CD24 expression is important in male urothelial tumorigenesis and metastasis in mice and is androgen regulated

Overexpression of CD24, a glycosyl phosphatidylinositol-linked sialoglycoprotein, is associated with poor outcome in urothelial carcinoma and contributes to experimental tumor growth and metastasis. However, the requirement for CD24 (Cd24a in mice) in tumorigenesis and spontaneous metastasis from the orthotopic site remains uncharacterized. Using N-butyl-N-(4-hydroxybutyl) nitrosamine induction of invasive and metastatic bladder cancer, we show that Cd24a-deficient male mice developed fewer bladder tumors than C57BL/6 control male mice. Evaluating only mice with evidence of primary tumors, we observed that Cd24a-deficient male mice also had fewer metastases than wild-type counterparts. In parallel observations, stratification of patients based on CD24 immunohistochemical expression in their tumors revealed that high levels of CD24 are associated with poor prognosis in males. In female patients and mice the above observations were not present. Given the significant role of CD24 in males, we sought to assess the relationship between androgen and CD24 regulation. We discovered that androgen receptor knockdown in UM-UC-3 and TCCSUP human urothelial carcinoma cell lines resulted in suppression of CD24 expression and cell proliferation. Androgen treatment also led to increased CD24 promoter activity, dependent on the presence of androgen receptor. In vivo, androgen deprivation resulted in reduced growth and CD24 expression of UM-UC-3 xenografts, and the latter was rescued by exogenous CD24 overexpression. These findings demonstrate an important role for CD24 in urothelial tumorigenesis and metastasis in male mice and indicate that CD24 is androgen regulated, providing the foundation for urothelial bladder cancer therapy with antiandrogens.