In ovarian cancer as in other cancers, perlecan expression occurs differently throughout progression of the disease. Perlecan staining is lost in ovarian basement membrane that has been breached by an invasive adenocarcinoma, which is in contrast to perlecan staining in the basement membranes of normal ovaries and those with benign tumors, where basement membrane is homogeneous and very similar in composition to that in other normal tissues. This is consistent with other results showing loss of perlecan in basement membranes affected by invasive cervical cancer spreading to the pelvic lymph nodes, which comes as no surprise due to the correlation of elevated levels of heparanase mRNA expression with invasion of similar cervical carcinoma. By contrast, tumor formation of the immortalized mouse epithelial cell line RT101 injected into rats was dependent on perlecan expression by the mouse cells and not on the presence of endogenous rat perlecan. RT101 cells with perlecan knocked down by antisense did not show tumor formation in this system, however cells expressing the antisense perlecan and a recombinant construct encoding domains I, II, and III of mouse perlecan did indeed show tumor formation. Thus in this system it does appear that tumor cell expression of perlecan is necessary for tumor aggregation. More research into GAG chain or core protein modification by invasive tumor cells as compared to benign tumor cells and normal tissue would be informative to better understand perlecans role in cancer migration.