Cadherins are Ca2(+)-dependent cell-cell adhesion molecules, and are involved in the formation and maintenance of the histo-architecture. Using cultured human leukemia cell lines (adult T cell leukemia and thymus-derived lymphoma cell lines), we obtained evidence that cadherins and catenins are expressed in these cell lines but not in normal leukocytes. Immunoblot analysis of cells using a pan-cadherin serum, directed against the conserved carboxyl-terminus of cadherins, revealed a major band of 130 kDa and a minor one of 135 kDa. The 130 kDa cadherin was also recognized by anti-N-cadherin antibodies. A human N-cadherin cDNA probe hybridized to a 4.3 kb mRNA isolated from cells immunologically positive for N-cadherin. Sequencing of the cDNA fragments isolated from the cells revealed a N-cadherin sequence. Cell surface expression of N-cadherin was confirmed by indirect immunofluorescence staining of the cells. Immunoblot and Northern blot analyses also revealed the presence of alpha-catenin, beta-catenin, and gamma-catenin (plakoglobin) in these cell lines. Immunoprecipitation with anti-N-cadherin antibodies and subsequent immunoblot analysis with anti-catenin antibodies revealed that N-cadherin is associated with alpha- and beta-catenins, a prerequisite for cadherins to be functional. These results suggest an important role of the cadherin-catenin complexes in the behavior of the leukemia cells.