A single nucleotide polymorphism in the DAB2IP gene is associated with risk of aggressive prostate cancer (PCa), and loss of DAB2IP expression is frequently detected in metastatic PCa. However, the functional role of DAB2IP in PCa remains unknown. Here, we show that the loss of DAB2IP expression initiates epithelial-to-mesenchymal transition (EMT), which is visualized by repression of E-cadherin and up-regulation of vimentin in both human normal prostate epithelial and prostate carcinoma cells as well as in clinical prostate-cancer specimens. Conversely, restoring DAB2IP in metastatic PCa cells reversed EMT. In DAB2IP knockout mice, prostate epithelial cells exhibited elevated mesenchymal markers, which is characteristic of EMT. Using a human prostate xenograft-mouse model, we observed that knocking down endogenous DAB2IP in human carcinoma cells led to the development of multiple lymph node and distant organ metastases. Moreover, we showed that DAB2IP functions as a scaffold protein in regulating EMT by modulating nuclear β-catenin/Tcell factor activity. These results show the mechanism of DAB2IP in EMT and suggest that assessment of DAB2IP may provide a prognostic biomarker and potential therapeutic target for PCa metastasis. P rostate cancer (PCa) has surpassed lung cancer as the leading cancer among American men (1). In the absence of metastasis, prostate cancer is largely a treatable disease. Thus, early diagnosis of patients who will develop PCa metastasis could reduce the mortality and morbidity associated with this disease. The development of metastasis depends on the migration and invasion of cancer cells from the primary tumor into the surrounding tissue. To acquire such invasive abilities, carcinoma cells may acquire unique phenotypic changes such as epithelial-tomesenchymal transition (EMT). EMT is a highly conserved cellular process that allows polarized, generally immotile epithelial cells to convert to motile mesenchymal-appearing cells. This process was initially recognized during several critical stages of embryonic development and has more recently been implicated in promoting carcinoma invasion and metastasis (2-4). During EMT, three major changes occur: (i) morphological changes from a cobblestone-like monolayer of epithelial cells to dispersed, spindle-shaped mesenchymal cells with migratory protrusions; (ii) changes of differentiation markers from cell-cell junction proteins and cytokeratin intermediate filaments to vimentin filaments and fibronectin; and (iii) acquisition of invasiveness through the extracellular matrix (4). Decreased E-cadherin expression or gain of vimentin expression is closely correlated with various indices of PCa progression, including grade, local invasiveness, dissemination into the blood, and tumor relapse after radiotherapy (5-8).A recent study using genome-wide association data reveals that a single nucleotide polymorphism probe located in the first intron of DAB2IP gene associates with the risk of aggressive PCa (9). The functional role of DAB2IP in PCa is poor...

In metastatic prostate cancer (PCa) cells, imbalance between cell survival and death signals such as constitutive activation of phosphatidylinositol 3-kinase (PI3K)-Akt and inactivation of apoptosisstimulated kinase (ASK1)-JNK pathways is often detected. Here, we show that DAB2IP protein, often down-regulated in PCa, is a potent growth inhibitor by inducing G 0/G1 cell cycle arrest and is proapoptotic in response to stress. Gain of function study showed that DAB2IP can suppress the PI3K-Akt pathway and enhance ASK1 activation leading to cell apoptosis, whereas loss of DAB2IP expression resulted in PI3K-Akt activation and ASK1-JNK inactivation leading to accelerated PCa growth in vivo. Moreover, glandular epithelia from DAB2IP ؊/؊ animal exhibited hyperplasia and apoptotic defect. Structural functional analyses of DAB2IP protein indicate that both proline-rich (PR) and PERIOD-like (PER) domains, in addition to the critical role of C2 domain in ASK1 activity, are important for modulating PI3K-Akt activity. Thus, DAB2IP is a scaffold protein capable of bridging both survival and death signal molecules, which implies its role in maintaining cell homeostasis.cell apoptosis ͉ prostate cancer ͉ signal transduction

Multiple and diverse cell adhesion molecules take part in intercellular and cell-extracellular matrix interactions of cancer. Cancer progression is a multi-step process in which some adhesion molecules play a pivotal role in the development of recurrent, invasive, and distant metastasis. A growing body of evidence indicates that alterations in the adhesion properties of neoplastic cells play a pivotal role in the development and progression of cancer. Loss of intercellular adhesion and the desquamation of cells from the underlying lamina propria allows malignant cells to escape from their site of origin, degrade the extracellular matrix, acquire a more motile and invasion phenotype, and finally, invade and metastasize. In addition to participating in tumor invasiveness and metastasis, adhesion molecules regulate or significantly contribute to a variety of functions including signal transduction, cell growth, differentiation, site-specific gene expression, morphogenesis, immunologic function, cell motility, wound healing, and inflammation. Cell adhesion molecule (CAM), a diverse system of transmembrane glycoproteins has been identified that mediates the cell-cell and cell-extracellular matrix adhesion and also serves as the receptor for different kinds of virus. We summarize recent progress regarding the role of CAM, particularly, immunoglobulin-CAMs and cadherins in the progression of cancer and discuss the potential application of CAMs in the development of cancer therapy mainly on urogenital cancer.

IFNg, a potent cytokine known to modulate tumor immunity and tumoricidal effects, is highly elevated in patients with prostate cancer after radiation. In this study, we demonstrate that IFNg can induce epithelial-to-mesenchymal transition (EMT) in prostate cancer cells via the JAK-STAT signaling pathway, leading to the transcription of IFN-stimulated genes (ISG) such as IFN-induced tetratricopeptide repeat 5 (IFIT5). We unveil a new function of IFIT5 complex in degrading precursor miRNAs (pre-miRNA) that includes pre-miR-363 from the miR-106a-363 cluster as well as pre-miR-101 and pre-miR-128, who share a similar 5 0 -end structure with pre-miR-363. These suppressive miRNAs exerted a similar function by targeting EMT transcription factors in prostate cancer cells. Depletion of IFIT5 decreased IFNg-induced cell invasiveness in vitro and lung metastasis in vivo. IFIT5 was highly elevated in high-grade prostate cancer and its expression inversely correlated with these suppressive miRNAs. Altogether, this study unveils a prometastatic role of the IFNg pathway via a new mechanism of action, which raises concerns about its clinical application.Significance: A unique IFIT5-XRN1 complex involved in the turnover of specific tumor suppressive microRNAs is the underlying mechanism of IFNg-induced epithelial-tomesenchymal transition in prostate cancer.See related commentary by Liu and Gao, p. 1032

DOC-2/DAB2 is a member of the disable gene family with tumor-inhibitory activity. Its down-regulation is associated with several neoplasms, and serine phosphorylation of its N terminus modulates DOC-2/DAB2's inhibitory effect on AP-1 transcriptional activity. We describe the cloning of DIP1/2, a novel gene that interacts with the N-terminal domain of DOC-2/DAB2. DIP1/2 is a novel GTPase-activating protein containing a Ras GTPase-activating protein homology domain (N terminus) and two other unique domains (i.e. 10 proline repeats and leucine zipper). Interaction between DOC-2/DAB2 and DIP1/2 is detected in normal tissues such as the brain and prostate. Altered expression of these two proteins is often detected in prostate cancer cells. Indeed, the presence of DIP1/2 effectively blocks mitogen-induced gene expression and inhibits the growth of prostate cancer. Thus, DOC-2/DAB2 and DIP1/2 appear to represent a unique negative regulatory complex that maintains cell homeostasis.