Fig 2: Regulatory role of PRKCE in the phosphorylation level of AURKB. a, b Analysis of PRKCE mRNA and protein expression differences in breast cancer cell MDA-MB-231 and corresponding PTX-resistant MDA-MB-231/PTX using quantitative PCR and Western blot. c Relative contents of PRKCE and phosphorylated PRKCE using Western blot after MDA-MB-231/PTX cells were treated with Bisindolylmaleimide I (1 μM) or PRKCE siRNA (20 nM) for 24 h. d Detection of the survival rate in different groups at different time points using CCK-8 method after cell treatment with PTX (0.5 μM) when MDA-MB-231/PTX cells were treated with Bisindolylmaleimide I (1 μM) or PRKCE siRNA (20 nM) for 24 h. One-way ANOVA with Tukey post hoc analysis. *P < 0.05 and **P < 0.01

Fig 3: The pattern diagram to reveal that AURKB is involved in exosome release and PTX efflux through the regulation of RAB27B expression. (Created with BioRender.com)

Fig 4: Involvement of AURKB in the regulation of exocrine secretion and PTX efflux in breast cancer cells. a Transmission electron micrographs of exosomes derived from MDA-MB-231 and MDA-MB-231/PTX cells. b Detection of related marker proteins in exosomes using Western blot. c Histogram of the relative exosome concentrations of MDA-MB-231 and MDA-MB-231/PTX cells after measurement of the relative exosome concentrations of MDA-MB-231 and MDA-MB-231/PTX cells by nanoparticle tracking analysis (NTA) and normalization with the number of cells. d Detection of the relative exocrine concentration in MDA-MB-231/PTX cells treated with BIM and transfected with RAB27B expression plasmid for 24 h; the sphingomyelinase inhibitor GW4869 was used as a positive control of inhibiting exosome secretion. e Measurement of the content of PTX in exosomes by HPLC–MS after the extraction of exosomes from the same culture supernatant when MDA-MB-231/PTX were treated with BIM and transfected with RAB27B expression plasmid for 24 h, and then treated by PTX (0.5 μM) for 2 h

Fig 5: Analysis on the expression of AURKB in breast cancer tissues and cells. a Analysis of AURKB mRNA expression difference in breast cancer tissues and normal control tissues by online tool ACLBI. b Analysis of the relative content of AURKB in 15 pairs of breast cancer tissues and corresponding para-cancerous tissues using quantitative PCR. c Detection of the expression of AURKB in breast cancer tissues and adjacent tissues using H&E and IHC staining. Scale bar, 50 μm. d, e Detection of the relative expression levels of AURKB mRNA and protein in multiple breast cancer cells and normal breast epithelial cells by quantitative PCR and Western blot. Paired t test and one-way ANOVA with Tukey post hoc analysis. *P < 0.05, **P < 0.01, and ns no significant difference