Investigation of the effects of mTOR inhibitors rapamycin and everolimus in combination with carboplatin on canine malignant melanoma cells.

BACKGROUND: Malignant melanoma in dogs is considered to be largely resistant to conventional chemotherapy, although responses to carboplatin have been documented. Invasion and early metastasis are common features of certain melanoma subtypes that contribute to tumour progression despite aggressive local and systemic therapy. Upregulation of the PI3K/AKT/mTOR pathway has been observed in canine malignant melanoma and may represent a potential target for therapy. Rapamycin (sirolimus) and everolimus are commercially available small molecule inhibitors that target mTOR and therefore may have anticancer activity in canine melanoma. It was hypothesized that there is synergism between rapamycin or everolimus and platinum chemotherapy, and that combination drug treatment would inhibit target/downstream proteins involved in cell viability/proliferation and increase cell death in canine melanoma cells. It was further hypothesized that rapamycin or everolimus would impact metabolism by reducing glycolysis in these cells. Four canine melanoma cell lines were treated in vitro with rapamycin and everolimus as sole treatment or combined with carboplatin. Cell viability, apoptosis, target modulation, and glycolytic metabolism were evaluated by crystal violet colourimetric assay, Annexin V/PI flow cytometry, western blotting, and Seahorse bioanalyzer, respectively. RESULTS: When combined with carboplatin chemotherapy, rapamycin or everolimus treatment was overall synergistic in reducing cell viability. Carboplatin-induced apoptosis was noted at 72 h after treatment compared to the vehicle control. Levels of phosphorylated mTOR were reduced by rapamycin and everolimus in all four cell lines, but activation of the downstream protein p70S6K was not consistently reduced by treatment in two of the cell lines. Both mTOR inhibitors decreased the extracellular acidification rate of canine melanoma cells, indicating reduced cancer cell glycolytic activity. CONCLUSIONS: Inhibition of mTOR by rapalogs, such as rapamycin and everolimus combined with carboplatin chemotherapy may have activity in canine melanoma. Future mechanistic investigation is warranted, including in vivo assessment of this combination therapy.

Recent and current clinical trials in canine appendicular osteosarcoma.

Osteosarcoma (OSA) is an aggressive primary bone tumor in the domestic dog that most often occurs within the appendicular skeleton. Despite the use of adjuvant chemotherapy, most dogs succumb to metastatic disease within 1 year of diagnosis. To improve this outcome, substantial research is currently focused on investigating novel therapies. Herein, we review emerging treatments and clinical trials that, if proven efficacious, could revolutionize the standard of care for canine appendicular OSA. This article includes a critical perspective on the safety, efficacy, and limitations of select immunotherapy, virotherapy, radiotherapy, targeted therapy, and personalized medicine trials, all of which reflect similar investigations taking place in human oncology. These clinical trials represent a major evolution in the overall approach to therapy for dogs with appendicular OSA that could have significant implications for improving survival.

Essais cliniques récents et en cours sur l'ostéosarcome appendiculaire canin. L'ostéosarcome (OSA) est une tumeur osseuse primaire agressive chez le chien domestique qui se produit fréquemment dans le squelette appendiculaire. Malgré l'utilisation de chimiothérapie complémentaire, la majorité des chiens succombent aux métastases en dedans d'une année du diagnostic. Afin d'améliorer ce résultat, de la recherche substantielle est actuellement concentrée sur l'étude de thérapies nouvelles. À cet égard, nous révisons les traitements émergents et les essais cliniques qui, s'ils s'avèrent efficaces, pourraient révolutionner le standard de soins pour les OSA appendiculaires canins. Le présent article inclus une perspective critique de la sécurité, l'efficacité et les limitations d'un choix d'immunothérapie, de virothérapie, de radiothérapie, de thérapies ciblées et d'essais médicaux personnalisés, qui reflètent tous des investigations similaires effectuées en oncologie humaine. Ces essais cliniques représentent une évolution majeure dans l'approche globale à la thérapie de chiens avec OSA appendiculaire qui pourrait avoir des implications significatives pour améliorer la survie.(Traduit par Dr Serge Messier).

Flow Cytometric Detection of Circulating Osteosarcoma Cells in Dogs.

