Characterization of β-catenin expression in canine osteosarcoma

Recent Advances in the Discovery of Biomarkers for Canine Osteosarcoma

Canine osteosarcoma (OSA) is an aggressive malignancy that frequently metastasizes to the lung and bone. Not only has there been essentially no improvement in therapeutic outcome over the past 3 decades, but there is also a lack of reliable biomarkers in clinical practice. This makes it difficult to discriminate which patients will most benefit from the standard treatment of amputation and adjuvant chemotherapy. The development of reliable diagnostic biomarkers could aid in the clinical diagnosis of primary OSA and metastasis; while prognostic, and predictive biomarkers could allow clinicians to stratify patients to predict response to treatment and outcome. This review summarizes biomarkers that have been explored in canine OSA to date. The focus is on molecular biomarkers identified in tumor samples as well as emerging biomarkers that have been identified in blood-based (liquid) biopsies, including circulating tumor cells, microRNAs, and extracellular vesicles. Lastly, we propose future directions in biomarker research to ensure they can be incorporated into a clinical setting.

Unraveling the chaotic genomic landscape of primary and metastatic canine appendicular osteosarcoma with current sequencing technologies and bioinformatic approaches

Osteosarcoma is a rare disease in children but is one of the most common cancers in adult large breed dogs. The mutational landscape of both the primary and pulmonary metastatic tumor in two dogs with appendicular osteosarcoma (OSA) was comprehensively evaluated using an automated whole genome sequencing, exome and RNA-seq pipeline that was adapted for this study for use in dogs. Chromosomal lesions were the most common type of mutation. The mutational landscape varied substantially between dogs but the lesions within the same patient were similar. Copy number neutral loss of heterozygosity in mutant TP53 was the most significant driver mutation and involved a large region in the middle of chromosome 5. Canine and human OSA is characterized by loss of cell cycle checkpoint integrity and DNA damage response pathways. Mutational profiling of individual patients with canine OSA would be recommended prior to targeted therapy, given the heterogeneity seen in our study and previous studies.

β Lapachone blocks the cell cycle and induces apoptosis in canine osteosarcoma cells

ABSTRACT: Osteosarcoma is a malignant tumor of primitive bone cells with a high incidence in dogs and humans. The need for more effective drugs with less adverse consequences has pushed the development of chemotherapeutic agents from plants and other natural sources. The aim of this study was to verify the cytotoxic effects of β-lapachone, a compound present in the sawdust of Tabebuia sp. (popularly known as ipê) wood, on canine osteosarcoma cells subcultured and treated in different concentrations (0.1μm, 0.3μm e 1.0μm) and exposure times (24h, 48h e 72h). Results were obtained through Trypan blue dye exclusion, tetrazolium reducing method, cell survival assay, Annexin V-FITC and Propidium Iodine labeling, JC-1 dye labeling and cell cycle kinetics e analysis. The group treated with 0.3μm β-lapachone presented higher decrease in cell viability (80.27%, 24h, 47.41%, 48h and 35.19%, 72h) and greater progression of cytotoxicity (19.73%, 24h, 52.59%, 48h and 64.81%, 72h). The lower IC50 (0.180μm) was verified in the group treated for 72 hours. Cell growth after treatment decreased as concentration and time of exposure increased, with 0.50% survival fraction at the concentration of 1.0μm. Initial apoptosis was the most frequent type of cell death in all groups, reaching bottom in the 24-hour group treated with 0.1μm (4.26%) and peaking in the 72-hour group treated with 1.0μm (85.89%). Mitochondrial depolarization demonstrated a dose-dependent phenomenon, indicating the intrinsic apoptosis. Cell growth inhibition by blocking cell cycle in the G0/G1 phase related to the exposure the time. β-lapachone is cytotoxic for canine osteosarcoma cells, induces apoptosis and promotes cell cycle arrest in G0/G1 phase.

