Objective—To determine the effect of pamidronate
disodium on the in vitro viability of osteosarcoma
cells and non-neoplastic cells from dogs.
Sample Population—3 osteosarcoma and 1 fibroblast
cell lines derived from dogs.
Procedure—Cell counts and cell viability assays were
performed in cultures of osteosarcoma cells (POS,
HMPOS, and COS31 cell lines) and fibroblasts after
24, 48, and 72 hours of incubation with pamidronate
at concentrations of 0.001 to 1,000µM or with no
drug (control treatment). Percentage viability was
determined in cell samples for each concentration of
pamidronate and each incubation time. A DNA fragmentation
analysis was performed to assess bisphosphonate-
Results—Osteosarcoma cell viability decreased significantly
in a concentration- and time-dependent
manner at pamidronate concentrations ranging from
100 to 1,000µM, most consistently after 48 and 72
hours' exposure. In treated osteosarcoma cells, the
lowest percentage cell viability was 34% (detected
after 72 hours' exposure to 1,000µM pamidronate).
Conversely, 72 hours' exposure to 1,000µM
pamidronate did not significantly reduce fibroblast viability
(the lowest percentage viability was 76%). After
72 hours of exposure, pamidronate did not cause
DNA fragmentation in POS or HMPOS cells.
Conclusions and Clinical Relevance—Results indicate
that pamidronate may have the potential to inhibit
osteosarcoma growth in dogs, possibly through a
nonapoptotic mechanism. The clinical relevance of
these in vitro findings remains to be determined, but
administration of pamidronate may potentially be indicated
as an adjuvant treatment in chemotherapeutic
protocols used in dogs. (Am J Vet Res 2005;66:
Objective—To determine whether exposure of
canine osteosarcoma cells to deracoxib or piroxicam
results in decreased viability, whether the cytotoxic
effects of deracoxib and piroxicam involve induction
of apoptosis, and whether deracoxib is a more
potent inhibitor of osteosarcoma cell growth than
Sample Population—1 fibroblast and 3 osteosarcoma
Procedure—Cell counts and viability assays were
performed using osteosarcoma cells (POS, highly
metastatic POS, and canine osteosarcoma cell 31)
and fibroblasts after 72 hours of incubation with deracoxib
at concentrations of 0.5µM to 500µM or piroxicam
at concentrations of 1µM to 1,000µM.
Percentage viability was determined for each concentration.
A DNA fragmentation analysis was performed
to assess drug-induced apoptosis.
Results—Concentration of deracoxib required for
50% inhibition of cell viability (IC50) was reached in all
3 osteosarcoma cell lines and ranged from 70 to
150µM, whereas the IC50 for piroxicam was only
reached in the POS cell line at 500µM. Neither deracoxib
nor piroxicam induced sufficient toxicity in
fibroblasts to reach an IC50. Exposure of osteosarcoma
cells to cytotoxic concentrations of deracoxib and
piroxicam did not result in DNA fragmentation.
Conclusions and Clinical Relevance—Intermediate
and high concentrations of deracoxib and high concentrations
of piroxicam were cytotoxic to osteosarcoma
cells; neither drug inhibited cell viability at typical
plasma concentrations in dogs. Deracoxib inhibited
viability of cells at concentrations that did not
affect fibroblast viability. There was no evidence of
apoptosis induction for either drug; however, only 1
cell line was evaluated for apoptosis induction and
only for a limited selection of drug concentrations.
(Am J Vet Res 2005;66:1961–1967)
Objective—To determine response rates and survival
times for cats with lymphoma treated with the University
of Wisconsin-Madison chemotherapy protocol.
Animals—38 cats with lymphoma.
Procedure—Medical records were reviewed, and
information on age, sex, breed, FeLV and FIV infection
status, anatomic form, clinical stage, and survival
time was obtained. Immunophenotyping was
Results—Mean ± SD age of the cats was 10.9 ± 4.4
years. Overall median survival time was 210 days
(interquartile range, 90 to 657 days), and overall duration
of first remission was 156 days (interquartile
range, 87 to 316 days). Age, sex, anatomic form, and
clinical stage were not significantly associated with
duration of first remission or survival time. Eighteen
of the 38 (47%) cats had complete remission, 14
(37%) had partial remission, and 6 (16%) had no
response. Duration of first remission was significantly
longer for cats with complete remission (654 days)
than for cats with partial remission (114 days). Median
survival time for cats with complete remission (654
days) was significantly longer than median survival
time for cats with partial remission (122 days) and for
cats with no response (11 days).
