title: Pharmacologically Inactive Bisphosphonates as an Alternative Strategy for Targeting Osteoclasts: In Vivo Assessment of 5-Fluorodeoxyuridine-Alendronate in a Preclinical Model of Breast Cancer Bone Metastases.
abstract: Bisphosphonates have effects that are antiresorptive, antitumor, and antiapoptotic to osteoblasts and osteocytes, but an effective means of eliciting these multiple activities in the treatment of bone metastases has not been identified. Antimetabolite-bisphosphonate conjugates have potential for improved performance as a class of bone-specific antineoplastic drugs. The primary objective of the study was to determine whether an antimetabolite-bisphosphonate conjugate will preserve bone formation concomitant with antiresorptive and antitumor activity. 5-FdU-ale, a highly stable conjugate between the antimetabolite 5-fluoro-2'-deoxyuridine and the bisphosphonate alendronate, was tested for its therapeutic efficacy in a mouse model of MDA-MB231 breast cancer bone metastases. In vitro testing revealed osteoclasts to be highly sensitive to 5-FdU-ale. In contrast, osteoblasts had significantly reduced sensitivity. Tumor cells were resistant in vitro but in vivo tumor burden was nevertheless significantly reduced compared with untreated mice. Sensitivity to 5-FdU-ale was not mediated through inhibition of farnesyl diphosphate synthase activity, but cell cycle arrest was observed. Although serum tartrate-resistant acid phosphatase (TRAP) levels were greatly reduced by both drugs, there was no significant decrease in the serum bone formation marker osteocalcin with 5-FdU-ale treatment. In contrast, there was more than a fivefold decrease in serum osteocalcin levels with alendronate treatment (p < 0.001). This finding is supported by time-lapse micro-computed tomography analyses, which revealed bone formation volume to be on average 1.6-fold higher with 5-FdU-ale treatment compared with alendronate (p < 0.001). We conclude that 5-FdU-ale, which is a poor prenylation inhibitor but maintains potent antiresorptive activity, does not reduce bone formation and has cytostatic antitumor efficacy. These results document that conjugation of an antimetabolite with bisphosphonates offers flexibility in creating potent bone-targeting drugs with cytostatic, bone protection properties that show limited nephrotoxicity. This unique class of drugs may offer distinct advantages in the setting of targeted adjuvant therapy and chemoprevention of bone diseases. © 2016 American Society for Bone and Mineral Research.
authors.affiliation: Department of Gynecology, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schem
authors.affiliation: Section of Biomedical Imaging, Department of Radiology and Neuroradiology, MOIN CC, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Tower
authors.affiliation: Department of Gynecology, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Kneissl
authors.affiliation: Department of Gynecology, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
authors.forename: Anna-Christina
authors.initials: AC
authors.lastname: Rambow
authors.affiliation: Section of Biomedical Imaging, Department of Radiology and Neuroradiology, MOIN CC, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.|Institute of Biomechanics, TUHH Hamburg University of Technology, Hamburg, Germany.
authors.forename: Graeme M
authors.initials: GM
authors.lastname: Campbell
authors.affiliation: Section of Biomedical Imaging, Department of Radiology and Neuroradiology, MOIN CC, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Desel
authors.affiliation: Section of Biomedical Imaging, Department of Radiology and Neuroradiology, MOIN CC, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
authors.forename: Timo
authors.initials: T
authors.lastname: Damm
authors.affiliation: Department of Gynecology, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.|Division of Molecular Oncology, Institute for Experimental Cancer Research, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Heilmann
authors.affiliation: Department of Trauma Surgery, Section Experimental Trauma Surgery, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Fuchs
authors.affiliation: Department of Nuclear Medicine, Section Radiopharmaceutical Chemistry, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
authors.forename: Maaz
authors.initials: M
authors.lastname: Zuhayra
authors.affiliation: Division of Molecular Oncology, Institute for Experimental Cancer Research, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Trauzold
authors.affiliation: Section of Biomedical Imaging, Department of Radiology and Neuroradiology, MOIN CC, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
authors.forename: Claus C
authors.initials: CC
authors.lastname: Glüer
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Sarah
authors.initials: S
authors.lastname: Schott
authors.affiliation: Section of Biomedical Imaging, Department of Radiology and Neuroradiology, MOIN CC, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Tiwari
mesh_terms: D019386:Alendronate / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D014408:Biomarkers, Tumor / Q000378:metabolism; D001859:Bone Neoplasms / Q000188:drug therapy / Q000556:secondary*; D001862:Bone Resorption / Q000150:complications / Q000188:drug therapy / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D004164:Diphosphonates / Q000494:pharmacology / Q000627:therapeutic use*; D005260:Female; D005472:Fluorouracil / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D006801:Humans; D015674:Mammary Neoplasms, Animal / Q000150:complications / Q000473:pathology*; D013058:Mass Spectrometry; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000378:metabolism; D010010:Osteoclasts / Q000187:drug effects / Q000378:metabolism*; D010012:Osteogenesis / Q000187:drug effects; D017368:Protein Prenylation / Q000187:drug effects; D000067996:RAW 264.7 Cells; D023041:Xenograft Model Antitumor Assays; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism
chemical_list: C575868:5-FdU-alendronate; D014408:Biomarkers, Tumor; D004164:Diphosphonates; D020169:Caspases; C000620839:Rap1 protein, mouse; D020827:rap1 GTP-Binding Proteins; D005472:Fluorouracil; D019386:Alendronate
keywords: 5-FDU-ALE; ANTIRESORPTIVES; BISPHOSPHONATES; BONE DISEASES