Recent studies have shown that the tumor microenvironment plays a significant role in the progression of solid tumors. As an abundant component of the tumor microenvironment, cancer associated fibroblasts (CAFs) have been shown to promote tumorigenesis and cancer aggressiveness, but their molecular characteristics remain poorly understood.
CAFs and normal fibroblasts (NFs) were isolated from freshly resected specimens from patients with colorectal cancer (CRC). RNA sequence was performed to obtain gene expression profiles of CAFs and NFs. We analyzed the profiles and compared gene expression differences between CAFs and NFs. Moreover, immunohistochemistry, proliferation assay and migration assay were performed for evaluating function of the isolated genes.
RNA sequencing analysis revealed that the gene sets related to the Wnt signaling pathway were highly expressed in CAFs, as well as TGFβ signaling, which is considered to be a regulator of CAFs. Among the components of this pathway, Wnt2 was specifically expressed. Thus, we performed immunohistochemical analysis on Wnt2 in 171 patients who underwent surgery for colorectal adenocarcinoma. Positive staining for Wnt2 was often observed in cancer stroma, although the immunoreactivity was negative or weak in cancer cells. Wnt2 expression in CAFs was significantly correlated with depth of tumor (P < 0.001), lymph node metastasis (P = 0.044), TNM stage (P = 0.010), venous invasion (P < 0.001), liver metastasis (P = 0.045), and recurrence (P = 0.013). Subsequent in vitro analyses revealed that cancer cell invasion and migration were significantly decreased in a conditioned medium from immortalized CAFs transfected with siRNA targeting Wnt2.
The present study showed that Wnt2 expression in CAFs was significantly related to factors leading to tumor progression, such as depth of tumor invasion and lymph node metastasis, as revealed by immunochemical examination. We also demonstrated that Wnt2 protein derived from CAFs induced cancer cell migration and invasion in CRC. These findings suggest that Wnt2 secreted by CAFs is a key role as a critical mediator in CRC progression and is a potential therapeutic target for CRC.
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Legal entity responsible for the study
Japan Society for the Promotion of Science.
All authors have declared no conflicts of interest.