Analysis of MDA-MB-231 cells after silencing of UGDH and EPI treatment. MDA-MB-231 cells were transfected with a specific siRNA against UGDH gene (siUGDH) using a random sequence siRNA as negative control (siSCR). After 24 h, 1 µM EPI (1 EPI) was added to complete 48 h of incubation. UGDH mRNA levels were obtained by real-time quantitative PCR using Taqman probes (A). Cell viability was measured performing a MTT assay (B) and cytotoxicity was determined evaluating the activity of lactate dehydrogenase (LDH) enzyme in cell supernatants (C). Early apoptosis (D,E) was detected by flow cytometry using AnnexinV-FITC stain. Histograms (E) show the most representative of three independent experiments performed with 50,000 events/condition. n = 3, mean ± SEM, * p < 0.05, ** p < 0.01, *** p < 0.001. (F) Microarray dataset GSE54326 specific for different breast cancer cell lines was used for comparing differential UGDH expression levels in tumor cells resistant to anthracyclines treatment and control cells. In each case, NCBI GEO2R tool was used to analyze UGDH levels.