Osteosarcoma (OSA) is a malignant tumor of middle-aged dogs and adolescent humans. The clinical outcome of OSA has not improved over more than three decades, and dogs typically succumb to metastatic disease within 6 months despite tumor resection through limb amputation and adjuvant chemotherapy. Therefore, undetectable tumor cells with potential to form metastases are present at diagnosis. An assay to identify canine immortalized and primary OSA cells through flow cytometric detection of intracellular collagen 1 (Col I) and osteocalcin was optimized, and applied to blood samples from tumor-bearing dogs for detection of circulating tumor cells (CTCs). Spiking variable number of OSA cells into normal dog blood recovered 50-60% of Col I positive cells with high forward and variable side light scatter. An algorithm to exclude nonviable, doublet, and autofluorescent cells was applied to sequential blood samples from three dogs obtained prior to and after limb amputation, and at approximately, triweekly intervals over 121, 142, and 183 days of chemotherapy, respectively. Dogs had >100 CTC/106 leukocytes prior to amputation, variably frequent CTC during chemotherapy, and an increase up to 4,000 CTC/106 leukocytes within 4 weeks before overt metastases or death. Sorted CTCs were morphologically similar to direct tumor aspirates and positive for Col I. Although preliminary, findings suggest that CTCs are frequent in canine OSA, more numerous than carcinoma CTC in humans, and that an increase in CTC frequency may herald clinical deterioration. This assay may enable enumeration and isolation of OSA CTC for prognostic and functional studies, respectively. © 2019 International Society for Advancement of Cytometry.

Osteosarcoma in the Post Genome Era: Preclinical Models and Approaches to Identify Tractable Therapeutic Targets.

PURPOSE OF REVIEW: Osteosarcoma (OS) is the most common cancer of bone, yet is classified as a rare cancer. Treatment and outcomes for OS have not substantively changed in several decades. While the decoding of the OS genome greatly advanced the understanding of the mutational landscape of OS, immediately actionable therapeutic targets were not apparent. Here we describe recent preclinical models that can be leveraged to identify, test, and prioritize therapeutic candidates. RECENT FINDINGS: The generation of multiple high fidelity murine models of OS, the spontaneous disease that arises in pet dogs, and the establishment of a diverse collection of patient-derived OS xenografts provide a robust preclinical platform for OS. These models enable evidence to be accumulated across multiple stages of preclinical evaluation. Chemical and genetic screening has identified therapeutic targets, often demonstrating cross species activity. Clinical trials in both PDX models and in canine OS have effectively tested new therapies for prioritization. Improving clinical outcomes in OS has proven elusive. The integrated target discovery and testing possible through a cross species platform provides validation of a putative target and may enable the rigorous evaluation of new therapies in models where endpoints can be rapidly assessed.

Murine models of osteosarcoma: A piece of the translational puzzle.

Osteosarcoma (OS) is the most common cancer of bone in children and young adults. Despite extensive research efforts, there has been no significant improvement in patient outcome for many years. An improved understanding of the biology of this cancer and how genes frequently mutated contribute to OS may help improve outcomes for patients. While our knowledge of the mutational burden of OS is approaching saturation, our understanding of how these mutations contribute to OS initiation and maintenance is less clear. Murine models of OS have now been demonstrated to be highly valid recapitulations of human OS. These models were originally based on the frequent disruption of p53 and Rb in familial OS syndromes, which are also common mutations in sporadic OS. They have been applied to significantly improve our understanding about the functions of recurrently mutated genes in disease. The murine models can be used as a platform for preclinical testing and identifying new therapeutic targets, in addition to testing the role of additional mutations in vivo. Most recently these models have begun to be used for discovery based approaches and screens, which hold significant promise in furthering our understanding of the genetic and therapeutic sensitivities of OS. In this review, we discuss the mouse models of OS that have been reported in the last 3-5 years and newly identified pathways from these studies. Finally, we discuss the preclinical utilization of the mouse models of OS for identifying and validating actionable targets to improve patient outcome.

An evaluation of TAZ and YAP crosstalk with TGFß signalling in canine osteosarcoma suggests involvement of hippo signalling in disease progression.

