Targeted Suicide Gene Therapy with Retroviral Replicating Vectors for Experimental Canine Cancers

Cancer in dogs has increased in recent years and is a leading cause of death. We have developed a retroviral replicating vector (RRV) that specifically targets cancer cells for infection and replication. RRV carrying a suicide gene induced synchronized killing of cancer cells when administered with a prodrug after infection. In this study, we evaluated two distinct RRVs derived from amphotropic murine leukemia virus (AMLV) and gibbon ape leukemia virus (GALV) in canine tumor models both in vitro and in vivo. Despite low infection rates in normal canine cells, both RRVs efficiently infected and replicated within all the canine tumor cells tested. The efficient intratumoral spread of the RRVs after their intratumoral injection was also demonstrated in nude mouse models of subcutaneous canine tumor xenografts. When both RRVs encoded a yeast cytosine deaminase suicide gene, which converts the prodrug 5-fluorocytosine (5-FC) to the active drug 5-fluorouracil, they caused tumor-cell-specific 5-FC-induced killing of the canine tumor cells in vitro. Furthermore, in the AZACF- and AZACH-cell subcutaneous tumor xenograft models, both RRVs exerted significant antitumor effects. These results suggest that RRV-mediated suicide gene therapy is a novel therapeutic approach to canine cancers.

Potential therapeutic efficiency of pan-ERBB inhibitors for canine glioma

Canine glioma is one of the most common brain tumors with poor prognosis, making effective chemotherapy highly desirable. Previous studies have suggested that ERBB4, a signaling molecule involving one of the epidermal growth factor receptors (EGFR), may be a promising therapeutic target. In this study, the anti-tumor effects of pan-ERBB inhibitors, which can inhibit the phosphorylation of ERBB4, were evaluated both in vitro and in vivo using a canine glioblastoma cell line. The results demonstrated that both afatinib and dacomitinib effectively reduced the expression of phosphorylated ERBB4, and significantly decreased the number of viable cells, ultimately prolonging the survival time of orthotopically xenografted mice. Further downstream of ERBB4, afatinib was found to suppress the expression of phosphorylated Akt and phosphorylated Extracellular signal-related kinases1 and 2 (ERK1/2) and induced apoptotic cell death. Thus, pan-ERBB inhibition is a promising therapeutic strategy for the treatment of canine gliomas.

microRNA-203 inhibits migration and invasion of canine tonsillar squamous cell carcinoma cells by targeting SLUG

Objective

Squamous cell carcinoma (SCC) occurring in the tonsils (TSCC) has a poorer prognosis than SCC occurring in other regions of the oral cavity (non-tonsillar SCC [NTSCC]) because it easily metastasizes to distant organs. This study aimed to elucidate the molecular mechanisms underlying the migration and invasion of TSCC cells in vitro.

Materials and methods

This study focused on differential microRNA (miRNA) expression using microRNA microarrays and quantitative polymerase chain reaction in canine TSCC and NTSCC tissues and cell lines. A target gene of the miRNA involved in cell migration and invasion was validated by wound healing, transwell, and luciferase assays.

Results

miR-203 expression was lower in TSCC tissues than in the normal oral mucosa and NTSCC tissues. Transfection of the miR-203 mimic resulted in the downregulation of mesenchymal marker protein expression and attenuation of cell migration and invasion in TSCC cells, but not in NTSCC cells. A dual-luciferase assay revealed that miR-203 directly targeted the mesenchymal transcription factor SLUG. SLUG overexpression enhances the migration of TSCC cells.

Conclusion

Our study indicates that the miR-203/SLUG axis may be involved in the metastatic mechanisms of TSCC.

