nitrophenols and Bone-Neoplasms

High-grade conventional osteosarcoma is the most common primary bone tumor. Prognosis for osteosarcoma patients is poor and resistance to chemotherapy is common. We performed an siRNA screen targeting members of the Bcl-2 family in human osteosarcoma cell lines to identify critical regulators of osteosarcoma cell survival. Silencing the anti-apoptotic family member Bcl-xL but also the pro-apoptotic member Bak using a SMARTpool of siRNAs as well as 4/4 individual siRNAs caused loss of viability. Loss of Bak impaired cell cycle progression and triggered autophagy. Instead, silencing Bcl-xL induced apoptotic cell death. Bcl-xL was expressed in clinical osteosarcoma samples but mRNA or protein levels did not significantly correlate with therapy response or survival. Nevertheless, pharmacological inhibition of a range of Bcl-2 family members showed that inhibitors targeting Bcl-xL synergistically enhanced the response to the chemotherapeutic agent, doxorubicin. Indeed, in osteosarcoma cells strongly expressing Bcl-xL, the Bcl-xL-selective BH3 mimetic, WEHI-539 potently enhanced apoptosis in the presence of low doses of doxorubicin. Our results identify Bcl-xL as a candidate drug target for sensitization to chemotherapy in patients with osteosarcoma.

Topics: Antineoplastic Combined Chemotherapy Protocols; Apoptosis; bcl-X Protein; Benzopyrans; Biphenyl Compounds; Bone Neoplasms; Cell Line, Tumor; Cohort Studies; Doxorubicin; Drug Synergism; Enzyme Inhibitors; Humans; Immunohistochemistry; Lung Neoplasms; Nitriles; Nitrophenols; Osteosarcoma; Piperazines; Sulfonamides; Tissue Array Analysis; Transfection

Chondrosarcoma is refractory to conventional chemotherapy. BH-3 mimetics ABT-737 and ABT-263 are synthetic small-molecule inhibitors of anti-apoptotic proteins B-cell lymphoma-2 (Bcl2) and Bcl-xL, which play a critical role in survival of chondrosarcoma cells.. Chondrosarcoma cell lines SW-1353 and CS-1 were used as the disease model. We used immunoblotting to assess the expression of target molecules Bcl2 and Bcl-xL, and the apoptotic inducers Bcl2-associated X (Bax) and Bcl2-antagonist/killer (Bak). In vitro growth inhibition by BH-3 mimetics was confirmed by photomicroscopic cell counting and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay. Apoptotic induction was confirmed by Enzyme-Linked ImmunoSorbent Assay (ELISA). In vivo growth inhibition was assessed in a non-obese diabetic/severe combined immunodeficient (NOD/SCID) mouse model.. Expression of the target and effector molecules was confirmed in chondrosarcoma cell lines. BH3 mimetics significantly inhibited cell growth and induced apoptosis in vitro. Administration of ABT-263 inhibited chondrosarcoma growth and improved survival in a mouse model.. BH3 mimetics represent a novel treatment modality for chondrosarcoma.

Topics: Aniline Compounds; Animals; Antineoplastic Agents; Apoptosis; bcl-2 Homologous Antagonist-Killer Protein; bcl-2-Associated X Protein; Biphenyl Compounds; Blotting, Western; Bone Neoplasms; Cell Proliferation; Chondrosarcoma; Disease Models, Animal; Humans; Male; Mice; Mice, Inbred NOD; Mice, SCID; Middle Aged; Molecular Mimicry; Molecular Targeted Therapy; Nitrophenols; Peptide Fragments; Piperazines; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Sulfonamides; Tumor Cells, Cultured; Xenograft Model Antitumor Assays

Alkaline phosphatase (ALP) is the most widely recognized biochemical marker for osteoblast activity. Although its precise function is poorly understood, it is believed to play a role in skeletal mineralization. The aim of this study was to develop an assay suitable for measuring the activity of this enzyme in microtiter plate format. Using the well-characterized osteoblast-like cell line Saos-2, this paper describes an optimized biochemical assay suitable for measuring ALP activity in tissue culture samples. We have determined that a p-nitrophenyl phosphate substrate concentration of 9 mM provides highest enzyme activities. We have found that cell concentration, and hence enzyme concentration, affects both the kinetics and precision of the assay. We also tested several methods of enzyme solubilization and found that freeze-thawing the membrane fractions twice at -70 degrees C/37 degrees C or freeze-thawing once with sonication yielded highest enzyme activities. The activity of the enzyme decreased by 10% after 7 days storage. This assay provides a sensitive and reproducible method that is ideally suited for measuring ALP activity in isolated osteoblastic cells, although sample preparation and storage can influence results.

Topics: Alkaline Phosphatase; Analysis of Variance; Bone Neoplasms; Buffers; Cell Count; Humans; Indicators and Reagents; Kinetics; Nitrophenols; Organophosphorus Compounds; Osteoblasts; Osteosarcoma; Reference Standards; Reproducibility of Results; Substrate Specificity; Tumor Cells, Cultured

Phosphodiesterase I (EC 3.1.4.1) activity was detected in normal human blood serum. The enzyme is stable at laboratory temperature for three days, but is inactivated at pH less than 7. The pH for optimum activity increases with the substrate concentration (under the conditions used, from pH 9.0 to 10.2) and, conversely, the Km increases with pH and buffer concentration. The enzyme is inhibited by ethylenediaminetetraacetate but not by phosphate (0.1 mol/liter). We developed a simple quantitative method for its determination, based on hydrolysis of the p-nitrophenyl ester of thymidine 5'-monophosphate and subsequent measurement of the liberated p-nitrophenol at 400 nm in NaOH (0.1 mol/liter). Normal values (mean +/- 2 SD) were determined to be 33 +/- 6.4 U/liter. Preliminary studies indicate that phosphodiesterase I activity is greater than normal in serum of patients with necrotic changes in the liver or kidney or in cases of breast cancer, but not in that of patients with myocardial infarction, bone cancer, lung cancer, or chronic liver cirrhosis.

Topics: Alkaline Phosphatase; Bone Neoplasms; Breast Neoplasms; Edetic Acid; Female; Humans; Kinetics; Liver Cirrhosis; Lung Neoplasms; Male; Myocardial Infarction; Nitrophenols; Phosphates; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Thymine Nucleotides