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Tyrosine kinase inhibitors reduce bcl-2 expression and induce apoptosis in androgen-dependent cells
1Department of Urology, Kidney Center, Saitama Medical School, Moroyamamachi 350-0495, Japan. ohigashi@med.keio.ac.jp
Abstract:
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.
Insights
Androgen withdrawal induces apoptosis in cancer cells via tyrosine kinases. Inhibiting these kinases reduces viable cells and bcl-2 expression, suggesting a new therapeutic target for androgen-dependent cancers.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- The precise signal transduction pathway linking androgen withdrawal to apoptosis in androgen-dependent cells remains unclear.
- Understanding this pathway is crucial for developing targeted therapies for androgen-dependent cancers.
Purpose of the Study:
- To investigate the role of tyrosine kinases in apoptosis and bcl-2 expression during androgen withdrawal in androgen-dependent cells.
- To elucidate the signal transduction pathway connecting androgen receptor activation to bcl-2 expression.
Main Methods:
- Utilized SC2G, an androgen-dependent mouse mammary carcinoma cell line.
- Administered herbimycin A (HMA), a tyrosine kinase inhibitor, and assessed cell viability, apoptosis (TUNEL assay, Annexin V staining), and bcl-2 mRNA levels (RT-PCR).
- Investigated the effect of caspase inhibitors and human bcl-2 gene transfection on HMA-induced apoptosis.
Main Results:
- Herbimycin A significantly decreased viable SC2G cells and induced apoptosis.
- HMA suppressed bcl-2 mRNA levels in a dose-dependent manner.
- Caspase inhibitors protected against HMA-induced apoptosis, and bcl-2 overexpression conferred tolerance to HMA.
Conclusions:
- HMA-sensitive tyrosine kinases regulate apoptosis and inhibit bcl-2 expression in androgen-dependent SC2G cells.
- Tyrosine kinases act as signal transducers between androgen receptor activation and bcl-2 expression.
- These findings highlight tyrosine kinases as potential therapeutic targets in androgen-dependent cancers.