The chemoresistance of Namalwa/MDR1 cells can be overcome in the presence of anti-CD19. Cells were cultured in media ± vincristine (VC; 25 and 50 nM). Cells were counted daily and viability was determined by trypan blue exclusion. (A) Namalwa/MDR1 cells cultured with vincristine for 3 weeks survived, whereas parental Namalwa cells died after 3 days. This is 1 representative experiment of 3 performed. (B) The cytotoxic effect of doxorubicin in Namalwa/MDR1 cells in media (▾) or media supplemented with HD37 (15 μg/mL; □) versus parental Namalwa cells (•). Cells were incubated overnight with 15 μg/mL HD37, then plated in triplicates in 96-well plates and incubated for 72 hours in the presence of different concentrations (5-50 nM) of doxorubicin (triplicates were used for each concentration). The cells were then pulsed with 3H-thymidine for 18 hours, harvested, and counted. The radioactivity in treated cells versus control cells was then determined. This is a representative experiment of 5 performed.
