Figure 4.

HST protein detection by IHC. (a–d) Testing on tissue sections for the specificity of the anti-HST antibody (CW001 clone, staining in panels (a) and (c)) with preabsorption of the antibody with recombinant HST protein (mass ratio of 1:5, overnight incubation at 4°C, markedly reduced or absent staining in (b) and (d)). (a and b) Same area of a HER2 IHC-2+ breast carcinoma; (c and d) same area of the corresponding NCBT. Herstatin staining is specific in the cytoplasm and perinuclear area of tumor cells (a) and in mast cells mostly observed around noncancerous breast elements (c). (e) Staining for HST protein in the cytoplasm of NCBT is faint but specific, as observed under high magnification. Asterisks in panels (a)–(e) point at mast cells. Arrows in panel (e) point at positive epithelial cells; arrowhead, positive endothelial cell. Scale bars, 50 µm.