Phosphatase Of Regenerating Liver Research Articles

Ubiquitin-Specific Protease 4-Mediated Deubiquitination and Stabilization of PRL-3 Is Required for Potentiating Colorectal Oncogenesis.

Ubiquitin specific protease 4 (USP4) is a deubiquitinating enzyme with key roles in the regulation of p53 and TGFβ signaling, suggesting its importance in tumorigenesis. However, the mechanisms and regulatory roles of USP4 in cancer, including colorectal cancer, remain largely elusive. Here, we present the first evidence that USP4 regulates the growth, invasion, and metastasis of colorectal cancer. USP4 expression was significantly elevated in colorectal cancer tissues and was significantly associated with tumor size, differentiation, distant metastasis, and poor survival. Knockdown of USP4 diminished colorectal cancer cell growth, colony formation, migration, and invasion in vitro and metastasis in vivo. Importantly, we found that phosphatase of regenerating liver-3 (PRL-3) is indispensable for USP4-mediated oncogenic activity in colorectal cancer. Mechanistically, we observed that USP4 interacted with and stabilized PRL-3 via deubiquitination. This resulted in activation of Akt and reduction of E-cadherin, critical regulators of cancer cell growth and metastasis. Examination of clinical samples confirmed that USP4 expression positively correlates with PRL-3 protein expression, but not mRNA transcript levels. Taken together, our results demonstrate that aberrant expression of USP4 contributes to the development and progression of colorectal cancer and reveal a critical mechanism underlying USP4-mediated oncogenic activity. These observations suggest that the potential of harnessing proteolytic degradation processes for therapeutic manipulation may offer a much-needed new approach for improving colorectal cancer treatment strategies.

Do phosphatase of regenerating liver-3, matrix metalloproteinases-2, matrix metalloproteinases-9, and epidermal growth factor receptor-1 predict response to therapy and survival in glioblastoma multiforme?

Poor survival of the glioblastoma multiforme (GBM) has been attributed in part to the invasive nature of the lesion making complete surgical removal near impossible. Phosphatase of regenerating liver-3 (PRL-3), matrix metalloproteinases-2 and -9 (MMP-2 and MMP-9), and epidermal growth factor receptor (EGFR-1) play a role in invasive nature of tumor cells. This study was conducted to evaluate PRL-3, MMP-2, MMP-9, and EGFR-1 (markers) expression in cases to GBM and to correlate their expression with therapy response and survival. GBM cases (n = 62) underwent surgery followed by radiation (n = 34) and chemoradiation (n = 28). Using WHO Response Evaluation Criteria in Solid Tumors criteria response to therapy was assessed at 3 months and cases followed up for survival. Expression of markers was assessed by immunohistochemistry as a percentage of positive tumor cells in hot spots. Kaplan-Meier, ANOVA, Chi-square test, univariate, and multivariate Cox-regression analysis was done. Response to therapy was evident in 54.8% cases of responders with the mean survival of 494.03 ± 201.13 days and 45.2% cases of non responders (278.32 ± 121.66 days) with P = 0.001. Mean survival for the patient's opted chemoradiation was 457.43 ± 222.48 days which was approximately 3 months greater than those who opted radiation alone (P = 0.029). We found PRL-3 overexpression was an independent, significant, poor prognostic factor for survival by multivariate analysis (P = 0.044). Cases negative for MMP's and EGFR showed increased survival, but the difference was insignificant. PRL-3 expression appears to be related to an adverse disease outcome.

PRL-3 disrupts epithelial architecture by altering the post-mitotic midbody position.

