Figure 2.

Loss of Arpin expression in breast carcinoma cells. Arpin expression was examined by immunofluorescence in consecutive cryosections of breast biopsies. Normal alveolar ducts are composed of two epithelial layers; the inner luminal layer expresses keratin 8, whereas the surrounding basal myoepithelial layer expresses keratin 17. Arpin is highly expressed in both epithelial cell types compared with fibroblasts in the conjunctive tissue. Breast carcinomas in situ display proliferation of luminal epithelial cells, where Arpin expression is reduced. Arpin expression is retained in the myoepithelial layer. Invasive cells, having lost all epithelial characteristics, even though they still express keratin 8, displayed strongly suppressed Arpin expression.