Immunohistochemical evaluation of alpha-catenin expression in human gastric cancer

Abstract

E-cadherin (E-cad) plays a major role in the maintenance of cell-cell adhesion in epithelial tissues, and impaired E-cad expression correlates with tumour invasion and metastasis. Alpha-catenin (α-cat), an undercoat protein of adherens junctions, binds to the cytoplasmic domain of E-cad and is essential for linking E-cad to actin-based cytoskeleton. We investigated E-cad and α-cat expression in 60 human gastric cancers immunohistochemically. The 60 gastric cancers were classified into 18 (30%) in which α-cat expression was preserved, and 42 (70%) reduced cases. The reduction of α-cat expression was significantly related to dedifferentiation, depth of invasion, infiltrative growth and lymph node metastasis. We also examined the co-expression of α-cat and E-cad. Seventeen (28%) tumours preserved both molecules [α-cat(+)/E-cad(+)] and 33 (55%) tumours reduced both [α-cat(−)/E-cad(−)], whereas 9 (15%) tumours exhibited α-cat(−)/E-cad(+). The frequency of lymph node metastasis in α-cat(−)/E-cad(+) tumour (67%) was significantly higher than that in α-cat(+)/E-cad(+) tumours (24%) and was close to that in α-cat(−)/E-cad(−) tumours (82%). The frequency of haematogenous liver metastasis in α-cat(−)/E-cad(+) tumours (44%) was significantly higher than that in α-cat(+)/E-cad(+) tumours (6%) or α-cat(−)/E-cad(−) tumours (9%). Thus, in all E-cad(+) tumours, the frequency of lymph node and liver metastasis was higher in α-cat(−) tumours than in α-cat(+) tumours. α-Cat expression is apparently better at predicting tumour invasion and metastasis than E-cad expression.