Expression of integrin alpha 3 in gastric and colorectal cancers: its relation to wall contraction and mode of invasion.

We macroscopically classified 25 gastric and 23 colorectal advanced cancers into "contracted" and "uncontracted" types, and found immunohistochemically that integrin subunit alpha 3 was more frequently expressed in the extracellular matrix (ECM) in the former than in the latter (75%:9/12 vs. 38%: 5/13 in gastric and 86%:6/7 vs. 25%:4/16 in colorectal cancers, respectively). Integrin subunit alpha 3 was also expressed more frequently in cancers producing transforming growth factor-beta (TGF-beta), which is related to ECM deposition, integrin expression and cell mobility, than in those which did not produce TGF-beta (67%:10/15 vs. 40%:4/10 in gastric and 57%:4/7 vs. 38%:6/16 in colorectal cancers, respectively). In addition, integrin subunit alpha 3 was not expressed in 2 benign gastric ulcers combined with gastric cancer elsewhere in the stomach. On the other hand, a retrospective analysis of 107 cases of rectal cancer which recurred after a curative operation revealed that local recurrence was more frequent in "contracted" than "uncontracted" types (44%:11/25 vs. 26%:21/82). These results may suggest that the abundant interstitial fibrosis which leads to remarkable gastric or colorectal wall contraction is a result of the interaction between cancer cells and ECM, along with the expression of integrin and/or the production of TGF-beta. This fibrosis may also be closely related to the mode of gastric and colorectal cancer invasion.