Sensitivity of osteosarcoma cells to HDAC inhibitor AR-42 mediated apoptosis.

BACKGROUND: Osteosarcoma (OS) is the most common primary bone tumor in both humans and dogs and is the second leading cause of cancer related deaths in children and young adults. Limb sparing surgery along with chemotherapy has been the mainstay of treatment for OS. Many patients are not cured with current therapies, presenting a real need for developing new treatments. Histone deacetylase (HDAC) inhibitors are a promising new class of anticancer agents. In this study, we investigated the activity of the novel HDAC inhibitor AR-42 in a panel of human and canine OS cell lines. METHODS: The effect of AR-42 and suberoylanilide hydroxamic acid (SAHA) alone or in combination with doxorubicin on OS cell viability was assessed. Induction of histone acetylation after HDAC inhibitor treatment was confirmed by Western blotting. Drug-induced apoptosis was analyzed by FACS. Apoptosis was assessed further by measuring caspase 3/7 enzymatic activity, nucleosome fragmentation, and caspase cleavage. Effects on Akt signaling were demonstrated by assessing phosphorylation of Akt and downstream signaling molecules. RESULTS: AR-42 was a potent inhibitor of cell viability and induced a greater apoptotic response compared to SAHA when used at the same concentrations. Normal osteoblasts were much less sensitive. The combination of AR-42 with doxorubicin resulted in a potent inhibition of cell viability and apparent synergistic effect. Furthermore, we showed that AR-42 and SAHA induced cell death via the activation of the intrinsic mitochondrial pathway through activation of caspase 3/7. This potent apoptotic activity was associated with the greater ability of AR-42 to downregulate survival signaling through Akt. CONCLUSIONS: These results confirm that AR-42 is a potent inhibitor of HDAC activity and demonstrates its ability to significantly inhibit cell survival through its pleiotropic effects in both canine and human OS cells and suggests that spontaneous OS in pet dogs may be a useful large animal model for preclinical evaluation of HDAC inhibitors. HDAC inhibition in combination with standard doxorubicin treatment offers promising potential for chemotherapeutic intervention in both canine and human OS.

Postoperative adjuvant combination therapy with doxorubicin and noncytotoxic suramin in dogs with appendicular osteosarcoma.

Although conventional treatment of dogs with osteosarcoma (OSA) by amputation and chemotherapy results in reported survival times (STs) of 262-413 days, no major improvements in STs have occurred in the past 2 decades. Suramin is a polysulfonated napthylurea, which at noncytotoxic concentrations in vitro, increases tumor sensitivity to chemotherapy, including doxorubicin. The study authors evaluated the combination of noncytotoxic suramin and doxorubicin after amputation in dogs with OSA. The hypothesis was that treatment of dogs with appendicular OSA with amputation, adjuvant doxorubicin, and noncytotoxic suramin would be well tolerated and result in STs at least comparable to those of doxorubicin alone. Forty-seven dogs received 6.75 mg/kg of suramin IV followed by 30 mg/m(2) of doxorubicin IV 4 hr later. Treatment was repeated q 2 wk for five doses. The median disease free time (DFI) was 203 days (range, 42-1,580+ days) and the median ST for all dogs was 369 days (range, 92-1,616+ days). There was no statistical difference in ST and DFI between greyhounds and nonngreyhounds. Adjuvant doxorubicin and noncytotoxic suramin was well tolerated in dogs with OSA following amputation. Additional studies are needed to determine if this combination treatment protocol provides additional clinical benefit compared with doxorubicin alone.

Effects of gemcitabine and gemcitabine in combination with carboplatin on five canine transitional cell carcinoma cell lines.

