium (OGM) in a time-dependent manner (P < 0.0001, vs. vehicle). NBT was upregulated within 12 hours after OGM treatment. In addition, decreasing NBT by treatment with 40μM GGTI-286 significantly abolished the osteoblastic differentiation of pGCTB-SCs (P < 0.0001, vs. OGM). The selective Rac1 inhibitor, NSC23766, also suppressed the OGM-induced osteoblastic differentiation and NBT in pGCTB-SCs. Furthermore, in GCTB clinical samples, the NBTs were significantly associated with the tumor ossification following denosumab treatment (P = 0.003 for entire and peripheral tumor, and P = 0.02 for intra-tumor of GCTB) as well as endogenous intra-tumoral ossification. ConclusionsIn summary, our findings suggest a close relationship between the NBT and the osteoblastic differentiation of GCTB. Investigations of NBTs in naïve GCTB samples will provide a promising biomarker for predicting the ossification of GCTB following denosumab treatment. |
