THE ROLE OF BASEMENT-MEMBRANE IN COLORECTAL-CANCER INVASION AND LIVERMETASTASIS

Background. Basement membrane (BM) is a specialized extracellular matr ix component that plays a key role in tumor invasion and metastasis. M ethods. Immunohistochemical staining for two major components of BM, t ype IV collagen (C IV), and laminin (LN), utilizing avidin-biotin-pero xidase complex detection to examine 182 primary colorectal cancers (pT 2 or greater) and 20 liver metastases. Results. The distribution of C IV was the same as of LN in colorectal cancer tissue, and in normal ti ssue. Both C IV and LN staining were more frequently positive in the s uperficial zone but infrequently in the deep zone of the primary tumor . BM preservation, C IV and LN staining in both the superficial and de ep zones, was seen in 18.7% of the subjects. The rate of BM preservati on significantly decreased with increasing histologic grade (P < 0.01) . No correlation was observed between pT number and BM preservation. T he rate of BM preservation in cases of liver metastasis was 84.4%, sig nificantly higher than the rate in cases without liver metastasis (P < 0.001). BM was observed even at the advancing front of tumor invasion and was preserved in 95.0% of the liver metastases. Conclusions. BM i s a functional substance that appears to accompany cancer rather than function as a structural barrier against cancer invasion and liver met astasis.