Identification of oncofetal fibronectin in patients with advanced epithelial ovarian cancer: Detection in ascitic fluid and localization to primary sites and metastatic implants

BACKGROUND. The mechanisms by which metastatic ovarian cancer adheres to peritoneal surfaces are not well understood. A role for tumor-derived extracellular matrix adhesive molecules such as fibronectin (FN) has been proposed. Because oncofetal fibronectin (onfFN) isoforms function in the adhesion of trophoblasts and have been identified in association with several malignancies, we sought to study onfFN in patients with advanced epithelial ovarian cancer. METHODS. Total FN was identified with the nonspecific anti- FN monoclonal antibody CAF. OnfFN was identified using the specific monoclonal antibodies FDC-6 and X18A4. These antibodies were applied to: 1) ascitic fluid from advanced epithelial ovarian cancer patients and peritoneal fluid from patients without pathologic conditions and 2) tissue sections of primary lesions and metastatic ovarian cancer implants. Comparative histologic specimens included normal ovarian tissue and small bowel implants of endometriosis. RESULTS. When measured by sandwich enzyme-linked immunoadsorbent assay, all peritoneal fluids (32 malignant and 32 benign) contained marked quantities of total (CAF reactive) FN, although malignant ascites had higher concentrations than benign samples (173.2 ± 36.8 μg/mL vs. 76.4 ± 31.8 μg/mL; P = 0.001). Malignant ascites also had significantly higher levels of onfFN than benign peritoneal fluid (FDC-6: 3.4 ± 0.6 vs. 0.9 ± 0.2 μg/mL; and X18A4: 5.1 ± 1.3 vs. 1.1 ± 0.4 μg/mL; P = 0.0001). Immunohistochemical staining of malignant lesions revealed prominent localization of both CAF reactive FN and onfFN to the stroma surrounding epithelial tumor nests. More delicate fibrillar staining within tumor nests also was evident. In contrast, implants of endometriosis revealed strong stromal staining for CAF reactive FN but not for onfFN. CONCLUSIONS. These results demonstrate the presence of onfFN in advanced ovarian malignancies. We speculate that onfFN may participate in tumor-associated peritoneal adhesive interactions.