Enrofloxacin enhances the effects of chemotherapy in canine osteosarcoma cells with mutant and wild-type p53

DNA Damage Response (DDR) proteins in canine cancer as potential research targets in comparative oncology

The DNA damage response (DDR) is a complex signal transduction network that is activated when endogenous or exogenous genotoxins damage or interfere with the replication of genomic DNA. Under such conditions, the DDR promotes DNA repair and ensures accurate replication and division of the genome. High levels of genomic instability are frequently observed in cancers and can stem from germline loss‐of‐function mutations in certain DDR genes, such as BRCA1, BRCA2, and p53, that form the basis of human cancer predisposition syndromes. In addition, mutation and/or aberrant expression of multiple DDR genes are frequently observed in sporadic human cancers. As a result, the DDR is considered to represent a viable target for cancer therapy in humans and a variety of strategies are under investigation. Cancer is also a significant cause of mortality in dogs, a species that offers certain advantages for experimental oncology. Domestic dogs present numerous inbred lines, many of which display predisposition to specific forms of cancer and the study of which may provide insight into the biological basis of this susceptibility. In addition, clinical trials are possible in dogs and may lead to therapeutic insights that could ultimately be extended to humans. Here we review what is known specifically about the DDR in dogs and discuss how this knowledge could be extended and exploited to advance experimental oncology in this species.

Local Administration of Carboplatin in Poloxamer 407 After an Ulnar Osteosarcoma Removal in a Dog

An 8 yr old male castrated hound presented for a left distal ulnar osteosarcoma. Staging (computed tomography and nuclear scintigraphy) did not reveal any metastases. A limb-sparing ulnectomy with local adjunctive carboplatin in a poloxamer copolymer gel (poloxamer 407) was performed. The patient recovered without complications after surgery. No wound healing complications or adverse effects occurred after local use of carboplatin in poloxamer 407. The local recurrence-free interval was 296 days from surgery, and the survival time was 445 days from initial diagnosis. This is the first report in the veterinary literature of using poloxamer 407 as a carrier for local delivery of chemotherapeutic drugs in a clinical patient.

The interaction between RUNX2 and core binding factor beta as a potential therapeutic target in canine osteosarcoma

Osteosarcoma remains the most common primary bone tumour in dogs with half of affected dogs unable to survive 1 year beyond diagnosis. New therapeutic options are needed to improve outcomes for this disease. Recent investigations into potential therapeutic targets have focused on cell surface molecules with little clear therapeutic benefit. Transcription factors and protein interactions represent underdeveloped areas of therapeutic drug development. We have utilized allosteric inhibitors of the core binding factor transcriptional complex, comprised of core binding factor beta (CBFβ) and RUNX2, in four canine osteosarcoma cell lines Active inhibitor compounds demonstrate anti-tumour activities with concentrations demonstrated to be achievable in vivo while an inactive, structural analogue has no activity. We show that CBFβ inhibitors are capable of inducing apoptosis, inhibiting clonogenic cell growth, altering cell cycle progression and impeding migration and invasion in a cell line-dependent manner. These effects coincide with a reduced interaction between RUNX2 and CBFβ and alterations in expression of RUNX2 target genes. We also show that addition of CBFβ inhibitors to the commonly used cytotoxic chemotherapeutic drugs doxorubicin and carboplatin leads to additive and/or synergistic anti-proliferative effects in canine osteosarcoma cell lines. Taken together, we have identified the interaction between components of the core binding factor transcriptional complex, RUNX2 and CBFβ, as a potential novel therapeutic target in canine osteosarcoma and provide justification for further investigations into the anti-tumour activities we describe here.

A genetically engineered microRNA-34a prodrug demonstrates anti-tumor activity in a canine model of osteosarcoma

Osteosarcoma (OSA) represents the most common primary bone tumor in humans and pet dogs. Little progress has been made with regard to viable treatment options in the past three decades and patients presenting with metastatic disease continue to have a poor prognosis. Recent mouse studies have suggested that microRNA-34a (miR-34a) may have anti-tumor activities in human OSA models. Due to the conservation of microRNA across species, we hypothesized that a bioengineered miR-34a prodrug (tRNA/miR-34a) would have similar effects in canine OSA, providing a valuable preclinical model for development of this therapeutic modality. Using a panel of canine OSA cell lines, we found that tRNA/miR-34a reduced viability, clonogenic growth, and migration and invasion while increasing tumor cell apoptosis. Furthermore, canine OSA cells successfully process the tRNA/miR-34a into mature miR-34a which reduces expression of target proteins such as platelet derived growth factor receptor alpha (PDGFRα), Notch1 and vascular endothelial growth factor (VEGF). Additionally, our subcutaneous OSA xenograft model demonstrated in vivo tumor growth delay, increased necrosis and apoptosis by tRNA/miR-34a, and decreased cellular proliferation ability. Taken together, these data support that this novel microRNA-based therapy may possess clinical utility in a spontaneously-occurring large animal model of OSA, which can then serve to inform the clinical development of this therapy for human OSA patients.