ABSTRACTDisruption of epithelial architecture is a fundamental event during epithelial tumorigenesis. We show that the expression of the cancer-promoting phosphatase PRL-3 (PTP4A3), which is overexpressed in several epithelial cancers, in polarized epithelial MDCK and Caco2 cells leads to invasion and the formation of multiple ectopic, fully polarized lumens in cysts. Both processes disrupt epithelial architecture and are hallmarks of cancer. The pathological relevance of these findings is supported by the knockdown of endogenous PRL-3 in MCF-7 breast cancer cells grown in three-dimensional branched structures, showing the rescue from multiple-lumen- to single-lumen-containing branch ends. Mechanistically, it has been previously shown that ectopic lumens can arise from midbodies that have been mislocalized through the loss of mitotic spindle orientation or through the loss of asymmetric abscission. Here, we show that PRL-3 triggers ectopic lumen formation through midbody mispositioning without altering the spindle orientation or asymmetric abscission, instead, PRL-3 accelerates cytokinesis, suggesting that this process is an alternative new mechanism for ectopic lumen formation in MDCK cysts. The disruption of epithelial architecture by PRL-3 revealed here is a newly recognized mechanism for PRL-3-promoted cancer progression.

PRL-3 promotes gastric cancer migration and invasion through a NF-κB-HIF-1α-miR-210 axis.

Phosphatase of regenerating liver-3 (PRL-3) has been implicated in controlling cancer cell invasiveness. Deregulated expression of PRL-3 is involved in cancer progression and predicts poor overall survival. Recent studies have revealed critical roles for microRNAs in various cellular processes, including tumorigenic development. In this study, we aimed to explore the linkage between PRL-3 and microRNAs in gastric cancer. We found that PRL-3 transcript levels were positively correlated with miR-210 levels in gastric cancer tissues. In gastric cancer cells, PRL-3 upregulated miR-210 expression in a HIF-1α-dependent fashion under normoxia and hypoxia. In addition, PRL-3 activated NF-κB signaling and promoted HIF-1α expression through modulating phosphorylation of p65. NF-κB signaling, HIF-1α, and miR-210 partially contributed to PRL-3-induced migration and invasion. Furthermore, the levels of PRL-3, HIF-1α, and miR-210 transcripts inversely affected the overall survival of gastric cancer patients. Our work identified the existence of a PRL-3-NF-κB-HIF-1α-miR-210 axis, thus providing new insight into the role of PRL-3 in promoting gastric cancer invasiveness. PRL-3 regulates microRNA in gastric cancer. PRL-3 elevates hsa-miR-210 by upregulating HIF-1α. PRL-3 activates a NF-κB-HIF-1α-miR-210 axis by enhancing the phosphorylation of p65. PRL-3 promotes cell migration and invasion via the NF-κB-HIF-1α-miR-210 axis. High levels of PRL-3 and miR-210 are related with poor OS in gastric cancer.

Characterization of the protein tyrosine phosphatase PRL from Entamoeba histolytica

Protein tyrosine phosphatase of regenerating liver (PRL) is a group of phosphatases that has not been broadly studied in protozoan parasites. In humans, PRLs are involved in metastatic cancer, the promotion of cell migration and invasion. PTPs have been increasingly recognized as important effectors of host–pathogen interactions. We characterized the only putative protein tyrosine phosphatase PRL (PTP EhPRL) in the eukaryotic human intestinal parasite Entamoeba histolytica. Here, we reported that the EhPRL protein possessed the classical HCX5R catalytic motif of PTPs and the CAAX box characteristic of the PRL family and exhibited 31–32% homology with the three human PRL isoforms. In amebae, the protein was expressed at low but detectable levels. The recombinant protein (rEhPRL) had enzymatic activity with the 3-o-methyl fluorescein phosphate (OMFP) substrate; this enzymatic activity was inhibited by the PTP inhibitor o-vanadate. Using immunofluorescence we showed that native EhPRL was localized to the cytoplasm and plasma membrane. When the trophozoites interacted with collagen, EhPRL relocalized over time to vesicle-like structures. Interaction with fibronectin increased the presence of the enzyme in the cytoplasm. Using RT-PCR, we demonstrated that EhPRL mRNA expression was upregulated when the trophozoites interacted with collagen but not with fibronectin. Trophozoites recovered from amoebic liver abscesses showed higher EhPRL mRNA expression levels than normal trophozoites. These results strongly suggest that EhPRL may play an important role in the biology and adaptive response of the parasite to the host environment during amoebic liver abscess development, thereby participating in the pathogenic mechanism.