OBJECTIVE: To evaluate in vitro effects of gemcitabine alone and in combination with carboplatin on canine transitional cell carcinoma (TCC) cell lines. SAMPLE: In vitro cultures of 5 canine TCC cell lines. PROCEDURES: Cells were treated with gemcitabine, carboplatin, or a combination of both at various concentrations. Cell proliferation was assessed via a fluorescence-based microplate cell proliferation assay. Cell cycle was evaluated via propidium iodide staining, and apoptosis was assessed by measurement of caspase 3 and 7 enzymatic activity. Synergy between gemcitabine and carboplatin was quantified via combination index analyses. RESULTS: Treatment of 5 canine TCC cell lines with gemcitabine or carboplatin decreased cell proliferation, increased apoptosis, and induced cell cycle arrest. Cell cycle arrest and apoptosis were markedly increased when cell lines were treated with both gemcitabine and carboplatin simultaneously or sequentially. Order of administration during sequential treatment did not consistently affect cell proliferation results in TCC cell lines. When TCC cell lines were treated with gemcitabine and carboplatin in combination at therapeutically relevant concentrations (gemcitabine concentration, < 10µM; carboplatin concentration, < 250µM), a significant decrease in cell proliferation was observed, compared with cell proliferation following treatment with gemcitabine or carboplatin alone. In combination, the effects of gemcitabine and carboplatin were synergistic in 3 of 5 cell lines and additive in the other 2. CONCLUSIONS AND CLINICAL RELEVANCE: Gemcitabine had antitumor effects on canine TCC cells in vitro, and the combination of gemcitabine and carboplatin had synergistic activity at biologically achievable concentrations.

Development of a brain metastatic canine prostate cancer cell line.

BACKGROUND: Prostate cancer in men has a high mortality and morbidity due to metastatic disease. The pathobiology of prostate cancer metastasis is not well understood and cell lines and animal models that recapitulate the complex nature of the disease are needed. Therefore, the goal of the study was to establish and characterize a new prostate cancer line derived from a dog with spontaneous prostate cancer. METHODS: A new cell line (Leo) was derived from a dog with spontaneous prostate cancer. Immunohistochemistry and PCR were used to characterize the primary prostate cancer and xenografts in nude mice. Subcutaneous tumor growth and metastases in nude mice were evaluated by bioluminescent imaging, radiography and histopathology. In vitro chemosensitivity of Leo cells to therapeutic agents was measured. RESULTS: Leo cells expressed the secretory epithelial cytokeratins (CK)8, 18, and ductal cell marker, CK7. The cell line grew in vitro (over 75 passages) and was tumorigenic in the subcutis of nude mice. Following intracardiac injection, Leo cells metastasized to the brain, spinal cord, bone, and adrenal gland. The incidence of metastases was greatest to the central nervous system (80%) with a lower incidence to bone (20%) and the adrenal glands (16%). In vitro chemosensitivity assays demonstrated that Leo cells were sensitive to Velcade and an HDAC-42 inhibitor with IC(50) concentrations of 1.9 nm and 0.95 µm, respectively. CONCLUSION: The new prostate cancer cell line (Leo) will be a valuable model to investigate the mechanisms of the brain and bone metastases.

Dickkopf-1 (DKK-1) stimulated prostate cancer growth and metastasis and inhibited bone formation in osteoblastic bone metastases.

