Cten, a COOH-terminal tensin-like protein with prostate restricted expression, is down-regulated in prostate cancer.

Tensin is a signaling molecule that binds to actin filaments and localizes to focal adhesions. Recently, we have discovered that tensin represents a new gene family with related members that are expressed in a variety of tissues. In this study, we report the identification and characterization of a new COOH-terminal tensin-like molecule, cten. Human cten cDNA encodes a 715 amino acid sequence containing the Src homology 2 and phosphotyrosine-binding domains that are similar to the COOH termini of tensin molecules. Although cten is shorter and does not have the actin-binding domain found in other tensins, analysis of the genomic structure has suggested that cten is related to the tensin gene family. In addition, cten also localizes to focal adhesions. In contrast to other tensin members, cten expression is restricted to prostate and placenta by Northern blot analysis. Furthermore, examination of cten expression in prostate cancer/cell lines has revealed its down-regulation in tumor samples. Our studies have suggested that during evolution, cten has preserved its role in mediating signal transduction at focal adhesions through the Src homology 2 and phosphotyrosine-binding domains but has lost its function in binding to actin filaments. The evolutionary divergence has produced the first focal adhesion protein specifically expressed in the prostate and the placenta, which may be involved in preventing prostate tumor formation.

Inhibitory effects of a luteinizing hormone-releasing hormone agonist on basal and epidermal growth factor-induced cell proliferation and metastasis-associated properties in human epidermoid carcinoma A431 cells.

The purpose of this study was to investigate the effects of a potent LHRH agonist, [D-Trp(6)]LHRH on the basal and EGF-induced cell proliferation and the metastasis-associated properties in A431 human epidermoid carcinoma. [D-Trp(6)]LHRH time-dependently inhibited the basal and EGF-stimulated growth of A431 cancer cells. It is assumed that phosphorylation/dephosphorylation of cellular proteins is highly related to cell growth. This study demonstrates that [D-Trp(6)]LHRH decreased the basal and EGF-induced total cellular kinase activity, particularly the tyrosine phosphorylation of several cellular proteins including the EGFR. In contrast, [D-Trp(6)]LHRH did not cause detectable changes in basal and EGF-stimulated serine/threonine phosphorylation of A431 cellular proteins. The inhibitory effect of [D-Trp(6)]LHRH on A431 cell proliferation was associated with apoptosis as evidenced by the cell morphology and DNA integrity (ladder pattern), the expression of interleukin 1beta-converting enzyme (ICE) and activation of caspase. Furthermore, EGF could rescue the remaining attached A431 cells following [D-Trp(6)]LHRH treatment for 48 hr, which suggests that limited exposure to [D-Trp(6)]LHRH did not channel all cells to irreversible apoptotic process. We also determined the effects of [D-Trp(6)]LHRH on metastasis-associated properties in A431 cells. [D-Trp(6)]LHRH reduced both basal and EGF-stimulated secretion of MMP-9 and MMP-2. In addition, [D-Trp(6)]LHRH suppressed the basal and EGF-induced invasive activity of A431 cells based on an in vitro invasion assay. In conclusion, this study indicates that [D-Trp(6)]LHRH may act partly through activating tyrosine phosphatase activity to inhibit cell proliferation and the metastasis-associated properties of A431 cancer cells. Our work suggests that [D-Trp(6)]LHRH may be therapeutically useful in limiting the tumor growth and metastasis of some neoplasms.