Changing expression of E- and P-cadherin during rat tongue carcinogenesis induced by 4-nitroquinoline 1-oxide.

BACKGROUND: Oral squamous cell carcinoma (SCC) develops from pre-malignant lesions, but the role of cell adhesion molecules such as E-cadherin (E-CD) and P-cadherin (P-CD) in the pre-malignant stage has not been elucidated. METHODS: The expression of E-CD and P-CD was examined immunohistochemically and biochemically in a 4-nitroquinoline 1-oxide (4NQO)-induced rat model of carcinogenesis. RESULTS: The expression of E-CD in the pre-malignant stage was the same as that in the normal epithelium. The expression of P-CD was even throughout the prickle cell layer in the dysplasia stage. E-CD and P-CD were expressed in essentially the same locations in SCC and in the pre-malignant stage. P-CD expression was very strong in the pre-malignant stage, compared to that in normal epithelium. CONCLUSIONS: Aberrant P-CD expression in E-CD-positive cells may play a crucial role in the progression of the pre-malignant stage of 4NQO-induced carcinogenesis, and may activate mechanisms responsible for cell proliferation.

Correlation of P-cadherin and beta-catenin expression and phosphorylation with carcinogenesis in rat tongue cancer induced with 4-nitroquinoline 1-oxide.

Using biochemical and immunohistochemical techniques, we have investigated P-cadherin, beta-catenin, c-src and c-met protein expression, and phosphorylation of beta-catenin in a rat model of tongue cancer induced with 4-nitroquinoline 1-oxide. Six-week-old male Sprague-Dawley rats were given either normal drinking water (controls) or 50 ppm 4NQO solution as drinking water for 16 and 20 weeks. This treatment produced dysplasia and well-differentiated squamous cell cancer in rat tongues after 16 and 20 weeks, respectively. In controls, P-cadherin and beta-catenin were expressed only in cell membranes of tongue suprabasal epithelial cells, whereas strong reaction to P-cadherin antibody was observed during carcinogenesis, especially in nests of cancer cells. However, dysplastic and cancer cells expressed beta-catenin not only in cell membranes but also in the nuclear and cytoplasmic compartments. During carcinogenesis, immunohistochemical reaction to phosphotyrosine increased gradually. Reaction to the c-src product was strongest at the dysplastic stage and, to the c-met product, at the cancer stage. In addition, western blotting analysis showed a marked increase in the expression of beta-catenin and phosphotyrosine in dysplastic and cancer cells compared with the controls. Using immunoprecipitation and western blotting techniques, we found that phosphorylated beta-catenin gradually increased during carcinogenesis. These experiments demonstrate that cell-cell adhesion in epithelial cells was reduced by phosphorylation of beta-catenin and that beta-catenin overexpression in nuclear and cytoplasmic compartments during carcinogenesis and the production of the c-met product that is associated with the phosphorylation of beta-catenin in tongue cancer.