The peptidyl-prolyl isomerase Pin I is prevalently overexpressed in human cancers and is regarded as a new diagnostic and therapeutic target. Pin] interacts with several proteins involved in cell cycle events in a phosphorylation-dependent manner. Among them, NIMA (never in mitosis, gene A) was first identified to interact with Pin 1. In this report, we found that Pin I could interact with Nek6, one of the human NIMA-related kinases (Neks). This interaction was confirmed by GST pull-down assay, which was further confirmed by immunoprecipitation experiments, as well as immunofluorescence colocalization. We further studied Pin I and Nek6 mRNA level in 40 pairs of hepatocellular carcinoma cases, finding significant correlations between Nek6 and Pint mRNA expression levels in these samples. (c) 2006 Elsevier Inc. All rights reserved.