Fig. 2: Pgp expression and function is linked to LXR activity.

A Correlation analysis in TNBC tumors of LXRα or LXRβ with ABCA1 and Pgp gene expression obtained from METABRIC (n = 313) and TCGA (n = 95) datasets accessed via cBioportal. Statistical significance was assessed using Pearson’s correlation test with linear regression. B–G performed in MDA.MB.468 cells except where indicated. Pgp expression measured at 4 h and 16 h after ligand exposure at mRNA level (B) and after 24 h for protein analysis (C). D siRNA knockdown of LXRα or LXRβ. B–F Symbols show independent replicates and bars show mean with SEM. Statistical analysis was performed using 2-way ANOVA and is representative of three independent replicates with SEM. (E) Colony forming assay in MDA.MB.468 cells after siLXRα showing GW3965 (GW) no longer protects cells from epirubicin in the absence of LXRα. (F) MTT in MDA.MB.468 cells after siPGP shows GW no longer protects cells from epirubicin in the absence of Pgp. (G) MDA.MB.468 and MDA.MB.231 cells were pre-treated with LXR ligands or vehicle for 16 h and Pgp inhibitor (verapamil 20 μM [V20]) or vehicle for 30 min, before loading with epirubicin (50 μM) for 1 h. The half-life of the intra-cellular epirubicin signal was calculated using dissociation one phase exponential decay. NB: epirubicin curve data are replicated in each graph for visualization purposes. Data shown are mean with SEM of three or four independent replicates each made from six technical replicates. Significance was calculated using non-linear regression curve comparison against epirubicin (EPI) only curve.