The functional role of nuclear factor of activated T-cells (NFAT), while it has been extensively investigated in the immune system, remains uncertain in
bladder cancer development. We here aim to assess the effects of
cyclosporine A (CsA) and
tacrolimus (
FK506),
immunosuppressants known to specifically inactivate the NFAT pathway in immune cells, on neoplastic transformation of urothelial cells. Immunohistochemistry revealed that the expression levels of NFATc1, a NFAT
isoform shown to function as an oncogene in a
sarcoma model, were elevated in urothelial
neoplasms, compared with non-neoplastic urothelial tissues, and in low-grade and high-grade papillary urothelial
carcinomas, compared with papillary urothelial
neoplasms of low malignant potential. In an immortalized normal urothelial cell line SVHUC, CsA and
FK506 reduced NFATc1 expression, NFAT transcriptional activity, and the expression of c-myc, a downstream target of NFATc1 signals. Treatment with CsA or
FK506 in the SVHUC cells undergoing neoplastic transformation induced by exposure to a chemical
carcinogen 3-methylcholanthrene resulted in strong inhibition in colony formation in vitro as well as
tumor formation in NOD-SCID mice. CsA and
FK506 were additionally found to up-regulate the expression of several molecules that play a protective role in bladder
tumorigenesis, including p53, p21, and p27, and down-regulate that of oncogenic genes, such as
cyclin D1,
cyclin D3, and
cyclin E, in SVHUC cells with the
carcinogen challenge. Thus, CsA and
FK506 likely inhibit urothelial
tumorigenesis. These findings offer a potential chemopreventive approach for urothelial
tumors using NFAT inhibitors.