thioacetamide and Neoplasms

Up-regulation of the folding machinery of the heat-shock protein 90 (Hsp90) chaperone protein is crucial for cancer progression. The two Hsp90 isoforms (α and β) play different roles in response to chemotherapy. To identify isoform-selective inhibitors of Hsp90(α/β)/cochaperone p23 interactions, we developed a dual-luciferase (Renilla and Firefly) reporter system for high-throughput screening (HTS) and monitoring the efficacy of Hsp90 inhibitors in cell culture and live mice. HTS of a 30,176 small-molecule chemical library in cell culture identified a compound, N-(5-methylisoxazol-3-yl)-2-[4-(thiophen-2-yl)-6-(trifluoromethyl)pyrimidin-2-ylthio]acetamide (CP9), that binds to Hsp90(α/β) and displays characteristics of Hsp90 inhibitors, i.e., degradation of Hsp90 client proteins and inhibition of cell proliferation, glucose metabolism, and thymidine kinase activity, in multiple cancer cell lines. The efficacy of CP9 in disrupting Hsp90(α/β)/p23 interactions and cell proliferation in tumor xenografts was evaluated by non-invasive, repetitive Renilla luciferase and Firefly luciferase imaging, respectively. At 38 h posttreatment (80 mg/kg × 3, i.p.), CP9 led to selective disruption of Hsp90α/p23 as compared with Hsp90β/p23 interactions. Small-animal PET/CT in the same cohort of mice showed that CP9 treatment (43 h) led to a 40% decrease in (18)F-fluorodeoxyglucose uptake in tumors relative to carrier control-treated mice. However, CP9 did not lead to significant degradation of Hsp90 client proteins in tumors. We performed a structural activity relationship study with 62 analogs of CP9 and identified A17 as the lead compound that outperformed CP9 in inhibiting Hsp90(α/β)/p23 interactions in cell culture. Our efforts demonstrated the power of coupling of HTS with multimodality molecular imaging and led to identification of Hsp90 inhibitors.

Topics: Acetamides; Animals; Benzoquinones; Blotting, Western; Cell Line, Tumor; Drug Discovery; High-Throughput Screening Assays; HSP90 Heat-Shock Proteins; Humans; Imidazoles; Immunoprecipitation; Intramolecular Oxidoreductases; Lactams, Macrocyclic; Lead; Luciferases, Firefly; Luciferases, Renilla; Mice; Mice, Nude; Neoplasms; Positron-Emission Tomography; Prostaglandin-E Synthases; Protein Folding; Protein Isoforms; Pyrazines; Small Molecule Libraries; Thioacetamide; Thiophenes; Tomography, X-Ray Computed; Tritium

Topics: Animals; Carcinogens; Humans; Indicators and Reagents; Neoplasms; Occupational Exposure; Thioacetamide

Liver cirrhosis and hepatocellular carcinomas are two major causes of morbidity and mortality worldwide, and can synergistically interact to expedite the tumor progression. How fibrosis promotes the hepatoma growth remains completely unexplained. Using an in situ murine hepatoma model together with fibrosis induction by thioacetamide (TAA), the hepatoma growth and the immune factors in the fibrotic liver were analyzed. We found that TAA-fibrosis induction enhanced hepatoma cell growth in the liver and increased the mortality of hepatoma-bearing mice. The tumor-infiltrating CD4(+) or CD8(+) T cells are downregulated by fibrosis induction. The Foxp3(+) regulatory T cells (Treg) cells were induced. We conclude that fibrosis induction causes further immunosuppression, in which Treg cells exert a downregulation effect on the antitumor immunity.

Topics: Animals; Carcinogens; Carcinoma, Hepatocellular; CD4-Positive T-Lymphocytes; Cell Line, Tumor; Cell Proliferation; Forkhead Transcription Factors; Immune Tolerance; Liver Cirrhosis; Liver Neoplasms, Experimental; Lymphocyte Count; Male; Mice; Mice, Inbred BALB C; Neoplasms; T-Lymphocytes, Regulatory; Thioacetamide; Tumor Escape

It was possible, by reverse-phase high-pressure liquid chromatography (HPLC) to separate thiourea, thioacetamide, and phenobarbitone with retention times of 1.4, 1.7, and 4.7 min, respectively. Thiourea and thioacetamide are known carcinogens. Substances such as phenobarbitone, thiourea, and thioacetamide, which may be encountered in our environment, can now be identified by this technique. It is also recommended that this HPLC technique should be used routinely in the screening of the purity of substances which are being subjected to toxicity, carcinogenicity, mutagenicity, and teratogenicity evaluation. A mixture of impurities in the sodium phenobarbitone was removed in the synthesis of the 5-ethyl-5-phenyl-barbituric acid (phenobarbitone). These substances which were not thiourea or thioacetamide could have been responsible for the positive result in the in vitro degranulation test for carcinogens with sodium phenobarbitone.

Topics: Abnormalities, Drug-Induced; Acetamides; Animals; Chromatography, High Pressure Liquid; Mice; Mutagenicity Tests; Neoplasms; Phenobarbital; Rats; Thioacetamide; Thiourea

Topics: Acetates; Amides; Carcinogens; Liver Neoplasms; Liver Neoplasms, Experimental; Neoplasms; Thioacetamide; Tissue Culture Techniques

Topics: Acetates; Bile Duct Neoplasms; Bile Ducts; Carcinogens; Humans; Neoplasms; Thioacetamide

Topics: Animals; Liver; Liver Neoplasms; Neoplasms; Rats; Thioacetamide; Thiourea