Detachment of cell-cell adhesion is indispensable for the first step of invasion and metastasis of cancer. This mechanism is frequently associated with the impairment of either E-cadherin expression or function. However, mechanisms of such abnormalities have not been fully elucidated. In this study, we demonstrated that the function of E-cadherin was completely abolished in the human gastric cancer cell line HSC-39, despite the high expression of E-cadherin, because of mutations in one of the E-cadherin-associated cytoplasmic proteins, -catenin. Although immunofluorescence staining of HSC-39 cells by using an anti-E-cadherin antibody (HECD-1) revealed the strong and uniform expression of E-cadherin on the cell surface, cell compaction and cell aggregation were not observed in this cell. Western blotting (immunoblotting) using HECD-1 exhibited a 120-kDa band which is equivalent to normal E-cadherin. Northern (RNA) blotting demonstrated a 4.7-kb band, the same as mature E-cadherin mRNA. Immunoprecipitation of metabolically labeled proteins with HECD-1 revealed three bands corresponding to E-cadherin, ␣-catenin, and ␥-catenin and a 79-kDa band which was apparently smaller than that of normal -catenin, indicating truncated -catenin. The 79-kDa band was immunologically identified as -catenin by using immunoblotting with anti--catenin antibodies. Examination of -catenin mRNA by the reverse transcriptase-PCR method revealed a transcript which was shorter than that of normal -catenin. The sequencing of PCR product for -catenin confirmed deletion in 321 bases from nucleotides ؉82 to ؉402. Southern blotting of -catenin DNA disclosed mutation at the genomic level. Expression vectors of -catenin were introduced into HSC-39 cells by transfection. In the obtained transfectants, E-cadherin-dependent cell-cell adhesiveness was recovered, as revealed by cell compaction, cell aggregation, and immunofluorescence staining. From these results, it was concluded that in HSC-39 cells, impaired cell-cell adhesion is due to mutations in -catenin which results in the dysfunction of E-cadherin.
The Stiegmann‐ligator has been recently proved to be useful for the treatment of esophageal varices. With those ligators, however, we found difficulty in performing ligation when the pathological change was on the tangent line or relatively large, such as F3, or associated with concentrated RC signs. To overcome these problems, we modified the Stiegmann O‐ring ligator by diagonally cutting the tip of the inner sleeve. Using this ligator, we conducted some animal‐model experiments and clinical trials. In all cases, the remodeled ligator covered a wider range of lesions. We no longer encountered difficulties in performing ligation with the remodeled ligator when pathological changes were on the tangent line. The procedure did not cause any complications apart from temporary chest discomfort after surgery.
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