Simvastatin Possesses Antitumor and Differentiation-Promoting Properties That Affect Stromal Cells in Giant Cell Tumor of Bone.

Giant cell tumor of bone (GCTB) is a locally aggressive destructive bone lesion. The management of pulmonary metastasis and local recurrence after the surgical treatment of GCTB remains a challenge. Pathologically, stromal cells in GCTB are known as primary neoplastic cells and are recognized as incompletely differentiated preosteoblasts. Therefore, inducing GCTB stromal cells to differentiate into cells with a mature osteoblastic phenotype may stop tumor growth and recurrence. In this study, we aimed to investigate how simvastatin, a clinically approved and commonly used statin that has been known to promote the maturation of cells of the osteogenic lineage, affects GCTB stromal cells. We found that simvastatin effectively inhibited cell viability by suppressing proliferation and by inducing apoptosis in GCTB stromal cells. Moreover, simvastatin treatment upregulated the expression of genes related to osteogenic maturation, such as runt-related transcription factor 2, osteopontin, and osteocalcin, and increased the mineralization of the extracellular matrix in GCTB stromal cells. Ingenuity pathway analysis was used to discover that the vitamin D receptor pathway was involved in the simvastatin-induced osteogenic differentiation of GCTB stromal cells by upregulating the 1,25-dihydroxyvitamin D metabolism. Taken together, this in vitro study demonstrates the antitumor and differentiation-promoting effects of simvastatin on GCTB stromal cells and suggests the possibility of using simvastatin as an adjuvant therapy for GCTB. These findings support further clinical investigation of the efficacy of using simvastatin as an adjuvant therapy for GCTB to reduce recurrence and distant metastasis after surgical treatment. © 2019 Orthopedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:297-310, 2020.

Paclitaxel Induce Apoptosis of Giant Cells Tumor of Bone via TP53INP1 Signaling.

OBJECTIVE: To evaluate the antitumor capability and to investigate the underlying molecular mechanism of paclitaxel. METHODS: First, cck-8 and apoptosis assays were used to determine survival and apoptotic effects of HS 737.T cells under treatment of paclitaxel. Next, RNA-seq and bioinformatics were used to determine the differentially expressed genes and to analyze the pathway involved. Quantitative real-time polymerase chain reaction was used to verify the accuracy of some differentially expressed genes (DEG). ClueGO was used to decode and visualize functionally grouped GO terms of differentially expressed genes, and to map the DEG protein-protein interactions (PPI) network. Western blotting was used to check the expression of target genes, the cleavage of Caspase-3 and PARP1, and the phosphorylation level of p53. Finally, transcriptomics, bioinformatics, and RNAi were used to estimate the antitumor capability and to identify the underlying mechanisms of paclitaxel in GCTB. RESULTS: Our data revealed that paclitaxel had significant time-dependent effects on the viability and induced apoptosis of HS 737.T cells. RNA-seq and bioinformatics analysis showed that apoptosis, death receptor signaling pathway, TNF signaling pathway, and TP53 regulated transcription of cell death genes pathway were closely associated with paclitaxel in the treatment of GCTB. Western bolt results revealed that paclitaxel induced cleavage of Caspase-3 and PARP1, and increased the phosphorylation level of p53 in HS 737.T cells. RNAi results showed that the expression level of TP53INP1 was significantly decreased in HS737.T cells (the decrease was more than 70%). In addition, we found that the inhibitory ratios of paclitaxel on HS737.T cells deficient in TP53INP1 were less than in HS737.T cells with empty vector (19.88 and 40.60%, respectively). Hence, our data revealed that TP53INP1 regulated paclitaxel-driven apoptosis in HS737.T cells. CONCLUSION: Paclitaxel can significantly repress cell proliferation and induce apoptosis of HS 737.T cells through activating Caspase-3, PARP1, p53, and TP53INP1. Paclitaxel may be an effective drug in the management of GCTB.

Stimulation of osteogenic differentiation in stromal cells of giant cell tumour of bone by zoledronic acid.

Therapeutic effects of zoledronic acid (ZOL) on giant cell tumour of bone (GCT) have been proven. Apoptosis induction was considered to be one of the mechanisms of ZOL tumour inhibition. In this study, we presented the possibility of an osteogenic differentiation stimulation mechanism of ZOL and further investigated dosage and time effects. We treated stromal cells of GCT (GCTSC) with ZOL for 48 hours at different concentrations (0 µM, 0.01 µM, 0.1 µM, 1 µM, 5 µM, 30 µM) and assessed apoptotic and osteogenic differentiation markers with immunohistochemical techniques and real-time quantitative RT-PCR. Our results suggested that ZOL enhanced mRNA expression of Cbfa-1, osterix and osteocalcin genes with a maximum effect at 1 µM in GCTSC. Time course experiments indicated a time dependent osteogenic differentiation effect. In conclusion, ZOL may be considered as an adjuvant in the treatment of GCT not only by inducing apoptosis but also by stimulating osteogenic differentiation of remaining tumor stromal cells after surgery.

The efficacy of chemical adjuvants on giant-cell tumour of bone. An in vitro study.

