Effects of mithramycin on transplantable canine perianal gland carcinoma (CAC-9) in nude mice: biochemical, histomorphometric, and ultrastructural investigations

A serially transplantable perianal gland carcinoma (CAC-9) was developed in nude mice from a hypercalcemic dog that has been maintained through passage 20. Tumor doubling rate of CAC-9 was 3.1 +/- 0.4 days. Mithramycin (MMC) injected intraperitoneally (8 mg/kg) into nude mice bearing CAC-9 markedly decreased the tumor volume 2 weeks post-injection. MMC returned the elevated serum and urine calcium levels in mice with CAC-9 back to similar values as controls. The few remaining viable tumor cells after MMC were large and had numerous aggregations of intermediate filaments that displaced cytoplasmic organelles. Histomorphometric evaluation of lumbar vertebrae reveled no significant differences in bone resorption of nude mice bearing CAC-9 compared to saline-treated controls. This rapidly growing tumor line in nude mice associated with mild hypercalcemia will be a useful animal model to evaluate combinations of chemotherapy for cancer-associated hypercalcemia.