Compound haploinsufficiency of Dok2 and Dusp4 promotes lung tumorigenesis.

Recurrent broad-scale heterozygous deletions are frequently observed in human cancer. Here we tested the hypothesis that compound haploinsufficiency of neighboring genes at chromosome 8p promotes tumorigenesis. By targeting the mouse orthologs of human DOK2 and DUSP4 genes, which were co-deleted in approximately half of human lung adenocarcinomas, we found that compound-heterozygous deletion of Dok2 and Dusp4 in mice resulted in lung tumorigenesis with short latency and high incidence, and that their co-deletion synergistically activated MAPK signaling and promoted cell proliferation. Conversely, restoration of DOK2 and DUSP4 in lung cancer cells suppressed MAPK activation and cell proliferation. Importantly, in contrast to downregulation of DOK2 or DUSP4 alone, concomitant downregulation of DOK2 and DUSP4 was associated with poor survival in human lung adenocarcinoma. Therefore, our findings lend in vivo experimental support to the notion that compound haploinsufficiency, due to broad-scale chromosome deletions, constitutes a driving force in tumorigenesis.

PRL-3 Promotes Ubiquitination and Degradation of AURKA and Colorectal Cancer Progression via Dephosphorylation of FZR1.

The oncogenic phosphatase PRL-3 is highly expressed in metastatic colorectal cancer but not in nonmetastatic colorectal cancer or noncolorectal cancer metastatic cancers. Although the proinvasive capacity of PRL-3 has been validated in multiple types of cancer, its impact on colorectal cancer progression and the underlying mechanisms remain poorly understood. Here, we report that overexpressed PRL-3 stimulates G2-M arrest, chromosomal instability (CIN), self-renewal, and growth of colorectal cancer cells in xenograft models, while colorectal cancer cell proliferation is decreased. PRL-3-induced G2-M arrest was associated with decreased expression of Aurora kinase A (AURKA). PRL-3-promoted slow proliferation, CIN, self-renewal, and growth in xenografts were counteracted by ectopic expression of AURKA. Conversely, knockdown of PRL-3 resulted in low proliferation, S-phase arrest, impaired self-renewal, increased apoptosis, and diminished xenograft growth independently of AURKA. Analysis of colorectal cancer specimens showed that expression of PRL-3 was associated with high status of CIN and poor prognosis, which were antagonized by expression of AURKA. PRL-3 enhanced AURKA ubiquitination and degradation in a phosphatase-dependent fashion. PRL-3 interacted with AURKA and FZR1, a regulatory component of the APC/CFZR1 complex. Destabilization of AURKA by PRL-3 required PRL-3-mediated dephosphorylation of FZR1 and assembly of the APC/CFZR1 complex. Our study suggests that PRL-3-regulated colorectal cancer progression is collectively determined by distinct malignant phenotypes and further reveals PRL-3 as an essential regulator of APC/CFZR1 in controlling the stability of AURKA. SIGNIFICANCE: Dephosphorylation of FZR1 by PRL-3 facilitates the activity of APC/CFZR1 by destabilizing AURKA, thus influencing aggressive characteristics and overall progression of colorectal cancer.

Up-Regulation of Phosphatase in Regenerating Liver-3 (PRL-3) Contributes to Malignant Progression of Hepatocellular Carcinoma by Activating Phosphatase and Tensin Homolog Deleted on Chromosome Ten (PTEN)/Phosphoinositide 3-Kinase (PI3K)/AKT Signaling Pathway.

