Phosphatase of regenerating liver (PRL-3) promotes cancer metastasis through enhanced cell motility and invasiveness, however its role in tumorigenesis remains unclear. Herein, we reported that PRL-3 interacts with telomere-related protein RAP1. PRL-3 promotes the cytosolic localization of RAP1, which is counteracted by silencing of PRL-3. Immunohistochemical staining of colon cancer tissue array (n = 170) revealed that high level of PRL-3 associates with cytosolic localization of RAP1 (p = 0.01). Microarray analysis showed that PRL-3 regulates expression of diverse genes and enhances phosphorylation of p65 subunit of NF-kappa B in a RAP1-dependent manner. Furthermore, PRL-3 transcriptionally activates RAP1 expression, which is counteracted by ablating p65. Therefore, our results demonstrate PRL-3 as a novel regulator of NF-kappa B signaling pathway through RAP1. (C) 2012 Elsevier Inc. All rights reserved.