BACKGROUND: Osteosarcoma (OSA) is the most common bone cancer in canines. Both transforming growth factor beta (TGFß) and Hippo pathway mediators have important roles in bone development, stemness, and cancer progression. The role of Hippo signalling effectors TAZ and YAP has never been addressed in canine OSA. Further, the cooperative role of TGFß and Hippo signalling has yet to be explored in osteosarcoma. To address these gaps, this study investigated the prognostic value of TAZ and YAP alone and in combination with pSmad2 (a marker of active TGFß signalling), as well as the involvement of a TGFß-Hippo signalling crosstalk in tumourigenic properties of OSA cells in vitro. An in-house trial tissue microarray (TMA) which contained 16 canine appendicular OSA cases undergoing standard care and accompanying follow-up was used to explore the prognostic role of TAZ, YAP and pSmad2. Published datasets were used to test associations between TAZ and YAP mRNA levels, metastasis, and disease recurrence. Small interfering RNAs specific to TAZ and YAP were utilized in vitro alone or in combination with TGFß treatment to determine their role in OSA viability, proliferation and migration. RESULTS: Patients with low levels of both YAP and pSmad2 when evaluated in combination had a significantly longer time to metastasis (log-rank test, p = 0.0058) and a longer overall survival (log rank test, p = 0.0002). No similar associations were found for TAZ and YAP mRNA levels. In vitro, TAZ knockdown significantly decreased cell viability, proliferation, and migration in metastatic cell lines, while YAP knockdown significantly decreased viability in three cell lines, and migration in two cell lines, derived from either primary tumours or their metastases. The impact of TGFß signaling activation on these effects was cell line-dependent. CONCLUSIONS: YAP and pSmad2 have potential prognostic value in canine appendicular osteosarcoma. Inhibiting YAP and TAZ function could lead to a decrease in viability, proliferation, and migratory capacity of canine OSA cells. Assessment of YAP and pSmad2 in larger patient cohorts in future studies are needed to further elucidate the role of TGFß-Hippo signalling crosstalk in canine OSA progression.

The DNA helicase recql4 is required for normal osteoblast expansion and osteosarcoma formation.

RECQL4 mutations are associated with Rothmund Thomson Syndrome (RTS), RAPADILINO Syndrome and Baller-Gerold Syndrome. These patients display a range of benign skeletal abnormalities such as low bone mass. In addition, RTS patients have a highly increased incidence of osteosarcoma (OS). The role of RECQL4 in normal adult bone development and homeostasis is largely uncharacterized and how mutation of RECQL4 contributes to OS susceptibility is not known. We hypothesised that Recql4 was required for normal skeletal development and both benign and malignant osteoblast function, which we have tested in the mouse. Recql4 deletion in vivo at the osteoblastic progenitor stage of differentiation resulted in mice with shorter bones and reduced bone volume, assessed at 9 weeks of age. This was associated with an osteoblast intrinsic decrease in mineral apposition rate and bone formation rate in the Recql4-deficient cohorts. Deletion of Recql4 in mature osteoblasts/osteocytes in vivo, however, did not cause a detectable phenotype. Acute deletion of Recql4 in primary osteoblasts or shRNA knockdown in an osteoblastic cell line caused failed proliferation, accompanied by cell cycle arrest, induction of apoptosis and impaired differentiation. When cohorts of animals were aged long term, the loss of Recql4 alone was not sufficient to initiate OS. We then crossed the Recql4fl/fl allele to a fully penetrant OS model (Osx-Cre p53fl/fl). Unexpectedly, the Osx-Cre p53fl/flRecql4fl/fl (dKO) animals had a significantly increased OS-free survival compared to Osx-Cre p53fl/fl or Osx-Cre p53fl/flRecql4fl/+ (het) animals. The extended survival was explained when the Recql4 status in the tumors that arose was assessed, and in no case was there complete deletion of Recql4 in the dKO OS. These data provide a mechanism for the benign skeletal phenotypes of RECQL4 mutation syndromes. We propose that tumor suppression and osteosarcoma susceptibility are most likely a function of mutant, not null, alleles of RECQL4.

In vitro evaluation of a simulated pneumoperitoneum environment using carbon dioxide on canine transitional cell carcinoma.

OBJECTIVE: To assess the impact of a simulated CO2 pneumoperitoneum environment on the viability and proliferation of canine transitional cell carcinoma (TCC) cells in vitro. STUDY DESIGN: In vitro study. METHODS: A control Madin-Darby canine kidney (MDCK) cell line and 3 canine TCC cell lines were exposed to 100% CO2 at pressure of 0, 5, 10, or 15 mmHg for 2 hours by using an airtight chamber and a mechanical insufflator at 37°C. Culture media pH was measured. Viability and proliferation were assessed by using a resazurin assay and trypan blue dye, respectively. RESULTS: The pH in the media significantly decreased immediately after CO2 exposure but returned to normal within 1 hour. The viability of the cell lines was variably affected at the evaluated pressures. Insufflation pressure of 10 mmHg resulted in significantly decreased cell viability compared with control. The impact of 15 mmHg CO2 was comparable to 0 mmHg and control. CO2 insufflation pressure had no significant effects on proliferation up to 7 days postexposure. Conclusion/Clinical significance: A positive pressure CO2 environment significantly decreased the viability of TCC and MDCK cells under specific conditions without influencing their proliferation up to 7 days postexposure. Investigating these effects in clinical patients undergoing CO2 laparoscopy is essential to assess for port site metastasis or peritoneal carcinomatosis in order to translate these in vitro results to clinical recommendations.

