Paclitaxel (taxol) inhibits protein isoprenylation and induces apoptosis in PC-3 human prostate cancer cells.
Paclitaxel was examined for its effects on cell survival, internucleosomal DNA fragmentation, and protein isoprenylation in the human prostate cancer cell line PC-3. Treatment of cells with paclitaxel at 5-60 nM for 24 hr resulted in a dose-dependent inhibition of cell viability (IC50, 31.2 nM), which was partially prevented by supplementing the cell culture medium with two nonsterol polyisoprenyl compounds, farnesyl-pyrophosphate (-PP) and geranylgeranyl-PP (3 microM each). Furthermore, agarose gel electrophoresis of DNA extracted from cells treated with paclitaxel (15-60 nM) for 24 hr showed DNA laddering with production of fragments of 180-base pair multiples, indicating the occurrence of apoptotic cell death. Internucleosomal DNA fragmentation by paclitaxel was also detected by a photometric enzyme immunoassay using antihistone antibodies; if culture medium was supplemented with farnesyl-PP and geranylgeranyl-PP (3 microM each), a reduction in mono- and oligonucleosome production was observed. The post-translational incorporation of metabolites of (RS)-[5-3H]mevalonolactone (100 microCi/ml) into prenylated proteins of PC-3 cells was inhibited by paclitaxel at 30 and 60 nM. In addition, the immunoprecipitation of p21ras and p21rap-1 proteins from PC-3 cells exposed to paclitaxel (30 and 60 nM) and labeled with (RS)-[5-3H]mevalonolactone showed a substantial inhibition of the incorporation of farnesyl and geranylgeranyl prenoid groups, respectively, into the aforementioned proteins. These results indicate that the inhibition of protein isoprenylation is a novel component of the complex biochemical effects of the drug and plays an important role in the mechanism of paclitaxel cytotoxicity in PC-3 cells.
Danesi
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R
Division of Hematology/Oncology, University of Virginia, Charlottesville 22908, USA.
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D017209:Apoptosis / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D008297:Male; D015689:Oncogene Protein p21(ras) / Q000037:antagonists & inhibitors / Q000378:metabolism; D017239:Paclitaxel / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D017368:Protein Prenylation / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D020668:rap GTP-Binding Proteins
D019204:GTP-Binding Proteins; D015689:Oncogene Protein p21(ras); D020668:rap GTP-Binding Proteins; D017239:Paclitaxel