acetyl-aspartyl-glutamyl-valyl-aspartal and herbimycin

The signal transduction pathway showing how androgen withdrawal induces apoptosis in androgen-dependent cells has not been clearly understood. In these studies, we focused on the behavior of tyrosine kinases in androgen-dependent cells and investigated its correlation with apoptosis and bcl-2 expression. We used SC2G, an androgen-dependent mouse mammary carcinoma cell line, which had been cloned from Shionogi Carcinoma 115 (SC115). When SC2G cells were cultured with herbimycin A (HMA), a potent tyrosine kinase inhibitor, the number of viable cells decreased significantly after 24 h. Terminal deoxyribonucleotidyltransferase-mediated dUTP-biotin nick end labeling and flow cytometric analysis of annexin V staining showed that HMA induced apoptosis of SC2G cells. The level of bcl-2 mRNA in SC2G cells was suppressed by HMA in a dose-dependent manner on RT-PCR. Preincubation with caspase inhibitors protected HMA-induced apoptosis of SC2G cells. When a human bcl-2 gene was transfected in SC2G cells and overexpressed, SC2G cells seemed to acquire tolerance for HMA. These data indicate that HMA-sensitive tyrosine kinase(s) can regulate apoptosis and inhibit bcl-2 expression in SC2G mouse androgen-dependent cells. Tyrosine kinase(s) seemed to be a member of signal transduction between androgen receptor activation and bcl-2 expression.

Topics: Animals; Apoptosis; Benzoquinones; Caspases; Cell Separation; Cell Survival; Cysteine Proteinase Inhibitors; Dose-Response Relationship, Drug; Enzyme Inhibitors; Gene Expression Regulation, Enzymologic; Gonadal Steroid Hormones; Humans; In Situ Nick-End Labeling; Lactams, Macrocyclic; Mammary Neoplasms, Experimental; Mice; Oligopeptides; Protein-Tyrosine Kinases; Proto-Oncogene Proteins c-bcl-2; Quinones; Rifabutin; RNA, Messenger; Testosterone; Transfection; Tumor Cells, Cultured

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