Expression of the ABCG2 multidrug transporter is a marker of cancer stem cells and
a predictor of recurrent malignant disease. Understanding how human ABCG2 expression
is modulated by pharmacotherapy is crucial in guiding therapeutic recommendations
and may aid rational drug development. Genome edited reporter cells are useful in
investigating gene regulation and visualizing protein activity in live cells but require
precise targeting to preserve native regulatory regions. Here, we describe a fluorescent
reporter assay that allows the noninvasive assessment of ABCG2 regulation in human
lung adenocarcinoma cells. Using CRISPR-Cas9 gene editing coupled with homology-directed
repair, we targeted an eGFP coding sequence to the translational start site of ABCG2,
generating ABCG2 knock-out and in situ tagged ABCG2 reporter cells. Using the engineered
cell lines, we show that ABCG2 is upregulated by a number of anti-cancer medications,
HDAC inhibitors, hypoxia-mimicking agents and glucocorticoids, supporting a model
in which ABCG2 is under the control of a general stress response. To our knowledge,
this is the first description of a fluorescent reporter assay system designed to follow
the endogenous regulation of a human ABC transporter in live cells. The information
gained may guide therapy recommendations and aid rational drug design.