Contrast-enhanced CT features of pyloric lesions in 17 dogs: Case series

Pyloric outflow obstructions can be caused by several types of lesions. When a thickened gastric wall and pyloric mass are detected, malignant neoplasia must be differentiated from chronic hypertrophic pyloric gastropathy. CT can characterize gastric tumors. However, based on the authors' review of the literature, there is limited information about the CT findings of pyloric lesions. The purpose of this retrospective case series study was to assess the CT findings of canine pyloric lesions. The following CT parameters were recorded: anatomical area, involved area, lesion shape, growth patterns of wall thickening lesions, enhancement pattern of the lesion in the early and delayed phases, lymphomegaly, and pulmonary metastasis. Seventeen dogs were included in this study and had the following final diagnoses: hyperplasia (five dogs), adenoma (five dogs), adenocarcinoma (three dogs), gastrointestinal stromal tumor (GIST; two dogs), polyposis (one dog), and pyogenic granuloma (one dog). Hyperplasia, adenoma, and polyposis formed mass lesions that involved the mucosal layer. Lymphomegaly was detected in two Jack Russell terriers with hyperplasia; however, the causes were unknown because we did not perform biopsies. All adenocarcinomas formed wall-thickened lesion that involved the outer layer, with lymphomegaly. All GISTs formed mass lesion that involved the outer layer. The pyogenic granulomas formed symmetric wall-thickened lesion that involved the mucosal and outer layers. CT facilitated the characterization of canine pyloric lesions using contrast enhancement, based on the involved area and lesion shape. However, polyposis may require caution in diagnosis based on CT findings alone.

Fetal outcomes with and without the use of sugammadex in pregnant patients undergoing non-obstetric surgery: a multicenter retrospective study

BACKGROUND

The influence of sugammadex exposure during pregnancy on progesterone withdrawal and miscarriage is unknown. We aimed to compare the fetal outcomes in pregnant patients who had undergone non-obstetric surgery with and without sugammadex.

METHODS

We retrospectively reviewed the medical charts of pregnant women who underwent non-obstetric surgery at three tertiary perinatal care centers in Japan from January 2013 to December 2020. The women were divided into those who received general anesthesia with sugammadex (GA with SGX) and those who received general anesthesia without sugammadex (GA without SGX). We compared miscarriages and preterm births within four weeks after surgery.

RESULTS

Among the 124 women, 73 and 51 were included in the GA with SGX and GA without SGX groups, respectively. The two groups showed no differences in the rate of miscarriages or preterm births (3.0 % vs 4.3 %; odds ratio 1.42, 95 % confidence interval 0.19 to 10.47; P = 1.00). The SGX and no SGX groups were missing outcomes for 8.2 % and 7.8 % of cases, respectively.

CONCLUSIONS

Having GA with SGX or GA without SGX did not result in different rates of miscarriage or preterm birth within four weeks after the procedure. These findings do not exclude a potential association between sugammadex exposure during pregnancy and adverse pregnancy outcomes. Missing data may have obscured possible adverse outcomes from sugammadex exposure.

Perioperative Management of Robotic-Assisted Gynecological Surgery in a Super Morbidly Obese Patient

We report the perioperative management of a 32-year-old woman with super-morbid obesity (body mass index (BMI) of 60.9 kilograms per meter squared (kg/m²)) who underwent a robotic-assisted total laparoscopic hysterectomy in a hospital that was not specialized for obese patients. She successfully reduced her BMI by 10% using dietary restrictions in five weeks, and her surgery was performed two weeks later by consultation between gynecologists and anesthesiologists. This case demonstrates that the determination of the optimal time for surgery by consultation between physicians is crucial in the care of such a complex patient in hospitals that are not specialized for morbidly obese patients. Weight reduction in the preoperative period should be considered for super-morbid obesity patients with malignant diseases, even if the duration of preoperative optimization is shorter than four to eight weeks.

Single-modality palliative radiotherapy versus palliative radiotherapy after chemotherapy failure for cats with nasal lymphoma

Published studies describing outcomes for cats with nasal lymphoma (NLSA) receiving first-line palliative radiation (PRT) versus PRT after chemotherapy failure are currently lacking. The aims of this retrospective observational study were to compare outcomes for cats with NLSA that were treated with these two methods. A total of 48 cats were included in analyses; 32 receiving PRT alone and 16 receiving PRT after chemotherapy failure. The treatment response, progression-free survival (PFS), disease-specific survival (DSS), overall survival (OS), and incidence rate of systemic disease were compared between the two groups. The overall response rate (ORR) was calculated from the same target lesions between pre-RT (within a week before starting PRT) and post-RT (on date of PRT completion) by computed tomography (CT) imaging. The ORR was 94% in cats that received PRT alone, 13 had a complete response (CR) and 17 had a partial response (PR). The ORR was 88% in cats that received PRT after chemotherapy failure, with five having CR and nine with PR. There were no significant differences in the ORR between the two groups. The PFS, DSS, and OS significantly increased in the cats that received PRT alone compared to the cats that received PRT after chemotherapy failure (median PFS: 336 vs 228 days, P = 0.0012, median DSS: 360 vs 242 days, P = 0.0025, median OS: 346 vs 242 days, P = 0.0036, respectively). The incidence rate of systemic disease significantly increased in 75% (12/16) of cats receiving PRT after chemotherapy failure compared to 41% (13/32) of cats receiving PRT alone. The results suggested that clinical outcomes may improve in cats with NLSA with first-line PRT compared to PRT after chemotherapy failure.