BACKGROUND: Osteoblastic bone metastasis is the predominant phenotype observed in prostate cancer patients and is associated with high patient mortality and morbidity. However, the mechanisms determining the development of this phenotype are not well understood. Prostate cancer cells secrete several osteogenic factors including Wnt proteins, which are not only osteoinductive but also oncogenic. Therefore, the purpose of the study was to investigate the contribution of the Wnt signaling pathway in prostate cancer growth, incidence of bone metastases, and osteoblastic phenotype of bone metastases. The strategy involved overexpressing the Wnt antagonist, DKK-1, in the mixed osteoblastic and osteolytic Ace-1 prostate cancer cells. METHODS: Ace-1 prostate cancer cells stably expressing human DKK-1 or empty vector were established and transduced with lentiviral yellow fluorescent protein (YFP)-luciferase (Luc). The Ace-1/vector(YFP-LUC) and Ace-1/DKK-1(YFP-LUC) cells were injected subcutaneously, intratibially, or in the left cardiac ventricle in athymic mice. RESULTS: Unexpectedly, DKK-1 significantly increased Ace-1 subcutaneous tumor mass and the incidence of bone metastases after intracardiac injection of Ace-1 cells. DKK-1 increased Ace-1 tumor growth associated with increased phospho46 c-Jun amino-terminal kinase by the Wnt noncanonical pathway. As expected, DKK-1 decreased the Ace-1 osteoblastic phenotype of bone metastases, as confirmed by radiographic, histopathologic, and microcomputed tomographic analysis. DKK-1 decreased osteoblastic activity via the Wnt canonical pathway evidenced by an inhibition of T-cell factor activity in murine osteoblast precursor ST2 cells. CONCLUSION: The present study showed that DKK-1 is a potent inhibitor of bone growth in prostate cancer-induced osteoblastic metastases.

AR-42, a novel HDAC inhibitor, exhibits biologic activity against malignant mast cell lines via down-regulation of constitutively activated Kit.

Histone hypoacetylation occurs in many cancers and inhibition of histone deacetylation is a promising approach to modulate these epigenetic changes. Our laboratory previously demonstrated that the histone deacetylase inhibitors (HDACis) vorinostat and AR-42 reduced the viability of a canine malignant mast cell line. The purpose of this study was to further investigate the mechanisms of pan-HDAC inhibition in normal and malignant mast cells. Mouse and canine malignant mast cell lines expressing various Kit mutations, normal canine mast cells, and primary canine malignant mast cells were treated with AR-42 (a novel HDACi) and effects on cell viability, cycling, and signaling were evaluated. Treatment with AR-42 induced growth inhibition, cell- cycle arrest, apoptosis, and activation of caspases-3/7. AR-42 promoted hyperacetylation of H3, H4, and alpha-tubulin, and up-regulation of p21. Down-regulation of Kit occurred after AR-42 treatment via inhibition of Kit transcription. Disassociation between Kit and heat shock protein 90 (HSP90) and up-regulation of HSP70 were observed after AR-42 treatment, suggesting potential loss of HSP90 chaperone function. Lastly, AR-42 down-regulated the expression of p-Akt, total Akt, phosphorylated STAT3/5 (pSTAT3/5), and total STAT3/5. In summary, AR-42 exhibits in vitro and ex vivo biologic activity against malignant mast cells, representing a promising therapeutic approach for malignant mast cell disease.

Evaluation of the effects of histone deacetylase inhibitors on cells from canine cancer cell lines.

OBJECTIVE: To determine whether exposure of canine cancer cells to histone deacetylase (HDAC) inhibitors S(+)-N-hydroxy-4-(3-methyl-2-phenyl-butyrylamino)benzamide (OSU-HDAC42) or suberoylanilide hydroxamic acid (SAHA) results in increased histone acetylation and decreased cell viability and whether any changes in viability involve induction of apoptosis or alterations in progression of the cell cycle. SAMPLE POPULATION: 9 canine cancer cell lines. PROCEDURES: Cells from 9 canine cancer cell lines were treated with dimethyl sulfoxide vehicle, OSU-HDAC42, or SAHA, then assays of cell viability were performed. Histone acetylation was assessed by use of western blot analysis. Apoptosis was assessed via ELISA to detect fragmentation of cytoplasmic nucleosomal DNA and western blot analysis to detect cleavage of caspase 3. Cell cycle analysis was performed by use of propidium iodide staining and flow cytometry. RESULTS-Concentrations of OSU-HDAC42 and SAHA required to achieve 50% inhibition of cell viability (IC(50)) were reached in cells of 6 and 4 canine cancer cell lines, respectively, and ranged from approximately 0.4 to 1.3 microM for OSU-HDAC42 and 0.6 to 4.8 microM for SAHA. Cells from T-cell lymphoma, mast cell tumor, osteosarcoma, and histiocytic sarcoma lines were most sensitive to HDAC inhibition, with IC(50)s of < 1 microM for OSU-HDAC42 and < 5 microM for SAHA. Induction of apoptosis was indicated via cleavage of caspase 3 and increases in cytoplasmic nucleosomes and the subG(1) cell population. CONCLUSIONS AND CLINICAL RELEVANCE: Micromolar concentrations of HDAC inhibitors OSU-HDAC42 and SAHA induced histone acetylation, cytotoxicity, and apoptosis in canine cancer cells. In general, OSU-HDAC42 was more potent than SAHA.

