RESUMEN
The enzyme cyclooxygenase-2 (COX-2) is abundantly expressed in colon cancer cells and plays a key role in colon tumorigenesis. Compounds inhibiting COX-2 transcriptional activity have therefore potentially a chemopreventive property against colon tumor formation. An assay method for estimating COX-2 transcriptional activity in human colon cancer cells was established using a beta-galactosidase reporter gene system, and examination was made of various medicinal herbs and their ingredients for an inhibitory effect on COX-2 transcriptional activity. We found that berberine, an isoquinoline alkaloid present in plants of the genera Berberis and Coptis, effectively inhibits COX-2 transcriptional activity in colon cancer cells in a dose- and time-dependent manner at concentrations higher than 0.3 microM. The present findings may further explain the mechanism of anti-inflammatory and anti-tumor promoting effects of berberine.
Asunto(s)
Berberina/farmacología , Neoplasias del Colon/enzimología , Isoenzimas/biosíntesis , Prostaglandina-Endoperóxido Sintasas/biosíntesis , Transcripción Genética/efectos de los fármacos , División Celular/efectos de los fármacos , Neoplasias del Colon/genética , Cicloheximida/farmacología , Ciclooxigenasa 2 , Genes Reporteros/efectos de los fármacos , Humanos , Isoenzimas/genética , Proteínas de la Membrana , Plásmidos , Prostaglandina-Endoperóxido Sintasas/genética , Inhibidores de la Síntesis de la Proteína/farmacología , Transfección , Células Tumorales CultivadasRESUMEN
Activator protein 1 (AP-1) is a transcription factor which plays a critical role in inflammation and carcinogenesis. The present study was conducted to investigate the effect of berberine, an isoquinoline alkaloid present in plants of the genera Berberis and Coptis, on the activity of AP-1 using a reporter gene assay in human hepatoma cells. Berberine was shown to inhibit AP-1 activity in a dose- and time-dependent manner at concentrations higher than 0.3 microM. Berberine inhibited AP-1 activity almost completely as low as 10 microM after 48 h treatment. The inhibitory effect on AP-1 activity in cancer cells may further explain the anti-tumor promoting activity of berberine.
Asunto(s)
Berberina/farmacología , Carcinoma Hepatocelular/metabolismo , Neoplasias Hepáticas/metabolismo , Factor de Transcripción AP-1/antagonistas & inhibidores , Carcinoma Hepatocelular/patología , Humanos , Neoplasias Hepáticas/patología , Células Tumorales CultivadasRESUMEN
The mechanism for cisplatin resistance in cisplatin-resistant KCP-4 cells was studied. Although multidrug resistance-associated protein (MRP) was not detected in KCP-4 cells, the cells were more resistant to heavy metals than multidrug-resistant C-A120 cells that overexpressed MRP. KCP-4 cells expressed metallothionein, but it was scarcely involved in cisplatin resistance in these cells. KCP-4 cells did not express canalicular multispecific organic anion transporter (cMOAT). The glutathione (GSH) level was 4.7-fold higher in KCP-4 cells than in KB-3-1 cells. When the GSH level in KCP-4 cells was decreased by treating the cells with buthionine sulfoximine and nitrofurantoin, the accumulation of and sensitivity to cisplatin in the cells were increased. C-A120 cells were only 3.0-fold more resistant to cisplatin than KB-3-1 cells and this resistance was not affected by the increased glutathione level. The accumulation of platinum in C-A120 and KCP-4 cells was 68.5 and 20.4% of that in KB-3-1 cells, respectively, while the intracellular levels of antimony potassium tartrate in C-A120 and KCP-4 cells were 13.2 and 9.9% of that in KB-3-1 cells, respectively. The ATP-dependent efflux of antimony was enhanced in both C-A120 and KCP-4 cells. These results, taken together, suggest an efflux pump for heavy metals different from MRP and cMOAT is involved in cisplatin resistance in KCP-4 cells.