A subsequent RT-PCR analysis for stemness marker genes was performed, with the results showing that the expression of stemness markers (NANOG, OCT4B, KLF4, SOX2, and C-MYC) was significantly increased in shKRT19 virus-infected MDA-MB231 cells and downregulated in KRT19 overexpressing KU-CSLC cells, as compared to scramble or vector infected MDA-MB231 or KU-CSLC cells, respectively (Figure 3D,E), suggesting that KRT19 may regulate cell growth and sphere formation ability in breast cancer. This evidence concerns the gene KLF4 and breast cancer.