AML-369: Studying Drug Resistance: NB4 as an APL Model

Abstract

Context The NB4 cell line has been used as an in vitro model of acute promyelocytic leukemia (APL) in many studies. Current treatment paradigms call for the administration of ATRA and ATO as differentiating agents in patients with newly diagnosed APL. For a subset of patients, resistance to conventional treatment remains a clinical issue and is poorly understood. Objective The purpose of this study was to evaluate whether resistance to ATRA and ATO can influence the susceptibility of APL cells to anthracycline therapy like doxorubicin using the NB4 cell line as an in vitro model. Design Wild type NB4 cells as well as NB4 cells resistant to both ATRA and ATO (NB4-RAA) were cultured in suspension in RPMI and 10% fetal calf serum. NB4-RAA were established in Dr. Jimenez's lab from the wild type NB4 parent cell line. Resistance was achieved after exposing NB4 cells to increasing concentrations of ATRA and ATO over a period of twelve months. NB4 and NB4-RAA were plated in multi-wells at 50,000 cells/mL and exposed to different concentrations of doxorubicin. Cell counts were taken at 24 and 48 hours after treatment. Results NB4 and NB4-RAA were exposed to 0 μg/mL (Control), 0.001 μg/mL, 0.01 μg/mL, 0.05 μg/mL, and 0.1 μg/mL. The viability of both cell lines decreased at similar levels at 24 h and 48 h when exposed to concentrations of doxorubicin higher than 0.01 μg/mL (p Conclusion These results indicate that resistance to ATRA and ATO in APL cells does not confer subsequent resistance to anthracyclines such as doxorubicin. As a result, doxorubicin targets a pathway that is distinct from that of ATRA & ATO. No difference in cell viability was found between naive NB4 and resistant NB4-RAA when exposed to the same concentrations of doxorubicin. Our results indicate the effectiveness of overcoming resistance to frontline APL therapy by using doxorubicin.