BACKGROUND The purpose of the study was to investigate the functional roles of phosphatase in regenerating liver-3 (PRL-3) in hepatocellular carcinoma (HCC), as well as the related molecular mechanisms. MATERIAL AND METHODS HCC tissues and adjacent normal tissues were collected from 124 HCC patients. The mRNA and protein levels of PRL-3 were detected using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot assays, respectively. The relationship between PRL-3 expression and clinical characteristics of HCC patients was evaluated by chi-square test. MTT and Transwell assays were performed to estimate cell proliferation and motility, respectively. RESULTS The expression of PRL-3 was significantly increased in HCC tissues and cells at both protein and mRNA levels (P<0.01 for all). Furthermore, the up-regulation of PRL-3 was positively correlated with hepatic vascular invasion (P=0.019), lymph node metastasis (P=0.012), and TNM stage (P=0.001). The knockdown of PRL-3 suppressed HCC cell proliferation, migration, and invasion, and PR3K/AKT pathway activity was also obviously inhibited in HCC cells with PRL-3 deficiency. The levels of PTEN were negatively associated with PRL-3 expression. PRL-3 might inhibit the protein level of PTEN through enhancing its phosphorylation level. The transfection of si-PTEN can reverse the anti-tumor action caused by PRL-3 knockdown in HCC cells. CONCLUSIONS Up-regulation of PRL-3 may activate the PI3K/AKT signaling pathway and enhance malignant progression of HCC through targeting PTEN.

miR-219a-5p represses migration and invasion of osteosarcoma cells via targeting EYA2.

EYA2 is the developmental transcription factor and phosphatase, playing an important role in numerous species in regulating cell death and differentiation. Recent studies showed that EYA2 is dysregulated and involved in the progression of various cancers. However, the expression and role of EYA2 in osteosarcoma remains unclear. Here, we found that EYA2 expression was evidently upregulated osteosarcoma (OS) tissue and cell lines. Next, we predicted EYA2-targeting miRNAs, which was further evaluated using a dual luciferase reporter assay. We found that miR-219a-5p significantly repressed EYA2 expression via binding to the 3'-UTR of EYA2. Furthermore, overexpressed miR-219a-5p significantly repressed OS cell invasion and migration, which was reversed by overexpressed EYA2. While silenced miR-219a-5p induced OS cell invasion and migration, which was reversed by silenced EYA2. In conclusion, our study revealed that miR-219a-5p function as tumour suppressor regulates OS cell invasiveness by repressing EYA2 expression.

PRL­3 increases the aggressive phenotype of prostate cancer cells in vitro and its expression correlates with high-grade prostate tumors in patients.

The increased expression of phosphatase of regenerating liver-3 (PRL­3) has been shown to be associated with the aggressive and metastatic phenotype of different solid tumors. However, it is not known whether PRL­3 plays a similar role in the progression of prostate cancer (PCa). In this study, immunoblot analysis of androgen receptor (AR)-positive PCa lines (LNCaP and LNCaP­SF) revealed the constitutive cytoplasmic expression of PRL­3, and stimulation with R1881 (AR agonist) rapidly increased the nuclear translocation of PRL­3. The AR-negative cell lines exhibited negligible PRL­3 expression, and the ectopic overexpression of PRL­3 increased both the proliferative and invasive potential of PC3 and DU145 cells. In addition, we measured PRL­3 protein expression in human prostate tumor sections. A high-density prostate tumor microarray (TMA) was immunostained to assess whether PRL­3 expression and its subcellular localization (cytoplasmic and nuclear levels) is associated with the Gleason score (GS), Gleason grade (GG) and tumor stage (T-stage). Digital image analysis (DIA) revealed that PRL­3 expression was significantly higher in the malignant cores, as compared to the non­malignant areas. Increases in both total and nuclear PRL­3 levels were also associated with a higher GS and GG. Metastatic tumors (T4­stage) had lower cytoplasmic, but higher nuclear PRL­3 levels. Furthermore, the nuclear/cytoplasmic ratio for PRL­3 in the tumors graded as GS7 could effectively distinguish between indolent (3+4) and aggressive (4+3) disease. Thus, our experiments using PCa lines suggested that PRL­3 is an AR-regulated gene and its androgen-induced nuclear localization may increase the aggressive behavior of PCa cells. Furthermore, the digital analysis of immunostained tumor sections suggested that PRL­3 may be an effective biomarker of high-grade PCa, and its nuclear/cytoplasmic ratio may be used to distinguish between indolent vs. aggressive tumors.