In vitro and in vivo activity of liposome-encapsulated curcumin for naturally occurring canine cancers

Curcumin has well-established anti-cancer properties in vitro, however, its therapeutic potential has been hindered by its poor bioavailability. Lipocurc is a proprietary liposome-encapsulated curcumin formulation that enables intravenous delivery and has been shown to reach its highest concentration within lung tissue. The goal of this study was to characterize the anti-cancer and anti-angiogenic activity of Lipocurc in vitro, in addition to evaluating Lipocurc infusions in dogs with naturally occurring cancer. We therefore evaluated the effect of Lipocurc, relative to free curcumin, on the viability of canine osteosarcoma, melanoma and mammary carcinoma cell lines, as well as the ability of Lipocurc to inhibit endothelial cell viability, migration and tube formation. We also undertook a pilot clinical trial consisting of four weekly 8-hour Lipocurc infusions in 10 cancer-bearing dogs. Tumour cell proliferation was inhibited by curcumin at concentrations exceeding those achievable in the lung tissue of dogs. Similarly, equivalent high concentrations of Lipocurc and curcumin also inhibited endothelial cell viability, migration and tube formation. Four out of six dogs completing planned infusions of Lipocurc experienced stable disease; however, no radiographic responses were detected.

Comparative oncology approach to drug repurposing in osteosarcoma

BACKGROUND

Osteosarcoma is an orphan disease for which little improvement in survival has been made since the late 1980s. New drug discovery for orphan diseases is limited by the cost and time it takes to develop new drugs. Repurposing already approved FDA-drugs can help overcome this limitation. Another limitation of cancer drug discovery is the lack of preclinical models that accurately recapitulate what occurs in humans. For OS using dogs as a model can minimize this limitation as OS in canines develops spontaneously, is locally invasive and metastasizes to the lungs as it does in humans.

METHODS

In our present work we used high-throughput screens to identify drugs from a library of 2,286 FDA-approved drugs that demonstrated selective growth inhibition against both human and canine OS cell lines. The identified lead compound was then tested for synergy with 7 other drugs that have demonstrated activity against OS. These results were confirmed with in vitro assays and an in vivo murine model of OS.

RESULTS

We identified 13 drugs that demonstrated selective growth inhibition against both human and canine OS cell lines. Auranofin was selected for further in vitro combination drug screens. Auranofin showed synergistic effects with vorinostat and rapamycin on OS viability and apoptosis induction. Auranofin demonstrated single-agent growth inhibition in both human and canine OS xenografts, and cooperative growth inhibition was observed in combination with rapamycin or vorinostat. There was a significant decrease in Ki67-positive cells and an increase in cleaved caspase-3 levels in tumor tissues treated with a combination of auranofin and vorinostat or rapamycin.

CONCLUSIONS

Auranofin, alone or in combination with rapamycin or vorinostat, may be useful new treatment strategies for OS. Future studies may evaluate the efficacy of auranofin in dogs with OS as a prelude to human clinical evaluation.

The animal-dependent risk factors in canine osteosarcomas

Canine osteosarcoma (OSA) is a malignant neoplastic tumor, which develops from the primitive mesenchymal stem cell, that has or can acquire the capacity to produce neoplastic osteoid with possible neoplastic bone formation. Predisposition of some dog breeds to OSA indicates genetic background of oncogenesis. The aim of the study was to characterize animal-dependent risk factors for canine osteosarcoma development in Poland. The study was conducted on canine patients diagnosed cytologically or histopathologically as having OSA, and data on age, breed, sex, as well as tumor location and character were recorded. No sex predisposition to OSA was observed, mongrels were significantly underrepresented. Large and giant dogs accounted for 47% and 35% of all pedigree dogs, respectively, and both proved predisposed to OSA. A vast majority of OSA developed in the skeleton (appendicular skeleton was more commonly affected than axial skeleton), soft tissues were affected less often. Rottweiler dogs are strongly predisposed to OSA, suggesting that the genetic background is involved in the tumor development, and indicates that dogs of this breed are a promising object for further studies on OSA pathogenesis.