Canine sarcomas as a surrogate for the human disease

Pet dogs are becoming increasingly recognized as a population with the potential to inform medical research through their treatment for a variety of maladies by veterinary health professionals. This is the basis of the One Health initiative, supporting the idea of collaboration between human and animal health researchers and clinicians to study spontaneous disease processes and treatment in animals to inform human health. Cancer is a major health burden in pet dogs, accounting for approximately 30% of deaths across breeds. As such, pet dogs with cancer are becoming increasingly recognized as a resource for studying the pharmacology and therapeutic potential of anticancer drugs and therapies under development. This was recently highlighted by a National Academy of Medicine Workshop on Comparative Oncology that took place in mid-2015 (http://www.nap.edu/21830). One component of cancer burden in dogs is their significantly higher incidence of sarcomas as compared to humans. This increased incidence led to canine osteosarcoma being an important component in the development of surgical approaches for osteosarcoma in children. Included in this review of sarcomas in dogs is a description of the incidence, pathology, molecular characteristics and previous translational therapeutic studies associated with these tumors. An understanding of the patho-physiological and molecular characteristics of these naturally occurring canine sarcomas holds great promise for effective incorporation into drug development schemas, for evaluation of target modulation or other pharmacodynamic measures associated with therapeutic response. These data could serve to supplement other preclinical data and bolster clinical investigations in tumor types for which there is a paucity of human patients for clinical trials.

Adenocarcinoma of the posterior segment of the gastrointestinal tract in dogs - clinical, endoscopic, histopathological and immunohistochemical findings

Of all the tumours in dogs, three percent are located in the intestines, and 36-60% of those tumours affect the large intestine. Adenocarcinomas of the intestines account for 20-35% of the gastrointestinal tumours and for almost 60% of the large intestine tumours. The aim of the study was to analyze clinical disorders and endoscopic, histopathological and immunohistochemical changes in colorectal adenocarcinomas in dogs with the use of the E-cadherin, β-catenin, cytokeratin 20 (CK20), Ki-67 and minichromosome maintenance 3 (MCM-3). The study comprised 11 dogs of both genders and of different breeds diagnosed with adenocarcinoma of the large intestine. They were from 4 to 11 years old. The large intestine adenocarcinoma was diagnosed in all the patients. 72.7% cases were diagnosed with a rectal adenocarcinoma, and 27.3% were found to have a colonic adenocarcinoma. All the studied proteins were expressed at different levels and, together with the histological findings, indicated different levels of malignancy (G). The statistical analysis revealed no statistically significant differences between the expression of E-cadherin and β-catenin in the studied tissues (p=0.79) and between the expression of Ki-67 andMCM-3 (p=0.39). A strong positive correlation was found between the expression of E-cadherin and β-catenin (r=0.86; p<0.05). The diagnosis of adenocarcinomas of the large intestine may be facilitated by the introduction of immunohistochemical studies using appropriate cell markers. They may also aid in the accurate evaluation of the biological character of the tumours, their origin, the connections between tumour cells and the mitotic index. That, in turn, may help determine the malignancy and the choice of treatment.

Diversity of Histologic Patterns and Expression of Cytoskeletal Proteins in Canine Skeletal Osteosarcoma

Osteosarcoma (OS), the most common bone tumor, includes OS of the head (OSH) and appendicular OS (OSA). In dogs, it is classified into 6 histologic subtypes: osteoblastic, chondroblastic, fibroblastic, telangiectatic, giant cell, and poorly differentiated. This study investigated the significance of the histologic classification relevant to clinical outcome and the histologic and immunohistochemical relationships between pleomorphism and expression of cytoskeletal proteins in 60 cases each of OSH and OSA. Most neoplasms exhibited histologic diversity, and 64% of OS contained multiple subtypes. In addition to the above 6 subtypes, myxoid, round cell, and epithelioid subtypes were observed. Although the epithelioid subtypes were observed in only OSH, no significant difference in the frequency of other subtypes was observed. Also, no significant relevance was observed between the clinical outcome and histologic subtypes. Cytokeratin (CK) was expressed in both epithelioid and sarcomatoid tumor cells in various subtypes, and all CK-positive tumor cells also expressed vimentin. Vimentin and α-smooth muscle actin (SMA) were expressed in all subtypes. A few SMA-positive spindle-shaped tumor cells exhibited desmin expression. Glial fibrillary acidic protein-positive tumor cells were observed in many subtypes, and some of these cells showed neurofilament expression. Although OSH exhibited significantly stronger immunoreactivity for SMA than OSA, no significant difference in other cytoskeletal proteins was observed. Some tumor cells had cytoskeletal protein expression compatible with the corresponding histologic subtypes, such as CK in the epithelioid subtype and SMA in the fibroblastic subtype. Thus, canine skeletal OS is composed of pleomorphic and heterogenous tumor cells as is reflected in the diversity of histologic patterns and expression of cytoskeletal proteins.

