Concomitant Loss of p120-Catenin and β-Catenin Membrane Expression and Oral Carcinoma Progression with E-Cadherin Reduction

<div><p>The binding of p120-catenin and β-catenin to the cytoplasmic domain of E-cadherin establishes epithelial cell-cell adhesion. Reduction and loss of catenin expression degrades E-cadherin-mediated carcinoma cell-cell adhesion and causes carcinomas to progress into aggressive states. Since both catenins are differentially regulated and play distinct roles when they dissociate from E-cadherin, evaluation of their expression, subcellular localization and the correlation with E-cadherin expression are important subjects. However, the same analyses are not readily performed on squamous cell carcinomas in which E-cadherin expression determines the disease progression. In the present study, we examined expression and subcellular localization of p120-catenin and β-catenin in oral carcinomas (<i>n</i> = 67) and its implications in the carcinoma progression and E-cadherin expression using immunohitochemistry. At the invasive front, catenin-membrane-positive carcinoma cells were decreased in the dedifferentiated (p120-catenin, <i>P</i> < 0.05; β-catenin, <i>P</i> < 0.05) and invasive carcinomas (p120-catenin, <i>P</i> < 0.01; β-catenin, <i>P</i> < 0.05) and with the E-cadherin staining (p120-catenin, <i>P</i> < 0.01; β-catenin, <i>P</i> < 0.01). Carcinoma cells with β-catenin cytoplasmic and/or nuclear staining were increased at the invasive front compared to the center of tumors (<i>P</i> < 0.01). Although the p120-catenin isoform shift from three to one associates with carcinoma progression, it was not observed after TGF-β, EGF or TNF-α treatments. The total amount of p120-catenin expression was decreased upon co-treatment of TGF-β with EGF or TNF-α. The above data indicate that catenin membrane staining is a primary determinant for E-cadherin-mediated cell-cell adhesion and progression of oral carcinomas. Furthermore, it suggests that loss of p120-catenin expression and cytoplasmic localization of β-catenin fine-tune the carcinoma progression.</p> </div

Correlation of percentage of catenin- and E-cadherin-positive carcinoma cells.

<p>A: The percentage of β-catenin-membrane-positive and –cytoplasm-positive at the invasive front were inversely correlated (<i>P</i> < 0.01, R² = 0.11). B: The positive correlation of the percentage of membrane-positive carcinoma cells for p120-catenin and β-catenin at the invasive front (<i>P</i> < 0.01, R² = 0.33). C: The percentage of membrane-positive carcinoma cells for p120-catenin and E-cadherin at the invasive front showed the positive correlation (<i>P</i> < 0.01, R² = 0.60). Cluster analysis grouped carcinomas into p120^high/E-cadherin^high (green) and p120^low/E-cadherin^low (red) fractions. D: The positive correlation between the percentage of membrane-positive carcinoma cells for β-catenin and E-cadherin at the invasive front (<i>P</i> < 0.01, R² = 0.29) was observed. Carcinoma cells were categorized into β-catenin^high/E-cadherin^high (green) and β-catenin^low/E-cadherin^low (red) fractions.</p

Localization of p120-catenin and β-catenin in oral normal epithelium.

<p>Expression and localization of p120-catenin (A, B) and β-catenin (D, E) in oral normal epithelium was examined by immunostaining. Arrowheads indicate the basal cells. D: negative control. Bar = 65 µm (A, C, E), and 4.3 µm (B, D).</p

Expression of p120-catenin and β-catenin in oral carcinoma cells and normal keratinocytes.

<p>Membrane binding fraction and membrane non-binding fraction of oral carcinoma cells (TSU, KOSC2, KOSC3, Ca9.22, HSC2, OSC19, SCCKN) and normal keratinocytes (HaCaT) were subjected to the immunoblot for p120-catenin (isoform 1-4) and β-catenin. Na/K ATPase and β-actin were probed as the control of membrane binding protein and membrane non-binding protein, respectively.</p

Effects of TGF-β, EGF and TNF-α on expression of catenins.

<p>Oral carcinoma cells (TSU, KOSC2, HSC2, SCCKN) and HaCaT cells were treated with TGF-β (lane b), TNF-α (lane c), EGF (lane d), TGF-β/TNF-α (lane e) or TGF-β/EGF (lane f), and subjected to immunoblot for p120-catenin and β-catenin. PBS was used to treat cells as a control (lane a). β-actin was used for the internal control.</p