Modeling the influence of cell-cell contact and TGF-ß signaling on the epithelial mesenchymal transition in MCF7 breast carcinoma cells.

The epithelial mesenchymal transition (EMT) is a process by which cells lose their adhesive nature and gain the migratory properties associated with mesenchymal cells. This transition allows cells to migrate away from a primary tumor while maintaining their newly acquired invasive behavior, suggesting that there is a bistable switch between the epithelial and mesenchymal phenotypes. In recent experimental work, we found evidence of this bistability in the MCF7 breast carcinoma cell line (Gasior et al., 2019). Underlying the complex processes governing EMT, we identify a feedback loop between E-cadherin, a protein involved in cellular adhesion, and Slug, a transcription factor that is upregulated during EMT. Here, we present a simple mathematical model that examines the relationship between E-cadherin and Slug in response to pro-epithelial and pro-mesenchymal factors, cell-cell contact and TGF-ß, respectively. We hypothesize that cell-cell contact is a critical component in the transition from the epithelial to the mesenchymal phenotype and that it is possible to initiate EMT with the loss of cell-cell contact or the activation of the TGF-ß signaling pathway. We propose a reversible bistable switch in response to a loss of cell-cell contact but an irreversible bistable switch when the cell is exposed to TGF-ß. Taken together, this model shows that acquiring and retaining invasive behavior by cells with high levels of cell-cell contact is not impossible but, instead, depends on the cooperation between the two switches. The predictions of this model for E-cadherin and Slug levels were compared against relative gene expression data from our recent experiments with MCF7 cells (Gasior et al., 2019). Our model works well to predict E-cadherin and Slug mRNA expression in low confluence experiments, while also highlighting issues that arise when comparing experimental results to theoretical predictions.

International Guidelines for Veterinary Tumor Pathology: A Call to Action.

Standardization of tumor assessment lays the foundation for validation of grading systems, permits reproducibility of oncologic studies among investigators, and increases confidence in the significance of study results. Currently, there is minimal methodological standardization for assessing tumors in veterinary medicine, with few attempts to validate published protocols and grading schemes. The current article attempts to address these shortcomings by providing standard guidelines for tumor assessment parameters and protocols for evaluating specific tumor types. More detailed information is available in the Supplemental Files, the intention of which is 2-fold: publication as part of this commentary, but more importantly, these will be available as "living documents" on a website (www.vetcancerprotocols.org), which will be updated as new information is presented in the peer-reviewed literature. Our hope is that veterinary pathologists will agree that this initiative is needed, and will contribute to and utilize this information for routine diagnostic work and oncologic studies. Journal editors and reviewers can utilize checklists to ensure publications include sufficient detail and standardized methods of tumor assessment. To maintain the relevance of the guidelines and protocols, it is critical that the information is periodically updated and revised as new studies are published and validated with the intent of providing a repository of this information. Our hope is that this initiative (a continuation of efforts published in this journal in 2011) will facilitate collaboration and reproducibility between pathologists and institutions, increase case numbers, and strengthen clinical research findings, thus ensuring continued progress in veterinary oncologic pathology and improving patient care.

Alternative lengthening of telomeres does exist in various canine sarcomas.

Alternative lengthening of telomeres (ALT) is a telomere maintenance mechanism (TMM) found in some human tumors such as sarcomas. Canine tumors are not characterized for ALT and the study aim was to identify if the ALT phenotype exists in canine sarcomas. Sixty-four canine sarcoma samples (20 snap-frozen, 44 FFPE) as well as six canine sarcoma cell lines were screened for ALT by C-circle assay. ALT was further evaluated by measuring telomere length via qPCR and telomere restriction-fragments including pulsed-field electrophoresis. ALT-associated proteins were validated by immunohistochemistry. Further, telomerase activity (TA) and gene expression were analyzed by TRAP and qPCR. DNA from 20 human neuroblastomas and 8 sarcoma cell lines served as comparative controls. ALT was detected in 9.4% (6/64) canine sarcomas including aggressive subtypes as hemangiosarcoma, osteosarcoma, and histiocytic sarcoma. C-circle levels were comparable with human ALT-positive controls. All ALT tumors demonstrated loss of ATRX expression and 5/6 showed strong p53 expression. TA was detected in 93% (14/15) snap-frozen samples including a sarcoma with ALT activity. This tumor showed long heterogeneous telomeres, and a high level of colocalization of DAXX with telomeres. One sarcoma was ALT and TA negative. All canine and human sarcoma cell lines were ALT negative. In this study, we demonstrated that canine sarcomas use ALT. As in humans, ALT was identified in aggressive sarcomas subtypes and coexisted with TA in one tumor. Overall, canine sarcomas seem to share many similarities with their human counterparts and appear an attractive model for comparative telomere research. © 2016 Wiley Periodicals, Inc.