Conclusions and Clinical Relevance—Results suggested
that a high percentage of cats with lymphoma
will respond to treatment with the University of
Wisconsin-Madison chemotherapy protocol. Age,
sex, anatomic form, and clinical stage were not significantly
associated with duration of first response or
survival time, but initial response to treatment was.
(J Am Vet Med Assoc 2005;227:1118–1122)
Objective—To compare survival times for cats with hyperthyroidism treated with iodine 131, methimazole, or both and identify factors associated with survival time.
Design—Retrospective case series.
Procedure—Medical records of cats in which hyperthyroidism had been confirmed on the basis of high serum thyroxine concentration, results of thyroid scintigraphy, or both were reviewed.
Results—55 (33%) cats were treated with 131I alone, 65 (39%) were treated with methimazole followed by 131I, and 47 (28%) were treated with methimazole alone. Twenty-four of 166 (14%) cats had preexisting renal disease, and 115 (69%) had preexisting hepatic disease. Age was positively correlated (r = 0.4) with survival time, with older cats more likely to live longer. Cats with preexisting renal disease had significantly shorter survival times than did cats without preexisting renal disease. When cats with preexisting renal disease were excluded, median survival time for cats treated with methimazole alone (2.0 years; interquartile range [IQR], 1 to 3.9 years) was significantly shorter than median survival time for cats treated with 131I alone (4.0 years; IQR, 3.0 to 4.8 years) or methimazole followed by 131I (5.3 years; IQR, 2.2 to 6.5 years).
Conclusions and Clinical Relevance—Results suggest that age, preexisting renal disease, and treatment type were associated with survival time in cats undergoing medical treatment of hyperthyroidism.
Objective—To evaluate the toxicity and efficacy of a modification of a previously evaluated combination of lomustine, vincristine, procarbazine, and prednisone (LOPP) as a rescue protocol for refractory lymphoma in dogs.
Design—Retrospective case series.
Animals—33 dogs with a cytologic or histologic diagnosis of lymphoma that developed resistance to their induction chemotherapy protocol.
Procedures—Lomustine was administered on day 0 of the protocol. Vincristine was administered on day 0 and again 1 time on day 14. Procarbazine and prednisone were administered on days 0 through 13 of the protocol. This cycle was repeated every 28 days.
Results—Median time from initiation to discontinuation of the University of Florida LOPP protocol was 84 days (range, 10 to 308 days). Overall median survival time was 290 days (range, 51 to 762 days). Overall response rate with this protocol was 61% (20/33), with 36% (12) having a complete response and 24% (8) having a partial response. Toxicosis rates were lower than for the previously published LOPP protocol.
Conclusions and Clinical Relevance—The University of Florida LOPP protocol may be an acceptable alternative to the mechlorethamine, vincristine, procarbazine, and prednisone protocol as a rescue protocol for dogs with lymphoma.
Objective—To investigate the effects of bevacizumab, a human monoclonal antibody against vascular endothelial growth factor, on the angiogenesis and growth of canine osteosarcoma cells xenografted in mice.
Animals—27 athymic nude mice.
Procedures—To each mouse, highly metastasizing parent osteosarcoma cells of canine origin were injected into the left gastrocnemius muscle. Each mouse was then randomly allocated to 1 of 3 treatment groups: high-dose bevacizumab (4 mg/kg, IP), low-dose bevacizumab (2 mg/kg, IP), or control (no treatment). Tumor growth (the number of days required for the tumor to grow from 8 to 13 mm), vasculature, histomorphology, necrosis, and pulmonary metastasis were evaluated.
Results—Mice in the high-dose bevacizumab group had significantly delayed tumor growth (mean ± SD, 13.4 ± 3.8 days; range, 9 to 21 days), compared with that for mice in the low-dose bevacizumab group (mean ± SD, 9.4 ± 1.5 days; range, 7 to 11 days) or control group (mean ± SD, 7. 2 ± 1.5 days; range, 4 to 9 days). Mice in the low-dose bevacizumab group also had significantly delayed tumor growth, compared with that for mice in the control group.
Conclusions and Clinical Relevance—Results indicated that bevacizumab inhibited growth of canine osteosarcoma cells xenografted in mice, which suggested that vascular endothelial growth factor inhibitors may be clinically useful for the treatment of osteosarcoma in dogs.
Impact for Human Medicine—Canine osteosarcoma is used as a research model for human osteosarcoma; therefore, bevacizumab may be clinically beneficial for the treatment of osteosarcoma in humans.
