a, b WB and real-time PCR analyses of the protein and mRNA expression of EMT transcription factors in MCF7 cells stably transfected with control shRNA or SLFN5 shRNA. c Immunofluorescence staining of ZEB1 enhancement by SLFN5 shRNA transfection. d, e WB and real-time PCR analyses of the protein and mRNA expression of EMT transcription factors in MDA-MB-231 cells stably transfected with control or SLFN5 overexpression vector. f Immunofluorescence staining of ZEB1 downregulation following transfection with a SLFN5 overexpression vector. g Morphological changes in MCF7 cells stably transfected with SLFN5 shRNA combined with either control shRNA or ZEB1 shRNA. h, i WB and real-time PCR analyses of the protein and mRNA expression of ZEB1, E-cad and vimentin in MCF7 cell lines stably transfected with SLFN5 shRNA combined with control shRNA or with ZEB1 shRNA. j, k Migration and invasion determination of MCF7 cells stably transfected with SLFN5 shRNA combined with either control shRNA or ZEB1 shRNA. l Morphological changes in MDA-MB-231 cells stably transfected with SLFN5 combined with either control or ZEB1 overexpression vector. m, n WB and real-time PCR analyses of the protein and mRNA expression of ZEB1, E-cad and vimentin in MDA-MB-231 cells stably transfected with SLFN5 combined with either control or ZEB1 overexpression vector. o, p Migration and invasion determination of MDA-MB-231 cells stably transfected with SLFN5 combined with either control or ZEB1 overexpression vector. q Immunohistochemistry analyses of SLFN5 and ZEB1 expression in clinical BRCA luminal A and triple-negative subtypes. Staining scores of SLFN5 and ZEB1 were calculated based on the percentage of positive cells and staining intensity (mean ± SD, n = 5). SLFN5 and ZEB1 expression exhibited opposite trends. H&E staining was used to identify pathological features of cancer. **P < 0.01.