Osteosarcoma of the middle phalanx in a horse

An 11‐year‐old Thoroughbred gelding was presented for lameness investigation following acute onset hindlimb lameness, which developed during a period of paddock turnout. Clinical examination revealed a swelling over the dorsolateral aspect of the pastern that was painful on digital palpation. Radiography of this area was consistent with an aggressive bone lesion involving both joint surfaces of the middle phalanx with pathological fracture and distal collapse of this bone. On this basis, the horse was subjected to euthanasia. Post mortem histopathological examination revealed presence of an osteosarcoma without involvement of the articular cartilage. This bone tumour is extremely rare in horses and has not been reported in this anatomical location.     

Treatment of appendicular osteosarcoma in a horse

A 14‐year‐old Arabian gelding was examined for a mass on the lateral aspect of the left tarsus and proximal lateral metatarsus. Radiography revealed a predominately osteolytic lesion involving the fourth tarsal bone and the proximal third and fourth metatarsal bone. Results of histopathological examination of the mass prior to surgery were consistent with an undifferentiated sarcoma. The mass was surgically excised and the remaining bone defect treated with absorbable beads containing cisplatin. Histology and immunohistochemistry of the mass removed at surgery revealed a telangiectatic osteosarcoma. The surgical site healed uneventfully and the horse was performing as a low level jumper 8.5 years after surgery.     

USE OF FORCE PLATE ANALYSIS TO EVALUATE THE EFFICACY OF EXTERNAL BEAM RADIATION TO ALLEVIATE OSTEOSARCOMA PAIN

A standard of therapy for osteosarcoma includes amputation with or without adjuvant chemotherapy. There is a subset of dogs with osteosarcoma that are unsuitable for amputation. We evaluated kinetic variables in dogs with appendicular osteosarcoma treated with a single 8 Gy dose of radiation. Eighteen pet dogs with appendicular osteosarcoma received one 8 Gy fraction of palliative radiation on day 0. Force plate measurements and clinical assessments were made on days 0, 7, 14, and 21. Peak vertical forces ( F _z) were recorded for each limb and a symmetric index (SI) was calculated. There were no significant changes in kinetic parameters after one 8 Gy dose of radiation therapy. Nine of these 18 dogs exhibited increased limb function at day 21 based on force plate analysis. Significant factors affecting F _z included gender and tumor location. There was a significant correlation between F _z and response to therapy based on SI at day 21. SI seems to be useful to objectively assess response in this mixed population of dogs. One 8 Gy fraction of radiation therapy alone did not reduce lameness associated with appendicular osteosarcoma, but a subset of dogs did have improved limb function after a single dose.     

Intraoperative extracorporeal irradiation for limb sparing in 13 dogs

OBJECTIVE: To evaluate extracorporeal intraoperative radiation therapy (IORT) as a treatment method for limb and joint sparing in dogs with appendicular sarcomas in sites other than the distal aspect of the radius. STUDY DESIGN: Retrospective study. ANIMALS: Thirteen client-owned dogs. METHODS: The bone tumor database and medical records (1998-2002) were reviewed for dogs with primary appendicular bone tumors treated with IORT limb-sparing surgery and adjuvant chemotherapy. The segment of bone containing the tumor was isolated from adjacent soft tissue and an osteotomy performed distant to the tumor. The bone segment was exteriorized, irradiated (70 Gy single fraction), and then stabilized with internal fixation. Adjuvant chemotherapy was administered. Lameness was graded and local and distant tumor control was determined. Associations between intra- and postoperative variables with complications and Kaplan-Meier survival analysis for median disease-free interval and survival time were calculated. RESULTS: Limb function was good or excellent in 10 dogs (77%). Postoperative complications (9 dogs, 69%) included deep infection, fracture of the irradiated bone, and implant failure. Surgical failure was more likely if a single implant was used to stabilize the osteotomized bone and if deep infection developed postoperatively. In 3 dogs, tumors recurred locally within bone in the radiation field. The disease-free and overall success rates of extracorporeal IORT for limb and joint preservation were 46% and 54%, respectively. CONCLUSIONS: Extracorporeal IORT provides a novel alternative to traditional techniques for preservation of joint and limb function in dogs with primary appendicular sarcomas. A minimum of 2 implants and intramedullary bone cement should be used to stabilize the osteotomized bone to minimize postoperative complications. Extracorporeal IORT should be used with caution in dogs with tumors of the distal tibia because of a high complication rate. Dogs with tumors in areas of good soft-tissue coverage, such as the humerus and femur, may be good candidates for limb and joint-sparing surgery using extracorporeal IORT. CLINICAL RELEVANCE: Extracorporeal IORT is a surgical technique that can be used for limb and joint salvage in dogs with primary appendicular sarcomas in sites usually not amenable to traditional limb-sparing techniques.     

Sensitivity of osteosarcoma cell lines to autophagy inhibition as determined by pharmacologic and genetic manipulation

Pharmacologic inhibition of autophagy can be achieved using lysosomotropic agents such as hydroxychloroquine (HCQ) that interfere with fusion of the autophagosome to the lysosome thus preventing completion of the recycling process. The goal of the present study is to determine the sensitivity of eight canine (cOSA) and four human (hOSA) osteosarcoma tumour cell lines to antiproliferative and cytotoxic effects of lysosomal autophagy inhibitors, and to compare these results to the autophagy-dependence measured using a CRISPR/Cas9 live-cell imaging assay in OSA and other tumour cell lines. Antiproliferative and cytotoxic response to HCQ and Lys05 was determined using live cell imaging and YOYO-1 staining. CRISPR/Cas9 live cell imaging screen was done using species specific guide RNA's and transfection of reagents into cells. Response to autophagy core genes was compared to response to an essential (PCNA) and non-essential (FOXO3A) gene. cOSA and hOSA cell lines showed similar antiproliferative and cytotoxic responses to HCQ and Lys05 with median lethal dose (D_m) values ranging from 4.6–15.8 μM and 2.1–5.1 μM for measures of anti-proliferative response, respectively. A relationship was observed between antiproliferative responses to HCQ and Lys05 and VPS34 CRISPR score with D_m values correlating with VPS34 response (r = 0.968 and 0.887) in a species independent manner. The results show that a subset of cOSA and hOSA cell lines are autophagy-dependent and sensitive to HCQ at pharmacologically-relevant exposures.