Effect of etidronate disodium on the development of bone lesions in an animal model of bone metastasis using the human prostate cancer cell line PC-3.

We have established an animal model of bone metastasis using the PC-3 human prostate tumor cell line. In order to assess whether inhibition of bone resorption would prevent the development of bone metastasis, the diphosphonate etidronate (EHDP) was administered to 20 mice at a dose of 30 mg/kg subcutaneously daily starting 2 days prior to injection of tumor cells. Control mice received daily injections of the saline vehicle. In the EHDP-treated mice, there was no significant reduction in the incidence of bone metastasis, the size of the lesions, or the number of bone lesions per mouse. Approximately 50% of the mice developed bone metastasis, which was similar to the control group and similar to what was observed in earlier studies with this animal model. Histomorphometric analysis of bones showed marked inhibition of mineralization in EHDP-treated mice, thus indicating biological effect on the bone. Therefore, the use of EHDP in biologically effective doses failed to reduce the incidence, size, or number of bone metastases in this animal model.

Patterns of metastasis by the human prostate cancer cell line PC-3 in athymic nude mice.

Cells from the PC-3 human prostate cancer cell line were evaluated in athymic nude mice in order to determine the influence of size of the primary tumor and site inoculation on the incidence and pattern of metastasis. At autopsy, all organs, including the skeleton, were evaluated for metastasis. Subcutaneous injections resulted in metastases to the draining axillary lymph node and lungs (56% and 13%, respectively), and were correlated with size of the primary tumor. Tail vein injection resulted in a high incidence of lung metastasis, while injection into the peritoneal space, spleen, and seminal vesicles resulted in intraabdominal tumor growth, liver metastasis, and large tumors within the seminal vesicles, respectively. Skeletal metastases were not observed in any of the animals studied. We conclude that injection of PC-3 cells into various sites results in different patterns of metastasis, but may not constitute an entirely suitable animal model of human prostate cancer due to the lack of metastasis to the skeleton.