PRL-3 Promotes the Malignant Progression of Melanoma via Triggering Dephosphorylation and Cytoplasmic Localization of NHERF1

Phosphatase of regenerating liver-3 (PRL-3) has been reported to have a critical role in metastatic progression of cancers. Here, we investigate how PRL-3 increases the malignant degree of melanoma cells. The expression of PRL-3 increased gradually during the malignant progression of melanoma. The phosphorylation of Akt was elevated in highly malignant melanoma cells, which was accompanied by a decrease in nuclear phosphatase and tensin homolog (PTEN). The phosphorylation of NHERF1 in the serine site was regulated by PRL-3 and showed cytoplasmic translocation upon dephosphorylation, which resulted in a decrease in nuclear PTEN. The co-translocation of NHERF1 and PTEN from the nucleus to the cytoplasm was observed during the malignant progression of melanoma cells. Tumor growth was inhibited significantly, and the survival was prolonged upon knockdown of cytoplasmic NHERF1 in B16BL6 cells prior to the inoculation into mice. Taken together, to our knowledge previously unreported, we have identified NHERF1 as a potential substrate of PRL-3. Its phosphorylation status as well as its change in cellular localization and association with PTEN correlated with the malignant progression of melanoma. Our data provide an explanation for how PRL-3 promotes the malignant progression of melanoma, as well as a diagnostic marker or therapeutic target for malignant melanoma.

Elevated phosphatase of regenerating liver 3 (PRL-3) promotes cytoskeleton reorganization, cell migration and invasion in ectopic stromal cells from endometrioma

Elevated phosphatase of regenerating liver 3 (PRL-3) promotes cytoskeleton reorganization, cell migration and invasion in ectopic stromal cells from endometrioma

Procyanidins Negatively Affect the Activity of the Phosphatases of Regenerating Liver.

Natural polyphenols like oligomeric catechins (procyanidins) derived from green tea and herbal medicines are interesting compounds for pharmaceutical research due to their ability to protect against carcinogenesis in animal models. It is nevertheless still unclear how intracellular pathways are modulated by polyphenols. Monomeric polyphenols were shown to affect the activity of some protein phosphatases (PPs). The three phosphatases of regenerating liver (PRLs) are close relatives and promising therapeutic targets in cancer. In the present study we show that several procyanidins inhibit the activity of all three members of the PRL family in the low micromolar range, whereas monomeric epicatechins show weak inhibitory activity. Increasing the number of catechin units in procyanidins to more than three does not further enhance the potency. Remarkably, the tested procyanidins showed selectivity in vitro when compared to other PPs, and over 10-fold selectivity toward PRL-1 over PRL-2 and PRL-3. As PRL overexpression induces cell migration compared to control cells, the effect of procyanidins on this phenotype was studied. Treatment with procyanidin C2 led to a decrease in cell migration of PRL-1- and PRL-3-overexpressing cells, suggesting the compound-dependent inhibition of PRL-promoted cell migration. Treatment with procyanidin B3 led to selective suppression of PRL-1 overexpressing cells, thereby corroborating the selectivity toward PRL-1- over PRL-3 in vitro. Together, our results show that procyanidins negatively affect PRL activity, suggesting that PRLs could be targets in the polypharmacology of natural polyphenols. Furthermore, they are interesting candidates for the development of PRL-1 inhibitors due to their low cellular toxicity and the selectivity within the PRL family.

Combined expression of metastasis related markers Naa10p, SNCG and PRL-3 and its prognostic value in breast cancer patients.

Combinations of multiple biomarkers representing distinct aspects of metastasis may have better prognostic value for breast cancer patients, especially those in late stages. In this study, we evaluated the protein levels of N-α-acetyltransferase 10 protein (Naa10p), synuclein-γ (SNCG), and phosphatase of regenerating liver-3 (PRL-3) in 365 patients with breast cancer by immunohistochemistry. Distinct prognostic subgroups of breast cancer were identified by combination of the three biomarkers. The Naa10p+SNCG-PRL-3- subgroup showed best prognosis with a median distant metastasis-free survival (DMFS) of 140 months, while the Naa10p-SNCG+PRL-3+ subgroup had the worst prognosis with a median DMFS of 60.5 months. Multivariate analysis indicated Naa10p, SNCG, PRL-3, and the TNM classification were all independent prognostic factors for both DMFS and overall survival (OS). The three biomarker combination of Naa10p, SNCG and PRL-3 performed better in patients with lymph node metastasis, especially those with more advanced tumors than other subgroups. In conclusion, the combined expression profile of Naa10p, SNCG and PRL-3, alone or in combination with the TNM classification system, may provide a precise estimate of prognosis of breast cancer patients.

