Wnt2 secreted by tumor fibroblasts promotes tumor growth and cell motility in esophageal carcinoma

Abstract

Interaction between neoplastic and stromal cells plays an important role in the tumor progression. Recently, we found that Wnt2 was frequently overexpressed in fibroblasts isolated from tumor tissue (TFs) compared to fibroblasts from non-tumor tissue (NFs) in esophageal squamous cell carcinoma (ESCC). In the present study, we studied the effect of TF-secreted Wnt2 in ESCC development via the tumor-stroma interaction. Quantitative real-time PCR found that Wnt2 expression was about 4 folds higher in the TFs than the NFs. Interestingly, no visible protein expression of WNT2 was detected in all tested ESCC cancer cell lines and clinical ESCC samples. Immunohistochemistry study showed that WNT2(+) cells was were mainly detected in the boundary between stroma and tumor tissue or scattered within tumor tissue. Furthermore, Wnt2-positive ESCC (defined as 5 or more Wnt2(+) cells observed in 200× microscopy field) was detected in 22/51 cases, which was significantly associated with the lymph node metastases (P=0.001), advanced TNM stage (P=0.001) and disease-specific survival (P<0.0001). To further investigate the effect of secreted Wnt2 on ESCC cells, an in vitro Wnt2 secreting system was established using Chinese hamster ovary (CHO) cells and conditioned medium was collected for functional study. Functional assays demonstrated that secreted Wnt2 could promote cell growth and cell migration. Molecular study found that the cell growth promoting effect of Wnt2 was via activating Wnt/β-catenin signaling pathway and subsequently upregulating cyclin D1 and c-myc expression. Wnt2 could also induce epithelial-mesenchymal transition (EMT) and promote cell motility. In conclusion, our data demonstrate that TF-secreted Wnt2 can promote cell growth through activating the canonical Wnt/β-catenin signaling pathway and increase cell motility by inducing EMT in esophageal cancer cells. Further characterization of the effect of Wnt2 secreted by TF on cancer development and progression will reveal the molecular mechanisms of how TF provide cancer cells a suitable microenvironment and find new therapeutic targets for cancer treatment.