High expression of fibroblast activation protein is an adverse prognosticator in gastric cancer

Background: Human Fibroblast Activation Protein (FAP) is a surface glycoprotein expressed on cancer associated fibroblasts in the majority of epithelial cancers. Tumor promoting effects of FAP expression was reported in several cancers. However, in gastric cancer, its clinical significance is unclear. Methods: Sections of primary human gastric cancer (adenocarcinoma) and adjacent normal gastric tissue specimens were collected from 112 patients. Immunohistochemistry method was used to evaluate FAP expression on sections. The overall percentage of FAP staining was assessed semi quantitatively (score=1, 2, 3). Prognostic value of FAP expression in gastric cancer was evaluated. Results: The gastric cancer tissues showed a higher amount of FAP positive cells than adjacent normal gastric tissues. High expression of FAP was correlated with primary tumor invasion (P value=0.042) and high TNM stage (P value=0.036). In survival analysis, patients with high expression of FAP showed shorter overall survival and progression free survival compared with patients showed low expression of FAP (P value=0.026 and 0.015, respectively). High expression of FAP was identified as an independent prognosticator of gastric cancer as well (P value=0.017). Conclusion: Our data suggested that FAP positive cells were accumulated in gastric cancer tissues. Meanwhile, patients whose gastric tumors have high level of FAP expression were more likely to have aggressive disease development and poor survival. Studies that elucidate the mechanism of how the FAP positive cells promote gastric cancer development are needed.