Retrospective evaluation of toceranib (Palladia) treatment for canine metastatic appendicular osteosarcoma.

This retrospective study evaluated the outcomes of dogs with macroscopic pulmonary metastasis of appendicular osteosarcoma (OSA) treated with toceranib. Medical records of 20 dogs with macroscopic pulmonary metastasis of OSA that received toceranib were reviewed. The median dose and duration of toceranib administration were 2.52 mg/kg (range: 2.12 to 2.72 mg/kg) and 60 days (range: 17 to 231 days). The median progression free survival (PFS) and overall survival (OS) were 36 days (range: 17 to 231 days) and 90 days (range: 17 to 433 days), respectively. The clinical benefit rate was 10% (2/20; 1 partial response and 1 stable disease). The longest length of initial pulmonary nodules had significant impact on both PFS (P = 0.01) and OS (P = 0.02). The prognosis for dogs with metastatic OSA was poor with only 10% of dogs showing clinical benefit from toceranib. These results suggest that toceranib may not improve outcome in dogs with macroscopic pulmonary metastasis of OSA.

Évaluation rétrospective du traitement avec tocéranib (Palladia) pour l'ostéosarcome appendiculaire métastatique canin. Cette étude rétrospective a évalué les résultats des chiens souffrant de métastase pulmonaire macroscopique de l'ostéosarcome appendiculaire (OSE) traité avec tocéranib. Les dossiers médicaux de 20 chiens atteints de métastase pulmonaire macroscopique d'OSE qui ont reçu tocéranib ont été évalués. La dose médiane et la durée de l'administration de tocéranib étaient de 2,52 mg/kg (étendue de 2,12 à 2,72 mg/kg) et de 60 jours (étendue de 17 à 231 jours). La progression de survie libre (PSL) médiane et la survie totale (ST) étaient de 36 jours (étendue de 17 à 231 jours) et de 90 jours (étendue de 17 à 433 jours), respectivement. Le taux de bienfaits cliniques étaient de 10 % (2/20; 1 réponse partielle et 1 maladie stable). Le plus long intervalle avant l'apparition des nodules pulmonaires initiaux avait un impact important sur la PSL (P = 0,01) et la ST (P = 0,02). Le pronostic pour les chiens atteints d'OSE métastatique était mauvais et seulement 10 % des chiens ont manifesté des bienfaits cliniques lors de l'usage de tocéranib. Ces résultats suggèrent que le tocéranib pourraient ne pas améliorer les résultats cliniques chez les chiens souffrant de métastase pulmonaire macroscopique causée par OSE.(Traduit par Isabelle Vallières).

Evaluation of toxicity of a chronic alternate day metronomic cyclophosphamide chemotherapy protocol in dogs with naturally occurring cancer.

Sterile hemorrhagic cystitis (SHC) is an important complication of cyclophosphamide chemotherapy in dogs as it is reported in up to 23% of cases with various protocols. The current study reports toxicities of a protocol of metronomic cyclophosphamide, and identifies risk factors for development of adverse effects. A retrospective cohort study of dogs treated with metronomic cyclophosphamide at an intended dose of 25 mg/m2 every other day was conducted. Fifty dogs were included with a median length of treatment of 90 days (range: 1 to 1305 days). Treatment was discontinued in 22 dogs (44%) due to adverse effects; 16 dogs (32%) developed SHC after a median time of 127.5 days (range: 54 to 1305 days). Higher cumulative dose was significantly associated with a higher risk of SHC development (P = 0.048). Therefore, close monitoring and/or prophylactic treatments should be considered for patients receiving chronic metronomic cyclophosphamide therapy.