MMP7 is required to mediate cell invasion and tumor formation upon Plakophilin3 loss.

Plakophilin3 (PKP3) loss results in increased transformation in multiple cell lines in vitro and increased tumor formation in vivo. A microarray analysis performed in the PKP3 knockdown clones, identified an inflammation associated gene signature in cell lines derived from stratified epithelia as opposed to cell lines derived from simple epithelia. However, in contrast to the inflammation associated gene signature, the expression of MMP7 was increased upon PKP3 knockdown in all the cell lines tested. Using vector driven RNA interference, it was demonstrated that MMP7 was required for in-vitro cell migration and invasion and tumor formation in vivo. The increase in MMP7 levels was due to the increase in levels of the Phosphatase of Regenerating Liver3 (PRL3), which is observed upon PKP3 loss. The results suggest that MMP7 over-expression may be one of the mechanisms by which PKP3 loss leads to increased cell invasion and tumor formation.

Phosphatase of regenerating liver-3 regulates the expression of Snail in human colon cancer cells LoVo through tumor microenvironment

Objective To investigate the interaction between colon cancer cells and hepatic cell (L02), and it’s influence to Snail expression in tumor cells. Methods Lo Vo cells which transfected with phosphatase of regenerating liver- 3(PRL- 3)and human hepatic cells(L02)simulated tumor microenvironment were cocultured by 0- 5 day, reverse transcriptase- polymerase chain reaction (RT- PCR)and Western blotting were used to examine Snail expression of Lo Vo cells, and the migration of Lo Vo cells also be detected. Results Used by RT- PCR and Western blotting it was found out that Lo Vo cells(transfected with PRL- 3) were reduced Snail express after cocultured with hepatic cells, the inhibition rates were 34. 06%, 37. 82%, 39. 91%, 64. 07%, 73. 58%(P< 0. 05), LoVo cells(without transfected PRL- 3) decreased expression of Snail was not obvious.Besides, coculture also depress the migration of Lo Vo cells. Conclusion PRL- 3 depress the migration of Lo Vo cells through reduced Snail expression in liver metastasis of colon cancer microenvironment. Key words: Phosphatase of regenerating liver-3; LoVo; Hepatic cell; Snail

PRL-3 mediates the protein maturation of ULBP2 by regulating the tyrosine phosphorylation of HSP60.

Many malignant cells release the NKG2D ligand ULBP2 from their cell surface to evade immunosurveillance by NK cells and CD8 T cells. Although the shedding mechanism remains unclear, various inhibitors of matrix metalloproteinases have been shown to efficiently block the release of soluble ULBP2. The clinical use of these inhibitors, however, is limited because of adverse side effects. Using high-throughput screening technique, we identified a specific inhibitor of phosphatase of regenerating liver 3 (PRL-3) that could reduce the level of soluble ULBP2 in the culture supernatant of various cancer cell lines. Inhibition or gene knockdown of PRL-3 did not reduce ULBP2 shedding, but rather suppressed posttranslational maturation of ULBP2, resulting in intracellular retention of immature ULBP2. We then found that ULBP2 was constitutively associated with heat shock protein HSP60. Complete maturation of ULBP2 required tyrosine phosphorylation of HSP60 which was mediated by PRL-3.

