Role of ABCB1 and ABCG2 in the multidrug resistance of hypopharyngeal carcinoma FaDu cell line

Abstract

To investigate the expression of multidrug resistance gene ABCB1 and ABCG2 in FaDu cells (human hypopharyngeal carcinoma cell line) and the multidrug resistance (MDR) cell lines FaDu/T transformed from FaDu cells by taxol and underlying mechanisms of MDR. The multidrug resistance sensitivities of FaDu and FaDu/T to cisplatin (DDP), 5-fluorouracil (5-FU), doxorubicin (Dox), and vincristine (VCR) were examined by methyl-thiazolyl-tetrazolium (MTT) assay. The mRNA and protein expressions of multidrug resistance genes ABCB1 and ABCG2 were analysed with RT-PCR, Western blot and laser confocal microscopy. JNK signal proteins were detected through Western blot. The multidrug resistance of FaDu/T cells to Taxol, DDP, 5-FU, ADM and VCR was more than that of FaDu cells. The expression of ABCB1 in FaDu/T cells was significantly higher than that in FaDu cells (t = 22.42, P < 0.05), but the expression of ABCG2 in FaDu/T cells was significantly lower than that in FaDu cells (t = 10.06, P < 0.05). JNK signal was inhibited in FaDu or FaDu/T cells and the inhibited JNK was reactivated by taxol or anisomycin (an activator for MAPK signal transduction pathways). Anisomycin down-regulated the expression of ABCB1 (F = 33.72, P < 0.05) and up-regulated the expression of ABCG2 (F = 220.16, P < 0.05) in FaDu/T cells, but not in FaDu/T cells pretreated by JNK inhibitor SP600125 (P > 0.05). The overexpression of ABCB1 and the down-regulation of ABCG2 in FaDu/T cells were the main features of MDR in hypopharyngeal carcinomas, in which JNK signal transduction pathways could play an important role.