Precisely Targeted Reporters Reveal ABCG2 Regulation in Live Lung Cancer Cells

Abstract

Expression of the ABCG2 multidrug transporter is a marker of cancer stem cells and an indicator of poor disease outcome. Understanding the effect of pharmacotherapy on ABCG2 expression is critical in guiding therapy recommendations and may help rational drug development. Engineered reporter cell lines are useful in monitoring gene regulation and protein activity in live cells but rely on precise targeting to preserve native regulatory functions. Here, we generated a number of precision‐engineered, fluorescent human cell lines that interrogate ABCG2 regulation in live lung cancer cells. Using homology‐based CRISPR engineering, we targeted a promoterless eGFP to the translational start site of the ABCG2 gene, generating ABCG2 knockout and in situ tagged ABCG2 reporter cells. Using the engineered cell lines, we show that anti‐cancer medications, HDAC inhibitors and hypoxia‐mimicking agents induce ABCG2 expression. In addition, we provide evidence that the glucocorticoid receptor is a specific, positive regulator of the ABCG2 gene. To our knowledge, this is the first fluorescent reporter assay designed to follow the endogenous regulation of a human ABC transporter in live cells. The information gained may direct therapy recommendations and assist rational drug design. Support or Funding Information This research has been supported mainly by OTKA‐NKFIH grant NK 115375, but also by NKFIH K104903 and the NVKP_16‐1‐2016‐0005 program from the National Research, Development and Innovation Office. This work has also been supported by research grant OTKA‐NKFIH K128011, awarded to GV. A Borsy was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences (HA: BO/00579/17/5), through the New National Excellence Program of the Ministry of Human Resources (HA: ÚNKP‐18‐4‐SE‐11).