title: Osteoclasts direct bystander killing of bone cancer.
abstract: Primary and metastatic bone cancers are difficult to eradicate and novel approaches are needed to improve treatment and extend life. As bone cancer grows, osteoclasts, the principal bone-resorbing cells of the body, are recruited to and activated at sites of cancer. In this investigation, we determined if osteoclast lineage cells could function as a cell-based gene delivery system to bone cancers. We used the cytosine deaminase (CD) 5-fluorocytosine (5-FC) enzyme/prodrug system and studied bone marrow and bones from transgenic mice expressing a novel CD gene regulated by the osteoclast tartrate-resistant acid phosphatase (TRAP) gene promoter (Tg/NCD). DsRed2-labeled 2472 sarcoma cells were placed in Tg/NCD osteoclastogenic cultures and treated with 5-FC. 5-FC treatment resulted in profound bystander killing (90%; P < 0.05). The effect of 5-FC treatment on osteoclast lineage cells was most dramatic when administered at the beginning of the 7-day cultures, suggesting that mature osteoclasts are less sensitive to 5-FC. Evaluation of osteoclast-directed bystander killing in vivo revealed dramatic killing of bone cancer with only a modest effect on osteoclast number. Specifically, 5-FC treatment of tumor-bearing Tg/NCD mice or Tg/NCD bone marrow transplanted C3H mice (Tg/NCD-C3H) resulted in 92% and 44% reductions in tumor area, respectively (P < 0.05). Eight of ten 5-FC-treated Tg/NCD mice had complete bone tumor killing and five of six 5-FC-treated Tg/NCD-C3H mice had reduced tumor compared with controls. In addition, Tg/NCD osteoclasts were resistant to 5-FC treatment in vivo, a very important feature, as it identifies osteoclasts as an ideal CD gene delivery system.
authors.affiliation: Department of Orthopedic Surgery, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Margaret L
authors.initials: ML
authors.lastname: Ramnaraine
authors.forename: Wendy E
authors.initials: WE
authors.lastname: Mathews
authors.forename: James M
authors.initials: JM
authors.lastname: Donohue
authors.forename: Christine M
authors.initials: CM
authors.lastname: Lynch
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Goblirsch
authors.forename: Denis R
authors.initials: DR
authors.lastname: Clohisy
mesh_terms: D000135:Acid Phosphatase / Q000235:genetics; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000493:pharmacokinetics / Q000494:pharmacology; D001859:Bone Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology* / Q000628:therapy*; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D043525:Cytosine Deaminase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D005437:Flucytosine / Q000493:pharmacokinetics / Q000494:pharmacology*; D015316:Genetic Therapy; D007527:Isoenzymes / Q000235:genetics; D051379:Mice; D008809:Mice, Inbred C3H; D008822:Mice, Transgenic; D010010:Osteoclasts / Q000187:drug effects / Q000201:enzymology / Q000473:pathology* / Q000502:physiology; D011401:Promoter Regions, Genetic; D012509:Sarcoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology* / Q000628:therapy; D000071681:Tartrate-Resistant Acid Phosphatase
chemical_list: D000964:Antimetabolites, Antineoplastic; D007527:Isoenzymes; D005437:Flucytosine; D000135:Acid Phosphatase; C000605511:Acp5 protein, mouse; D000071681:Tartrate-Resistant Acid Phosphatase; D043525:Cytosine Deaminase