OBJECTIVETo study the effect of tissue environment on the invasiveness of carcinoma cells and the implication of expression of matrix metalloproteinases.

METHODSTissue from a human gastric carcinoma was transplanted and passaged subcutaneously in nude mice. After the 3rd passage, the xenografts were also transplanted into the abdominal cavity of nude mice. The invasiveness of xenografts at the two locations were observed morphologically and the expressions of MMP-2, MMP-7, MMP-9, MMP-13, TM1-MMP, TM2-MMP and TM3-MMP were monitored by immunohistochemistry.

RESULTSThe subcutaneous xenografts of human gastric carcinoma in nude mice presented as expanding outgrowths with limited invasion. Except for MMP-7, the other 6 MMPs (MMP-2, MMP-9, MMP-13, TM1-MMP, TM2-MMP, TM3-MMP) were not expressed in the neoplastic cells nor in the tumor stroma. In contrast, the intra-peritoneal xenografts displayed an invasive growth pattern accompanied by more fibrous stroma. All MMPs examined were expressed in the tumor cells at the invasive fronts and in the adjacent stroma.

CONCLUSIONSInvasiveness and expression of MMPs were obviously diverse in human gastric carcinoma cells when grafted at different anatomic locations in nude mice, thus indicating: (1) There exists a close interaction between tumor cells and surrounding stromal cells. The tissue environment may play a definitive role in the tumor phenotype. (2) The expression of MMPs is closely related to the growth pattern and the invasiveness of tumor cells. MMPs produced by the stroma cells at the invasion front may be linked to the invasiveness of neoplastic cells.