A Theoretical Model of the Wnt Signaling Pathway in the Epithelial Mesenchymal Transition.

BACKGROUND: Following the formation of a primary carcinoma, neoplastic cells metastasize by undergoing the epithelial mesenchymal transition (EMT), which is triggered by cues from inflammatory and stromal cells in the microenvironment. EMT allows epithelial cells to lose their highly adhesive nature and instead adopt the spindle-like appearance, as well as the invasive and migratory behavior, of mesenchymal cells. We hypothesize that a bistable switch between the epithelial and mesenchymal phenotypes governs EMT, allowing the cell to maintain its mesenchymal phenotype even after it leaves the primary tumor microenvironment and EMT-inducing extracellular signal. RESULTS: This work presents a simple mathematical model of EMT, specifically the roles played by four key proteins in the Wnt signaling pathway: Dishevelled (Dvl), E-cadherin, ß-catenin, and Slug. The model predicts that following activation of the Wnt pathway, an epithelial cell in the primary carcinoma must attain a threshold level of membrane-bound Dvl to convert to the mesenchymal-like phenotype and maintain that phenotype once it has migrated away from the primary tumor. Furthermore, sensitivity analysis of the model suggests that in both the epithelial and the mesenchymal states, the steady state behavior of E-cadherin and the transcription factor Slug are sensitive to changes in the degradation rate of Slug, while E-cadherin is also sensitive to the IC50 (half-maximal) concentration of Slug necessary to inhibit E-cadherin production. The steady state behavior of Slug exhibits sensitivity to changes in the rate at which it is induced by ß-catenin upon activation of the Wnt pathway. In the presence of sufficient amount of Wnt ligand, E-cadherin levels are sensitive to the ratio of the rate of Slug activation via ß-catenin to the IC50 concentration of Slug necessary to inhibit E-cadherin production. CONCLUSIONS: The sensitivity of E-cadherin to the degradation rate of Slug, as well as the IC50 concentration of Slug necessary to inhibit E-cadherin production, shows how the adhesive nature of the cell depends on finely-tuned regulation of Slug. By highlighting the role of ß-catenin in the activation of EMT and the relationship between E-cadherin and Slug, this model identifies critical parameters of therapeutic concern, such as the threshold level of Dvl necessary to inactivate the GSK-3ß complex mediating ß-catenin degradation, the rate at which ß-catenin translocates to the nucleus, and the IC50 concentration of Slug needed to inhibit E-cadherin production.

Canine and human sarcomas exhibit predominant FGFR1 expression and impaired viability after inhibition of signaling.

Fibroblast growth factor receptors (FGFRs) are important in malignant progression of several human epithelial tumors. However, little is known about FGFRs in canine or human soft tissue sarcomas. Thus, our aim was to investigate expression of FGFRs and their involvement in cell survival in sarcomas of both species. FGFR1-4 and FGFRL1 transcripts as well as IIIb/IIIc splice variants of FGFR1-3 were evaluated in 3 canine- and 6 human sarcoma cell lines and 19 spontaneous canine sarcomas by SYBRqPCR. FGFR1 protein expression was assessed by immunohistochemistry. Growth inhibitory effects of FGFR1 inhibitor PD166866 and dominant negative recombinant FGFR adenoviral expression constructs (dnFGFR) on tumor cell lines were analyzed. Profiling of multiple FGFR transcripts detected comparable co-expression in most of human and canine sarcoma cell lines and canine tumor specimens. This indicates existence of closely related regulation mechanisms for FGFR expression in sarcomas of both species. FGFR1 with splice variant IIIc was consistently expressed with highest transcript levels. In 88% of the spontaneous tumor samples a heterogeneous FGFR1 protein expression was observed. Significant growth inhibition and cell death was seen after infection with dnFGFR1 in canine and human sarcoma cells, but not with dnFGFR3 and 4. PD166866 showed selective cytotoxicity with IC50 values between 12.1 and 26.4 µM. FGFR1 inhibition blocked ligand-induced tyrosine phosphorylation of ERK1/2 mitogen-activated protein kinase isoforms. This study emphasizes the important role FGFR1, especially splice variant IIIc, likely plays in sarcomas. Inhibitory small molecules could be of potential use for targeted therapy in aggressive sarcomas of both species.

