Site‐specific human breast cancer (MDA‐MB‐231) metastases in nude rats: Model characterisation and in vivo effects of ibandronate on tumour growth

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Abstract
Animal models are important tools to study the development of bone metastases and to evaluate strategies for their prevention and treatment. We here describe a new model in which tumour inoculation is achieved by injection of cancer cells into the femoral artery. This approach results in the development of multiple osteolytic lesions in the distal femora and proximal tibiae within 18 days after inoculation, with a success rate of 95–100% and no additional comorbidity. In untreated animals, osteolyses expanded continuously at a growth rate of 4.7–8.2 mm2/4 days, causing extensive destruction of resident bone structures by the tumour, significant loss of tibial bone density and a transient rise in urinary bone resorption markers. Continuous daily treatment with ibandronate (10 μg/kg) inhibited further growth of fully established metastases and reduced the mean osteolytic growth rate to 0.03 mm2/4 days. In lesions 2/4 days). When ibandronate was started 3 days prior to tumour cell inoculation, the development of osteolytic lesions was substantially reduced (take rate only 17%) and bone density and structure were mostly preserved. We conclude that the intra-arterial approach used in this new model of metastatic bone disease results in site-specific osteolytic lesions with high take rates, steady tumour growth and no additional morbidity. While serial bone marker assessments did not prove useful to monitor osteolytic growth, our studies provide in vivo evidence that ibandronate treatment induces tumour remission by reversal of tumour growth.