Pathological significance of fibroblast activation protein and its association with angiogenesis in colorectal carcinoma

Abstract

Background/aim Fibroblast activation protein (FAP) as one of the complex tumor environment is expressed in activated fibroblasts and associated with poor prognosis in cancer. FAP expression in colon cancer lacks sufficient evidence to serve a significant role in angiogenesis. This study aimed to clarify the association of FAP expression with angiogenesis in the prognosis of colorectal carcinoma (CRC). Materials and methods A total of 50 biopsies of CRC were evaluated by immunohistochemistry for investigating FAP expression and microvascular density (MVD) using CD34 protein. In terms of FAP-positive cells and FAP staining intensity, tumors were classified as high and low expression. With respect to tumor vascularity, cases were classified into hypovascular tumors and hypervascular ones. Both of FAP expression and MVD were correlated with histological tumor grade, stage, and lymph node metastases and also with each other. Results FAP expression was significantly higher in malignant cases than normal nontumor tissue samples. The percentage of FAP-positive cells was significantly correlated with grade, T-stages, and lymph node metastases, while FAP intensity was significantly associated with high tumor stage only. Hypervascularity was significantly correlated with high T-stages and lymph nodes metastasis. A significant correlation was found between FAP expression percentage and MVD. Conclusion This study indicates that FAP is overexpressed in primary CRC and is associated with poor prognosis. The authors suggested that FAP may be used as a prognostic marker and could be reliable for predicting the angiogenic activity of CRC. Further studies are recommended applying FAP as a diagnostic marker for CRC and for evaluating its promising role as an excellent target for antitumor therapy.