Figure 4.

EPSTI1 is expressed in immature breast epithelial cells. A: EPSTI1 is highly expressed in basal-like breast cancer. Multicolor confocal imaging of cryostat sections of tubular differentiated human breast cancer without nuclear pleomorphism (left) and of basal-like breast cancer (right) stained with keratin K7/8 (blue), keratin K5 (red), and EPSTI1 (green). EPSTI1 is highly expressed in the nuclei of the basal-like breast carcinoma. (Scale bar = 50 μm). B: EPSTI1 staining correlates with quiescence. Multicolor imaging of human breast cancer stained with EPSTI1 (green), Ki-67 (red), and nuclear stain (blue). Note the segregation of cells staining for EPSTI1 and Ki-67, showing that cells expressing EPSTI1 are not cycling (Scale bar = 50 μm). C: EPSTI1 expression is associated with breast cancer subtypes with poor prognosis. Gene expression profiles of 196 breast carcinomas previously obtained using cDNA microarrays. The box plot shows that EPSTI1 expression is significantly higher in breast cancer subtypes with poor prognosis (basal-like, luminal B, and ErbB2+ subtypes) than in those with good prognosis (P < 0.001). The dot indicates an outlier. D: EPSTI1 expression in residual normal breast tissue is confined to suprabasal epithelial cells. Multicolor confocal imaging of residual normal breast tissue in the vicinity of breast cancer tissue stained for differentiated cells within the luminal epithelial lineage as defined by progesterone receptor (PgR, red, left) or within the myoepithelial lineage as defined by p63 (red, right), and in both instances costained with EPSTI1 (green) and nucleus counterstain (blue). Dotted lines indicate outline of normal epithelial structures. Note that EPSTI1-positive cells neither belong to the luminal nor the myoepithelial lineage as illustrated in the schematic figure in lower panel (Scale bar = 50 μm).