RESUMEN
Many isoprenylated proteins are known to participate in signal transduction, but not all have been identified. Using an in vitro prenylation screen, two human cDNAs (PTP(CAAXI) and PTP(CAAX2)) homologous to the rat PRL-1 and human OV-1 protein tyrosine phosphatase genes were identified. PTP(CAAXI) and PTP(CAAX2) were farnesylated in vitro by mammalian farnesyl:protein transferase, and epitope-tagged PTP(CAAX2) was prenylated in epithelial cells. Overexpression of PTP(CAAXI) and PTP(CAAX2) in epithelial cells caused a transformed phenotype in culture and tumor growth in nude mice. Thus, PTP(CAAXI) and PTP(CAAX2) represent a novel class of isoprenylated, oncogenic protein tyrosine phosphatases.
Asunto(s)
Transferasas Alquil y Aril , Prenilación de Proteína , Proteínas Tirosina Fosfatasas/metabolismo , Transferasas/metabolismo , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Proteínas de Ciclo Celular , Transformación Celular Neoplásica , Cricetinae , Humanos , Proteínas Inmediatas-Precoces/genética , Proteínas Inmediatas-Precoces/metabolismo , Proteínas de la Membrana , Ratones , Datos de Secuencia Molecular , Proteínas de Neoplasias , Fenotipo , Proteínas Tirosina Fosfatasas/genética , Células Tumorales CultivadasRESUMEN
BACKGROUND: Perillyl alcohol has chemotherapeutic activity against pancreas cancers that have a K-ras oncogene, and it inhibits the prenylation of Ras and other proteins in many cell types. MATERIALS AND METHODS: We tested the hypothesis that perillyl alcohol would impair Ras farnesylation and Ras signal transduction pathways in pancreatic tumor cells. RESULTS: In B12/13 pancreatic tumor cells that had a K-ras oncogene, perillyl alcohol inhibited total protein prenylation and decreased Ras farnesylation. However, the decrease in Ras farnesylation was not sufficient to affect Ras GTP/GDP ratios or MAP kinase phosphorylation. We then investigated the effects of perillyl alcohol on H-Ras vs. K-Ras. Interestingly, H-Ras, but not K-Ras, farnesylation was inhibited by perillyl alcohol, and perillyl alcohol inhibited MAP kinase phosphorylation in H-ras but not K-ras oncogene-transformed pancreatic cells. CONCLUSIONS: The antitumor activity of perillyl alcohol against pancreatic cancers may stem from its ability to inhibit the prenylation of growth-regulatory proteins other than K-Ras, including H-Ras.
Asunto(s)
Antineoplásicos/farmacología , Monoterpenos , Neoplasias Pancreáticas/tratamiento farmacológico , Prenilación de Proteína/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Terpenos/farmacología , Proteínas ras/metabolismo , Animales , Cricetinae , Mesocricetus , Neoplasias Pancreáticas/metabolismo , Neoplasias Pancreáticas/patología , FosforilaciónRESUMEN
Perillyl alcohol has antitumor activity toward pancreas and other cancers with low toxicity. Here, we have investigated the mechanism of action responsible for the differential sensitivity of malignant versus non-malignant pancreatic cells to the drug. We report that the rate of apoptosis is over 6-fold higher in perillyl alcohol-treated pancreatic adenocarcinoma cells than in untreated cells, and that the effect of perillyl alcohol on pancreatic tumor cells is significantly greater than its effect on non-malignant pancreatic ductal cells. Moreover, the perillyl alcohol-induced increase in apoptosis in all of the pancreatic tumor cells is associated with a 2- to 8-fold increase in the expression of the proapoptotic protein Bak, but Bak expression is not affected by perillyl alcohol in non-malignant cells. Thus, the antitumor activity of perillyl alcohol toward pancreatic cancers may be due to preferential stimulation of Bak-induced apoptosis in malignant versus normal cells. Bak may, therefore, be a useful biomarker for the chemopreventive and therapeutic effects of perillyl alcohol.