Immunohistochemical and transcriptomic characterization of T and myeloid cell infiltrates in canine malignant melanoma.

Immune checkpoint inhibitor therapy can provide significant clinical benefit in patients with certain cancer types including melanoma; however, objective responses are only observed for a subset of patients. Mucosal melanoma is a rare melanoma subtype associated with a poor prognosis and, compared with cutaneous melanoma, is significantly less responsive to immune checkpoint inhibitors. Spontaneous canine tumours have emerged as valuable models to inform human cancer studies. In contrast to human melanoma, most canine melanomas are mucosal-an incidence that may be leveraged to better understand the subtype in humans. However, a more comprehensive understanding of the immune landscape of the canine disease is required. Here, we quantify tumour infiltrative T and myeloid cells in canine mucosal (n = 13) and cutaneous (n = 5) melanomas using immunohistochemical analysis of CD3 and MAC387 expression, respectively. Gene expression analysis using the Canine IO NanoString panel was also performed to identify genes and pathways associated with immune cell infiltration. T and myeloid cell densities were variable with geometric means of 158.7 cells/mm2 and 166.7 cells/mm2, respectively. Elevated T cell infiltration was associated with increased expression of cytolytic genes as well as genes encoding the coinhibitory checkpoint molecules PD-1, CTLA-4, TIM-3 and TIGIT; whereas increased myeloid cell infiltration was associated with elevated expression of protumourigenic cytokines. These data provide a basic characterization of the tumour microenvironment of canine malignant melanoma and suggest that, like human melanoma, inherent variability in anti-tumour T cell responses exists and that a subset of canine melanomas may respond better to immunomodulation.

Thermal dose fractionation affects tumour physiological response.

PURPOSE: It is unknown whether a thermal dose should be administered using a few large fractions with higher temperatures or a larger number of fractions with lower temperatures. To evaluate this we assessed the effect of administering the same total thermal dose, approximately 30 CEM43T(90), in one versus three to four fractions per week, over 5 weeks. MATERIALS AND METHODS: Canine sarcomas were randomised to receive one of the hyperthermia fractionation schemes along with fractionated radiotherapy. Tumour response was based on changes in tumour volume, oxygenation, water diffusion quantified using MRI, and a panel of histological and immunohistochemical end points. RESULTS: There was a greater reduction in tumour volume and water diffusion at the end of therapy in tumours receiving one hyperthermia fraction per week. There was a weak but significant association between improved tumour oxygenation 24 h after the first hyperthermia treatment and extent of volume reduction at the end of therapy. Finally, the direction of change of HIF-1α and CA-IX immunoreactivity after the first hyperthermia fraction was similar and there was an inverse relationship between temperature and the direction of change of CA-IX. There were no significant changes in interstitial fluid pressure, VEGF, vWF, apoptosis or necrosis as a function of treatment group or temperature. CONCLUSIONS: We did not identify an advantage to a three to four per week hyperthermia prescription, and response data pointed to a one per week prescription being superior.

Feasibility of using gene expression analysis to study canine soft tissue sarcomas.