PRL-3/PTP4A3 phosphatase regulates integrin ß1 in adhesion structures during migration of human ocular melanoma cells.

In a previous transcriptomic analysis of 63 ocular melanomas of the uvea, we found that expression of the PRL-3/PTP4A3 gene, encoding a phosphatase that is anchored to the plasma membrane, was associated with the risk of metastasis, and a poor prognosis. We also showed that PRL-3 overexpression in OCM-1 ocular melanoma cells significantly increased cell migration in vitro and invasiveness in vivo, suggesting a direct role for PRL-3 in the metastatic spreading of uveal melanoma. Here, we aimed to identify PRL-3 substrates at the plasma membrane involved in adhesion to the extracellular matrix. We focused on integrin ß1, which is the most highly expressed integrin in our cohort of uveal melanomas. We show that preventing PRL-3 anchorage to the plasma membrane i) abolishes PRL-3-induced migration in OCM-1 cells, ii) specifically enhances the spreading of OCM-1 cells overexpressing PRL-3, and iii) favors the maturation of large focal adhesions (FAs) containing integrin ß1 on collagen I. Knockdown experiments confirmed integrin ß1 involvement in PRL3-induced migration. We identified interactions between PRL-3 and integrin ß1, as well as with FAK P-Y397, an auto-activated form of Focal Adhesion Kinase found in FAs. We also show that integrin ß1 may be dephosphorylated by PRL-3 in its intracytoplasmic S/T region, an important motif for integrin-mediated cell adhesion. Finally, we observed that PRL-3 regulated the clustering of integrin ß1 in FAs on collagen I but not on fibronectin. This work identifies PRL-3 as a new regulator of cell adhesion structures to the extracellular matrix, and further supports PRL-3 as a key actor of metastasis in uveal melanoma, of which molecular mechanisms are still poorly understood.

Susceptibility of naïve and differentiated PC12 cells to Japanese encephalitis virus infection.

Japanese encephalitis is a mosquito-borne disease caused by Japanese encephalitis virus (JEV) infection. Although JEV infects and replicates in cells with multiple tissue origins, neurons are the preferential cells for JEV infection. Currently, the identities of JEV cell tropism are largely unclear. To gain better insight into the underlying identities of JEV cell tropism, this study was designed to compare the JEV cell tropism with naïve or differentiated PC12 cells. Through nerve growth factor-differentiated PC12 cells, we discovered that JEV efficiently replicated in differentiated PC12 cells rather than naïve cells. Mechanistic studies revealed that viral adsorption/attachment seemed not to be a crucial factor. Supporting data showed that antagonizing postreceptor intracellular signaling of interferons, along with the activation of suppressor of cytokine signaling-3 (SOCS3) expression and protein tyrosine phosphatase activity, were apparent in differentiated PC12 cells after JEV infection. Independent of differentiating inducing agents, the upregulation of SOCS3 expression and protein tyrosine phosphatase activity, as well as preferential JEV tropism, were common in JEV-infected differentiated PC12 cells. Using cultured primary neurons, JEV efficiently replicated in embryonic neurons rather than adult neurons, and the preference was accompanied by higher SOCS3 expression and protein tyrosine phosphatase activity. Given that both SOCS3 and protein tyrosine phosphatases have been implicated in the process of neuronal differentiation, JEV infection seems to not only create an antagonizing strategy to escape host's interferon antiviral response but also takes advantage of cellular machinery to favor its replication. Taken together, current findings imply that dynamic changes within cellular regulators of antiviral machinery could be accompanied by events of neuronal differentiation, thus concurrently playing roles in the control of JEV cell tropism and replication. © 2017 IUBMB Life, 69(2):79-87, 2017.

Localizing PRL-2 expression and determining the effects of dietary Mg(2+) on expression levels.

