title: Cabozantinib targets bone microenvironment modulating human osteoclast and osteoblast functions.
abstract: Cabozantinib, a c-MET and vascular endothelial growth factor receptor 2 inhibitor, demonstrated to prolong progression free survival and improve skeletal disease-related endpoints in castration-resistant prostate cancer and in metastatic renal carcinoma. Our purpose is to investigate the direct effect of cabozantinib on bone microenvironment using a total human model of primary osteoclasts and osteoblasts.Osteoclasts were differentiated from monocytes isolated from healthy donors; osteoblasts were derived from human mesenchymal stem cells obtained from bone fragments of orthopedic surgery patients. Osteoclast activity was evaluated by tartrate resistant acid phosphatase (TRAP) staining and bone resorption assays and osteoblast differentiation was detected by alkaline phosphatase and alizarin red staining.Our results show that non-cytotoxic doses of cabozantinib significantly inhibit osteoclast differentiation (p=0.0145) and bone resorption activity (p=0.0252). Moreover, cabozantinib down-modulates the expression of osteoclast marker genes, TRAP (p=0.006), CATHEPSIN K (p=0.004) and Receptor Activator of Nuclear Factor k B (RANK) (p=0.001). Cabozantinib treatment has no effect on osteoblast viability or differentiation, but increases osteoprotegerin mRNA (p=0.015) and protein levels (p=0.004) and down-modulates Receptor Activator of Nuclear Factor k B Ligand (RANKL) at both mRNA (p<0.001) and protein levels (p=0.043). Direct cell-to-cell contact between cabozantinib pre-treated osteoblasts and untreated osteoclasts confirmed the indirect anti-resorptive effect of cabozantinib.We demonstrate that cabozantinib inhibits osteoclast functions "directly" and "indirectly" reducing the RANKL/osteoprotegerin ratio in osteoblasts.
authors.affiliation: Department of Medical Oncology, Campus Bio-Medico University of Rome, Rome, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Fioramonti
authors.affiliation: Department of Medical Oncology, Campus Bio-Medico University of Rome, Rome, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Santini
authors.affiliation: Department of Medical Oncology, Campus Bio-Medico University of Rome, Rome, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Iuliani
authors.affiliation: Department of Medical Oncology, Campus Bio-Medico University of Rome, Rome, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Ribelli
authors.affiliation: Department of Medical Oncology, Campus Bio-Medico University of Rome, Rome, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Manca
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Campus Bio-Medico of Rome, Rome, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Papapietro
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Campus Bio-Medico of Rome, Rome, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Spiezia
authors.affiliation: Department of Medical Oncology, Campus Bio-Medico University of Rome, Rome, Italy.
authors.forename: Bruno
authors.initials: B
authors.lastname: Vincenzi
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Campus Bio-Medico of Rome, Rome, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Denaro
authors.affiliation: Department of Surgical, Oncological and Oral Sciences, Section of Medical Oncology, University of Palermo, Palermo, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Russo
authors.affiliation: Department of Medical Oncology, Campus Bio-Medico University of Rome, Rome, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Tonini
authors.affiliation: Department of Medical Oncology, Campus Bio-Medico University of Rome, Rome, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Pantano
mesh_terms: D000813:Anilides / Q000494:pharmacology*; D017209:Apoptosis; D015153:Blotting, Western; D001862:Bone Resorption / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects*; D049109:Cell Proliferation; D002478:Cells, Cultured; D006801:Humans; D007124:Immunoenzyme Techniques; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010012:Osteogenesis / Q000187:drug effects / Q000502:physiology*; D053244:Osteoprotegerin / Q000235:genetics / Q000378:metabolism; D019859:Proto-Oncogene Proteins c-met / Q000235:genetics / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology*; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000813:Anilides; D053244:Osteoprotegerin; D011725:Pyridines; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human; C558660:cabozantinib; D019859:Proto-Oncogene Proteins c-met
keywords: bone microenvironment; cabozantinib; human primary cells; osteoprotegerin (OPG); receptor activator of nuclear factor-kb ligand (RANKL)