PGP and breast cancer: C/EBP-β LIP was induced by doxorubicin in epithelial MCF10A cells and in Pgp-negative breast cancer MCF7, SKBR3, and T47D cells, while Pgp-positive MDA-MB-231, JC and TUBO cells had a lower C/EBP-β LIP induction (Fig. 1b).