Functional analysis of the miR-145/Fascin1 cascade in canine oral squamous cell carcinoma

OBJECTIVES

Canine oral squamous cell carcinoma (SCC) often develops in the gingiva and tonsils. The biological behaviour of canine oral SCC is similar to that of human head and neck SCC (HNSCC). Inhibiting invasion and metastasis is major importance for the treatment of canine and human HNSCC. In this study, the significance of microRNA (miR)-145 and Fascin1 (FSCN1) in the invasion of canine oral SCC was explored.

MATERIALS AND METHODS

Canine oral SCC tissues and cell lines were used for miR-145 and FSCN1 expression analysis via real-time PCR and immunohistochemistry. Canine oral SCC cell lines were used for in vitro assays.

RESULTS

miR-145 was downregulated while FSCN1 mRNA was upregulated in canine oral SCC. Immunohistochemistry revealed that FSCN1 was upregulated in SCC when compared to normal mucosa. Transfection of canine SCC cells with miR-145 or FSCN1 siRNA suppressed cell growth and attenuated cell migration as well as invasion by inhibiting the epithelial-to-mesenchymal transition. Furthermore, the promoter region of miR-145 was highly methylated in SCC cell lines and tissues.

CONCLUSION

The expression profile and functions of miR-145 in canine oral SCC are similar to those in human HNSCC. Thus, canine oral SCC may represent a valuable preclinical model for human HNSCC.

Comparing the CT and MRI findings for canine primary hepatocellular lesions

BACKGROUND

Triple-phase CT and gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) MRI have been used to differentiate hepatocellular carcinomas (HCCs) in dogs.

METHODS

This retrospective case series aimed to compare the CT findings with MRI findings of 20 canine hepatocellular lesions, including eight poorly/moderately-differentiated HCCs, eight well-differentiated HCCs and four hyperplasias. CT data were analysed, and the following parameters were noted: vessel enhancement, enhancement pattern in the equilibrium phase, maximal transverse diameter, the lowest enhancement, and the attenuation values of each hepatocellular lesion in the precontrast and triple-phase series, including the arterial phase, portal phase and equilibrium phase. MRI data were analysed, and the following parameters were noted: signal intensities of each hepatocellular lesion on T2-weighted images and T1-weighted images, and signal intensity ratio of the hepatocellular lesions in the hepatobiliary phase.

RESULTS

In 62.5% of poorly/moderately-differentiated HCC and 75% of well-differentiated HCC, presumptive necrosis was detected on CT and MRI. In the hepatobiliary phase on MRI, the median signal intensity ratio of poorly/moderately-differentiated HCC (0.54 [range: 0.3-0.71]) was significantly lower than that of well-differentiated HCC (0.75 [range: 0.6-0.96]) and hyperplasia (0.79 [range: 071-0.98]; p = 0.02 and p = 0.02, respectively).

CONCLUSION

Gd-EOB-DTPA-enhanced MRI may be a superior modality for differentiating hepatocellular origin lesions.

Preliminary study of CT features of intermediate- and high-grade alimentary lymphoma and adenocarcinoma in cats