The prognosis given for canine soft tissue sarcomas (STSs) is based primarily on histopathologic grade. The decision to administer adjuvant chemotherapy is difficult since less than half of patients with high-grade STSs develop metastatic disease. We hypothesize that there is a gene signature that will improve our ability to predict development of metastatic disease in STS patients. The objective of this study was to determine the feasibility of using cDNA microarray and quantitative real-time PCR (qRT-PCR) analysis to determine gene expression patterns in metastatic versus nonmetastatic canine STSs, given the inherent heterogeneity of this group of tumors. Five STSs from dogs with metastatic disease were evaluated in comparison to eight STSs from dogs without metastasis. Tumor RNA was extracted, processed, and labeled for application to the Affymetrix Canine Genechip 2.0 Array. Array fluorescence was normalized using D-Chip software and data analysis was performed with JMP/Genomics. Differential gene expression was validated using qRT-PCR. Over 200 genes were differentially expressed at a false discovery rate of 5%. Differential gene expression was validated for five genes upregulated in metastatic tumors. Quantitative RT-PCR confirmed increased relative expression of all five genes of interest in the metastatic STSs. Our results demonstrate that microarray and qRT-PCR are feasible methods for comparing gene signatures in canine STSs. Further evaluation of the differences between gene expression in metastatic STSs and in nonmetastatic STSs is likely to identify genes that are important in the development of metastatic disease and improve our ability to prognosticate for individual patients.

Effect of a 1-hour IV infusion of doxorubicin on the development of cardiotoxicity in dogs as evaluated by electrocardiography and echocardiography.

Cardiotoxicity is a potentially life-threatening consequence of treatment with doxorubicin. Without reliable predictive or monitoring tests for early intervention, preventive methods are warranted. This study tested the hypothesis that a 1-hour infusion of doxorubicin would reduce the incidence of cardiotoxicity compared with historical incidences. Inclusion criteria for this retrospective trial were a minimum of three doses of doxorubicin administered as a 1-hour infusion in patients with at least two echocardiographic or electrocardiographic examinations during the course of treatment (median cumulative dose, 120 mg/m2). Of 133 dogs, 16 (12%) developed electrocardiographic abnormalities during or after treatment, which was statistically lower than the historical incidence of 17.7% (31 of 175 dogs). Only seven dogs (5.3%) developed abnormalities during the course of therapy. Three (2%) developed congestive heart failure.

The role of cellular contact and TGF-beta signaling in the activation of the epithelial mesenchymal transition (EMT).

The epithelial mesenchymal transition (EMT) is one step in the process through which carcinoma cells metastasize by gaining the cellular mobility associated with mesenchymal cells. This work examines the dual influence of the TGF-ß pathway and intercellular contact on the activation of EMT in colon (SW480) and breast (MCF7) carcinoma cells. While the SW480 population revealed an intermediate state between the epithelial and mesenchymal states, the MC7 cells exhibited highly adhesive behavior. However, for both cell lines, an exogenous TGF-ß signal and a reduction in cellular confluence can push a subgroup of the population towards the mesenchymal phenotype. Together, these results highlight that, while EMT is induced by the synergy of multiple signals, this activation varies across cell types.

Incidence and risk factors associated with development of clinical cardiotoxicity in dogs receiving doxorubicin.

BACKGROUND: Doxorubicin (DOX) can cause cumulative cardiotoxicity in dogs, but the incidence of clinical cardiotoxicity in dogs receiving DOX has not been determined. HYPOTHESIS/OBJECTIVES: To determine if the duration of DOX infusion influences the incidence of cardiotoxicity, to characterize the incidence of clinical cardiotoxicity in dogs during or after DOX chemotherapy, and to identify any risk factors associated with cardiotoxicity. ANIMALS: Four-hundred ninety-four dogs that received at least 1 dose of DOX for the treatment of cancer. METHODS: Retrospective study of dogs that received DOX from 2006 to 2015. RESULTS: Of 494 dogs, 20 (4.0%) developed clinical cardiotoxicity. The duration of DOX infusion was not significantly associated with clinical cardiotoxicity, whereas a higher cumulative dose of DOX, higher body weight, decreases in fractional shortening after 5 doses of DOX, and development of ventricular premature contractions were significantly associated with clinical cardiotoxicity. High-risk breeds for developing dilated cardiomyopathy had an incidence of 15.4%, whereas low-risk breeds had an incidence of 3.0%. CONCLUSIONS AND CLINICAL IMPORTANCE: Although the duration of DOX infusion did not influence the incidence of cardiotoxicity, premature contractions and decreases in fractional shortening should raise concern for the development of clinical cardiotoxicity. Overall, the incidence of clinical DOX-induced cardiotoxicity is low, but Boxers and other breeds at high risk for dilated cardiomyopathy may be at an increased risk.

