ABSTRACT
Objective To investigate the way that nasopharyngeal carcinoma (NPC) and NPC stem cells develops resistance to cisplatin through anti-reactive oxygen species mechanism. Methods Using CCK-8 cell counting kit, we measured the half inhibitory concentration of cisplatin against NPC cellsCNE-2and NPC stem cellsCNE-2S, and compared their resistant index. We examined the differences in the reactive oxygen species (ROS) levels, total glutathi?one (GSH) levels, and total superoxide dismutase (SOD) levels between CNE-2 and CNE-2S at different concentrations of cisplatin administration (0.1,0.5 and 1.0μmol·L-1). Using q-PCR, we determined the mRNA expression level of GSS, GCLC, GCLM, SOD1 and SOD2 after 48 hours administration of cisplatin at 1 μmol · L-1. Protein expression level of SOD2 was also tested using Western Blot after 48 hours administration of cisplatin at 1μmol · L-1. Upon silencing the SOD2 in NPC cell through siRNA, Trypan blue was used to analyze cell survival after cisplatin was administrated at 1μmol · L-1. Results The inhibition concentration of cisplatin against CNE-2 was higher than that against CNE-2S (μmol · L-1:9.8 ± 1.1 vs 2.4 ± 0.6,P<0.05). ROS levels in CNE-2 and CNE-2S both rise with cisplatin administration, but ROS levels of CNE-2 before and after cisplatin treatment were both higher than those in CNE-2S (P<0.05). The total gluta?thione levels in CNE-2 and CNE-2S were both increased after 1μmol·L-1 cisplatin treatment but there is no significant dif?ference in levels of glutathione between these two cell lines. After treated with cisplatin, SOD level were increased in both CNE-2S and CNE-2, but it is higher in CNE-2S than that in CNE-2 (P<0.05). The mRNA levels of GSS, GCLC, GCLM, and SOD1 were not different significantly between in CNE-2 and in CNE-2S with or without cisplatin treatment. However, SOD2 in CNE-2S were higher than that in CNE-2 on both mRNA and protein levels (P<0.05). Silenced SOD2 disrupted the resistance of cisplatin in CNE-2S. Conclusion These data suggest that NPC stem cells (CNE-2S) enhance its drug re?sistance to cisplatin through highly expression of SOD2 which posed anti-ROS capacity.