The phosphatase of regenerating liver (PRL) is a group of protein tyrosine phosphatases that play a key role in cancer progression and metastasis. We previously showed that PRL-2 modulates intracellular Mg(2+) levels and sustains cancer phenotypes by binding to the Mg(2+) transporter CNNM3. However, the physiological functions of PRL-2 in animals remain largely unknown. To better understand which cell types are associated with PRL-2 function, we characterized its expression in mouse tissues using a PRL-2 ß-galactosidase reporter mouse model. Our results demonstrated that PRL-2 was ubiquitously expressed, with the highest expression levels observed in the hippocampal pyramidal neurons, ependymal cells, cone and rod photoreceptor cells, endocardium, vascular and bronchial smooth muscle, and collecting ducts in the kidney. On the other hand, PRL-2 expression was undetectable or very low in the parenchymal cells of the liver and pancreas. Our results also indicated that PRL-2 is involved in cell-type-specific Mg(2+) homeostasis and that PRL-2 expression is potentially inversely regulated by dietary Mg(2+) levels.

Overexpression of protein tyrosine phosphatase 1B impairs glucose-stimulated insulin secretion in INS-1 cells.

BACKGROUND: Protein tyrosine phosphatase 1B (PTP1B) has been implicated as a negative regulator of insulin signaling. We reported previously that impaired glucose-stimulated insulin secretion (GSIS) in rats fed high-fat diet was associated with higher PTP1B protein levels in islets. The aim of the present study was to investigate the effect of increasing PTP1B on insulin secretion in ß-cells. METHODS: INS-1 cells were transduced with recombinant adenoviruses containing human PTP1B cDNA (Ad-PTP1B), or no exogenous gene (Ad-ctrl). The expression levels of PTP1B, insulin receptor (IR), insulin receptor substrate-1(IRS-1), glucokinase and glucose transporter-2 were evaluated by Western blot. Then insulin-stimulated IR and IRS tyrosine phosphorylation, and Akt pathway activation were measured. GSIS was also performed to evaluate INS-1 cells function. RESULTS: PTP1B expression level was increased 5.9-fold at 48h post-transduction. The overexpression of PTP1B had no effect on proliferation and apoptosis of INS-1 cells. Compared with control cells, INS-1 cells overexpressing PTP1B showed decrease in insulin-stimulated tyrosine phosphorylation of the insulin receptor (IR) and insulin receptor substrate-1(IRS-1) by 56.4% and 53.1%, respectively. In addition, Akt phosphorylation was reduced 59.6%. Moreover, in Ad-PTP1B-transduced cells, 16.7mM glucose caused a 1.6±0.2 fold increase (vs. 3.9±0.7 fold in nontransduced cells) in insulin secretion relative to secretion at 2.8mM glucose. Further analysis determined that overexpression of PTP1B induced down-regulated expression of glucokinase (42%) and glucose transporter-2 (48%). CONCLUSIONS: Our findings suggested that overexpression of PTP1B can inhibit GSIS in INS-1 cells through negatively regulating insulin signaling.

Overexpression of PTP4A3 is associated with metastasis and unfavorable prognosis in bladder cancer.

PURPOSE: Bladder cancer (BC) is the most common malignancy in urinary system. The prognosis of metastatic BC is poor, but there remains no reliable marker to early detect metastasis. Dysregulated prenylated protein tyrosine phosphatases (PTPs) are commonly associated with cancer metastasis. From a published BC transcriptome, we identified that PTP IVA3 (PTP4A3) was the most significantly upregulated gene implicated in tumor progression among genes related to prenylated PTPs. We therefore analyzed PTP4A3 expression in our well-characterized cohort of BC. METHODS: By immunohistochemistry, PTP4A3 expression was determined using H-score. PTP4A3 expression of 295 BCs was compared with clinicopathological parameters, and the effect of PTP4A3 on cancer-specific survival (CSS) and metastasis-free survival (MFS) was also examined. Two independent sets of BCs were used to assess PTP4A3 protein and transcript expression in normal urothelium and different stage tumors. RESULTS: PTP4A3 overexpression was significantly associated with higher pT stage (P < 0.001), nodal metastasis (P < 0.001), vascular invasion (P < 0.001), and perineural invasion (P = 0.021). In multivariate analysis, PTP4A3 overexpression was an independent predictor for CSS (P < 0.001) and MFS (P = 0.007). Notably, the difference in CSS and MFS between high and low PTP4A3-expressing tumors was also significant in muscle-invasive BCs. PTP4A3 protein expression showed significant and stepwise increments from normal urothelium to noninvasive BC, invasive BC, and metastatic foci (P < 0.001). PTP4A3 transcript was also obviously upregulated in high-stage BC (P < 0.001). CONCLUSIONS: PTP4A3 may play a role in BC oncogenesis and is a predictive marker of metastasis. PTP4A3 overexpression represents an independent prognosticator for BC, suggesting its potential theranostic value.