Involvement of phosphatase of regenerating liver-3 and E-cadherin in the process of the lymph node metastasis of gastric cancer

Objective To investigate the relationship between phosphatase of regenerating liver-3 (PRL-3) and E-cadherin with lymph node metastasis of gastric cancer, survival and prognosis. Methods The expression of PRL-3 and E-cadherin in 53 cases of gastric cancer tissues and 30 cases of normal gastric tissues was examined by immunohistochemical method. The relationship between PRL-3 and E-cadherin with the pathological parameters was statistically analyzed. Results PRL-3 was not expressed in normal gastric mucosa, and the positive expression of PRL-3 in gastric cancer tissues was 45. 3%(24/53).E-cadherin existed in most glandular cells of the cytoplasmic membrane, and the positive expression of E-cadherin in gastric cancer tissues was 54. 7%(29/ 53).The expression of PRL-3 was correlated with lymph node metastasis(P< 0. 01), Goseki grade(P< 0. 01), Borrmann classification(P< 0. 01) and infection of Helicobacter pylori(P< 0. 05).The expression of E-cadherin was correlated with lymph node metastasis(P< 0. 01), Borrmann classification(P< 0. 01) and infection of Helicobacter pylori(P< 0. 01).The expression of Lauren's type, PRL-3 expression and E-cadherin were independent predictive factors of survival in patients with gastric cancer. Conclusion The expression of PRL-3 and E-cadherin was related with lymph node metastasis, and two proteins were the independent predictors of survival in gastric cancer patients. Key words: Gastric cancer; Phosphatase of regenerating liver-3; E-cadherin; Lymph node metastasis

PRL-3 Mediates Survival of Primary Myeloma Cells

Introduction:Phosphatase of regenerating liver-3 (PRL-3) is a marker of aggressive and metastatic disease in a number of solid tumors. PRL-3 is expressed in primary multiple myeloma (MM) cells and MM cell lines, but not in normal plasma cells. We have previously shown that PRL-3 is induced in MM cells by interleukin (IL)-6 and other growth factors, and that PRL-3 promotes MM-cell migration (Fagerli et al, Blood, 2008). A study by Broyl et al (Blood, 2010) identified PRL-3 as a marker gene for a subgroup of patients with MM. In this study we examined the effect of the small molecular inhibitor PRL-3 Inhibitor I on primary MM cells, and we examined possible cellular targets of PRL-3 using a proteomics approach.Methods: Co-cultures of primary myeloma cells and pooled bone marrow stromal cells from several MM patients were grown for 3 days in the presence or absence of PRL-3 Inhibitor I. Apoptosis was determined by staining cells with YO-PRO-1. To examine cellular targets of PRL-3 we made PRL-3 overexpressing cells from the human MM cell line INA-6 by retroviral transduction (INA-6-PRL-3) and control cells (INA-6-MOCK). Stable isotope labeling by amino acids in cell culture (SILAC) was used for in vivo incorporation of 12C-Lysine (“light”) and 13C-Lysine (“heavy”) in these transduced cell lines, preparing them for Orbitrap mass spectrometry based quantitative proteomics. The experiments were performed three times. The results were analyzed using Ingenuity Pathway Analysis software (Quiagen).Results: PRL-3 Inhibitor I significantly reduced viability in all 9 primary MM cell samples tested, ranging from 5-70 % absolute reductions in viability at the top concentration of 40 µM. Proteomics analysis was performed on INA-6-PRL-3 and INA-6-MOCK cell lines at baseline and following incubation in IL-6-free media for 12 hours to deplete INA-6-MOCK cells of PRL-3. At 12 hours, a total of 6747 proteins were identified. 481 proteins were upregulated and 22 proteins downregulated by more than 2-fold in the INA-6-PRL-3 cells compared to INA-6-MOCK cells in 2 out of 3 experiments. Several proteins known to be important for cell survival and migration were upregulated in INA-6-PRL-3 cells, like CD44, Myc assosciated factor X (MAX) and Lyn. Pro-apoptotic proteins Caspase-1 and Caspase-2 were downregulated. Among canonical signaling pathways, there were most proteins belonging to the protein ubiquitination pathway (9,8 % of proteins; p<0,001).Conclusion: PRL-3 Inhibitor I induced apoptosis in primary MM cells. Quantitative proteomics analyses comparing PRL-3 overexpressing INA-6 cells to normal INA-6 cells identifies several proteins important for MM cell migration and survival. This study indicates that PRL-3 could be important in the pathogenesis of MM and a potential target in the treatment of MM. DisclosuresNo relevant conflicts of interest to declare.