A phase I trial of hyperthermia-induced interleukin-12 gene therapy in spontaneously arising feline soft tissue sarcomas.

Interleukin-12 (IL-12), a proinflammatory cytokine, shows anticancer properties. Systemically administered IL-12 causes dose-dependent toxicity. To achieve localized intratumoral gene expression, an adenoviral gene therapy vector with IL-12 controlled by a heat-inducible promoter (heat shock promoter 70B) was developed and tested in a phase I clinical trial in cats with spontaneously arising soft tissue sarcoma. A feasibility study was done in 16 cats with soft tissue sarcoma using murine IL-12 and/or enhanced green fluorescent protein adenoviral vectors under cytomegalovirus or heat shock promoter 70 control. Subsequently, we conducted a phase I clinical trial using an adenoviral feline IL-12 construct in 13 cats with soft tissue sarcoma. The soft tissue sarcomas were irradiated (48 Gy/16 fractions) followed by intratumoral injection of adenovirus. Twenty-four hours postinjection, tumors were heated (41 degrees C, 60 min). Tumor expression of feline IL-12 and IFN-gamma was determined. Cats were monitored for systemic toxicity. For the murine IL-12 construct, an association was noted between viral dose and murine IL-12 levels within tumor, whereas serum levels were minimal. Mild toxicity was noted at 10(11) plaque-forming units (pfu). With the feline IL-12 construct, high levels of feline IL-12 mRNA were detected in tumor biopsies with low or absent IFN-gamma mRNA following gene therapy. Hematologic and hepatic toxicities were noted at the highest viral doses and were associated with detection of IFN-gamma mRNA in tumor. It is possible to localize gene expression and limit systemic toxicity of IL-12 using the hyperthermia-induced gene therapy approach. The maximum tolerated dose of the feline IL-12 adenoviral vector was 10(10) pfu/tumor as dose-limiting toxicities were noted at the 4 x 10(10) pfu dose.

A tracer dose of technetium-99m-labeled liposomes can estimate the effect of hyperthermia on intratumoral doxil extravasation.

PURPOSE: A noninvasive method to monitor intratumoral Doxil delivery in individual patients during targeted tumor therapy is important to predict treatment response. The purpose of this study was to determine if a small tracer dose of technetium-99m (99mTc)-labeled liposomes could be used to quantify the effect of local hyperthermia on intratumoral Doxil extravasation. EXPERIMENTAL DESIGN: Experiments were carried out in a rat fibrosarcoma model with transplanted thigh tumors. Liposomes of approximately same size and composition as Doxil were radiolabeled using [technetium-99m (99mTc)]exametazime. Eight treatment groups received either Doxil, a tracer dose or a large dose of 99mTc-labeled liposomes, or a combination of tracer and Doxil, with or without hyperthermia. This design was chosen to assure that coadministration of both liposomal formulations did not influence their intratumoral distribution. Hyperthermia was done for 45 minutes. Scintigraphic images were obtained at 5 and 18 hours. At 18 hours, tumors were removed and gamma counts as well as doxorubicin concentrations were measured. RESULTS: Intratumoral extravasation of the 99mTc-labeled tracer could be imaged scintigraphically under normothermic and hyperthermic conditions. The thermal enhancement ratio was slightly higher for radiolabeled liposomes than for doxorubicin concentration. However, there was a significant positive correlation of intratumoral doxorubicin concentration and intratumoral uptake of the radiolabeled tracer (expressed as percentage of the injected dose per gram of tissue). Coadministration of radiolabeled liposomes did not negatively influence the amount of drug delivered with Doxil. CONCLUSIONS: The use of a radiolabeled tracer has potential value to monitor drug delivery and estimate the effect of an intervention aimed to increase liposomal accumulation, such as local hyperthermia.