PTP4A3 Independently Predicts Metastasis and Survival in Upper Tract Urothelial Carcinoma Treated with Radical Nephroureterectomy.

PURPOSE: Increasing evidence has shown that protein tyrosine phosphatases have dominant roles in setting the levels of tyrosine phosphorylation and promoting oncogenic processes. PTP4A3 has been implicated in cancer metastasis but to our knowledge the role of PTP4A3 in upper tract urothelial carcinoma is unknown. The aim of this study was to investigate the association of PTP4A3 with disease characteristics, distant metastasis and prognosis of upper tract urothelial carcinoma. MATERIALS AND METHODS: The importance of PTP4A3 was initially examined in paired normal urothelium, noninvasive upper tract urothelial carcinoma, invasive upper tract urothelial carcinoma and nodal metastatic tissue. The PTP4A3 transcript level was assessed in another 20 upper tract urothelial carcinoma samples by real-time reverse transcriptase-polymerase chain reaction. PTP4A3 protein expression was determined by immunohistochemistry using the H-score in 340 upper tract urothelial carcinoma samples. It was further correlated with clinicopathological factors, and disease specific and metastasis-free survival. RESULTS: The expression of PTP4A3 significantly increased from normal urothelium, noninvasive upper tract urothelial carcinoma and invasive upper tract urothelial carcinoma to nodal metastatic tissue (p <0.001). The PTP4A3 transcript level was also markedly up-regulated in higher stage upper tract urothelial carcinoma (p = 0.002). Over expression of PTP4A3 protein was significantly associated with advanced pT status, nodal metastasis, lymphovascular invasion and perineural invasion (each p <0.001) as well as with inferior disease specific and metastasis-free survival on multivariate analysis (each p <0.0001). In addition, it predicted metastasis in patients with pTa, pT1 and pT2 upper tract urothelial carcinoma. CONCLUSIONS: Results imply that PTP4A3 has a role in the carcinogenesis of upper tract urothelial carcinoma. PTP4A3 over expression independently predicted the metastasis and outcome of upper tract urothelial carcinoma, which was even more important in organ confined disease.

Oxytalan-positive peripheral ossifying fibromas express runt-related transcription factor 2, bone morphogenetic protein-2, and cementum attachment protein. An immunohistochemical study.

BACKGROUND: The peripheral ossifying fibroma (POF) represents one of the most common lesions of the periodontal tissues that may originate from the gingival soft tissues, the periosteum, or the periodontal ligament. AIM: To investigate the immunohistochemical expression of runt-related transcription factor 2 (Runx-2), bone morphogenetic protein-2 (BMP-2), and cementum attachment protein (CAP) in oxytalan-positive POF, to establish the use of POF as an in vivo model for the study of the periodontal ligament. MATERIALS AND METHODS: Thirty tumors that presented clinical and histologic features of POF, as well as oxytalan fibers, were included in the study. Immunohistochemical expression of Runx-2, BMP-2, and CAP was evaluated by light microscopy. RESULTS: Runx-2, BMP-2, and CAP were abundantly expressed by POFs; 22 of 30 tumors expressed positive staining for Runx-2, twenty-six tumors for BMP-2, and twenty-five tumors for CAP. The expression of Runx-2 was abundant in POFs where bone was histologically present (P = 0.04) and of BMP-2 in POFs where dystrophic calcifications were present (P = 0.03). CONCLUSION: It is suggested that oxytalan-positive POFs, purportedly originating from the periodontal ligament, express molecules that are specific to bone and cementum (Runx-2, BMP-2), or cementum only (CAP). Thus, the cell populations present in the lesion belong to the mineralized-tissue-forming cell lineages, the cementoblastic or osteoblastic lineage.

