Previously, we identified the
calcium-activated
nucleotidase 1 (CANT1) transcript as up-regulated in
prostate cancer. Now, we studied CANT1
protein expression in a large cohort of nearly 1000 prostatic tissue samples including normal tissue,
prostatic intraepithelial neoplasia (PIN), primary
carcinomas,
metastases, and castrate-resistant
carcinomas, and further investigated its functional relevance. CANT1 displayed predominantly a Golgi-type immunoreactivity with additional and variable cytoplasmic staining. In comparison to normal tissues, the staining intensity was significantly increased in PIN lesions and
cancer. In
cancer, high CANT1 levels were associated with a better prognosis, and castrate-resistant
carcinomas commonly showed lower CANT1 levels than primary
carcinomas. The functional role of CANT1 was investigated using RNA interference in two
prostate cancer cell lines with abundant endogenous CANT1
protein. On CANT1 knockdown, a significantly diminished cell number and
DNA synthesis rate, a cell cycle arrest in G(1) phase, and a strong decrease of cell transmigration rate and wound healing capacity of CANT1 knockdown cells was found. However, on forced CANT1 overexpression, cell proliferation and migration remained unchanged. In summary, CANT1 is commonly overexpressed in the vast majority of primary prostate
carcinomas and in the precursor lesion PIN and may represent a novel prognostic
biomarker. Moreover, this is the first study to demonstrate a functional involvement of CANT1 in
tumor biology.