Comparative proteomic investigation of metastatic and non-metastatic osteosarcoma cells of human and canine origin

Osteosarcoma is the most common bone cancer in dogs and people. In order to improve clinical outcomes, it is necessary to identify proteins that are differentially expressed by metastatic cells. Membrane bound proteins are responsible for multiple pro-metastatic functions. Therefore characterizing the differential expression of membranous proteins between metastatic and non-metastatic clonal variants will allow the discovery of druggable targets and consequently improve treatment methodology. The objective of this investigation was to systemically identify the membrane-associated proteomics of metastatic and non-metastatic variants of human and canine origin. Two clonal variants of divergent in vivo metastatic potential from human and canine origins were used. The plasma membranes were isolated and peptide fingerprinting was used to identify differentially expressed proteins. Selected proteins were further validated using western blotting, flow cytometry, confocal microscopy and immunohistochemistry. Over 500 proteins were identified for each cell line with nearly 40% of the proteins differentially regulated. Conserved between both species, metastatic variants demonstrated significant differences in expression of membrane proteins that are responsible for pro-metastatic functions. Additionally, CD147, CD44 and vimentin were validated using various biochemical techniques. Taken together, through a comparative proteomic approach we have identified several differentially expressed cell membrane proteins that will help in the development of future therapeutics.

Direct Capture of Functional Proteins from Mammalian Plasma Membranes into Nanodiscs

Mammalian plasma membrane proteins make up the largest class of drug targets yet are difficult to study in a cell free system because of their intransigent nature. Herein, we perform direct encapsulation of plasma membrane proteins derived from mammalian cells into a functional nanodisc library. Peptide fingerprinting was used to analyze the proteome of the incorporated proteins in nanodiscs and to further demonstrate that the lipid composition of the nanodiscs directly affects the class of protein that is incorporated. Furthermore, the functionality of the incorporated membrane proteome was evaluated by measuring the activity of membrane proteins: Na(+)/K(+)-ATPase and receptor tyrosine kinases. This work is the first report of the successful establishment and characterization of a cell free functional library of mammalian membrane proteins into nanodiscs.

Targeting tumor vasculature with aptamer-functionalized doxorubicin-polylactide nanoconjugates for enhanced cancer therapy

An A10 aptamer (Apt)-functionalized, sub-100 nm doxorubicin-polylactide (Doxo-PLA) nanoconjugate (NC) with controlled release profile was developed as an intravenous therapeutic strategy to effectively target and cytoreduce canine hemangiosarcoma (cHSA), a naturally occurring solid tumor malignancy composed solely of tumor-associated endothelium. cHSA consists of a pure population of malignant endothelial cells expressing prostate-specific membrane antigen (PSMA) and is an ideal comparative tumor model system for evaluating the specificity and feasibility of tumor-associated endothelial cell targeting by A10 Apt-functionalized NC (A10 NC). In vitro, A10 NCs were selectively internalized across a panel of PSMA-expressing cancer cell lines, and when incorporating Doxo, A10 Doxo-PLA NCs exerted greater cytotoxic effects compared to nonfunctionalized Doxo-PLA NCs and free Doxo. Importantly, intravenously delivered A10 NCs selectively targeted PSMA-expressing tumor-associated endothelial cells at a cellular level in tumor-bearing mice and dramatically increased the uptake of NCs by endothelial cells within the local tumor microenvironment. By virtue of controlled drug release kinetics and selective tumor-associated endothelial cell targeting, A10 Doxo-PLA NCs possess a desirable safety profile in vivo, being well-tolerated following high-dose intravenous infusion in mice, as supported by the absence of any histologic organ toxicity. In cHSA-implanted mice, two consecutive intravenous infusions of A10 Doxo-PLA NCs exerted rapid and substantial cytoreductive activities within a period of 7 days, resulting in greater than 70% reduction in macroscopic tumor-associated endothelial cell burden as a consequence of enhanced cell death and necrosis.

