title: A dose- and time-controllable syngeneic animal model of breast cancer microcalcification.
abstract: The development of novel diagnostic agents for the detection of breast cancer microcalcifications requires a reliable animal model. Based on previous work from our group, we hypothesized that a single systemic injection of recombinant bone morphogenetic protein-2 (rBMP-2) could be used to create such a model. The cDNA encoding mature human BMP-2 was expressed in BL21(DE3) bacteria, purified to homogeneity, and refolded as a dimer. Bioactivity was confirmed using a C2C12 alkaline phosphatase assay. rBMP-2 was radiolabeled with (99m)Tc, and its biodistribution and clearance were quantified after both intravenous (IV) and intraperitoneal (IP) injection. Fischer 344 rats bearing syngeneic R3230 breast tumors received a single intraperitoneal injection of rBMP-2 at a specified dose. Tumor microcalcification was quantified over time using micro-single photon emission computed tomography (SPECT) and microcomputed tomography (CT). rBMP-2 could be expressed in E. coli at high levels, isolated at >95% purity, and refolded to a bioactive dimer. Beta-phase half-life was 30.5 min after IV administration and 47.6 min after IP administration. Renal excretion was the primary mode of clearance. A single IP injection of >or=50 microg rBMP-2 when tumors were not yet palpable resulted in dose-dependent microcalcification in 8 of 8 R3230 tumors. No calcification was found in control tumors or in normal tissues and organs of animals injected with rBMP-2. Tumor calcification increased progressively between weeks 2 and 4 post-rBMP-2 injection. A single IP injection of rBMP-2 in rats bearing a syngeneic breast cancer will produce dose-dependent and time-dependent microcalcifications. This animal model lays the foundation for the development of novel diagnostic radiotracers for breast cancer.
authors.affiliation: Division of Hematology/Oncology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
authors.forename: Fangbing
authors.initials: F
authors.lastname: Liu
authors.forename: Preeti
authors.initials: P
authors.lastname: Misra
authors.forename: Elaine P
authors.initials: EP
authors.lastname: Lunsford
authors.forename: Joanne T
authors.initials: JT
authors.lastname: Vannah
authors.forename: Yuxia
authors.initials: Y
authors.lastname: Liu
authors.forename: Robert E
authors.initials: RE
authors.lastname: Lenkinski
authors.forename: John V
authors.initials: JV
authors.lastname: Frangioni
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000737:chemistry / Q000235:genetics / Q000493:pharmacokinetics / Q000633:toxicity; D002114:Calcinosis / Q000139:chemically induced / Q000000981:diagnostic imaging*; D018076:DNA, Complementary / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D005260:Female; D006207:Half-Life; D006801:Humans; D007274:Injections, Intraperitoneal; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000000981:diagnostic imaging* / Q000473:pathology; D008657:Metabolic Clearance Rate; D009368:Neoplasm Transplantation; D017510:Protein Folding; D051381:Rats; D011916:Rats, Inbred F344; D011994:Recombinant Proteins / Q000737:chemistry / Q000493:pharmacokinetics / Q000633:toxicity; D013667:Technetium; D013997:Time Factors; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed; D014185:Transplantation, Isogeneic
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D018076:DNA, Complementary; D011994:Recombinant Proteins; D013667:Technetium