The nucleolar protein NIFK promotes cancer progression via CK1α/β-catenin in metastasis and Ki-67-dependent cell proliferation

Nucleolar protein interacting with the FHA domain of pKi-67 (NIFK) is a Ki-67-interacting protein. However, its precise function in cancer remains largely uninvestigated. Here we show the clinical significance and metastatic mechanism of NIFK in lung cancer. NIFK expression is clinically associated with poor prognosis and metastasis. Furthermore, NIFK enhances Ki-67-dependent proliferation, and promotes migration, invasion in vitro and metastasis in vivo via downregulation of casein kinase 1 alpha (CK1 alpha), a suppressor of pro-metastatic TCF4/beta-catenin signaling. Inversely, CK1 alpha is upregulated upon NIFK knockdown. The silencing of CK1 alpha expression in NIFK-silenced cells restores TCF4/beta-catenin transcriptional activity, cell migration, and metastasis. Furthermore, RUNX1 is identified as a transcription factor of CSNK1A1 (CK1 alpha) that is negatively regulated by NIFK. Our results demonstrate the prognostic value of NIFK, and suggest that NIFK is required for lung cancer progression via the RUNX1-dependent CK1 alpha repression, which activates TCF4/beta-catenin signaling in metastasis and the Ki-67-dependent regulation in cell proliferation.