Figure 4.
Effect of selecting HCT15-2A cells in NSC73306. Following selection in 1 μg/ml NSC73306, HCT15-2A-R cells demonstrate resistance to NSC73306 (A). Selection with NSC73306 for three weeks reversed resistance to P-gp substrates (B) (blue bars represent pre-selection drug resistance set to 100%, red bars represent post-selection effect, yellow bars represent elimination of P-gp function by PSC833). Loss of surface P-gp expression, as measured by MRK-16 FACS analysis (C) and function, as measured by Calcein accumulation (D), occurred following a three week selection with NSC73306. Immunoblots showing expression of Pgp in crude membranes (E) or whole cell lysates (F). The effect of NSC73306 treatment on Pgp expression is shown with GAPDH as a control (F).