MiR-29c mediates epithelial-to-mesenchymal transition in human colorectal carcinoma metastasis via PTP4A and GNA13 regulation of ß-catenin signaling.

BACKGROUND: Distant metastasis is the major cause of cancer-related death, and epithelial-to-mesenchymal transition (EMT) has a critical role in this process. Accumulating evidence indicates that EMT can be regulated by microRNAs (miRNAs). miR-29c has been implicated as a tumor suppressor in several human cancers. However, the role of miR-29c in the progression of colorectal cancer (CRC) metastasis remains largely unknown. PATIENTS AND METHODS: The expression of miR-29c was examined by qRT-PCR in a cohort of primary CRC (PC) and distant liver metastasis (LM) tissues. A series of in vivo and in vitro assays were carried out in order to elucidate the functions of miR-29c and the molecular mechanisms underlying the pathogenesis of metastatic CRC. RESULTS: miR-29c was markedly downregulated in PCs with distant metastasis and determined to be an independent predictor of shortened patient survival. But LM tissues showed higher levels of miR-29c than that in PC tissues. In CRC cells, miR-29c dramatically suppressed cell migration and invasion abilities in vitro and cancer metastasis in vivo. In addition, miR-29c inhibited EMT and negatively regulated Wnt/ß-catenin signaling pathway. Guanine nucleotide binding protein alpha13 (GNA13) and protein tyrosine phosphatase type IVA (PTP4A) were identified as direct targets of miR-29c, which acted through ERK/GSK3ß/ß-catenin and AKT/GSK3ß/ß-catenin pathways, respectively, to regulate EMT. Furthermore, significant associations between miR-29c, its target genes (GNA13 and PTP4A) and EMT markers were validated in both PC and LM tissues. CONCLUSION: Our findings highlight the important role of miR-29c in regulating CRC EMT via GSK-3ß/ß-catenin signaling by targeting GNA13 and PTP4A and provide new insights into the metastatic basis of CRC.

Phosphatase of regenerating liver-3 is regulated by signal transducer and activator of transcription 3 in acute myeloid leukemia.

Overexpression of protein-tyrosine phosphatase of regenerating liver 3 (PRL-3) has been identified in about 50% of patients with acute myeloid leukemia (AML). The mechanism of regulation of PRL-3 remains obscure. Signal transducer and activator of transcription 3 (STAT3), a latent transcriptional factor, has also been often found to be activated in AML. We first identified STAT3-consensus-binding sites in the promoter of PRL-3 genes. Then we experimentally validated the direct binding and transcriptional activation. We applied shRNA-mediated knockdown and overexpression approaches in STAT3(-/-) liver cells and leukemic cells to validate the functional regulation of PRL-3 by STAT3. A STAT3 core signature, derived through data mining from publicly available gene expression data, was employed to correlate PRL-3 expression in large AML patient samples. We discovered that STAT3 binds to the -201 to -210 region of PRL-3, which was conserved between human and mouse. Importantly, PRL-3 protein was significantly reduced in mouse STAT3-knockout liver cells compared with STAT3-wild type counterparts, and ectopic expression of STAT3 in these cells led to a pronounced increase in PRL-3 protein. We demonstrated that STAT3 functionally regulated PRL-3, and STAT3 core signature was enriched in AML with high PRL-3 expression. Targeting either STAT3 or PRL-3 reduced leukemic cell viability. Silencing PRL-3 impaired invasiveness and induced leukemic cell differentiation. In conclusion, PRL-3 was transcriptionally regulated by STAT3. The STAT3/PRL-3 regulatory loop contributes to the pathogenesis of AML, and it might represent an attractive therapeutic target for antileukemic therapy.

PRL-3 and E-cadherin show mutual interactions and participate in lymph node metastasis formation in gastric cancer.

