Panel A shows MDR1 mRNA expression in L428-P, L428-R, and L428-R off drug for 5 months. qRT-PCR for MDR1 mRNA expression performed in triplicate wells and repeated three times. A two-sample t-test showed that there is significant expression level difference for comparisons L 428-P vs L 428-R (p-value<0.0001), L 428-P vs L 428-R Off (p-value<0.001), and L 428-R Off vs L 428-R (p-value = 0.003). Panel B shows Western blot for P-glycoprotein (PgP, protein product of MDR1 mRNA) in L428-P, L428-R, and L428-R off drug for 5 months. L428-R had more MDR1 mRNA and PgP as compared to L428-R off drug or L428-P. Panel C shows MTS assays performed in triplicate wells and averaged over 3 separate experiments. Cells were seeded in 96-well plates at 5,000 cells per well. A four-parameter log-logistic model was fitted to assess inhibitory effect of L428-R with and without verapamil, respectively. The estimated IC50s (±standard error) are 76 (± 23) and 297 (±12), respectively.