Objective—To evaluate outcomes of radical excision of feline injection-site sarcomas (ISS) via assessment of local recurrence and metastasis rates, survival times, and complications associated with surgery.
Design—Retrospective case series.
Animals—91 cats with ISS.
Procedures—Medical records of cats that had radical excision of ISS without adjunctive treatment were reviewed. Information extracted included sex, type of surgical procedure, histologic tumor grade, tumor diameter, time from tumor detection to definitive surgery, complications associated with surgery, whether tumors recurred locally or metastasized, and survival times. Diagnosis of ISS was histologically confirmed, and additional follow-up was performed.
Results—Overall median survival time was 901 days. Thirteen of 91 (14%) cats had local tumor recurrence; 18 (20%) cats had evidence of metastasis after surgery. Median survival time of cats with and without recurrence was 499 and 1,461 days, respectively. Median survival time of cats with and without metastasis was 388 and 1,528 days, respectively. Tumor recurrence and metastasis were significantly associated with survival time, whereas other examined variables were not. Major complications occurred in 10 cats, including 7 with incisional dehiscence.
Conclusions and Clinical Relevance—Radical excision of ISS resulted in a metastasis rate similar to rates reported previously; the local recurrence rate appeared to be substantially less than rates reported after less aggressive surgeries, with or without adjuvant treatment. Major complication rates were similar to rates reported previously after aggressive surgical resection of ISS. Radical excision may be a valuable means of attaining an improved outcome in the treatment of feline ISS.
Objective—To develop an IM xenograft model of canine osteosarcoma in mice for the purpose of evaluating effects of radiation therapy on tumors.
Animals—27 athymic nude mice.
Procedures—Mice were randomly assigned to 1 of 3 groups of 9 mice each: no treatment (control group), radiation at 10 Gy, or radiation at 15 Gy. Each mouse received 5 × 105 highly metastasizing parent osteosarcoma cells injected into the left gastrocnemius muscle. Maximum tumor diameter was determined with a metric circles template to generate a tumor growth curve. Conscious mice were restrained in customized plastic jigs allowing local tumor irradiation. The behavior and development of the tumor xenograft were assessed via evaluations of the interval required for tumor-bearing limbs to reach diameters of 8 and 13 mm, extent of tumor vasculature, histomorphology of tumors, degree of tumor necrosis, and existence of pulmonary metastasis and clinical disease in affected mice.
Results—Tumor-bearing limbs grew to a diameter of 8 mm (0.2-g tumor mass) in a mean ± SEM interval of 7.0 ± 0.2 days in all mice. Interval to grow from 8 to 13 mm was significantly prolonged for both radiation therapy groups, compared with that of the control group. Histologic evaluation revealed the induced tumors were highly vascular and had characteristics consistent with those of osteosarcoma. Pulmonary metastasis was not detected, and there was no significant difference in percentage of tumor necrosis between groups.
Conclusions and Clinical Relevance—A reliable, repeatable, and easily produced IM xenograft model was developed for in vivo assessment of canine osteosarcoma.
Objective—To characterize the radiosensitivity and capacity for sublethal damage repair (SLDR) of radiation-induced injury in 4 canine osteosarcoma cell lines.
Sample Population—4 canine osteosarcoma cell lines (HMPOS, POS, COS 31, and D17).
Procedures—A clonogenic colony-forming assay was used to evaluate the cell lines' intrinsic radiosensitivities and SLDR capacities. Dose-response curves for the cell lines were generated by fitting the surviving fractions after radiation doses of 0 (control cells), 1, 2, 3, 6, and 9 Gy to a linear quadratic model. To evaluate SLDR, cell lines were exposed to 2 doses of 3 Gy (split-dose experiments) at an interval of 0 (single 6-Gy dose), 2, 4, 6, or 24 hours, after which the surviving fractions were assessed.
Results—Mean surviving fraction did not differ significantly among the 4 cell lines at the radiation doses tested. Mean surviving fraction at 2 Gy was high (0.62), and the α/β ratios (predictor of tissue sensitivity to radiation therapy) for the cell lines were low (mean ratio, 3.47). The split-dose experiments revealed a 2.8- to 3.9-fold increase in cell survival when the radiation doses were applied at an interval of 24 hours, compared with cell survival after radiation doses were applied consecutively (0-hour interval).
Conclusions and Clinical Relevance—Results indicated that these canine osteosarcoma cell lines are fairly radioresistant; α/β ratios were similar to those of nonneoplastic, lateresponding tissues. Future clinical investigations should involve increasing the fraction size in a manner that maximizes tumor killing without adverse effects on the nonneoplastic surrounding tissues.