Tumourigenic canine osteosarcoma cell lines associated with frizzled-6 up-regulation and enhanced side population cell frequency

An increased serum alkaline phosphatase concentration is known to be associated with a negative prognosis in canine and human osteosarcoma. To expand upon previous studies regarding the biological relevance of increased serum alkaline phosphatase as a negative prognostic factor, xenogeneic heterotopic transplants were performed using six canine primary osteosarcoma cell lines generated from patients with differing serum alkaline phosphatase concentrations (three normal and three increased). Three of the six cell lines were capable of generating tumours and tumour formation was independent of the serum alkaline phosphatase status of the cell line. Microarray analysis identified 379 genes as being differentially expressed between the tumourigenic and non-tumourigenic cell lines. Frizzled-6 was upregulated to the greatest extent (7.78-fold) in tumourigenic cell lines compared with non-tumourigenic cell lines. Frizzled-6, a co-receptor for Wnt ligands has been associated with enhanced tumour-initiating cells and poor prognosis for other tumours. The increased expression of frizzled-6 was confirmed by quantitative reverse transcription polymerase chain reaction (QPCR) and Western blot analysis. Additionally, the tumourigenic cell lines also had an increase in the percentage of side population cells compared with non-tumourigenic cell lines (5.89% versus 1.58%, respectively). There were no differences in tumourigenicity, frizzled-6 or percentage of side population cells noted between osteosarcoma cell lines generated from patients of differing serum alkaline phosphatase concentration. However, to our knowledge this is the first study to identified frizzled-6 as a possible marker of osteosarcoma cell populations with enhanced tumourigenicity and side population cells. Future work will focus on defining the role of frizzled-6 in osteosarcoma tumourigenesis and tumour-initiating cells.

Expression of β-catenin and mesenchymal markers in canine prostatic hyperplasia and carcinoma

β-catenin is a nuclear signalling molecule that is associated with human prostatic neoplasia and the epithelial-mesenchymal transition (EMT) process. The present study evaluates immunohistochemically the expression of β-catenin and the mesenchymal markers vimentin, desmin, calponin and smooth muscle actin (SMA) in four normal canine prostates and prostate samples from 15 dogs with benign prostatic hyperplasia (BPH) and six with prostatic carcinoma (PC). β-catenin was located on the membrane of normal epithelial cells, while the same marker had both cytoplasmic and membrane expression in hyperplastic cells and a nuclear redistribution in PC. Vimentin-positive luminal cells were observed in two of the 15 cases of BPH and in all PC samples, suggesting the conversion of neoplastic epithelial cells to a mesenchymal type. SMA was consistently negative in PC, but there was mild desmin and calponin immunoreactivity in these lesions. As in men, β-catenin is involved in canine prostatic carcinogenesis, thus further validating the use of this animal model to study human prostatic disease.

β-Catenin transcriptional activity is minimal in canine osteosarcoma and its targeted inhibition results in minimal changes to cell line behaviour

Canine osteosarcoma (OS) is an aggressive malignancy associated with poor outcomes. Therapeutic improvements are likely to develop from an improved understanding of signalling pathways contributing to OS development and progression. The Wnt signalling pathway is of interest for its role in osteoblast differentiation, its dysregulation in numerous cancer types, and the relative frequency of cytoplasmic accumulation of β-catenin in canine OS. This study aimed to determine the biological impact of inhibiting canonical Wnt signalling in canine OS, by utilizing either β-catenin siRNA or a dominant-negative T-cell factor (TCF) construct. There were no consistent, significant changes in cell line behaviour with either method compared to parental cell lines. Interestingly, β-catenin transcriptional activity was three-fold higher in normal canine primary osteoblasts compared to canine OS cell lines. These results suggest canonical Wnt signalling is minimally active in canine OS and its targeted inhibition is not a relevant therapeutic strategy.

TWIST interacts with β-catenin signaling on osteosarcoma cell survival against cisplatin

Both TWIST and Wnt/β-catenin signaling reportedly play important roles in osteosarcoma development. In the present study, we explored the regulatory effect of TWIST on β-catenin in osteosarcoma cells and assessed how the functional interaction between TWIST and β-catenin would impact osteosarcoma cell survival against chemotherapy agent cisplatin. Overexpression and knockdown of TWIST were respectively performed in Saos-2 and MG-63 osteosarcoma cells. Overexpression of TWIST in Saos-2 cells significantly decreased the soluble β-catenin level, phosphorylation of glycogen synthase kinase-3β (GSK-3β) at serine 9, the mRNA level of β-catenin signaling target genes, and cell survival against cisplatin, which was strengthened by knocking down β-catenin. Knockdown of TWIST in MG-63 cells significantly increased the soluble β-catenin level, phosphorylation of GSK-3β at serine 9, the mRNA level of β-catenin signaling target genes, and cell survival against cisplatin, which was reversed by knocking down β-catenin or phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002. In conclusion, we demonstrate that TWIST decreases osteosarcoma cell survival against cisplatin by decreasing the soluble β-catenin level through a PI3K-dependent manner. This study provides the first evidence of a functional link between TWIST and β-catenin signaling in osteosarcoma cells, which adds fresh insights into the molecular mechanism of osteosarcoma development.

