The basement membrane (BM), a structure of crucial importance in the invasion and metastasis of cancers, was studied immunohistochemically using colorectal cancer tissues. In addition, BM-like structures formed in the primary culture of cancer cells were compared to the BM of primary cancers. BM was stained with antibodies specific for laminin, type IV collagen, fibronectin, and heparan sulfate proteoglycan. In the normal colon these compounds were detected in the glandular BM, vascular BM and perinervium by immunostaining. Components of the BM were not stained in some cancer tissues, and BM staining essentially disappeared in the invasive front of cancer in several cases. Of whole cancer tissues, 10 of 23 cases (43.5%) were BM positive and the remaining 13 cases (56.5%) were negative. A three dimensional primary culture of colorectal cancer cells was performed in collagen gel. The cancer cells obtained from primary cancers which had densely stained for BM formed a BM-like structure in primary culture, but those from negatively stained cancer tissues showed no BM-like structures. The BM-like structure in the primary culture was shown to have the same components as the true BM by immunohistochemistry, and this membranous structure was shown to have originated in the cancer cells. In the primary culture without any BM-like structures, granules containing BM components were observed around tumor cell clusters. The primary culture of tumor cells in collagen gel is closely related to the original tumor tissues and therefore may provide a good model system for the investigation of BM in cancer.

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