PRL2 Phosphatase Regulate Early Stage T-Cell Development through Fine-Tuning SCF/Kit Signaling

The phosphatase of regenerating liver (PRL) family of phosphatases, consisting of PRL1, PRL2, and PRL3, represents an intriguing group of proteins being validated as biomarkers and therapeutic targets in human cancer. We have been investigating the role of PRL2 in normal / malignant hematopoiesis and found that PRL2 is important for HSC self-renewal (Kobayashi et al., Stem Cells, 2014). The receptor tyrosine kinase KIT can balance quiescence for HSC maintenance and proliferation for progeny supply. The defects seen in the PRL2-deficient hematopoietic and testis cells recapitulate the phenotype of c-Kit mutant mice, suggesting that the SCF/KIT signaling may be impaired in the absence of PRL2 (Kobayashi et al., Stem Cells, 2014; Dong et al., JBC, 2013). Given that KIT also plays critical role in maintaining postnatal T-lymphopoiesis in thymus, we hypothesized that PRL2 is important for T cell development.Here we report that loss of PRL2 impairs T-lymphopoiesis both in vitro and in vivo. PRL2 deficiency resulted in marked reduction of splenocyte and thymocyte counts compared to wild type (WT) mice. While we observed modest increase in the frequency of early T cell progenitor (ETP), DN2, and DN3 cells in PRL2 deficient thymus, T-cell reconstitution was dramatically decreased after HSC transplantation. T-cell number in the peripheral blood (PB) of recipient mice repopulated with PRL2-null HSCs was 30 times less than that of the WT HSCs (WT: 2288.6±579.8/µl vs PRL2 null: 69.5±22.1/µl, p<0.00001). Although the frequency of donor-derived thymocytes in recipient thymus was 91±6.1% in WT, PRL2 null HSCs contributed only 7.1±4.9% (p<0.00001) in the recipient thymus. By detailed fractionation, surprisingly, chimerism in ETP was comparable between WT and PRL2 null cells (WT: 91.8±10.1% vs PRL2 null: 59.6±13.5%, p<0.01). Importantly, the chimerism of PRL2-null thymocytes fell down to 10% in gated DN2, whereas WT HSCs consistently contributed around 90%, suggesting that the DN1-to-DN2 transition requires PRL2. Next, we evaluated the in vitro T-cell generation by utilizing the Delta-Like1 (DLL1) expressing OP9 (DL-OP9) stromal cells. While wild type KSLs produced massive amount of T-cells (fold increase: 33,000±3371) 22 days following plating onto the DL-OP9, PRL2 null KSLs only generated limited amount of T-cells (fold increase: 1765±665, p<0.0001), demonstrating that PRL2 is important for T-cell proliferation. We also monitored the generation of ETPs from KSLs in DL-OP9 cultures and observed significant expansion of ETPs derived from WT KSLs compared to that of the PRL2 null KSLs (fold increase: 183.8±14.4 vs 12.5±4.3, p<0.001). However, when sorted DN3 cells from WT and PRL2 KO thymus were plated onto DL-OP9, we saw similar increase in cell expansion, suggesting PRL2 regulate early T-cell development.WhilePRL2 is a dual specificity protein phosphatase, its substrates are unknown. To identifyPRL2 substrates in hematopoietic cells, we performed a protein phosphatase substrate trap assay. We utilized a GST-tagged PRL2/CS-DA mutant, in which the catalyticsite cysteine was mutated to serine, so that PRL2 binds to its substrates better, but is unable todephosphorylate them. We found that the mutant PRL2/CS-DA showed enhanced association with KIT than WT PRL2 in Kasumi-1 cells, suggesting that KIT is a potential PRL2 substrate. The PRL2 and KIT interaction was further confirmed by the Immunoprecipitation (IP) assay in 293T cells expressing KIT. We also detected the association of PRL2 with SHP2, CBL and PLC-g in Kasumi-1 cells, which are important regulators of KIT activation and stability. Moreover, PRL2 KO hematopoietic progenitor cells show decreased KIT phosphorylation at tyrosine 703 following SCF stimulation, suggesting that PRL2 may modulate KIT activation in these cells. To evaluate the impact of SCF signal strength on T-cell proliferation, we cultured sorted lympho-primed multipotent progenitor cells (LMPPs) from WT and KO mice onto DLL-Fc coated plates with graded doses of SCF (0.2, 1, 5, 25 ng/ml). The total number of cells generated from SCF treated WT LMPPs was significantly higher than that of the KO LMPPs in a dosage dependent manner. KO exhibited 6 times less sensitive to SCF than WT, indicating that PRL2 fine-tunes SCF signal intensity in early T-cell.Taken together, we have identified a critical role for PRL2 in T-cell proliferation and maintenance through fine-tuning SCF/KIT signaling. DisclosuresNo relevant conflicts of interest to declare.