Phase I trial of doxorubicin-containing low temperature sensitive liposomes in spontaneous canine tumors.

PURPOSE: To determine the maximum tolerated dose, dose-limiting toxicities, and pharmacokinetic characteristics of doxorubicin encapsulated in a low temperature sensitive liposome (LTSL) when given concurrently with local hyperthermia to canine solid tumors. EXPERIMENTAL DESIGN: Privately owned dogs with solid tumors (carcinomas or sarcomas) were treated. The tumors did not involve bone and were located at sites amenable to local hyperthermia. LTSL-doxorubicin was given (0.7-1.0 mg/kg i.v.) over 30 minutes during local tumor hyperthermia in a standard phase I dose escalation study. Three treatments, given 3 weeks apart, were scheduled. Toxicity was monitored for an additional month. Pharmacokinetics were evaluated during the first treatment cycle. RESULTS: Twenty-one patients were enrolled: 18 with sarcomas and 3 with carcinomas. Grade 4 neutropenia and acute death secondary to liver failure, possibly drug related, were the dose-limiting toxicities. The maximum tolerated dose was 0.93 mg/kg. Other toxicities, with the possible exception of renal damage, were consistent with those observed following free doxorubicin administration. Of the 20 dogs that received > or = 2 doses of LTSL-doxorubicin, 12 had stable disease, and 6 had a partial response to treatment. Pharmacokinetic variables were more similar to those of free doxorubicin than the marketed liposomal product. Tumor drug concentrations at a dose of 1.0 mg/kg averaged 9.12 +/- 6.17 ng/mg tissue. CONCLUSION: LTSL-doxorubicin offers a novel approach to improving drug delivery to solid tumors. It was well tolerated and resulted in favorable response profiles in these patients. Additional evaluation in human patients is warranted.

Ezrin and moesin expression in canine and feline osteosarcoma.

Biological features of canine osteosarcomas (OS) differ markedly from those found in feline and resemble more human osteosarcomas, in particular for their high rate of metastasis and poor prognosis. Ezrin, radixin and moesin are members of the ERM protein family and link the actin cytoskeleton with the cell membrane. Ezrin and moesin have been shown to be of prognostic significance in tumor progression due to their role in the metastatic process. The objective of this study was to analyze ezrin and moesin protein expression in a series of dog (n = 16) and cat (n = 8) osteosarcoma samples using immunohistochemistry and western blot techniques. We found that cat OS have a higher moesin expression compared to dog OS, however, the active phosphorylated forms of moesin and ezrin Tyr353 were more abundant in the dog samples. A statistically significant difference was found for the low and high immunohistochemical scores of ezrin and pan-phospho-ERM proteins between cat and dog. Although phospho-ezrin Thr567 was higher in feline OS, the membranous localization in dog OS samples indicates the presence of the biologically active form. Therefore, the observed differences in phosphorylated forms of ezrin and moesin status should be further studied to demonstrate if they are relevant for different biological behavior between dog and cat OS.

Thermal dose is related to duration of local control in canine sarcomas treated with thermoradiotherapy.

PURPOSE: To test that prospective delivery of higher thermal dose is associated with longer tumor control duration. EXPERIMENTAL DESIGN: 122 dogs with a heatable soft tissue sarcoma were randomized to receive a low (2-5 CEM43 degrees CT90) or high (20-50 CEM43 degrees CT90) thermal dose in combination with radiotherapy. Most dogs (90%) received four to six hyperthermia treatments over 5 weeks. RESULTS: In the primary analysis, median (95% confidence interval) duration of local control in the low-dose group was 1.2 (0.7-2.1) years versus 1.9 (1.4-3.2) years in the high-dose group (log-rank P = 0.28). The probability (95% confidence interval) of tumor control at 1 year in the low-dose versus high-dose groups was 0.57 (0.43-0.70) versus 0.74 (0.62-0.86), respectively. Using multivariable procedure, thermal dose group (P = 0.023), total duration of heating (P = 0.008), tumor volume (P = 0.041), and tumor grade (P = 0.027) were significantly related to duration of local tumor control. When correcting for volume, grade, and duration of heating, dogs in the low-dose group were 2.3 times as likely to experience local failure. CONCLUSIONS: Thermal dose is directly related to local control duration in irradiated canine sarcomas. Longer heating being associated with shorter local tumor control was unexpected. However, the effect of thermal dose on tumor control was stronger than for heating duration. The heating duration effect is possibly mediated through deleterious effects on tumor oxygenation. These results are the first to show the value of prospectively controlled thermal dose in achieving local tumor control with thermoradiotherapy, and they establish a paradigm for prescribing thermoradiotherapy and writing a thermal prescription.