E-cadherin, a transmembrane adhesion molecule, and phosphatase of regenerating liver 3 (PRL-3) protein, a member of the family of tyrosine phosphatases, seem to be responsible for cancer cell migration. Therefore, the study objective was to determine a correlation between PRL-3 and E-cadherin, to assess their expression in neoplastic tissue and normal mucosa of the stomach, to analyze their effect on cancer advancement, and to evaluate their potential as prognostic markers in gastric cancer. The expressions of PRL-3 and E-cadherin were assessed immunohistochemically in 71 patients with gastric cancer. Positive expression of PRL-3 was observed in 42.2 % of gastric cancer cases, whereas E-cadherin expression was abnormal in 38 % of cases. The study revealed that the positive PRL-3 expression and abnormal E-cadherin expression were associated with mucinous gastric carcinoma and lymph node involvement. The former was also related to the infiltrating type of tumor and abnormal E-cadherin expression. The expression of PRL-3, but not of E-cadherin, was associated with shorter survival of patients. PRL-3 and E-cadherin exhibit interactions in gastric cancer and are involved in the formation of lymph node metastases. The PRL-3 protein can be an independent predictive factor of overall survival in gastric cancer patients.

Mdm2 is required for maintenance of the nephrogenic niche.

The balance between nephron progenitor cell (NPC) renewal, survival and differentiation ultimately determines nephron endowment and thus susceptibile to chronic kidney disease and hypertension. Embryos lacking the p53-E3 ubiquitin ligase, Murine double minute 2 (Mdm2), die secondary to p53-mediated apoptosis and growth arrest, demonstrating the absolute requirement of Mdm2 in embryogenesis. Although Mdm2 is required in the maintenance of hematopoietic stem cells, its role in renewal and differentiation of stem/progenitor cells during kidney organogenesis is not well defined. Here we examine the role of the Mdm2-p53 pathway in NPC renewal and fate in mice. The Six2-GFP::Cre(tg/+) mediated inactivation of Mdm2 in the NPC (NPC(Mdm)2(-/-)) results in perinatal lethality. NPC(Mdm)2(-/-) neonates have hypo-dysplastic kidneys, patchy depletion of the nephrogenic zone and pockets of superficially placed, ectopic, well-differentiated proximal tubules. NPC(Mdm2-/-) metanephroi exhibit thinning of the progenitor GFP(+)/Six2(+) population and a marked reduction or loss of progenitor markers Amphiphysin, Cited1, Sall1 and Pax2. This is accompanied by aberrant accumulation of phospho-γH2AX and p53, and elevated apoptosis together with reduced cell proliferation. E13.5-E15.5 NPC(Mdm2-/-) kidneys show reduced expression of Eya1, Pax2 and Bmp7 while the few surviving nephron precursors maintain expression of Wnt4, Lhx1, Pax2, and Pax8. Lineage fate analysis and section immunofluorescence revealed that NPC(Mdm2-/-) kidneys have severely reduced renal parenchyma embedded in an expanded stroma. Six2-GFP::Cre(tg/+); Mdm2(f/f) mice bred into a p53 null background ensures survival of the GFP-positive, self-renewing progenitor mesenchyme and therefore restores normal renal development and postnatal survival of mice. In conclusion, the Mdm2-p53 pathway is essential to the maintenance of the nephron progenitor niche.

Liver kinase B1 expression promotes phosphatase activity and abrogation of receptor tyrosine kinase phosphorylation in human cancer cells.

