Expression of αv integrin family in gastric carcinomas:: Increased αvβ6 is associated with lymph node metastasis

To investigate the alterations as to integrin expression in human gastric carcinomas, we analyzed the alphav subunit and 5 types of beta subunits using reverse transcription-polymerase chain reaction (RT-PCR) and competitive RT-PCR. The incidence of alphav, beta6 and beta8 expression was significantly higher in carcinoma tissues than in nonneoplastic gastric mucosal tissues (NGMTs). Out of 18 carcinoma cases with coexpression of alphav and beta6 subunits, which was demonstrated by RT-PCR, 17 cases (94%) showed lymph node metastasis (p = 0.0033). This tendency was confirmed by immunohistochemistry; most cases (23/28, 82%) in which alphavbeta6 integrin was immunohistochemically detected showed lymph node metastasis (p = 0.0193). RT-PCR and immunohistochemical studies showed that gastric carcinoma tissues expressed beta5 subunit in all cases. Furthermore, in a quantitative analysis using competitive RT-PCR, the mean level of beta5 expression was approximately 140 times higher in gastric carcinomas than in NGMTs. Most gastric carcinoma cases (27/38, 71%) were immunohistochemically positive for beta8 subunit. These findings suggest that some members of the alphav integrin family (alphavP5, alphavbeta6, alphavbeta8) are up-regulated, and that alphavbeta6 integrin may be involved in the lymphatic metastasis of gastric carcinomas.