Parthenolide As a Therapeutic for Disseminated Canine Neoplasms.

This study provides a unique translational research opportunity to help both humans and dogs diagnosed with diseases that carry dismal prognoses in both species: histiocytic sarcoma (HS), hemangiosarcoma (HSA), and disseminated mastocytosis/mast cell tumor (MCT). Although exceedingly rare in humans, these so called "orphan diseases" are relatively more common in dogs. For these and other more commonplace cancers like lymphoma (Lym), dogs are an excellent translational model for human disease due to remarkably similar disease biology. In this study, assays were performed to assess the therapeutic potential of parthenolide (PTL), a known canonical nuclear factor kappa B (NF-κB) signaling inhibitor with additional mechanisms of antineoplastic activity, including alteration of cellular reduction-oxidation balance. Canine cell lines and primary cells are sensitive to PTL and undergo dose-dependent apoptosis after exposure to drug. PTL exposure also leads to glutathione depletion, reactive oxygen species generation, and NF-κB inhibition in canine cells. Standard-of-care therapeutics broadly synergize with PTL. In two canine HS cell lines, expression of NF-κB pathway signaling partners is downregulated with PTL therapy. Preliminary data suggest that PTL inhibits NF-κB activity of cells and extends survival time in a mouse model of disseminated canine HS. These data support further investigation of compounds that can antagonize canonical NF-κB pathway signaling in these cancers and pave the way for clinical trials of PTL in affected dogs. As dogs are an excellent natural disease model for these cancers, these data will ultimately improve our understanding of their human disease counterparts and hopefully improve care for both species. SIGNIFICANCE STATEMENT: Disseminated neoplasms in human and canine cancers are challenging to treat, and novel therapeutic approaches are needed to improve outcomes. Parthenolide is a promising treatment for histiocytic sarcoma, hemangiosarcoma, and mast cell neoplasia.

Immunohistochemical evidence of NF-kB activation in canine lymphomas, histiocytic sarcomas, hemangiosarcomas, and mast cell tumors.

Increased or constitutive activation of nuclear factor kappa B (NF-kB) is a feature of many chronic disease processes, including cancer. While NF-kB overactivation has been documented extensively in human oncology, there is a relative paucity of data documenting the same phenomenon in veterinary medicine. To assess NF-kB activity, antibodies to p65 and p100/p52, which are components of NF-kB heterodimers, were first validated for specificity and canine cross-reactivity via Western blot and labeling of immortalized cell pellets. Then, nuclear labeling for these antibodies was assessed via QuPath software in over 200 tumor tissue samples (10 hemangiosarcomas, 94 histiocytic sarcomas, 71 lymphomas, and 28 mast cell tumors) and compared to immunolabeling in appropriate normal tissue counterparts. Greater than 70% of spontaneous canine tumors evaluated in this study had more nuclear p65 and p100/p52 immunoreactivity than was observed in comparable normal cell populations. Specifically, 144/204 (70.58%) of tumors evaluated had positive p65 nuclear labeling and 179/195 (91.79%) had positive p100/p52 nuclear labeling. Surprisingly, greater nuclear p100/p52 reactivity was associated with a longer progression-free survival (PFS) and overall survival (OS) in canine lymphomas. These results provide support and preliminary data to investigate the role of NF-kB signaling in different types of canine cancer.

Novel Treatments for Lymphoma.

Lymphoma is a common disease in companion animals. While conventional chemotherapy has the potential to induce remission and prolong life, relapse is common and novel treatments are needed to improve outcome. This review discusses recent modifications/adjustments to conventional standard of care therapy for canine and feline lymphoma, options for treatment or relapsed/refractory disease, and cutting-edge immunotherapy and small molecule-based approaches that are in varying stages of regulatory approval.

VDX-111 targets proliferative pathways in canine cancer cell lines.