Évaluation de la toxicité du protocole de chimiothérapie prolongée à la cyclophosphamide métronomique tous les deux jours chez les chiens atteints d'un cancer acquis naturellement. La cystite hémorragique stérile (CHS) est une complication importante de la chimiothérapie à la cyclophosphamide chez les chiens car elle est signalée dans jusqu'à 23 % des cas avec divers protocoles. L'étude actuelle signale les toxicités d'un protocole de cyclophosphamide métronomique et identifie les facteurs de risque pour le développement d'effets indésirables. Une étude rétrospective auprès d'une cohorte de chiens traités à l'aide de la cyclosphamide métronomique à une dose prévue de 25 mg/m2 tous les deux jours a été réalisée. Cinquante chiens ont été inclus avec une durée moyenne de traitement de 90 jours (fourchette : de 1 à 1305 jours). Le traitement a été discontinué chez 22 chiens (44 %) en raison des effets indésirables; 16 chiens (32 %) ont développé la CHS après une durée moyenne de 127,5 jours (fourchette : de 54 à 1305 jours). Une dose cumulative supérieure était significativement associée à un risque supérieur de développer la CHS (P = 0,048). Par conséquent, une surveillance étroite et/ou des traitements prophylactiques devraient être considérés pour les patients recevant une thérapie prolongée à la cyclophosphamide métronomique.(Traduit par Isabelle Vallières).

Effects of epidermal growth factor receptor kinase inhibition on radiation response in canine osteosarcoma cells.

BACKGROUND: Radiation therapy is a palliative treatment modality for canine osteosarcoma, with transient improvement in analgesia observed in many cases. However there is room for improvement in outcome for these patients. It is possible that the addition of sensitizing agents may increase tumor response to radiation therapy and prolong quality of life. Epidermal growth factor receptor (EGFR) expression has been documented in canine osteosarcoma and higher EGFR levels have been correlated to a worse prognosis. However, effects of EGFR inhibition on radiation responsiveness in canine osteosarcoma have not been previously characterized. This study examined the effects of the small molecule EGFR inhibitor erlotinib on canine osteosarcoma radiation responses, target and downstream protein expression in vitro. Additionally, to assess the potential impact of treatment on tumor angiogenesis, vascular endothelial growth factor (VEGF) levels in conditioned media were measured. RESULTS: Erlotinib as a single agent reduced clonogenic survival in two canine osteosarcoma cell lines and enhanced the impact of radiation in one out of three cell lines investigated. In cell viability assays, erlotinib enhanced radiation effects and demonstrated single agent effects. Erlotinib did not alter total levels of EGFR, nor inhibit downstream protein kinase B (PKB/Akt) activation. On the contrary, erlotinib treatment increased phosphorylated Akt in these osteosarcoma cell lines. VEGF levels in conditioned media increased after erlotinib treatment as a single agent and in combination with radiation in two out of three cell lines investigated. However, VEGF levels decreased with erlotinib treatment in the third cell line. CONCLUSIONS: Erlotinib treatment promoted modest enhancement of radiation effects in canine osteosarcoma cells, and possessed activity as a single agent in some cell lines, indicating a potential role for EGFR inhibition in the treatment of a subset of osteosarcoma patients. The relative radioresistance of osteosarcoma cells does not appear to be related to EGFR signalling exclusively. Angiogenic responses to radiation and kinase inhibitors are similarly likely to be multifactorial and require further investigation.

Reason for euthanasia in dogs with urothelial carcinoma treated with chemotherapy or radiation therapy or both: A retrospective observational study.

BACKGROUND: Clients want to know the ultimate cause of death in their pet after cancer treatment. The cause of euthanasia and investigation of urinary obstruction in treated dogs with urothelial carcinoma (UC) has not been specifically reported in veterinary literature. HYPOTHESIS/OBJECTIVES: Our hypothesis was that the majority of treated dogs with UC are euthanized secondary to primary tumor factors, such as urinary obstruction. ANIMALS: Fifty-nine client-owned dogs diagnosed with UC. METHODS: Retrospective observational study on clinical signs and disease at euthanasia of dogs with UC treated by radiation therapy or chemotherapy or both. RESULTS: The median overall survival time (OST) of all dogs was 339 days (range, 17-1996; 95% confidence interval [CI], 185-392; interquartile range [IQR], 112-505). Of dogs deemed to have been euthanized because of UC (50/59, 85%), the primary cause was considered to be local progression in 31/50 (62%), most often because of perceived complete or partial urinary obstruction (24/31, 77%). No variables were found to be predictive of urinary obstruction. The overall documented metastatic rate was 56%. In dogs euthanized because of UC, metastasis was deemed to be the cause in 19/50 (38%) dogs. CONCLUSIONS AND CLINICAL IMPORTANCE: Regardless of the type of treatment, UC in dogs has a poor prognosis and there is a continuing need to improve treatments that focus on local control of the primary tumor, given its high contribution to the decision for euthanasia. Proactive management to avoid the high frequency of urinary obstruction may be worthy of future investigation.