Various chemicals are commonly used as adjuvant treatment to surgery for giant-cell tumour (GCT) of bone. The comparative effect of these solutions on the cells of GCT is not known. In this study we evaluated the cytotoxic effect of sterile water, 95% ethanol, 5% phenol, 3% hydrogen peroxide (H(2)O(2)) and 50% zinc chloride (ZnCI(2)) on GCT monolayer tumour cultures which were established from six patients. The DNA content, the metabolic activity and the viability of the cultured samples of tumour cells were assessed at various times up to 120 hours after their exposure to these solutions. Equal cytotoxicity to the GCT monolayer culture was observed for 95% ethanol, 5% phenol, 3% H(2)O(2) and 50% ZnCI(2). The treated samples showed significant reductions in DNA content and metabolic activity 24 hours after treatment and this was sustained for up to 120 hours. The samples treated with sterile water showed an initial decline in DNA content and viability 24 hours after treatment, but the surviving cells were viable and had proliferated. No multinucleated cell formation was seen in these cultures. These results suggest that the use of chemical adjuvants other than water could help improve local control in the treatment of GCT of bone.

Cytokine synthesis by chondroblastoma: relation to local inflammation.

PURPOSE: To investigate cytokine production by chondroblastoma in inducing local inflammation and adjacent-joint arthritis. METHODS: Immunohistochemical analyses of curetted tissues using anti-human interleukin (IL)-1 beta, IL- 6, IL-8, and tumour necrosis factor (TNF)-alpha were performed for 6 patients with chondroblastoma and 3 patients with giant cell tumour (GCT) of bone. In addition, prostaglandin E2, IL-1 beta, IL-2, IL-4, IL-5, IL-6, IL-8, and TNF-alpha in the cyst fluid of one of the patients with chondroblastoma and 2 with GCT of bone were measured using immunoassay kits. RESULTS: More positive staining for IL-1 beta, IL-8, IL- 6, and TNF-alpha was shown in chondroblastoma than GCT of bone samples. Osteoclast-like giant cells in chondroblastomas showed positive staining for IL- 6 only. In addition, concentrations of IL-4, IL-6, and IL-8 in the cyst fluid were higher in the one patient with chondroblastoma than the 2 patients with GCT of bone. CONCLUSION: Cytokines such as IL-1 beta, IL-8, TNF-alpha, and particularly IL-6 play an important role in local inflammation in patients with chondroblastoma.

Bisphosphonates may reduce recurrence in giant cell tumor by inducing apoptosis.

Giant cell tumor of bone is an aggressive tumor characterized by extensive bone destruction and high recurrence rates. This tumor consists of stromal cells and hematopoietic cells that interact in an autocrine manner to produce tumoral osteoclastogenesis and bone resorption. This autocrine regulation may be disrupted by novel therapeutic agents. Nonspecific local adjuvant therapies such as phenol or liquid nitrogen have been used in the treatment of giant cell tumor, but specific adjuvant therapies have not been described. The bisphosphonates pamidronate and Zoledronate can induce apoptosis in giant cell tumor culture in a dose-dependent manner. We established giant cell tumor cultures from patients with extensive destruction of bone. One of the four cultures formed osteoclastlike giant cells in vitro after more than six passages without exogenous receptor activator of NF-kappaB ligand or macrophage colony stimulating factor. Annexin V staining, presence of active cleaved form of caspase-3, and disappearance of poly (ADP-ribose) polymerase on Western blotting indicated activation of apoptosis by bisphosphonates in giant cell tumor. These results indicate that topical or systemic use of pamidronate or zoledronate can be a novel adjuvant therapy for giant cell tumor by targeting osteoclastlike giant cells, mononuclear giant cell precursor cells, and the autocrine loop of tumor osteoclastogenesis.

P2Y2 receptors are expressed by human osteoclasts of giant cell tumor but do not mediate ATP-induced bone resorption.

Extracellular nucleotides acting through P2 receptors elicit a range of responses in many cell types. Previously, we have cloned the G-protein coupled P2Y2 receptor from a human osteoclastoma complementary deoxyribonucleic acid (cDNA) library and demonstrated its expression by reverse transcription linked (RT)-PCR and Southern analysis in a number of skeletal tissues, including a purified population of giant cells. In this study we have localized the expression of P2Y2 receptor transcripts to osteoclasts of giant cell tumor of bone by in situ hybridization. In osteoblasts and other cell types, the P2Y2 receptor is coupled to Ins(1,4,5)P3-mediated Ca2+ release from intracellular stores. In this study, the P2Y2 receptor agonists adenosine triphosphate (ATP) and uridine triphosphate (UTP) did not increase cytosolic free calcium concentration ([Ca2+]i) in giant cells isolated from osteoclastoma, while the G-protein coupled calcium sensing receptor agonist, Ni2+, elevated [Ca2+]i in the same cells. These data indicate that P2Y2 receptor transcripts expressed by giant cells are not presented at the surface of cells as functional receptors, or alternatively, functional receptors are coupled to an effector other than [Ca2+]i. ATPgammaS (10 micromol/L), but not UTP (10 micromol/L), significantly stimulated resorption by an enriched giant cell population. These results indicate that ATP-induced effects on resorption, following direct osteoclastic activation, are mediated by a P2 receptor other than the P2Y2 subtype. Nucleotides, released locally in the bone microenvironment in response to acute trauma or transient physical stress, will interact with a complement of P2 receptors expressed by both osteoclasts and osteoblasts to influence the remodeling process.