Aberrant receptor tyrosine kinase phosphorylation (pRTK) has been associated with diverse pathological conditions, including human neoplasms. In lung cancer, frequent liver kinase B1 (LKB1) mutations correlate with tumor progression, but potential links with pRTK remain unknown. Heightened and sustained receptor activation was demonstrated by LKB1-deficient A549 (lung) and HeLaS3 (cervical) cancer cell lines. Depletion (siRNA) of endogenous LKB1 expression in H1792 lung cancer cells also correlated with increased pRTK. However, ectopic LKB1 expression in A549 and HeLaS3 cell lines, as well as H1975 activating-EGF receptor mutant lung cancer cell resulted in dephosphorylation of several tumor-enhancing RTKs, including EGF receptor, ErbB2, hepatocyte growth factor receptor (c-Met), EphA2, rearranged during transfection (RET), and insulin-like growth factor I receptor. Receptor abrogation correlated with attenuation of phospho-Akt and increased apoptosis. Global phosphatase inhibition by orthovanadate or depletion of protein tyrosine phosphatases (PTPs) resulted in the recovery of receptor phosphorylation. Specifically, the activity of SHP-2, PTP-1ß, and PTP-PEST was enhanced by LKB1-expressing cells. Our findings provide novel insight on how LKB1 loss of expression or function promotes aberrant RTK signaling and rapid growth of cancer cells.

Poor prognosis of phosphatase of regenerating liver 3 expression in gastric cancer: a meta-analysis.

BACKGROUND: Overexpression of phosphatase of regenerating liver 3 (PRL-3) has been implicated in gastric cancer (GC) metastasis. Epidemiological studies have evaluated the relationship between PRL-3 expression and prognosis in GC. However, results still remains controversial. In this study, a meta-analysis was performed to evaluate the association of PRL-3 expression with overall survival (OS) and clinicopathological characteristics. METHODS: Literature databases were searched to identify eligible studies dated until April 2013. Summary hazard ratios (HRs) or odds ratios (ORs) with 95% confidence interval (95% CI) were calculated to estimate the association. RESULTS: A total of 1380 GC patients from six studies were included in the meta-analysis. Overall, the combined HR estimate for OS in a random-effect model was 1.89 (95% CI = 1.38-2.60; P<0.001). Results showed that PRL-3 overexpression was significantly associated with OS, indicating that it may be a biomarker for poor prognosis of GC. Both subgroup and sensitivity analyses further identified the prognostic role of PRL-3 expression in GC patients. Moreover, PRL-3 overexpression was significantly associated with tumor stage (OR = 2.25; 95% CI = 1.63-3.12; P<0.001), depth of invasion (OR = 2.03; 95% CI = 1.38-2.98; P<0.001), vascular invasion (OR = 2.52; 95% CI = 1.79-3.56; P<0.001), lymphatic invasion (OR = 3.74; 95% CI = 2.49-5.63; P<0.001), and lymph node metastasis (OR = 4.56; 95% CI = 2.37-8.76; P<0.001). However, when age, sex, tumor size, and tumor differentiation were considered, no obvious association was observed. CONCLUSIONS: This meta-analysis reveals significant association of PRL-3 overexpression with OS and some clinicopathological features in GC. PRL-3 may be a predicative factor of poor prognosis and aggressive tumor behavior in GC patients.

Oncogenic roles of PRL-3 in FLT3-ITD induced acute myeloid leukaemia.

FLT3-ITD mutations are prevalent mutations in acute myeloid leukaemia (AML). PRL-3, a metastasis-associated phosphatase, is a downstream target of FLT3-ITD. This study investigates the regulation and function of PRL-3 in leukaemia cell lines and AML patients associated with FLT3-ITD mutations. PRL-3 expression is upregulated by the FLT3-STAT5 signalling pathway in leukaemia cells, leading an activation of AP-1 transcription factors via ERK and JNK pathways. PRL-3-depleted AML cells showed a significant decrease in cell growth. Clinically, high PRL-3 mRNA expression was associated with FLT3-ITD mutations in four independent AML datasets with 1158 patients. Multivariable Cox-regression analysis on our Cohort 1 with 221 patients identified PRL-3 as a novel prognostic marker independent of other clinical parameters. Kaplan-Meier analysis showed high PRL-3 mRNA expression was significantly associated with poorer survival among 491 patients with normal karyotype. Targeting PRL-3 reversed the oncogenic effects in FLT3-ITD AML models in vitro and in vivo. Herein, we suggest that PRL-3 could serve as a prognostic marker to predict poorer survival and as a promising novel therapeutic target for AML patients.