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. 2020 Apr 29;12(5):1117. doi: 10.3390/cancers12051117

Figure 3.

Figure 3

Effect of doxorubicin treatment and drug holiday on canine CLBL-1 B-cell lymphoma cells. (a) After 6 cycles of DOX treatment (74 days) parental CLBL-1 cells showed a significant increase in P-glycoprotein activity (MAF 0.42 vs. 0.22), which was significantly reduced after a 27-day-long drug holiday (MAF 0.26). Flow cytometry histograms show the results of the calcein assay of cells assayed with (blue) or without (red) the Pgp inhibitor verapamil. (b) Changes of doxorubicin sensitivity as a result of drug treatment and drug holiday. Sequential DOX treatments of CLBL-1 cells resulted in a 9.2-fold increase of doxorubicin tolerance, which was significantly reduced following the period of drug holiday. Resistance of CLBL-1 DOX cells was abrogated in the presence of tariquidar (D + TQ). ** p < 0.01; *** p < 0.001; ns: not significant.