Effect of AT13387 on EBV-positive NPC cell line C666-1. (A) MTT assay showing dose dependent inhibition of C666-1 cells growth after 48 hrs of AT13387 treatment. (B) Cell growth assay showing the kinetics of growth inhibition determined by counting number of viable C666-1 cells on days 2, 4 and 7 after AT13387 treatment. Results are expressed as the mean ± S.D. of three separate trials; *p < 0.05. (C) DNA content analysis and (D) DAPI nuclei staining showed no significant apoptotic phenotype in AT13387-treated C666-1 after 48 hrs. Arrow indicated the sub-G1 peak of DNA profile. Scale bar = 20 μm. (E) Western-blotting analysis showing no significant change of pro-apoptotic and anti-apoptotic proteins in AT13387-treated C666-1 after 48 hrs and 96 hrs. Value represented the arbitrary unit of band intensity after normalization with β-actin.