CASE SERIES SUMMARY

The ultrasonographic findings of many feline intestinal tumours are similar. This study evaluated the CT features of intermediate- and high-grade alimentary lymphoma and adenocarcinoma in cats. CT was performed on six cats with adenocarcinoma and 14 cats with lymphoma. Comparisons between tumour types were conducted, focusing on CT features, including obstruction (present or absent), growth patterns of lesions (symmetry or asymmetry), layering enhancement (present or absent), location of the lesion, number of lesions (solitary or multiple), lymphadenopathy (present or absent), location of lymphadenopathy, pulmonary metastasis (present or absent) and maximum thickness (mm) of the lesion. The cats with adenocarcinoma (n = 5/6 [83%]) experienced intestinal obstruction significantly more often than cats with lymphoma (n = 0/14 [0%]; P = 0.0004). Layering enhancement was observed significantly more often in cats with adenocarcinoma (n = 6/6 [100%]) than in cats with lymphoma (n = 1/14 [7%]; P = 0.0002). Lymphadenopathy was detected significantly more often in cats with lymphoma (n = 14/14 [100%]) than in cats with adenocarcinoma (n = 2/6 [33%]) (P = 0.003). In cats with lymphoma, the intestine (12.1 ± 3.9 mm) was significantly thicker than that in cats with adenocarcinoma (6.4 ± 2.3 mm; P = 0.005).

RELEVANCE AND NOVEL INFORMATION

To the best of our knowledge, no reports have described the characteristics of feline intestinal tumours using CT. Layering enhancement was observed in cats with intestinal adenocarcinomas. No layering enhancement was observed in alimentary lymphoma in cats, but enlarged regional nodes were noted. Lesions with lymphoma were thicker than those with adenocarcinoma. These findings may help differentiate between adenocarcinomas and lymphomas.

SLUG is upregulated and induces epithelial mesenchymal transition in canine oral squamous cell carcinoma

SLUG, encoded by the Snai2 gene, is known to play a role in epithelial-mesenchymal transition (EMT), which contributes to cell invasion and metastasis in some types of human carcinomas. However, the mechanisms and roles of EMT in canine squamous cell carcinoma (SCC) have not yet been elucidated. We have previously established canine oral SCC cell lines, including tonsillar SCC, and in this study, we evaluated the effects of SLUG on the phenotypes regarding EMT of canine SCC cells. First, immunohistochemical analysis revealed that SLUG is upregulated in canine oral SCC tissues compared to that in non-tumoural oral mucosa. Furthermore, gain-of-function and loss-of-function of SLUG revealed that SLUG partly contributed to migration and invasion of cells, as well as the upregulation of EMT markers such as vimentin and SNAIL. Thus, the current study suggests that SLUG promotes cell migration and invasion through EMT induction in canine oral SCC, as well as human cancers.

Radiotherapy-induced tumor lysis syndrome in a dog with thymoma

A 13-year-old, female, mixed-breed dog with a huge cranial mediastinal mass underwent radiotherapy (RT). On the following day, the dog presented with lethargy and anorexia. Hematological examination revealed elevated levels of blood urea nitrogen, creatinine, inorganic phosphorus, potassium, lactate dehydrogenase, creatine phosphokinase and aspartate aminotransferase, decreased calcium level, and metabolic acidosis. Urine output markedly decreased. The patient recovered with fluid therapy and diuretic therapy; however, died suddenly from an unknown cause 11 days after RT completion. Histopathological examination after necropsy showed thymoma in the cranial mediastinum and extensive tubular necrosis of both kidneys which may be due to RT-induced tumor lysis syndrome (TLS). This report suggests that the risk of TLS should be evaluated in dogs with thymoma who undergo RT.

The NRG3/ERBB4 signaling cascade as a novel therapeutic target for canine glioma

Canine glioma is a common brain tumor with poor prognosis despite surgery and/or radiation therapy. Therefore, newer and more effective treatment modalities are needed. Neuregulin 3 (NRG3) has known to be a ligand of ERBB4. This study aimed to investigate the usefulness of the NRG3/ERBB4 signaling cascade as a novel therapeutic target in canine glioma. We found out that microRNA (miR)-190a was downregulated in canine brain tumor tissues, including glioma and meningioma. miR-190a directly targeted NRG3 and inhibited the growth of canine glioma cells. The level of p-Akt, which is a downstream target of ERBB4 signaling, was decreased by transfection with miR-190a. NRG3 silencing also suppressed cell growth and decreased the levels of p-Akt and p-ERK1/2, and NRG3 overexpression exhibited opposed effects in canine glioma J3T-1 cells. The mRNA level of erbb4 was significantly upregulated in glioma tissues compared with that in normal brain tissues and meningioma tissues. Furthermore, compared with gefitinib and lapatinib, afatinib exerted a greater inhibitory effect on the growth of canine glioma cells. In conclusion, NRG3/ERBB4 signaling is negatively regulated by miR-190a and contributes to the growth of canine glioma cells, indicating that it may be a promising therapeutic target in canine glioma.