Serum 25-hydroxyvitamin D concentrations in dogs with osteosarcoma do not differ from those of age- and weight-matched control dogs.

Vitamin D concentrations show an inverse correlation with incidence of certain tumors in people and dogs. Additionally, human osteosarcoma has been associated with dysregulation of vitamin D-dependent pathways. The study objective was to compare serum 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 in 20 dogs with osteosarcoma to age- and weight-matched control dogs. We hypothesized that dogs with osteosarcoma would have lower serum 25-hydroxyvitamin D than control dogs. The mean 25-hydroxyvitamin D3 concentrations for dogs with osteosarcoma and matched-controls were 34.95 ng/mL and 33.85 ng/mL, respectively (P = 0.784). Based on these data, 25-hydroxyvitamin D insufficiency might not be important in the pathogenesis of canine osteosarcoma.

Telomere Transcripts Target Telomerase in Human Cancer Cells.

Long non-coding transcripts from telomeres, called telomeric repeat-containing RNA (TERRA), were identified as blocking telomerase activity (TA), a telomere maintenance mechanism (TMM), in tumors. We expressed recombinant TERRA transcripts in tumor cell lines with TA and with alternative lengthening of telomeres (ALT) to study effects on TMM and cell growth. Adeno- and lentivirus constructs (AV and LV) were established for transient and stable expression of approximately 130 units of telomere hexanucleotide repeats under control of cytomegalovirus (CMV) and human RNase P RNA H1 (hH1) promoters with and without polyadenylation, respectively. Six human tumor cell lines either using telomerase or ALT were infected and analyzed for TA levels. Pre-infection cells using telomerase had 1%-3% of the TERRA expression levels of ALT cells. AV and LV expression of recombinant TERRA in telomerase positive cells showed a 1.3-2.6 fold increase in TERRA levels, and a decrease in TA of 25%-58%. Dominant-negative or small hairpin RNA (shRNA) viral expression against human telomerase reverse transcriptase (hTERT) results in senescence, not induced by TERRA expression. Population doubling time, cell viability and TL (telomere length) were not impacted by ectopic TERRA expression. Clonal growth was reduced by TERRA expression in TA but not ALT cell lines. ALT cells were not affected by treatments applied. Established cell models and tools may be used to better understand the role of TERRA in the cell, especially for targeting telomerase.

Carboplatin and doxorubicin combination chemotherapy for the treatment of appendicular osteosarcoma in the dog.

Twenty-four client-owned dogs with histologically diagnosed appendicular osteosarcoma (OSA) and no evidence of gross metastatic disease were treated with amputation or limb salvage followed by combination chemotherapy consisting of carboplatin (175mg/ m2 IV, day 1) and doxorubicin (15 mg/m2 IV, day 2) given on a 21-day cycle for a maximum of 4 cycles. Hematologic and gastrointestinal adverse effects were graded according to National Cancer Institute guidelines. Thoracic radiographs were obtained before the 3rd chemotherapy cycle and then every 2 months. Median disease-free interval was 195 days (95% confidence interval 111-228 days) and median survival was 235 days (95% confidence interval 150-283 days). Two patients required dose reductions: 1 for grade 3 thrombocytopenia and 1 for grade 3 adverse gastrointestinal effects. Patients with a longer duration of clinical signs before definitive diagnosis and surgery (greater than 30 days) were more likely to develop progressive disease and to die or be euthanized because of progressive disease on any day; hazard ratios were 3.0 (P = .02) and 3.7 (P .02), respectively. In conclusion, although this combination chemotherapy protocol was well tolerated, it did not provide any improvement over historical single-agent protocols.