Treatment of myeloid neoplasia with doxorubicin and cytarabine in 11 dogs.

Myelodysplastic syndrome (MDS) and acute myeloid leukaemia (AML) are primary myeloid neoplasms in dogs generally considered to have a poor outcome. In this study, we assessed toxicity, efficacy and outcome of concurrent administration of doxorubicin and cytarabine in 11 dogs with myeloid neoplasia. Bone marrow specimens were reviewed by three pathologists and classified as either MDS (n = 2), high grade MDS/early AML (MDS/AML; n = 4) or AML (n = 5). The median number of treatment cycles was 5 (range 1-9) and resolution of cytopenia was reported in 7 of 11 dogs including 2 dogs with MDS, 2 dogs with MDS/AML, and 3 dogs with AML. The median duration of remission in the seven responders was 344 days (range 109-1428) and the median overall survival for all dogs was 369 days. Adverse events consisted of predominantly low-grade gastrointestinal illness and myelosuppression. Three dogs developed grade V toxicity manifesting with heart failure (n = 2) at 369 and 1170 days after diagnosis and acute gastrointestinal side effects (n =1). Despite a limited sample size, these results suggest that a doxorubicin and cytarabine protocol may be considered as a therapeutic option in dogs with myeloid neoplasia. Protocol safety, in particular regarding myocardial toxicity, and efficacy should be further investigated.

Quantification of circulating tumour cells over time in dogs with appendicular osteosarcoma.

Enumeration of circulating tumour cells (CTC) has shown promise for prognostication and guidance of therapeutic decisions in human cancers. The objective of this study was to enumerate CTC over time in dogs with naturally occurring osteosarcoma (OSA), and to determine correlation with patient outcome. Twenty-six dogs with OSA and no evidence of metastatic disease at the time of amputation were enrolled. Dogs were assessed for lung metastases and CTC prior to and following amputation, and at each chemotherapy visit. Twenty-one dogs completed the study. Nineteen dogs were euthanized and two were alive and free of metastases. Overall survival time ranged from 88 to 1058 days (median survival time (MST) 374 days). Increased serum alkaline phosphatase activity, advanced age, and higher body weight were significantly associated with lower MST. Dogs with OSA had a mean of 356 (0 to 4443) CTC/106 leukocytes. In 12 of 15 dogs that developed radiographic evidence of metastasis, a pre-metastatic CTC spike was retrospectively detectable on average 36.5 (1-100 days) days prior to metastasis and was associated with significantly shorter MST (301 ± 64 vs. 626 ± 55 days; p = .0107). In a multivariable analysis, dogs with a CTC spike were 10× more likely to die compared with those without. These results suggest that a spike in CTC frequency precedes detection of metastasis in dogs with OSA and is associated with shorter survival. More frequent enumeration of CTC in a larger cohort of dogs with OSA may be warranted.

Retrospective study and review of ocular radiation side effects following external-beam Cobalt-60 radiation therapy in 37 dogs and 12 cats.

This retrospective study evaluated the ocular side effects of cancer-bearing dogs and cats treated with external-beam Cobalt-60 (Co-60) radiation in which one or both orbit(s) were included in the radiation field. A total of 37 dogs and 12 cats presented to the Ontario Veterinary College during the 10-year study period (1999-2009) were evaluated. The radiation protocols ranged from a maximum of 60 Gray (Gy) in 24 fractions for curative intent to a minimum of 8 Gy in 1 fraction for palliative treatment. The main ocular side effect reported in both dogs and cats was conjunctivitis (79% and 55%, respectively). Other common ocular side effects included eyelid lesions in dogs (44%), ulcerative keratitis in cats (36%), and keratoconjunctivitis sicca in both dogs and cats (44% and 27%, respectively). The high incidence of ocular side effects in both patient populations indicates a need for regular ophthalmic examinations as a component of routine follow-up for radiation therapy involving the orbit. Radiation damage to ocular tissues is also reviewed.