Assessment of biomarkers influencing treatment success on small intestinal lymphoma in dogs

This study aimed to determine a reliable therapeutic biomarker for localized small intestinal lymphoma (SIL) in dogs based on clinical and histopathological features. We retrospectively investigated 84 dogs with localized SIL, including 36 dogs receiving surgery and 48 dogs receiving chemotherapy. The dogs receiving surgery were divided into two subgroups: 18 dogs (group 1) with overall survival (OS) <120 days (median OS) and 18 dogs (group 2) with OS ≥120 days. Correspondingly, the dogs receiving chemotherapy were divided into 24 dogs (group 3) with OS <98 days (median OS) and 24 dogs (group 4) with OS ≥98 days. Clinical, haematological, histopathological and immunohistochemical analyses were comparatively evaluated among the four subgroups. There was no significant difference in OS between the surgery and chemotherapy groups. In dogs receiving surgery, the rate of Ki67-positive cells was significantly increased in group 1 compared to group 2 and showed no significant difference between groups 3 and 4. In dogs receiving chemotherapy, the rate of O6-methylguanine-DNA methyltransferase (MGMT) was significantly higher in group 3 than in group 4 and showed no significant difference between groups 1 and 2. Additionally, our data showed that OS in dogs with higher Ki67 expression might be significantly increased by chemotherapy than by surgery, that of those with higher MGMT expression might be significantly increased by surgery than by chemotherapy, and Ki67 and MGMT were independent of each other. Indices of Ki67 and MGMT are suggested therapeutic biomarkers to determine the optimal first-line treatment for localized SIL in dogs.

Establishing cell lines for canine tonsillar and non-tonsillar oral squamous cell carcinoma and identifying characteristics associated with malignancy

Canine tonsillar squamous cell carcinoma (TSCC) shows a higher metastasis rate than non-tonsillar oral SCC (NTSCC). The mechanisms of metastasis for TSCC have been less studied, because both TSCC and NTSCC cell lines are few. In this study, 6 cloned TSCC (TSCCLN#1-#6), which were from a metastatic lymph node, and 2 cloned NTSCC (oSCC-1 and -4) cell lines, which were from the primary lesion, were established, and their characteristics were evaluated in vitro and in vivo. Results showed that increased expression level of Vimentin in TSCC cell lines and increased expression levels of mesenchymal markers including Vimentin, Snail, and Slug in NTSCC cell lines corelated with the malignant phenotypes such as the cell growth and colony formation abilities in vitro. However, expression levels of mesenchymal markers and in vitro characteristics were unrelated to tumorigenic ability in nude mice. Additionally, the expression levels of E-cadherin and Vimentin were also evaluated by immunohistochemistry using the formalin-fixed paraffin embedded canine oral SCC tissues, and the results show that the expression level of Vimentin in TSCC was higher than in NTSCC. In conclusion, the cell lines established in this study might contribute to elucidating the mechanisms involved in TSCC metastasis.

An aortic body carcinoma with sarcomatoid morphology and chondroid metaplasia in a French Bulldog

An 11-year-old female French Bulldog was presented with a mass at the base of the heart, detected by X-ray and echocardiography. Clinical abnormality included abdominal retention by ascites. Radiation therapy was performed for 5 weeks. The mass volume didn’t change during the radiotherapy. The condition became worse and the dog died 6 months after the initial presentation and necropsy was performed. Grossly, the mass, 12.5 × 6.5 × 6.0 cm in size, was found at the base of the heart. Histopathological examination revealed that cardiac mass was composed of alveolar, bundle and diffuse proliferation of neoplastic cells. Most of the neoplastic cells showed a spindle morphology; in some areas small round or polyhedral neoplastic cells were observed. Occasional cartilage metaplasia was seen multifocal in the mass, and it was surrounded by the sarcomatoid proliferation. Electron microscopy revealed a few neuroendocrine granules in the cytoplasm of spindle and polyhedral neoplastic cells. Metastatic cells in the lungs which had not irradiated demonstrated typical morphology of aortic body tumors. Based on these findings, the case was diagnosed as an aortic body carcinoma with sarcomatoid morphology and chondroid metaplasia.