Biological activity of dihydroartemisinin in canine osteosarcoma cell lines.

OBJECTIVE: To evaluate the biological activity of dihydroartemisinin on canine osteosarcoma cell lines in vitro. SAMPLE POPULATION: 4 canine osteosarcoma cell lines. PROCEDURES: Cell viability assays were performed on canine osteosarcoma cell lines OSCA2, OSCA16, OSCA50, and D17 after 24, 48, and 72 hours of treatment with dihydroartemisinin at concentrations of 0.1 to 100 microM. Apoptosis was assessed by use of an ELISA for free nuclosomal DNA fragmentation and by western blot analysis for cleavage of caspase 3. Cell cycle analysis was performed by use of staining with propidium iodide and flow cytometry. Detection of reactive oxygen species (ROS) was conducted in the D17 cell line by use of 6-carboxy-2',7'-dihydrofluorescein diacetate and flow cytometry. RESULTS: The concentration of dihydroartemisinin required for 50% inhibition of cell viability (IC50) was achieved in all 4 canine osteosarcoma cell lines and ranged from 8.7 to 43.6 microM. Induction of apoptosis was evident as an increase in nucleosomal DNA fragmentation, cleavage of caspase 3, and an increase in the population in the sub G0/G1 phase of the cell cycle detected by flow cytometry. Exposure to dihydroartemisinin also resulted in a decrease in the G0/G1 population. Iron-dependent generation of ROS was detected in dihydroartemisinin-treated D17 cells; ROS generation increased in a dose-dependent manner. CONCLUSIONS AND CLINICAL RELEVANCE: Incubation with dihydroartemisinin resulted in biological activity against canine osteosarcoma cell lines, which included induction of apoptosis and arrest of the cell cycle. Clinical trials of dihydroartemisinin in dogs with osteosarcoma should be conducted.

A novel canine lymphoma cell line: a translational and comparative model for lymphoma research.

A novel canine lymphoma cell line, OSW, was established from the malignant pleural effusion of a dog with peripheral T-cell lymphoma. The immunoprofile as determined by flow cytometry was as follows: positive for CD45, CD49d, CD18, CD11a; weakly positive for CD11b, CD11c, CD11d; and negative for CD45RA, CD1a, CD1c, CD3, TCRalphabeta, TCRgammadelta, CD4, CD5, CD8a, CD8b, CD90(Thy1), CD21, MHCII, CD14(TUK4), CD34, and MPO. Immunocytochemistry of cytospin preparations was negative for cytoplasmic CD3, CD79a, and MPO, but was positive for CD20. The cell line had an oligoclonal T-cell receptor gamma (TCRgamma) gene rearrangement. Array comparative genomic hybridization (aCGH) and single locus probe (SLP) analysis showed that there were copy number increases of loci on dog chromosome 13 (CFA 13), and copy number decreases were evident for regions of CFA 11, 22, 26, 30 and 32, which include several of the more common chromosomal aberrations reported previously in canine lymphoma. The OSW cell line grows rapidly in vitro and is tumorigenic as a xenograft in SCID/NOD mice. OSW represents one of only a few reported canine lymphoma cell lines and is the most thoroughly characterized. This cell line and xenograft represent significant in vitro and in vivo models, respectively, for comparative and translational lymphoma research.