erbstatin and Carcinoma--Small-Cell

In our previous studies (S. Simizu, et al., 1996, Cancer Res. 56, 4978-4982), we reported that apoptosis of human small cell lung carcinoma (SCLC) cells induced by protein tyrosine kinase inhibitors, such as erbstatin and herbimycin A, was mediated by H2O2 via a newly synthesized protein(s). In the present study, we demonstrated that induction of apoptosis by erbstatin resulted in activation of caspase-3(-like) proteases, which are interleukin-1 beta-converting enzyme family proteases (caspases) and that inhibition of these protease activities reduced the extent of cell death and H2O2 generation. We also demonstrated that expression of apoptotic protein Bax was induced by erbstatin. Erbstatin-induced Bax expression was inhibited by the inhibitor of caspase-3(-like) proteases. These results indicate that generation of intracellular H2O2 and Bax expression in tyrosine kinase inhibitor-induced apoptosis were modulated by the activation of caspase-3(-like) proteases in SCLC cells.

Topics: Apoptosis; bcl-2-Associated X Protein; Benzoquinones; Carcinoma, Small Cell; Caspase 3; Caspases; Cysteine Endopeptidases; Cysteine Proteinase Inhibitors; Enzyme Activation; Enzyme Inhibitors; Enzyme Precursors; Humans; Hydrogen Peroxide; Hydroquinones; Kinetics; Lactams, Macrocyclic; Lung Neoplasms; Oligopeptides; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Quinones; Rifabutin; Tumor Cells, Cultured

Tyrosine kinase inhibitor, erbstatin, induced morphological apoptosis and DNA fragmentation in human small cell lung carcinoma (SCLC) cells. Erbstatin-induced apoptosis was inhibited by antioxidants, whereas erbstatin-inhibited tyrosine phosphorylation was not affected by them. Erbstatin was shown by means of flow cytometry to induce hydrogen peroxide generation. Furthermore, hydrogen peroxide induced morphological apoptosis and DNA fragmentation in the SCLC cells. We also demonstrated that erbstatin-induced hydrogen peroxide production and DNA fragmentation were partially suppressed by inhibition of protein synthesis. Thus, erbstatin-induced apoptosis would be due to hydrogen peroxide generation via newly synthesized protein.

Topics: Antioxidants; Apoptosis; Carcinoma, Small Cell; Cycloheximide; Enzyme Inhibitors; Humans; Hydrogen Peroxide; Hydroquinones; Lung Neoplasms; Protein-Tyrosine Kinases; Tumor Cells, Cultured