Progression of Oral Squamous Cell Carcinoma Accompanied with Reduced E-Cadherin Expression but Not Cadherin Switch

<div><p>The cadherin switch from E-cadherin to N-cadherin is considered as a hallmark of the epithelial-mesenchymal transition and progression of carcinomas. Although it enhances aggressive behaviors of adenocarcinoma cells, the significance and role of cadherin switch in squamous cell carcinomas (SCCs) are largely controversial. In the present study, we immunohistochemically examined expression of E-cadherin and N-cadherin in oral SCCs (<em>n</em> = 63) and its implications for the disease progression. The E-cadherin-positive carcinoma cells were rapidly decreased at the invasive front. The percentage of carcinoma cells stained E-cadherin at the cell membrane was reduced in parallel with tumor dedifferentiation (<em>P</em><0.01) and enhanced invasion (<em>P</em><0.01). In contrast, N-cadherin-positive cells were very limited and did not correlate with the clinicopathological parameters. Mouse tongue tumors xenotransplantated oral SCC cell lines expressing both cadherins <em>in vitro</em> reproduced the reduction of E-cadherin-positive carcinoma cells at the invasive front and the negligible expression of N-cadherin. These results demonstrate that the reduction of E-cadherin-mediated carcinoma cell-cell adhesion at the invasive front, but not the cadherin switch, is an important determinant for oral SCC progression, and suggest that the environments surrounding carcinoma cells largely affect the cadherin expression.</p> </div

<i>In vitro</i> and <i>in vivo</i> cadherin expression in oral carcinoma cell lines.

<p>A: <i>CDH1</i> and <i>CDH2</i> expression were quantitatively examined by the real-time PCR. Relative expression was standardized by the expression level of <i>ß-actin</i> in each sample and calibrated with the expression in HaCaT cells. B: Oral carcinoma cells (KOSC2, HSC2 and OSC19) cultured on glass slides were stained with antibodies against E-cadherin or N-cadherin. <i>Bar</i> = 10 µm. C: Oral carcinoma cells were transplanted into the mouse tongue, and subjected to the cadherin immunostaining. Arrows indicate carcinoma cells at the peripheries of tumor cell nests; Arrowheads indicate carcinoma cells at the invasive front; Double arrowheads indicate N-cadherin-positive carcinoma cells. <i>Bar</i> = 12.5 µm.</p

Reactivity of anti-cadherin antibodies.

<p>Reactivity of anti-E-cadherin and anti-N-cadherin antibodies was examined by the immunoblot. Antibodies against E-cadherin (a, Santa Cruz Biotechnology; b, R&D System) and N-cadherin (c, Invitrogen; d, Takara; e, LifeSpan Biosciences) were used. Arrows indicate a 125 kDa band and arrowheads a 120 kDa band. Antibody b and d were used for further experiments in this study.</p

Localization of cadherins in normal oral epithelium and oral carcinoma tissues.

<p>A: E-cadherin was localized at basal and suprabasal cells of normal oral epithelium (a). N-cadherin-positive cells were not existed in the epithelium (b). Negative control using non-immune mouse IgG instead of primary antibody (c). <i>Bar</i> = 50 µm. B: Carcinomas at the center of tumor (a, c, e) and the invasive front (b, d, f) were stained by anti-E-cadherin (a, c) and anti-N-cadherin (b, d) antibodies. Cadherins were stained at cell membrane (arrows) or cytoplasm (arrowheads). Insets; high power view of cells pointed by an arrow (a) and arrowheads (b, d). e,f: negative control. <i>Bar</i> = 12.5 µm, and 4.3 µm (insets).</p