Fig. 1

Doxorubicin induces C/EBP-β LIP in Pgp-negative but not in Pgp-positive breast cancer cells. Cells were cultured in the absence (−) or presence (+) of 5 μM doxorubicin (dox) for 24 h. a. Plasma-membrane extracts were probed with the indicated antibodies. The expression of pancadherin was used as control of equal protein loading. The figure is representative of 1 out of 3 experiments. b. Whole cell lysates were probed with an antibody recognizing both C/EBP-β LAP and LIP isoforms. The expression of β-tubulin was used as control of equal protein loading. The figure is representative of 1 out of 3 experiments. c-d. Lysosome activity (panel c) was analyzed in duplicates by a spectrophotometric assay, proteasome activity (panel d) was analyzed in duplicates by a chemiluminescence-based assay. Data are presented as means±SD (n = 3). e-f. Correlation between LIP band density upon doxorubicin treatment (panel b) and lysosome (panel c) or proteasome (panel d) activities. The mean band density of LIP was expressed as arbitrary units using the ImageJ software, setting the mean band density in MCF10A cells as 1