β-Catenin Does Not Confer Tumorigenicity When Introduced into Partially Transformed Human Mesenchymal Stem Cells

Although osteosarcoma is the most common primary malignant bone tumor in children and adolescents, its cell of origin and the genetic alterations are unclear. Previous studies have shown that serially introducing hTERT, SV40 large TAg, and H-Ras transforms human mesenchymal stem cells into two distinct sarcomas cell populations, but they do not form osteoid. In this study, β-catenin was introduced into mesenchymal stem cells already containing hTERT and SV40 large TAg to analyze if this resulted in a model which more closely recapitulated osteosarcoma. Results. Regardless of the level of induced β-catenin expression in the stable transfectants, there were no marked differences induced in their phenotype or invasion and migration capacity. Perhaps more importantly, none of them formed tumors when injected into immunocompromised mice. Moreover, the resulting transformed cells could be induced to osteogenic and chondrogenic differentiation but not to adipogenic differentiation. Conclusions. β-catenin, although fostering osteogenic differentiation, does not induce the malignant features and tumorigenicity conveyed by oncogenic H-RAS when introduced into partly transformed mesenchymal stem cells. This may have implications for the role of β-catenin in osteosarcoma pathogenesis. It also may suggest that adipogenesis is an earlier branch point than osteogenesis and chondrogenesis in normal mesenchymal differentiation.

Activation of the canonical Wnt/β-catenin signalling pathway is rare in canine malignant melanoma tissue and cell lines

Canine malignant melanoma is a highly aggressive tumour associated with a poor overall survival rate due to both local disease recurrence and its highly metastatic nature. Similar to advanced melanoma in man, canine oral melanoma is poorly responsive to conventional anti-cancer therapies. The lack of sustainable disease control warrants investigation of novel therapies, preferably targeting features specific to the tumour and different from normal cells. The Wnt signalling pathway is known to contribute to melanocytic lineage development in vertebrates and perturbation of the Wnt/β-catenin pathway has been implicated in numerous cancer types. Alterations of the Wnt/β-catenin pathway are suggested to occur in a subset of human melanomas, although the precise role of the Wnt/β-catenin pathway in melanoma is yet to be defined. This study investigates the activation status of the canonical Wnt/β-catenin pathway in canine malignant melanoma and its potential as a therapeutic target for treating this disease. The data indicate that canonical Wnt/β-catenin pathway activation is a rare event in canine oral malignant melanoma tissue and canine malignant melanoma cell lines.

Immunohistochemical investigation of cell cycle and apoptosis regulators (survivin, β-catenin, p53, caspase 3) in canine appendicular osteosarcoma

Background

Osteosarcoma (OSA) represents the most common canine primary bone tumour. Despite several pathways have been investigated so far, few molecules have been identified as prognostic tools or potential therapeutic targets, and there is still the need to find out molecular pathways with specific influence over OSA progression to facilitate earlier prognosis and treatment.

Aims of the present study were to evaluate the immunohistochemical pattern and levels of expression of a panel of molecules (survivin, β-catenin, caspase 3 -inactive and active forms- and p53) involved in cell cycle and apoptosis regulation in canine OSA samples, known to be of interest in the study also of human OSA, and to detect specific relations among them and with histological tumour grade, disease free interval (DFI) and overall survival (OS).

Results

Nuclear β-catenin immunostaining was detected in normal osteoblasts adjacent to the tumour, and in 47% of the cases. Cytoplasmic and/or membranous immunostaining were also observed. Nuclear survivin and p53 positive cells were found in all cases. Moderate/high cytoplasmic β-catenin expression (≥10% positive cells) was significantly associated with the development of metastasis (P = 0.014); moderate/high nuclear p53 expression (≥10% positive cells) was significantly associated with moderate/high histological grade (P = 0.017) and shorter OS (P = 0.049). Moderate/high nuclear survivin expression (≥15% positive cells) showed a tendency toward a longer OS (P = 0,088).