Combination Therapy with Reovirus and ATM Inhibitor Enhances Cell Death and Virus Replication in Canine Melanoma

Oncolytic virotherapy using reovirus is a promising new anti-cancer treatment with potential for use in humans and dogs. Because reovirus monotherapy shows limited efficacy in human and canine cancer patients, the clinical development of a combination therapy is necessary. To identify candidate components of such a combination, we screened a 285-compound drug library for those that enhanced reovirus cytotoxicity in a canine melanoma cell line. Here, we show that exposure to an inhibitor of the ataxia telangiectasia mutated protein (ATM) enhances the oncolytic potential of reovirus in five of six tested canine melanoma cell lines. Specifically, the ATM inhibitor potentiated reovirus replication in cancer cells along with promoting the lysosomal activity, resulting in an increased proportion of caspase-dependent apoptosis and cell cycle arrest at G2/M compared to those observed with reovirus alone. Overall, our study suggests that the combination of reovirus and the ATM inhibitor may be an attractive option in cancer therapy.

PTEN, A Target of Microrna-374b, Contributes to the Radiosensitivity of Canine Oral Melanoma Cells

Canine oral malignant melanoma (CoMM) is often treated by radiation therapy in veterinary medicine. However, not all cases are successfully managed by this treatment. For improved efficacy of radiation therapy, biomarkers predicting the radiosensitivity of melanoma cells need to be explored. Here, we, first, developed the radioresistant CoMM cell line, KMeC/R. We found that the expression level of phosphatase and tensin homolog (PTEN) of KMeC/R cells was significantly downregulated compared with KMeC cells. Overexpression of PTEN successfully restored the radiosensitivity of KMeC/R cells, and silencing of PTEN significantly increased the radioresistance of the CoMM cells tested. Next, we focused on microRNAs (miRNAs) to explore the mechanisms of downregulation of PTEN in KMeC/R cells. miR-374b was upregulated in KMeC/R cells compared with that in KMeC cells and in the irradiated CoMM cells tested. Furthermore, miR-374b directly targeted PTEN based on the luciferase activity assay. Moreover, the extrinsic miR-374b significantly increased the radioresistance of KMeC cells. In addition, the expression level of PTEN was significantly downregulated and that of miR-374b tended to be upregulated in recurrent CoMM tissues after radiation therapy compared with the pre-treatment tissues. Thus, the current study suggested that the miR-374b/PTEN signaling pathway possibly plays an important role in CoMM radiosensitivity.

Establishment of a novel experimental model for muscle-invasive bladder cancer using a dog bladder cancer organoid culture

In human and dogs, bladder cancer (BC) is the most common neoplasm affecting the urinary tract. Dog BC resembles human muscle‐invasive BC in histopathological characteristics and gene expression profiles, and could be an important research model for this disease. Cancer patient‐derived organoid culture can recapitulate organ structures and maintains the gene expression profiles of original tumor tissues. In a previous study, we generated dog prostate cancer organoids using urine samples, however dog BC organoids had never been produced. Therefore we aimed to generate dog BC organoids using urine samples and check their histopathological characteristics, drug sensitivity, and gene expression profiles. Organoids from individual BC dogs were successfully generated, expressed urothelial cell markers (CK7, CK20, and UPK3A) and exhibited tumorigenesis in vivo. In a cell viability assay, the response to combined treatment with a range of anticancer drugs (cisplatin, vinblastine, gemcitabine or piroxicam) was markedly different in each BC organoid. In RNA‐sequencing analysis, expression levels of basal cell markers (CK5 and DSG3) and several novel genes (MMP28,CTSE,CNN3,TFPI2,COL17A1, and AGPAT4) were upregulated in BC organoids compared with normal bladder tissues or two‐dimensional (2D) BC cell lines. These established dog BC organoids might be a useful tool, not only to determine suitable chemotherapy for BC diseased dogs but also to identify novel biomarkers in human muscle‐invasive BC. In the present study, for the 1st time, dog BC organoids were generated and several specifically upregulated organoid genes were identified. Our data suggest that dog BC organoids might become a new tool to provide fresh insights into both dog BC therapy and diagnostic biomarkers.

