Expression of alphav integrin family in gastric carcinomas: increased alphavbeta6 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 non-neoplastic 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 (alphavbeta5, alphavbeta6, alphavbeta8) are up-regulated, and that alphavbeta6 integrin may be involved in the lymphatic metastasis of gastric carcinomas.