benzyloxycarbonylvalyl-alanyl-aspartyl-fluoromethyl-ketone and Mesothelioma

Malignant mesothelioma (MM) is a cancer with uniformly poor responses to current therapeutic regimens. This study evaluates whether taurolidine, a novel antineoplastic agent, is effective against human MM cell lines and a murine model of human MM.. Cell growth inhibition and viability assays were performed on REN, LRK, and H28 cell lines after 24-72-h exposure to 0-200 microm taurolidine. Cell cycle analysis with annexin-V binding, terminal deoxynucleotidyl transferase-mediated nick end labeling assay, electron microscopy, and response to the general caspase inhibitor z-VAD-fmk were performed on MM cell lines after 24-72-h exposure to 50-150 microm taurolidine. Athymic mice were given i.p. injections of 20 x 10(6) REN cells, followed by i.p. taurolidine (17.5 or 20 mg), 3 days/week for up to 3 weeks. Tumors were assessed at day 30. All statistical tests were two-sided.. A 72-h exposure of MM cells to taurolidine showed IC50 of 28-42.7 microm and 50% viability at 49.8-135 microm. Annexin V assay for apoptosis revealed significant increases in annexin binding after 24-72-h exposure to 50-150 microm taurolidine (P <0.05), which was significantly inhibited by z-VAD (P <0.05). MM cells exposed to 50-150 microm taurolidine for 24-72 h showed terminal deoxynucleotidyl transferase-mediated nick end labeling staining consistent with apoptosis, as well as structural evidence of apoptosis via electron microscopy. In vivo, there were significant tumor reductions (62 to >99% reduction) for all dosage regimens compared with untreated controls (P <0.001). In addition, all control animals exhibited ascites and diaphragmatic tumors while treated animals did not.. Taurolidine has significant antineoplastic activity against MM in vitro and in vivo, in part, due to tumor cell apoptosis. These findings warrant further study for potential clinical usefulness.

Topics: Amino Acid Chloromethyl Ketones; Animals; Annexin A5; Antineoplastic Agents; Apoptosis; Body Weight; Caspases; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Cell Survival; Disease Models, Animal; Enzyme Inhibitors; Humans; In Situ Nick-End Labeling; Lung Neoplasms; Male; Mesothelioma; Mice; Mice, Nude; Microscopy, Electron; Phosphatidylserines; Taurine; Thiadiazines; Time Factors

Methionine aminopeptidase-2 (MetAP2) is the molecular target of the angiogenesis inhibitors, fumagillin and ovalacin. Fumagillin can also inhibit cancer cell proliferation, implying that MetAP2 may play a quite complex role in tumor progression. Here, we examined the expression and function of MetAP2 in an in vitro model of human mesothelioma. We found that mesothelioma cells expressed higher MetAP2 mRNA levels than primary normal mesothelial cells. Consistently, fumagillin induced apoptosis, owing to early mitochondrial damage, in malignant, but not in normal mesothelial cells. Transfection of mesothelioma cells with a MetAP2 anti-sense oligonucleotide determined a time-dependent inhibition of cell survival and induced nucleosome formation. Interestingly, mRNA and protein levels of the anti-apoptotic gene bcl-2 as well as telomerase activity were selectively reduced after MetAP2 inhibition in mesothelioma cells, whereas bcl-2 overexpression counteracted the effect of MetAP2 inhibition on telomerase activity and apoptosis. MetAP2 inhibition also increased caspase activity and the caspase inhibitor, zVAD-fmk, prevented fumagillin-induced apoptosis, but it did not alter telomerase activity. These results indicate that MetAP2 is a main regulator of proliferative and apoptotic pathways in mesothelioma cells and suggest that MetAP2 inhibition may represent a potential target for therapeutic intervention in human mesothelioma.

Topics: Amino Acid Chloromethyl Ketones; Aminopeptidases; Angiogenesis Inhibitors; Apoptosis; Caspase 3; Caspases; Cell Division; Cell Survival; Collagen; Cyclohexanes; Cysteine Proteinase Inhibitors; Endostatins; Fatty Acids, Unsaturated; Genes, bcl-2; Humans; Mesothelioma; Metalloendopeptidases; Oligodeoxyribonucleotides, Antisense; Peptide Fragments; Proto-Oncogene Proteins c-bcl-2; RNA, Messenger; Sesquiterpenes; Suramin; Telomerase; Thalidomide; Transcription, Genetic; Transfection; Tumor Cells, Cultured