The expression of 111 breast carcinogenesis-associated genes with 6 control genes were measured and compared under three different conditions of KLF4 overexpression in both non-tumorigenic mammary gland epithelial cell line MCF10A and cancer cell line MCF7: overexpression of KLF4-WT; expression of methylation-resistant KLF4-3K or control vector. The gene discussed is KLF4; the disease is cancer.