OST cells enhance the induction of matrix metalloproteinase (MMP)-9 by tumour necrosis factor (TNF)-α and the corresponding metastasis to lungs in vivo (Kawashima et al., 1994). We focused on the adhesive and migratory properties of OST cells, and investigated the expression of integrins in OST cells stimulated by TNFαin vitro. OST cells potentiated not only adhesion to the extracellular matrix (ECM) but also the migration on ECM. On competitive reverse transcription-polymerase chain reaction (RT-PCR) analyses, the amounts of α2 (4.9-fold), α5 (1.2-fold) and αv (4.9-fold) were upregulated by TNFα at the transcriptional level. Alpha-5 showed a slight increase by flow cytometry; however, α2 and αv integrins remained unchanged at the protein level. Immunofluorescence study disclosed integrins of α2β1 and α5β1 were much clustered at cell processes by TNFα stimulation, probably related to increased cell adhesion and migration. Therefore, the upregulation of α2β1 and α5β1 integrins seems to contribute to tumour invasion and metastatic potential.