Abstract Background: Doxorubicin (DOX) is frequently used for investigations of breast cancer using flow cytometry with fluorescent stains for apoptosis and necrosis. DOX interference, however, can occur with these fluorescent measurements which is not reported in many published reports. The objectives of this study were to identify such interference and to assess its extent. Methods: MDA-MB-231 and MCF-7 cells were incubated for 24 h with 0.1, 1, and 10 µM DOX. Cells were then stained for apoptosis and necrosis using two commercial assay kits. Fluorescence was measured with FL1 (apoptosis), FL2 (primary for DOX), and FL3 (necrosis) detectors in cells with DOX alone, with DOX plus stains, and in control cells without DOX. Measurements were repeated two to five times using replicates and trials. Statistics were evaluated by t-tests. Results: Overall, DOX fluorescence interference increased with concentration in both cell lines. After DOX incubation, cells stained with caspase 3/7 and SYTOX showed fluorescence in the FL1 detector indicating caspase 3/7 activation in apoptosis. But the DOX component of fluorescence with this detector ranged from 11 to 95%. Dox fluorescence in the FL3 detector for SYTOX measurements indicating necrosis ranged from 26 to 96% of total fluorescence. Cells stained with Annexin V (with the FITC label) and propidium iodide (PI) showed fluorescence in the FL1 detector for Annexin V indicating apoptosis. However, the DOX component of fluorescence ranged from 11 to 25%. DOX fluorescence in the FL3 detector for PI indicating necrosis ranged from 87 to 106%. Conclusions: Without correction for DOX interference, and even at low concentrations, substantial errors can occur for apoptosis and necrosis measurements using flow cytometry with these stains in breast cancer cells. At high DOX concentrations, the interference can erroneously indicate an extensive presence of these cell death processes. Corrections for DOX interference include background subtraction and flow cytometer compensation. Acknowledgments: The authors gratefully acknowledge financial support from the Agnes Varis Trust for Women in Science (REN), the Milton Lev Memorial Faculty Research Fund (CMO) as well as Saint Joseph’s University support for student research. The authors also thank Bin Chen, PhD, and Richard Howley for assistance with flow cytometry. Citation Format: Rachel E. Nicoletto, Richard Wilkes, Clyde M. Ofner. Investigation of doxorubicin interference in flow cytometry measurements of apoptosis and necrosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2527.
Read full abstract