Preclinical study

Breast Cancer Research and Treatment

, Volume 122, Issue 1, pp 87-94

First online:

A dose- and time-controllable syngeneic animal model of breast cancer microcalcification

  • Fangbing LiuAffiliated withDivision of Hematology/Oncology, Department of Medicine, Beth Israel Deaconess Medical Center
  • , Preeti MisraAffiliated withDivision of Hematology/Oncology, Department of Medicine, Beth Israel Deaconess Medical Center
  • , Elaine P. LunsfordAffiliated withLongwood Small Animal Imaging Facility, Beth Israel Deaconess Medical Center
  • , Joanne T. VannahAffiliated withLongwood Small Animal Imaging Facility, Beth Israel Deaconess Medical Center
  • , Yuxia LiuAffiliated withLongwood Small Animal Imaging Facility, Beth Israel Deaconess Medical Center
  • , Robert E. LenkinskiAffiliated withDepartment of Radiology, Beth Israel Deaconess Medical Center (BIDMC)
  • , John V. FrangioniAffiliated withDivision of Hematology/Oncology, Department of Medicine, Beth Israel Deaconess Medical CenterDepartment of Radiology, Beth Israel Deaconess Medical Center (BIDMC) Email author 

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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 99mTc, 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 ≥50 μg 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.

Keywords

Breast cancer Microcalcifications BMP-2 Animal models Micro-SPECT/CT Micro-CT