leptin and Osteosarcoma

Cancer and the use of a comprehensive anti-cancer treatment are unfavorable factors, which have a significant impact on bone mass accumulation, bone mineralization and consequently the occurrence of osteoporosis. Bone turnover is regulated by complex mechanisms, among which an important role play OPG/RANK/RANKL signaling pathway, adipokines, and fetuin-A. The aim of the study was to evaluate bone mineral density and concentrations of leptin and fetuin-A in patients with osteosarcoma after anti-cancer treatment.. The study included 50 children and adolescents aged 10-21 years. The study group consisted of 25 patients with osteosarcoma and 25 healthy counterparts as a control group. The examination was conducted 2 months after the last course of postoperative chemotherapy and included densitometric measurements: bone mineral content (BMC), bone mineral density (BMD), fat mass, lean mass and biochemical measurements: serum concentrations of calcium, magnesium, phosphate, 25-hydroksyvitamin D, alkaline phosphatase, leptin and fetuin-A. Concentrations of leptin and fetuin-A were determined by immunoenzymatic methods.. In patients with osteosarcoma after anti-cancer treatment, we observed significantly reduced bone mineral content, bone mineral density and lean body mass compared with the healthy children (p < 0.05, p < 0.01, p < 0.05, respectively). Mean values of z-score of the whole body BMD and z-score of the lumbar BMD L1-L4 were significantly lower in patients than in the controls (p < 0.001). The serum concentrations of phosphate, magnesium, and alkaline phosphatase in both studied groups were similar, while calcium was significantly lower (p < 0.05) in patients than in the healthy children. The concentration of 25-hydroxyvitamin D was about two-fold lower, while leptin approximately 2.5-fold higher in patients than in the controls. The mean value of fetuin-A was similar in both studied groups. Statistically significant positive correlations between body composition parameters and the values of BMD, as well as between anthropometric parameters and leptin and fetuin-A were observed.. The deficit in bone mass observed in patients with malignant bone tumors after anti-cancer treatment might be the result of decreased serum calcium and vitamin D concentrations. The observed correlation between anthropometric and biochemical parameters may indicate the link between bone and adipose tissue metabolism.

Topics: Adipose Tissue; Adolescent; Adult; Alkaline Phosphatase; alpha-2-HS-Glycoprotein; Anthropometry; Bone and Bones; Bone Density; Bone Neoplasms; Calcium; Child; Female; Humans; Leptin; Magnesium; Male; Osteosarcoma; Vitamin D; Young Adult

Leptin signaling influences osteoblastogenesis and modulates the fate of mesenchymal stem cells (MSCs) during bone and cartilage regeneration. Although MSCs abound in the osteosarcoma (OS) microenvironment, and leptin exhibits pro-tumorigenic properties, leptin's influence on OS progression and chemoresistant signaling in MSCs remains unclear. Using cell viability and apoptosis assays, we showed that medium conditioned by leptin-treated human MSCs promotes cisplatin resistance in cultured human OS cells. Moreover, GFP-LC3 expression and chloroquine treatment experiments showed that this effect is mediated by stimulation of autophagy in OS cells. TGF-β expression in MSCs was upregulated by leptin and suppressed by leptin receptor knockdown. Silencing TGF-β in MSCs also abolished OS cell chemoresistance induced by leptin-conditioned medium. Cisplatin resistance was also induced when leptin-conditioned MSCs were co-injected with MG-63 OS cells to generate subcutaneous xenografts in nude mice. Finally, we observed a significant correlation between autophagy-associated gene expression in OS clinical samples and patient prognosis. We conclude that leptin upregulates TGF-β in MSCs, which promotes autophagy-mediated chemoresistance in OS cells.

Topics: Animals; Antineoplastic Agents; Apoptosis; Bone Neoplasms; Carcinogenesis; Chloroquine; Cisplatin; Drug Resistance, Neoplasm; Leptin; Mesenchymal Stem Cells; Mice; Osteosarcoma; Transforming Growth Factor beta; Tumor Microenvironment; Up-Regulation; Xenograft Model Antitumor Assays

Sirtuin-1 (SIRT1) is a downstream target of Leptin, and its inhibition promotes p53-mediated apoptosis. This study aimed to evaluate the expression and prognostic significance of Leptin and SIRT1 in osteosarcoma. Leptin and SIRT1 levels in osteosarcoma samples from 89 patients were evaluated by immunohistochemical staining. The correlations between Leptin and SIRT1 expression with clinical parameters were analyzed by Spearman's test and Pearson's chi-squared test. Prognostic factors were identified by Univariate and multivariate Cox regression analysis. We found that Leptin and SIRT1 expression was low in 23.6% and 20.2%; moderate in 25.8% and 24.7%; and high in 50.5% and 55.1% of patients with osteosarcoma, respectively. Both Leptin and SIRT1 expression were significantly associated with the Enneking stage, distant metastasis and neo-adjuvant chemotherapy. Leptin expression and SIRT1 expression were significantly correlated and they were significantly associated with shorter overall survival. Among osteosarcoma patients who received neo-adjuvant chemotherapy, both Leptin and SIRT1 expression were significantly associated with overall survival of osteosarcoma patients in univariate analysis, but only SIRT1 expression was significantly associated with overall survival of osteosarcoma patients in multivariate analysis. In conclusion, Leptin and SIRT1 expressions are significantly associated with shorter overall survival of osteosarcoma patients, and SIRT1 expression is a significant independent prognostic indicator in patients with osteosarcoma.

