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Reversion of human prostate tumorigenic growth by azatyrosine
R M Benoit1, J Eiseman, S C Jacobs
1Department of Surgery, University of Maryland School of Medicine, Baltimore, USA.
Objectives:
Azatyrosine, an antibiotic isolated from a Streptomyces species, has been previously shown to have antitumor activity against ras- and neu-transformed fibroblasts and human epithelial cells. In this study, we investigated the effect of azatyrosine on human prostate cancer cell growth and the reversion potential of this antibiotic on prostate tumorigenic cell lines.
Methods:
Three androgen-independent human prostate cancer cell lines (TSU-Prl, DU-145, and PC-3) were cultured in the presence of azatyrosine and their growth rates were determined over a 7-day period. Following exhaustive treatment with azatyrosine for 5 weeks, three azatyrosine-resistant colonies were cloned from the PC-3 cell line and were subsequently established as stable cell lines. The growth characteristics of these azatyrosine-resistant clones were examined both in vitro and in vivo to establish their "potentially revertant" profiles.
Results:
Incubation with azatyrosine (for 7 days) resulted in greater than 95% in vitro growth inhibition of the three parental prostate cancer cell lines. Analysis of the biologic properties of these azatyrosine-resistant cell lines revealed: (1) a significant reduction in in vitro growth rates; (2) a decreased rate of DNA synthesis as measured by thymidine uptake; and (3) a decreased ability for colony formation in soft agar. Moreover all three azatyrosine-resistant clones exhibited suppressed tumorigenicity in severe combined immunodeficient (SCID) mice when compared with the parental cell line. An important observation was that one revertant clone demonstrated complete loss of tumorigenicity. On the basis of this biologic behavior, these cell lines were characterized as revertants. Cytogenetic analysis revealed gross chromosomal differences between the revertant clones and the parental cell line. Northern hybridization analysis demonstrated elevated expression of the K-rev-1 and bcl-2 but not the rrg mRNA transcripts in the revertant cell lines.
Conclusions:
These results suggest that azatyrosine inhibits prostate tumorigenic growth; it has a high reversion efficiency on human prostate cancer cells; and the K-rev-1 suppressor gene and the bcl-2 proto-oncogene could be potentially involved in the reversion mechanism mediated by azatyrosine. This reversion of prostate cancer cells to an apparently nontumorigenic phenotype points to a potentially significant therapeutic role for azatyrosine in the treatment of advanced prostate cancer.
Insights
Azatyrosine, an antibiotic, significantly inhibits human prostate cancer cell growth and induces reversion to a non-tumorigenic state. This suggests a potential therapeutic role for azatyrosine in advanced prostate cancer treatment.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Azatyrosine, an antibiotic from Streptomyces, exhibits antitumor activity.
- Prostate cancer remains a significant health concern, necessitating novel therapeutic strategies.
Purpose of the Study:
- To investigate the effects of azatyrosine on human prostate cancer cell growth.
- To evaluate the reversion potential of azatyrosine in prostate cancer cell lines.
Main Methods:
- Cultured three androgen-independent human prostate cancer cell lines (TSU-Prl, DU-145, PC-3) with azatyrosine.
- Developed azatyrosine-resistant clones and assessed their in vitro and in vivo growth characteristics.
- Performed cytogenetic and Northern hybridization analyses.
Main Results:
- Azatyrosine achieved >95% in vitro growth inhibition of prostate cancer cells.
- Resistant clones showed reduced growth rates, DNA synthesis, and soft agar colony formation.
- Resistant clones exhibited suppressed tumorigenicity in SCID mice, with one clone losing all tumorigenicity.
- Elevated K-rev-1 and bcl-2 mRNA expression observed in revertant cell lines.
Conclusions:
- Azatyrosine effectively inhibits prostate tumorigenic growth and demonstrates high reversion efficiency.
- K-rev-1 suppressor gene and bcl-2 proto-oncogene may be involved in azatyrosine-mediated reversion.
- Azatyrosine shows potential as a therapeutic agent for advanced prostate cancer.