*4.5. Taxol Survival Curve*

Flp-In-ABCB1, Flp-In-ABCB1-Q347/990A, Flp-In ABCB1-Qtriple, and Flp-In-vector control cells (1 × 10<sup>4</sup> ) were seeded into a 96 well dish in 100 µL of DMEM with high glucose and 10% FBS but without hygromycin and allowed to attach for several hours. Taxol (Cambridge Bioscience, Cambridge, UK) was added to a final concentration ranging from 0 nM to 10 µM and the cells cultured at 37 ◦C in a humidified incubator with 5% CO2. After 72 h the media was aspirated, the cells were detached with 30 µL TrypLE Express (ThermoFisher Sci, Waltham, MA, USA) which was quenched with 75 µL transport buffer and transferred to flow cytometry tubes. The entire population of cells of normal size and granularity, gated on the zero-drug condition, were counted in an ACEA NovoCyte flow cytometer (Agilent Technologies, Santa Clara, CA, USA). Cell number data were analyzed in Prism version 8 (GraphPad Software, San Diego, CA, USA). Curve fitting was achieved used non-linear regression.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/ 10.3390/ijms22168561/s1. Figure S1: Titration of transport substrates for development of flow cytometry assay; Figure S2: Confirmation of equivalent levels of ABCB1 at the plasma membrane ensured that any differences in transport activity were due to ABCB1 functionality rather than the transporter expression level.

**Author Contributions:** Conceptualization, K.J.L.; formal analysis, K.J.L. and F.B.; investigation, K.S., H.A.I., A.O. and K.J.L.; data curation, K.J.L.; writing—original draft preparation, K.J.L.; writing review and editing, K.S., H.A.I., A.O., F.B. and K.J.L.; supervision, K.J.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The raw data and materials generated in this study are available directly from K.J.L.

**Acknowledgments:** The authors would like to thank Gary Warnes, manager of the flow cytometry facility in the Blizard Institute for guidance and help with the flow cytometers and flow cytometry software used in this study.

**Conflicts of Interest:** The authors declare no conflict of interest.