Étude rétrospective et examen des effets secondaires de la radiation oculaire après une radiothérapie externe au cobalt-60 chez 37 chiens et 12 chats. Cette étude rétrospective a évalué les effets secondaires oculaires chez des chiens et des chats atteints du cancer traités avec une radiation externe au cobalt-60 (Co-60) lorsque l'une ou l'autre des orbites étaient incluses dans le champ de radiation. Un total de 37 chiens et de 12 chats présentés à l'Ontario Veterinary College durant la période d'étude de 10 ans (1999­2009) ont été évalués. Les protocoles de radiation s'échelonnaient de 60 Gray (Gy) en 24 fractions pour un traitement curatif à un minimum de 8 Gy en 1 fraction pour un traitement palliatif. Le principal effet secondaire oculaire signalé chez les chiens et les chats était la conjonctivite (79 % et 55 %, respectivement). D'autres effets secondaires communs étaient des lésions des paupières chez les chiens (44 %), une kératite ulcérative chez les chats (36 %) et une kératoconjonctivite sèche chez les chiens et les chats (44 % et 27 %, respectivement). L'incidence élevée d'effets secondaires oculaires dans les deux populations de patients signale le besoin d'examens ophtalmologiques réguliers comme élément d'un suivi de routine pour la radiothérapie touchant l'orbite. Les dommages de la radiation aux tissus oculaires sont également examinés.(Traduit par Isabelle Vallières).

Modulation of mTOR signaling by radiation and rapamycin treatment in canine mast cell cancer cells.

Rapamycin has been reported to reduce cancer cell survival in certain tumors following radiation therapy, but the mechanisms driving this phenomenon are unclear. Rapamycin inhibits mTOR signaling, a pathway responsible for several essential cell functions. The objective of this study was to investigate the effects of rapamycin and radiation on the activation and inhibition of mTOR signaling and the relationship between mTOR signaling and DNA damage response in vitro using canine mast cell tumor (MCT) cancer cell lines. Rapamycin rapidly inhibited S6K phosphorylation in a dose-dependent manner. Ionizing radiation (3, 6, or 10 Gy) was able to activate mTOR signalling, but the combination of radiation and rapamycin maintained mTOR inhibition. The comet assay revealed that co-treatment with rapamycin induced modest increases in the severity of DNA damage to MCT cells, but that these differences were not statistically significant. Although the relationship between mTOR and DNA damage response in MCT cancer cell lines remains unclear, our findings suggest the possibility of interaction, leading to enhancement of radiation response.

Il a été rapporté que la rapamycine réduisait la survie des cellules cancéreuses dans certaines tumeurs après une radiothérapie, mais les mécanismes à l'origine de ce phénomène ne sont pas clairs. La rapamycine inhibe la signalisation mTOR, une voie responsable de plusieurs fonctions cellulaires essentielles. L'objectif de cette étude était d'étudier les effets de la rapamycine et des radiations sur l'activation et l'inhibition de la signalisation mTOR et la relation entre la signalisation mTOR et la réponse aux dommages à l'ADN in vitro à l'aide de lignées cellulaires cancéreuses de tumeurs mastocytaires canines (MCT). La rapamycine a rapidement inhibé la phosphorylation de S6K de manière dose-dépendante. Le rayonnement ionisant (3, 6 ou 10 Gy) a pu activer la signalisation mTOR, mais la combinaison de rayonnement et de rapamycine a maintenu l'inhibition de mTOR. Le test des comètes a révélé que le co-traitement avec la rapamycine induisait des augmentations modestes de la gravité des dommages à l'ADN des cellules MCT, mais que ces différences n'étaient pas statistiquement significatives. Bien que la relation entre mTOR et la réponse aux dommages à l'ADN dans les lignées cellulaires cancéreuses MCT reste incertaine, nos résultats suggèrent la possibilité d'une interaction, conduisant à une amélioration de la réponse aux radiations.(Traduit par Docteur Serge Messier).

Prognostic significance of the urokinase plasminogen activator system in tissue and serum of dogs with appendicular osteosarcoma.