Reovirus changes the expression of anti-apoptotic and proapoptotic proteins with the c-kit downregulation in canine mast cell tumor cell lines

Although reovirus has reached phase II and III clinical trials in human cancers, the exact mechanism of reovirus oncolysis is still not completely understood. Previously, we have shown that canine mast cell tumor (MCT) cell lines were highly susceptible to reovirus, as compared with other kinds of canine cancer cell lines. In this study, we showed that reovirus infection not only led to the dephosphorylation but also downregulation of c-kit in four canine MCT cell lines, where c-kit activation is required for proliferation. Consistent with c-kit dysregulation, downstream signaling of c-kit, the level of Ras-GTP and phosphorylation of all the downstream effectors of Ras (Raf, MEK, and ERK) and Akt decreased in all the cell lines after reovirus infection, except for Akt in one of cell lines. Pro-apoptotic and anti-apoptotic proteins such as Bim, Bad and Mcl-1 were also altered by reovirus infection in these cell lines. In short, reovirus infection degraded c-kit in all the canine MCT cell lines, leading to the downregulation of downstream signaling of c-kit, which may relate to the cell death induced by reovirus.

Synthetic microRNA-205 exhibited tumour suppression in spontaneous canine malignant melanoma by intratumoral injection

MicroRNAs (miRNA) are small, noncoding RNA molecules consisting of 18 to 25 nucleotides. Malignant melanomas (MMs) are one of the most common malignancies in both dogs and humans. We previously reported that chemically modified synthetic miRNA-205 (miR-205BP/S3) inhibits melanoma growth in vitro and in vivo. The present study aimed to evaluate the efficacy of intratumoral administration of synthetic miR-205 for spontaneous CMMs and to evaluate its potential as systemic therapy. Ten dogs with various stages of MM were treated with miR-205BP/S3 injected into tumours. Adverse effects (AEs) were assessed in accordance with the Veterinary Cooperative Oncology Group-Common Terminology Criteria for Adverse Events (VCOG-CTCAE) v1.1 guidelines. Five cases attained complete remission (CR), three attained stable disease (SD), and two cases displayed characteristics of progressive disease (PD). In all cases, no changes were observed in the blood parameters upon miRNA administration, and miR-205BP/S3 administration did not yield any side effects. The present results suggest that intratumoral administration of miR-205BP/S3 is a potentially applicable treatment for canine melanoma.

Anti-tumour activity of oncolytic reovirus against canine histiocytic sarcoma cells

Canine histiocytic sarcoma is an aggressive, fatal neoplastic disease with a poor prognosis. Lomustine is generally accepted as the first-line systemic therapy, although this compound does not provide complete regression. Therefore, research into a novel approach against canine histiocytic sarcoma is needed. However, anti-tumour effects of oncolytic therapy using reovirus against histiocytic sarcoma are unknown. Here, we showed that reovirus has oncolytic activity in canine histiocytic sarcoma cell lines in vitro and in vivo. We found that reovirus can replicate and induce caspase-dependent apoptosis in canine histiocytic sarcoma cell lines. A single intra-tumoural injection of reovirus completely suppressed the growth of subcutaneously grafted tumours in NOD/SCID mice. Additionally, we demonstrated that susceptibility to reovirus-induced cell death was attributable to the extent of expression of type I interferons induced by reovirus infection in vitro. In conclusion, oncolytic reovirus appears to be an effective treatment option for histiocytic sarcoma, and therefore warrants further investigation in early clinical trials.

Prognostic significance of midline shift of the olfactory or frontal lobes of the brain in canine nasal carcinomas treated by palliative radiotherapy: a pilot study

Canine nasal carcinomas are often treated with radiotherapy. Presence of lysis of the cribriform plate by tumor invasion (stage 4 by modified Adams’s staging system) is a well-known prognostic factor. In this study, dogs with stage 4 disease were divided into two subgroups based on the presence or absence of midline shift of the olfactory or frontal lobes of the brain (Stage 4a: without presence of midline shift. Stage 4b: with midline shift). The median survival time of dogs with midline shift was significantly shorter than that of dogs without midline shift (64 vs. 208 days). Our results indicate that the finding of a midline shift might have a prognostic significance in dogs with nasal carcinoma treated with radiotherapy.

