The expression and function of Frizzled-7 in human renal cell carcinoma

Wnt/beta-catenin has emerged as an important signal pathway in renal cell carcinoma (RCC) pathogenesis. Frizzled 7 (Fzd7) is a member of Frizzled (Fzd) receptor family which binds with Wnt ligands and transduces canonical and non-canonical pathways. However, the expression of Fzd7 in human RCC is poorly investigated. 53 RCC tissues and peri-tumor tissues were collected from the patients treated with radical nephrectomy. The expression of Fzd7 was investigated by immunohistochemical staining. Three RCC cells were transfected with Fzd7shRNA and GFPshRNA to investigate the function of Fzd7 in RCC cells. The immunohistochemical analysis showed that Fzd7 protein expression level was significantly increased in RCC tissues when compared with peri-tumor tissues, which suggested that Fzd7 might be involved in the formation of tumors. However, the Fzd7 expression was not correlated with clinicopathological parameters. Three RCC cell lines: 786-O, Caki-1, and OS-RC-2 also expressed Fzd7. With Fzd7 expression being interfered by shRNA, the RCC cell proliferation was mildly decreased. Wnt3a could stimulate the RCC cells proliferation, but the stimulation was decreased when Fzd7 expression was interfered. Restoring the Fzd7 expression led to the proliferation stimulation effect of Wnt3a being restored. This paper suggests that Fzd7 may act as one of the molecules that take part in the course of RCC formation. Fzd7 can be activated by Wnt3a to stimulate cell proliferation.