hGAPDH, human GAPDH; mGAPDH, mouse GAPDH. PFDN1 functions as a transcriptional suppressor of cyclin A Although the nuclear location and function of PFDN1 in yeast has been reported,21 there are no publications reporting the existence of nuclear PFDN1 in mammalian cells. TGF-1/PFDN1/cyclin A axis is essential for EMT induction and metastasis of lung cancer cells. Introduction Lung cancer has become one of the most prevalent and lethal cancers worldwide, and metastasis is the main cause of its high mortality rate in patients.1 Detachment from the primary loci and the invasion of cancer cells into the surrounding tissues can be initiated by the loss of cellCcell adhesion and the gain of motility and invasive properties.2 During the past decade, mounting data Etoposide (VP-16) have shown Rcan1 that epithelial-mesenchymal transition (EMT) is a critical factor contributing to the invasion and distal metastasis of many epithelial-originated cancers. EMT has been characterized to be a fundamental biological event that has important roles in embryonic development, wound healing, chronic fibrosis and cancer metastasis.3 EMT causes the reorganization of the cytoskeleton and endows epithelial cells with a mesenchymal phenotype, which is important for mediating changes in cell identity and behavior. Various factors have been implicated in the control of EMT. Transforming growth factor (TGF)-1 is one of the strongest inducers of EMT and receives abundant attention owing to its potent pleiotropic effects implicated in a variety of patho-physiological processes, including cancer progression.4 An increasing number of molecules have been identified to be involved in TGF-1 signaling and associated cellular and biological events. Insulin receptor substrate-1,5 forkhead box transcription factor A2,6 and hepatocyte nuclear factor 67 were shown to be potent EMT suppressors. They are essential for maintaining the epithelial phenotype and are therefore important in the inhibition of EMT and its associated cellular events. Decreased expression levels of these molecules have been linked with TGF-1-induced EMT, growth and metastasis of lung cancers. In contrast, prostate transmembrane protein, androgen induced-1 is important for the plasticity of epithelial cells and its significant increase is required for TGF-1-induced EMT in lung cancer cells.8 These findings suggest that a TGF-1 signaling network is orchestrated to regulate the equilibrium between the epithelial and mesenchymal properties of various cells, which impacts cell fates and behavior decisions. Further investigation into the relevant aspects of TGF-1 signaling is important for deepening our understanding of EMT and could provide more precise mechanism-based clinical treatment of some cancers. Chaperone proteins have been shown to be involved in cancer development and progression.9, 10 However, little is known about their roles in TGF- signaling and the induction of EMT. It has been shown recently that chaperone proteins are involved in the induction of EMT and the metastasis of prostate cancer cells.11, 12 Until recently, the roles of co-chaperones in TGF–induced EMT and other relevant patho-physiological processes were poorly understood. Prefoldin (PFDN) is a co-chaperone protein that captures unfolded polypeptides and transfers Etoposide (VP-16) them to the chaperonin containing tailless complex polypeptide-1.13 PFDN exists in the cytosol as a complex containing six subunits. The involvement of PFDN subunits in cancer progression has been reported in several publications. PFDN subunits can interact with HDAC1 with high affinity in HepG2 hepatocarcinoma cells.14 PFDN4, a subunit of the PFDN complex, is decreased in colorectal cancer and is involved in the inhibition of cell growth and invasiveness.15 Prefoldin subunit 1 (PFDN1) is important in cytoskeletal rearrangement, as the phenotypes caused by PFDN1 depletion were all consistent with that of abnormal cytoskeletal functions.16, 17 Considering these findings and the close relationship between cytoskeletal rearrangement and EMT, we hypothesized that PFDN1 is an essential factor involved in the regulation of EMT and its accompanying biological events. Cyclin A (also known as cyclinA2) is important in cell cycle Etoposide (VP-16) regulation and is implicated in cell fate determination. Cyclin A depletion was shown to cause an increase in cytoskeletal rearrangement and cell migration in normal mammary epithelial cells.18 Compared with low invasive or primary tumors, the expression level of cyclin A is markedly lower in a highly invasive colon adenocarcinoma cell line, suggesting that.