Urokinase plasminogen activator (uPA) and its receptor uPAR promote cancer invasion and metastasis and are emerging therapeutic targets in both human and canine malignancies. While their clinical significance is well-characterized in multiple human tumor types, studies investigating their roles in osteosarcoma are lacking. The objectives of this study were to characterize serum and tissue uPA/uPAR expression in dogs with osteosarcoma and assess the prognostic significance. Serum samples and a tissue microarray of canine appendicular osteosarcoma were analyzed for uPA and uPAR expression by ELISA (n = 49) and immunohistochemistry (n = 38), respectively. Serum uPA activity was also measured by a chromogenic assay (n = 25). Survival analysis was performed by Kaplan-Meier survival analysis, log rank test, and Cox regression analysis. Serum uPA level was significantly higher in dogs with osteosarcoma than clinically healthy control dogs (median 1905 vs 1440 pg/ml, p = 0.008). The majority of canine osteosarcoma tissues expressed uPA (75.9%) or uPAR (77.6%), with 70.7% dual-positivity, indicating autocrine/paracrine activation of the pathway. Survival analysis revealed shorter progression free survival (PFS) in dogs with high serum uPA level in a discovery cohort (n = 29; median PFS 94 vs 266 days, p = 0.003) but not in a validation cohort (n = 23; median PFS 167 vs 490 days, p = 0.16). The difference was significant when both cohorts were combined (n = 49; median PFS 128 vs 266 days, p = 0.003). Serum uPAR and tissue uPA/uPAR levels were not prognostic. In Cox multivariate analysis, high serum uPA level and activity were both associated with poor prognosis, independent of serum ALP, tumor location, and peripheral lymphocyte/monocyte counts. These results indicate high utilization of the uPA pathway and association with disease progression in canine osteosarcoma. Further study involving prospective evaluation to confirm the prognostic significance is warranted. The high prevalence of tissue uPA and uPAR expression suggests the uPA system as a potential therapeutic target in canine osteosarcoma.

Pathology in Practice.

In collaboration with the American College of Veterinary Pathologists.

Evaluation of lymphocyte-specific programmed cell death protein 1 receptor expression and cytokines in blood and urine in canine urothelial carcinoma patients.

Urothelial carcinoma (UC) is the most common urinary tumour in dogs. Despite a range of treatment options, prognosis remains poor in dogs. In people, breakthroughs with checkpoint inhibitors have established new standards of care for muscle-invasive bladder cancer patients and elevated levels of programmed cell death protein 1 (PD-1) suggest immune checkpoint blockade may be a novel target for therapy. The goal of this study was to determine if canine UC patients express elevated levels of lymphocyte-specific PD-1 and/or urinary cytokine biomarkers compared to healthy dogs. Paired blood and urine were evaluated in 10 canine UC patients, five cystitis patients and 10 control dogs for lymphocyte-specific PD-1 expression via flow cytometry and relative cytokine expression. In UC patients, PD-1 expression was significantly elevated on CD8+ lymphocytes in urine samples. UC patients had a higher CD4:CD8 ratio in their urine compared to healthy dogs, however, there was no significant variation in the CD8:Treg ratio between any group. Cystitis patients had significantly elevated levels of CD4+ T cells, CD8+ T cells and Tregs in their blood samples compared to UC patients and healthy dogs. Cytokine analysis demonstrated significant elevations in urinary cytokines (granulocyte-macrophage colony-stimulating factor, interferon-gamma [IFN-γ], interleukin (IL)-2, IL-6 IL-7, IL-8 and IL-15, IP-10, KC-like, IL-18, monocyte chemoattractant protein-1 and tumour necrosis factor-alpha). Several of these cytokines have been previously correlated with both lymphocyte-specific PD-1 expression (IFN-γ, IL-2, IL-7 and IL-15) in muscle-invasive urothelial carcinoma in humans. Our results provide evidence of urinary lymphocyte PD-1 expression and future studies could elucidate whether veterinary UC patients will respond favourably to anti-PD-1 immune checkpoint inhibitor therapy.

Evaluation of PD-1 and PD-L1 expression in canine urothelial carcinoma cell lines.

Urothelial carcinoma (UC) is the most common urinary tumor in dogs and despite combinational therapies, only modest improvements in survival have been achieved in recent years. Given the utility of monoclonal antibodies against PD-1 and PD-L1 in human UC, we evaluated the protein and mRNA expression in three established canine urothelial carcinoma cell lines. Flow cytometry and western blot analysis confirmed cell line expression of both molecules in varying degrees. Reverse transcription PCR (RT-PCR) documented mRNA expression in all three cell lines for both PD-1 and PD-L1. Fluorescence microscopy was consistent with strong PD-1 and PD-L1 expression in the canine cell lines and was in line with previous human literature. Importantly, the flow cytometry work described in this study revealed higher cell intrinsic PD-1 expression in these cell lines which may have implications for tumor behavior and potential treatment opportunities in the future. Further work is necessary to determine the expression patterns in canine UC and potential for benefit with immunotherapy directed against PD-1 and PD-L1.