Sestamibi accumulation in human nasopharyngeal carcinoma cell lines in vitro

Sestamibi imaging is used to assess the staging of nasopharyngeal carcinoma (NPC), and to monitor response to therapy. Sestamibi was added to single-cell suspensions of the NPC cell lines CNE-1 and CNE-2Z, and aliquots were removed over 60 min and centrifuged to determine cell-associated radioactivity. Sestamibi accumulation reached similar plateau values in both cell lines within 30 min of addition. Saturating concentrations of P-glycoprotein (Pgp) modulators increased accumulation by 1.4-1.7 fold over controls. Hyperpolarization of the mitochondrial membrane with nigericin increased accumulation by 2.6-3.4 fold. In contrast, depolarization of the plasma membrane with isotonic high potassium buffer reduced accumulation to 70-75% of control values, and additional depolarization of the mitochondrial membrane with valinomycin further reduced accumulation to 21-29% of control levels. These results indicate that both cell lines contain a modest level of Pgp activity and that both are capable of further polarization of the mitochondria. This suggests that mitochondrial hyperpolarization is not the complete explanation for high accumulation of sestamibi in NPC.