VDX-111 (also identified as AMPI-109) is a vitamin D derivative which has shown anticancer activity. To further assess the function of this compound against multiple cancer types, we examined the efficacy of VDX-111 against a panel of 30 well characterized canine cancer cell lines. Across a variety of cancer types, VDX-111 induced widely variable growth inhibition, cell death, and migration inhibition, at concentrations ranging from 10 nM to 1 µM. Growth inhibition sensitivity did not correlate strongly with tumor cell histotype; however, it was significantly correlated with the expression of genes in multiple cell signaling pathways, including the MAPK and PI3K-AKT pathways. We confirmed inhibition of these signaling pathways as likely participants in the effects of VDX-111. These results suggest that a subset of canine tumors may be sensitive to treatment with VDX-111, and suggests possible predictive markers of drug sensitivity and pharmacodynamic biomarkers of drug exposure that could be employed in future clinical trials.

Early progression during or after cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy indicates poor outcome with rescue protocols in dogs with multicentric lymphoma.

BACKGROUND: Dogs with lymphoma that fail cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy (CHOP) before completion of their protocol are commonly thought to have poor long-term outcome, but no previous studies have evaluated the effect of early relapse on progression-free interval (PFI) or overall survival time (OST) for patients undergoing rescue chemotherapy. OBJECTIVE: Correlate rescue treatment outcomes in dogs with multicentric lymphoma with outcomes after 1st-line CHOP chemotherapy. METHODS: Data were collected from 6 previous retrospective or prospective studies in 187 dogs with multicentric lymphoma that received 1st-line CHOP chemotherapy and then received either lomustine (CCNU), L-asparaginase and prednisone (LAP), or rabacfosadine (RAB, Tanovea), with or without prednisone or L-asparaginase. RESULTS: The PFI after initiation of CHOP chemotherapy was significantly associated with response rate postprogression, PFI, and postrescue survival time (ST) for both rescue protocols. Immunophenotype (B- vs T-cell) was not significantly associated with response, PFI or OST for LAP but was significantly associated with response and PFI for RAB. CONCLUSION: Dogs that experience short PFI during or after 1st-line CHOP chemotherapy had lower response rates to rescue treatment, with shorter PFI and ST. Immunophenotype did not significantly affect outcome with LAP but was associated with PFI for RAB.

Alternating rabacfosadine and doxorubicin for treatment of naïve canine lymphoma.

The current standard of care treatment for canine lymphoma is a multi-agent, CHOP-based chemotherapy protocol. Single agent doxorubicin (DOX) is less burdensome; however, multi-agent chemotherapy protocols are often superior. The recently approved drug rabacfosadine (RAB, Tanovea) provides an attractive option for combination therapy with DOX, as both drugs demonstrate efficacy against lymphoma and possess different mechanisms of action. A previous study evaluating alternating RAB/DOX reported an overall response rate (ORR) of 84%, with a median progression-free survival time (PFS) of 194 days. The aim of this prospective trial was to evaluate the same protocol in an additional population of dogs. Fifty-nine dogs with treatment naïve lymphoma were enrolled. RAB (1.0 mg/kg IV) was alternated with DOX (30 mg/m2 IV) every 21 days for up to six total treatments (3 cycles). Response assessment and adverse event (AE) evaluation were performed every 21 days using VCOG criteria. The ORR was 93% (79% CR, 14% PR). The median time to maximal response was 21.5 days; median PFS was 199 days. T cell immunophenotype and lack of treatment response were predictive of inferior outcomes. AEs were mostly gastrointestinal. Six dogs developed presumed or confirmed pulmonary fibrosis; four were grade 5. One dog experienced grade 3 extravasation injury with RAB that resolved with supportive treatment. These data mirror those of the previously reported RAB/DOX study, and support the finding that alternating RAB/DOX is a reasonable treatment option for canine lymphoma.

Validation of ferroptosis in canine cancer cells to enable comparative oncology and translational medicine.

Ferroptosis is a cell death mechanism that has attracted significant attention as a potential basis for the development of new cancer therapies. Validation of ferroptosis biology in species commonly used in translation and pre-clinical development is a necessary foundation for enabling the advancement of such ferroptosis modulating drugs. Here, we demonstrate that canine cancer cells exhibit sensitivity to a wide range of ferroptosis-inducing perturbations in a manner indistinguishable from human cancer cells, and recapitulate characteristic patterns of ferroptotic response across tumor types seen in the human setting. The foundation provided herein establishes the dog as a relevant efficacy and toxicology model for ferroptosis and creates new opportunities to leverage the canine comparative oncology paradigm to accelerate the development of ferroptosis-inducing drugs for human cancer patients.