Conclusions

The present results confirmed p53 as negative prognostic marker, while suggested survivin as a potential positive prognostic indicator, rather than indicative of a poor prognosis. The detection of nuclear β-catenin immunostaining in normal osteoblasts and the absent/low expression in most of the OSAs, suggested that this pathway could not play a major role in oncogenic transformation of canine osteoblasts. Further studies are needed to confirm these hypotheses.

Prognostic factors in canine appendicular osteosarcoma - a meta-analysis

Background

Appendicular osteosarcoma is the most common malignant primary canine bone tumor. When treated by amputation or tumor removal alone, median survival times (MST) do not exceed 5 months, with the majority of dogs suffering from metastatic disease. This period can be extended with adequate local intervention and adjuvant chemotherapy, which has become common practice. Several prognostic factors have been reported in many different studies, e.g. age, breed, weight, sex, neuter status, location of tumor, serum alkaline phosphatase (SALP), bone alkaline phosphatase (BALP), infection, percentage of bone length affected, histological grade or histological subtype of tumor. Most of these factors are, however, only reported as confounding factors in larger studies. Insight in truly significant prognostic factors at time of diagnosis may contribute to tailoring adjuvant therapy for individual dogs suffering from osteosarcoma. The objective of this study was to systematically review the prognostic factors that are described for canine appendicular osteosarcoma and validate their scientific importance.

Results

A literature review was performed on selected studies and eligible data were extracted. Meta-analyses were done for two of the three selected possible prognostic factors (SALP and location), looking at both survival time (ST) and disease free interval (DFI). The third factor (age) was studied in a qualitative manner. Both elevated SALP level and the (proximal) humerus as location of the primary tumor are significant negative prognostic factors for both ST and DFI in dogs with appendicular osteosarcoma. Increasing age was associated with shorter ST and DFI, however, was not statistically significant because information of this factor was available in only a limited number of papers.

Conclusions

Elevated SALP and proximal humeral location are significant negative prognosticators for canine osteosarcoma.

Epithelial-mesenchymal transition as a fundamental mechanism underlying the cancer phenotype

Epithelial-mesenchymal transition (EMT) is a complex process involved in embryonic development, wound healing and carcinogenesis. During this process, epithelial cells lose their defining characteristics and acquire mesenchymal properties: loss of cell-cell adhesion; increased motility and invasiveness; resistance to apoptosis and changes in cellular morphology. EMT has been implicated as a driver of metastasis and tumour invasion, as this process allows cells to detach from their niche and migrate through blood and lymphatic vessels to invade different organs. This transition involves a diverse range of transcription factors, including Twist, Snail and ZEB1, and downstream transcriptional targets, including E-cadherin, β-catenin, fibronectin and vimentin. Recent evidence indicates that cancer stem cells are required for metastatic tumours to become established at a distant site, and that cancer cells undergoing EMT may develop stem-cell characteristics as well as increased invasive potential. The role of EMT in cancer biology is newly emerging in the human field, and to date very little has been done in veterinary medicine. EMT may therefore be an important molecular determinant of tumour metastasis, and further understanding of this process may lead to novel drug targets to be exploited in both veterinary and human medicine.

Wnt/β-catenin expression does not correlate with serum alkaline phosphatase concentration in canine osteosarcoma patients

Osteosarcoma is an aggressive malignancy of the bone and an increase in serum alkaline phosphatase concentration has clinical prognostic value in both humans and canines. Increased serum alkaline phosphatase concentration at the time of diagnosis has been associated with poorer outcomes for osteosarcoma patients. The biology underlying this negative prognostic factor is poorly understood. Given that activation of the Wnt signaling pathway has been associated with alkaline phosphatase expression in osteoblasts, we hypothesized that the Wnt/β-catenin signaling pathway would be differentially activated in osteosarcoma tissue based on serum ALP status. Archived canine osteosarcoma samples and primary canine osteosarcoma cell lines were used to evaluate the status of Wnt/β-catenin signaling pathway activity through immunohistochemical staining, western immunoblot analyses, quantitative reverse-transcription polymerase chain reaction, and a Wnt-responsive promoter activity assay. We found no significant difference in β-catenin expression or activation between OSA populations differing in serum ALP concentration. Pathway activity was mildly increased in the primary OSA cell line generated from a patient with increased serum ALP compared to the normal serum ALP OSA cell line. Further investigation into the mechanisms underlying differences in serum ALP concentration is necessary to improve our understanding of the biological implications of this negative prognostic indicator.