Can Fibulin-5 Induce Gastrointestinal Stromal Tumor Development?

Objective: Gastrointestinal stromal tumors are the most common primary mesenchymal tumors of the gastrointestinal tract and show Cajal cell differentiation. Fibulin-5 is a multifunctional extracellular matrix protein that inhibits epithelial and endothelial cell proliferation. Expression of fibulin-5 is down-regulated in various carcinomas. In contrast, fibulin-5 stimulates fibroblast and fibrosarcoma cells. In this study we aimed to investigate the expression of fibulin-5 in Cajal cells and gastrointestinal stromal tumors. Materials and Methods: Immunohistochemical fibulin-5 staining is performed on 34 (22 gastric and 12 small intestinal) gastrointestinal stromal tumors. Fibulin-5 staining intensity was scored in 4 quantitative categories and compared with clinicopathological features of the patients. Results: There was no staining in 4 of the gastrointestinal stromal tumors; weak staining in 20 cases, moderate staining in 6 cases, and strong staining in 4 cases were observed. In 3 cases Cajal cells were detected with fibulin-5 by moderately staining. The relationship between fibulin-5 staining intensity and age and gender of the cases, localization, size, grade, and the risk groups of the tumors wasn’t statistically significant. Conclusion: A great proportion of gastrointestinal stromal tumors show fibulin-5 expression, even if weak, in contrast to the infrequent fibulin-5 expression in Cajal cells. Based on these findings, it can be speculated that the expression of fibulin-5 in Cajal cells can be increase cell proliferation, but it would be useful to conduct new studies with larger series to clarify this issue. There is no correlation between fibulin-5 expression intensity and clinicopathological and prognostic data of gastrointestinal stromal tumors.