Expression of tumor endothelial markers (TEMs) in vitro in a canine hemangiosarcoma model of malignant angiogenesis

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Background: Expression of tumor endothelial markers (TEMs) in tumor-associated blood vessels presents opportunities for targeted therapy. TEM7 and TEM8 are selectively expressed and are associated with a worse prognosis in cancer patients. TEM expression is conserved across species, however species differences do exist as TEM7 is undetectable in murine tumor endothelium. Thus, further investigation of the role of TEMs in malignant angiogenesis is hindered by the lack of optimal animal tumor models. Canine hemangiosarcoma is relevant spontaneous model of malignant angiogenesis based on archetypal cell markers, endothelial functionality, growth factor/receptor expression, and angiogenic gene expression. The aims of this study were to characterize the in vitro expression of TEM7 and TEM8 in canine hemangiosarcoma as a novel model of malignant angiogenesis. Methods: Two canine hemangiosarcoma cell lines were assessed (Den and Fitz). Total RNA was isolated using standard technique, reverse transcribed to cDNA, and amplified by polymerase chain reaction (PCR) reaction using degenerate primers specific for human and murine TEM7 transcripts with forward and reverse primers. Protein expression of TEM7 and TEM8 in cell lysates was evaluated via Western blotting and cell surface expression was analyzed by flow cytometry. Polyclonal anti-TEM7 and anti-TEM8 antibodies (Sigma-Aldrich) were used with positive and negative controls. Results: Basal in vitro expression of TEM7 mRNA was confirmed in canine hemangiosarcoma, as well as in vitro protein expression of TEM7 and TEM8 via Western blotting and flow cytometry. Conclusions: The validation of TEM expression in canine hemangiosarcoma establishes TEM7 and TEM8 as promising targets for further evaluation in this novel model of malignant angiogenesis, and investigation of TEM-targeting is ongoing. This may represent a novel spontaneous animal tumor model for investigation of tumor vascular targeting.

Effect of fibroblast growth factor-2 on equine mesenchymal stem cell monolayer expansion and chondrogenesis

OBJECTIVE

To determine whether fibroblast growth factor-2 (FGF-2) treatment of equine mesenchymal stem cells (MSCs) during monolayer expansion enhances subsequent chondrogenesis in a 3-dimensional culture system.

ANIMALS

6 healthy horses, 6 months to 5 years of age.

PROCEDURES

Bone marrow-derived MSCs were obtained from 6 horses. First-passage MSCs were seeded as monolayers at 10,000 cells/cm(2) and in medium containing 0, 1, 10, or 100 ng of FGF-2/mL. After 6 days, MSCs were transferred to pellet cultures (200,000 cells/pellet) and maintained in chondrogenic medium. Pellets were collected after 15 days. Pellets were analyzed for collagen type II content by use of an ELISA, total glycosaminoglycan content by use of the dimethylmethylene blue dye-binding assay, and DNA content by use of fluorometric quantification. Semiquantitative PCR assay was performed to assess relative concentrations of collagen type II and aggrecan mRNAs.

RESULTS

Use of 100 ng of FGF-2/mL significantly increased pellet DNA and glycosaminoglycan content. Collagen type II content of the pellet was also increased by use of 10 and 100 ng of FGF-2/mL. Collagen type II and aggrecan mRNA transcripts were increased by treatment with FGF-2. Some control samples had minimal evidence of collagen type II and aggrecan transcripts after 35 cycles of amplification.

CONCLUSIONS AND CLINICAL RELEVANCE

FGF-2 treatment of bone marrow-derived MSC monolayers enhanced subsequent chondrogenic differentiation in a 3-dimensional culture. This result is important for tissue engineering strategies dependent on MSC expansion for cartilage repair.

The effects of radial shock waves on the metabolism of equine cartilage explantsin vitro

AIM

To investigate, in vitro, the effects of radial shock waves on the release of nitric oxide (NO) and synthesis of prostaglandin E2 (PGE2) and glycosaminoglycan (GAG), and liberation of GAG, from equine articular cartilage explants.

METHODS

Equine cartilage from normal metacarpophalangeal and metatarsophalangeal joints was exposed to radial shock waves at various impulse doses and then maintained as explants in culture for 48 h. Shock waves were delivered at 1,876 Torr pressure and a frequency of 10 Hz. Treatment groups consisted of a negative control group, or application of 500, 2,000, or 4,000 impulses by use of either a convex handpiece (Group A) or concave handpiece (Group B). Synthesis of GAG was measured using incorporation of 35S-labelled sodium sulphate. Additionally, the synthesis of NO and PGE2, and content of GAG of the explants and media were determined.

RESULTS

No significant effects (p>0.05) of radial shock-wave treatment were evident on the synthesis of NO or PGE2, or release of GAG by cartilage explants. However, radial shock waves decreased synthesis of GAG measured 48 h after exposure for all treatment groups other than the 500-impulse Group-A explants (p<0.05).

CONCLUSIONS

Radial shock waves impact the metabolism of GAG in chondrocytes in equine articular cartilage. Further studies will be required to fully investigate the impact of this effect on the health of joints, and to elucidate the clinical impact.