Development and characterization of monoclonal antibodies against canine PD-1 and PD-L1

Recent research has focused on immunotherapy, particularly with regard to cancer treatment. Programmed death-1 and programmed death ligand 1 (PD-1/PD-L1) pathway blockade is a central topic of the promising immunotherapy field. In veterinary medicine, observations of the PD-1/PD-L1 pathway, including the relationship between immune cells and diseases, have increased. In this study, monoclonal antibodies specific to canine PD-1 and PD-L1 were developed, and the antibodies against PD-1 and PD-L1 bind to PD-1 and PD-L1 overexpressing cells, respectively. Additionally, each antibody interfered with the interaction between PD-1 and PD-L1. The expression of PD-1 and PD-L1 was detected on activated T cells from canine peripheral blood mononuclear cells (PBMC), and, remarkably, was the first recorded instance of PD-L1 expression on canine immature dendritic cells. Production of IFN-γ by activated T cells increased significantly when incubated with anti-PD-1 antibody alone and with both anti-PD-1 and anti-PD-L1 antibodies, revealing the functional effects of the antibodies. The antibodies will be useful for research on immune systems and may be the first passive immunotherapy approach in canine cancer patients.

Establishment of a dog primary prostate cancer organoid using the urine cancer stem cells

Dog spontaneously develop prostate cancer (PC) like humans. Because most dogs with PC have a poor prognosis, they could be used as a translational model for advanced PC in humans. Stem cell‐derived 3‐D organoid culture could recapitulate organ structures and physiology. Using patient tissues, a human PC organoid culture system was established. Recent study has shown that urine cells also possess the characteristic of stem cells. However, urine cell‐derived PC organoids have never been produced. Therefore, we generated PC organoids using the dog urine samples. Urine organoids were successfully generated from each dog with PC. Each organoid showed cystic structures and resembled the epithelial structures of original tissues. Expression of an epithelial cell marker, E‐cadherin, and a myofibloblast marker, α‐SMA, was observed in the urine organoids. The organoids also expressed a basal cell marker, CK5, and a luminal cell marker, CK8. CD49f‐sorted basal cell organoids rapidly grew compared with CD24‐sorted luminal cell organoids. The population of CD44‐positive cells was the highest in both organoids and the original urine cells. Tumors were successfully formed with the injection of the organoids into immunodeficient mice. Treatment with a microtubule inhibitor, docetaxel, but not a cyclooxygenase inhibitor, piroxicam, and an mTOR inhibitor, rapamycin, decreased the cell viability of organoids. Treatment with a Hedgehog signal inhibitor, GANT61, increased the radiosensitivity in the organoids. These findings revealed that PC organoids using urine might become a useful tool for investigating the mechanisms of the pathogenesis and treatment of PC in dogs.

Oncolytic reovirus therapy: Pilot study in dogs with spontaneously occurring tumours

Oncolytic virotherapy is a novel treatment involving replication-competent virus in the elimination of cancer. We have previously reported the oncolytic effects of reovirus in various canine cancer cell lines. This study aims to establish the safety profile of reovirus in dogs with spontaneously occurring tumours and to determine a recommended dosing regimen. Nineteen dogs with various tumours, mostly of advanced stages, were treated with reovirus, ranging from 1.0 × 10⁸ to 5.0 × 10⁹ TCID₅₀ given as intratumour injection (IT) or intravenous infusion (IV) daily for up to 5 consecutive days in 1 or multiple treatment cycles. Adverse events (AEs) were graded according to the Veterinary Cooperative Oncology Group- Common Terminology Criteria for Adverse Events (VCOG-CTCAE) v1.1 guidelines. Viral shedding, neutralizing anti-reovirus antibody (NARA) production and immunohistochemical (IHC) detection of reovirus protein in the tumours were also assessed. AE was not observed in most dogs and events were limited to Grade I or II fever, vomiting, diarrhoea and inflammation of the injected tumour. No infectious virus was shed and all dogs had elevated NARA levels post-treatment. Although IHC results were only available in 6 dogs, 4 were detected positive for reovirus protein. In conclusion, reovirus is well-tolerated and can be given safely to tumour-bearing dogs according to the dosing regimen used in this study without significant concerns of viral shedding. Reovirus is also potentially effective in various types of canine tumours.