Topics: Adolescent; Adult; Biomarkers, Tumor; Bone Neoplasms; Child; Disease-Free Survival; Female; Humans; Immunohistochemistry; Kaplan-Meier Estimate; Leptin; Male; Osteosarcoma; Prognosis; Proportional Hazards Models; Sirtuin 1; Tissue Array Analysis; Young Adult

Fibroblast growth factor-23 (FGF23) is a circulating hormone that acts to correct hyperphosphatemic states by inhibiting renal phosphate reabsorption and to prevent hypervitaminosis D by feedback repressing 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) biosynthesis. FGF23 gene expression in the osteoblast/osteocyte is induced by the nuclear vitamin D receptor (VDR) bound to 1,25(OH)2D3, but cycloheximide sensitivity of this induction suggests that it may occur largely via secondary mechanisms requiring cooperating transcription factors. We therefore sought to identify 1,25(OH)2D3-regulated transcription factors that might impact FGF23 expression. Although neither leptin nor interleukin-6 (IL-6) alone affects FGF23 expression, leptin treatment was found to potentiate 1,25(OH)2D3 upregulation of FGF23 in UMR-106 cells, whereas IL-6 treatment blunted this upregulation. Genomic analyses revealed conserved binding sites for STATs (signal transduction mediators of leptin and IL-6 action) along with transcription factor ETS1 in human and other mammalian FGF23 genes. Further, STAT3, STAT1, ETS1, and VDR mRNAs were induced in a dose-dependent manner by 1,25(OH)2D3 in UMR-106 cells. Bioinformatic analysis identified nine potential VDREs in a genomic interval containing human FGF23. Six of the putative VDREs were capable of mediating direct transcriptional activation of a heterologous reporter gene when bound by a 1,25(OH)2D3-liganded VDR complex. A model is proposed wherein 1,25(OH)2D3 upregulates FGF23 production directly via multiple VDREs and indirectly via induction of STAT3, ETS1, and VDR transcription factors that are then activated via cell surface and intracellular signaling to cooperate in the induction of FGF23 through DNA looping and generation of euchromatin architecture.

Topics: Animals; Bone and Bones; Bone Neoplasms; Calcitriol; Cell Line; Cell Line, Tumor; Chlorocebus aethiops; COS Cells; Fibroblast Growth Factor-23; Fibroblast Growth Factors; Gene Expression Regulation; HEK293 Cells; Humans; Interleukin-6; Leptin; Models, Animal; Osteosarcoma; Rats; Receptors, Calcitriol; Signal Transduction; STAT Transcription Factors

Serum leptin levels are strongly and directly related to fat body mass (FBM). Bone mineral density (BMD) increases with FBM, and obesity has a protective effect against osteoporosis. We have previously demonstrated that leptin therapy has a significant effect in preventing ovariectomy-induced bone loss in rats and leptin also exerts direct osteogenic effects in vitro. To obtain a better understanding of the physiology and pharmacology of leptin in bone metabolism, we evaluated the leptin-induced signal transduction pathways and proliferative response in the human osteosarcoma cell line Saos-2.. Saos-2 cell lines were used. Leptin receptor common form (OB-Ra) and long form (OB-Rb) were detected by RT-PCR and immunocytochemistry. PI(3)-K activity was immunoprecipitated using antibodies directed against tyrosine-phosphorylated proteins and IRS-1. The activated form of p42/p44 MAPK was investigated in cytosolic extracts of confluent Saos-2 in response to leptin.. In this study, we tested the hypothesis that leptin might be a mediator linking obesity and bone cell proliferation. We found that Saos-2 cells expressed OB-Ra and OB-Rb. Leptin (10 nmol/L - 2 umol/L) caused a significant increase in the activation of PI (3)-K that was accompanied by an increase in cell proliferation dose dependently based on the [3H]-thymidine incorporation. The specific PI (3)-K inhibitors LY294002 and wortmannin blocked leptin-induced cell proliferation. Interestingly, leptin activated MAPK and the specific MAPK-inhibitor PD98059 blocked DNA synthesis induced by leptin.. Our data support the hypothesis that leptin may increase bone mass by stimulating osteoblast proliferation through activation of the P1 (3)-K and MAPK signaling pathways.

Topics: Bone and Bones; Cell Line, Tumor; Cell Proliferation; Enzyme Activation; Enzyme Inhibitors; Humans; Insulin Receptor Substrate Proteins; Leptin; MAP Kinase Signaling System; Osteosarcoma; Phosphatidylinositol 3-Kinases; Phosphoproteins; Phosphorylation; Signal Transduction; Tyrosine

Serum contents of leptin and soluble Fas antigen were measured in 28 patients with osteosarcoma, 7 with neuroectodermal bone tumors, and 17 healthy subjects. The incidence and levels of soluble Fas antigen in patients with osteosarcoma and neuroectodermal bone tumors were higher than in healthy subjects and did not depend on sex and age in both healthy subjects and patients. Serum concentration of leptin in women was higher than in men (both in healthy controls and patients) and was lower in healthy subjects compared to patients with osteosarcoma and neuroectodermal bone tumors. A trend to a negative correlation between the concentrations of leptin and soluble Fas antigen in female patients with osteosarcoma and male patients with neuroectodermal bone tumors was revealed. The role of leptin and soluble Fas antigen in the pathogenesis of primary bone tumors is discussed.

Topics: Adolescent; Adult; Apoptosis; Bone Neoplasms; fas Receptor; Female; Humans; Leptin; Male; Neuroectodermal Tumors; Osteosarcoma; Receptors, Leptin