Fig 1: DKK1 is expressed in the tumor microenvironment.A, C, E Normalized gene expression of DKK1 in healthy human breast tissues (n = 7) and triple-negative breast cancer (TNBC) (A, n = 18), HER2+ breast cancer (C, n = 4), ER+ breast cancer (E, n = 11) (GSE3744). B, D, F Representative images of multiplex immunohistochemistry (IHC) of TNBC (B, n = 20), HER2+ (D, n = 12), and ER+ (F, n = 8) human breast cancer subtypes stained for DKK1 (red), αSMA (green), PDGFRα (blue), and panCK (cyan). The green inset highlights the stromal area and the cyan inset highlights the tumor area. G Normalized gene expression of DKK1 in the stroma derived from normal breast tissue or invasive ductal carcinoma (IDC) (GSE8977). Results are shown as mean ± SEM. H Representative images of multiplex IHC of human ductal carcinoma in situ (DCIS) samples (n = 13) stained for DKK1 (red), αSMA (green), PDGFRα (blue), COL14a1 (white), and panCK (cyan) from patients who did not develop ipsilateral breast cancer (blue box) versus patients who developed ipsilateral breast cancer (red box). I–K Representative images of DKK1 staining by IHC (brown) in orthotopic PyMT tumors (I, n = 5), spontaneous MMTV-PyMT breast tumors (J, n = 5), and orthotopic 4T1 tumors (K, n = 4). L, M Representative images of multiplex IHC of spontaneous MMTV-PyMT breast tumors (L, n = 5), and orthotopic 4T1 tumors (M, n = 4) stained for DKK1 (red), αSMA (green), COL1a1 (white), and EpCAM (MMTV-PyMT tumor cells, cyan) or GFP (4T1 tumor cells, cyan). An unpaired t-test with a two-tailed P-value (A, C, E, G) was used to determine significance. Source data are provided as a Source Data file.