acetyl-aspartyl-glutamyl-valyl-aspartal 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

Vinblastine arrests cells in the G2/M phase of the cell cycle and subsequently induces cell death by apoptosis. We found that treatment of cells with vinblastine induced phosphorylation of Bcl-2, resulting in the dissociation of Bcl-2 and Bax. Moreover, vinblastine-induced apoptosis was suppressed by an inhibitor of caspase-3, Ac-DEVD-CHO; and a 17-kDa active fragment of caspase-3 was detected following vinblastine treatment, suggesting that caspase-3 is involved in vinblastine-induced apoptosis. However, Ac-DEVD-CHO affected neither vinblastine-induced Bcl-2 phosphorylation nor vinblastine-induced G2/M arrest. Vinblastine caused G2/M arrest prior to apoptosis, whereas vinblastine-induced apoptosis was not dependent on the duration of the G2/M phase. Thus, vinblastine-induced apoptosis might be mediated by the phosphorylation of Bcl-2, resulting in Bcl-2 inactivation, and by subsequent activation of caspase-3.

Topics: Apoptosis; Carcinoma, Small Cell; Caspase 3; Caspases; Cysteine Proteinase Inhibitors; Enzyme Activation; G2 Phase; Humans; Lung Neoplasms; Mitosis; Oligopeptides; Peptide Fragments; Phosphorylation; Proto-Oncogene Proteins c-bcl-2; Tumor Cells, Cultured; Vinblastine