benzyloxycarbonylvalyl-alanyl-aspartyl-fluoromethyl-ketone and Thyroid-Neoplasms

In this study, we evaluated the effect of the hsp70 inhibitor VER155008 on survival of anaplastic thyroid carcinoma (ATC) cells. In ATC cells, VER155008 increased the percentages of dead cells and vacuolated cells. VER155008 did not lead to the cleavage of caspase-3 protein regardless of pretreatment with z-VAD-fmk. VER155008 increased LC3-II protein levels but the protein levels were not changed by autophagy inhibitors. VER155008 caused the dilatation of endoplasmic reticulum (ER), and the increased mRNA levels of Bip and CHOP, suggesting paraptosis. VER155008-induced paraptosis was attenuated by pretreatment with cycloheximide. In conclusion, VER155008 induces paraptosis characterized by cytoplasmic vacuolation, independence of caspase, dilatation of ER and induction of ER stress markers in ATC cells. Moreover, VER155008-induced paraptosis requires de novo protein synthesis in ATC cells.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; Autophagy; Caspase 3; Caspase Inhibitors; Cell Line, Tumor; Endoplasmic Reticulum Chaperone BiP; Endoplasmic Reticulum Stress; Heat-Shock Proteins; HSP70 Heat-Shock Proteins; Humans; Microscopy, Electron, Transmission; Neoplasm Proteins; Purine Nucleosides; RNA, Messenger; Thyroid Carcinoma, Anaplastic; Thyroid Neoplasms; Transcription Factor CHOP; Vacuoles

Bovine seminal ribonuclease (BS-RNase), a natural dimeric homolog of bovine pancreatic RNase (RNase A), and HHP2-RNase, an engineered dimeric form of human pancreatic RNase (HP-RNase), are endowed with powerful antitumor effects. Here we show that BS- and HHP2-RNases, but not monomeric RNase A, induce apoptosis of human thyroid carcinoma cell lines. RNase-induced apoptosis was associated with activation of initiation caspase-8 and -9. This was followed by activation of executioner caspase-3, leading to the proteolytic cleavage of poly(ADP-ribose) polymerase. The caspase inhibitor Z-Val-Ala-Asp-(OMe)-fluoromethylketone protected thyroid cancer cells from BS-RNase-induced apoptosis. RNase-triggered apoptosis and caspase activation were accompanied by reduced phosphorylation of Akt/protein kinase B (PKB), a serine-threonine kinase that when phosphorylated is able to deliver survival signals to cancer cells. BS-RNase antitumor effects in nude mice were accompanied by caspase activation and apoptosis. Because of the high selectivity of apoptotic effects for malignant cells, BS- and HHP2-RNase are promising tools for the treatment of aggressive thyroid cancer.

Topics: Amino Acid Chloromethyl Ketones; Animals; Antineoplastic Agents; Apoptosis; Carcinoma; Caspase Inhibitors; Caspases; Cysteine Proteinase Inhibitors; Endoribonucleases; Humans; Mice; Mice, Nude; Phosphorylation; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Ribonuclease, Pancreatic; Thyroid Neoplasms; Tumor Cells, Cultured