ID1 and breast cancer: Downregulated genes (> 3-fold) had functions in breast cancer (cathepsin D, KRT5, and MAPK1), apoptosis (TNFSF8), drug resistance (ABCC3, ABCG2, and EGFR), tumor metastasis (CD44, EPHB2, ETV4, IL-18, MMP3, and MMP13), epithelial–mesenchymal transition (EMT; Caveolin-2, FGFBP1, integrin alpha 5, and SERPINE1), angiogenesis (CTGF, Fibronectin 1, ID1, IL1B, and IL6), and included stem cell transcription factors (HOXA7, KLF4, PCNA, POU5F1, SOX9, and STAT3) (data not shown).