Down-regulation of β(1C) integrin, an inhibitor of cell proliferation, in prostate carcinoma

The β(1C) integrin, a member of the cell adhesion receptor superfamily, is an alternatively spliced variant of the β(1A) subunit and, in contrast to its wild-type counterpart, inhibits cell proliferation in vitro. The expression of β(1C) integrin in tumor cell growth was investigated. In benign and neoplastic human prostate tissues, immunohistochemical analysis performed using affinity-purified antibodies specific for β(1C) demonstrated a predominant epithelial expression of β(1C) in benign prostate glands with marked staining of the apical, basal, and lateral surfaces. In the adjacent prostate adenocarcinoma glands, the β(1C) variant was dramatically down- regulated in 27 of 34 (79%) analyzed cases, whereas the expression and distribution of its wild-type counterpart, β(1A), remained unchanged. Tumors exhibiting different Gleason's patterns showed that β(1C) was down-regulated in comparison with the benign tissue regardless of the histological grade. Immunoblotting analysis, using affinity-purified antibodies specific for β(1C), was performed, in a quantitative manner, to compare β(1C) expression in benign and tumor prostate tissue. The results showed that β(1C) was expressed in benign prostate tissue whereas it was undetectable in prostate adenocarcinoma. Taken together, these data show that β(1C) integrin down- regulation in prostate tissues correlates with a neoplastic phenotype consistent with its in vitro growth-inhibitory properties. These findings indicate a novel pathophysiological rode for this integrin variant in tumorigenesis.