Methylation-associated silencing of miR-495 inhibit the migration and invasion of human gastric cancer cells by directly targeting PRL-3

Phosphatase of regenerating liver-3 (PRL-3) is believed to be associated with cell motility, invasion, and metastasis. Our previous work found that PRL-3 is highly overexpressed in gastric cancer (GC) tissue with peritoneal metastasis and directly involved in the pathogenesis of GC peritoneal metastasis. Moreover, we further found that the down-regulation of endogenous miR-495 expression plays a causative role in over expression of PRL-3 in GC peritoneal metastasis. However, the molecular regulation mechanisms by which endogenous miR-495 expression is down-regulated and PRL-3 promotes GC peritoneal metastasis remain to be clearly elucidated. Some studies have shown that the promoter methylation is closely related to the miRNA gene expression. Therefore, in present study, based on our previous findings, we will analysis whether DNA methylation is a major cause of the down-expression of endogenous miR-495, which results in PRL-3 overexpression in GC peritoneal metastasis. Methylation specific PCR (MSP) and sodium bisulfite sequencing method (BSP) detected miR-495 gene promoter methylation status. We treated GC cell lines with 5-Aza-2′-deoxycytidine (5-Aza-dC) to make the gene promoter methylation inactivation. By treating with 5-Aza-dC the migration and invasion of GC cells were significantly inhibited. And the miR-495 was overexpressing, corresponds to the mRNA and protein levels of PRL-3 were reduced, the ability of invasion and metastasis was inhibited. This study suggest that miR-495 have tumor suppressor properties and are partially silenced by DNA hypermethylation in GC, will provide new strategies for prevention and treatment of GC peritoneal metastasis.

Membrane protein CNNM4-dependent Mg2+ efflux suppresses tumor progression.

Intracellular Mg(2+) levels are strictly regulated; however, the biological importance of intracellular Mg(2+) levels and the pathways that regulate them remain poorly understood. Here, we determined that intracellular Mg(2+) is important in regulating both energy metabolism and tumor progression. We determined that CNNM4, a membrane protein that stimulates Mg(2+) efflux, binds phosphatase of regenerating liver (PRL), which is frequently overexpressed in malignant human cancers. Biochemical analyses of cultured cells revealed that PRL prevents CNNM4-dependent Mg(2+) efflux and that regulation of intracellular Mg(2+) levels by PRL and CNNM4 is linked to energy metabolism and AMPK/mTOR signaling. Indeed, treatment with the clinically available mTOR inhibitor rapamycin suppressed the growth of cancer cells in which PRL was overexpressed. In ApcΔ(14/+) mice, which spontaneously form benign polyps in the intestine, deletion of Cnnm4 promoted malignant progression of intestinal polyps to adenocarcinomas. IHC analyses of tissues from patients with colon cancer demonstrated an inverse relationship between CNNM4 expression and colon cancer malignancy. Together, these results indicate that CNNM4-dependent Mg(2+) efflux suppresses tumor progression by regulating energy metabolism.

Phosphatase of regenerating liver in hematopoietic stem cells and hematological malignancies

The phosphatases of regenerating liver (PRLs), consisting PRL1, PRL2 and PRL3, are dual-specificity protein phosphatases that have been implicated as biomarkers and therapeutic targets in several solid tumors. However, their roles in hematological malignancies are largely unknown. Recent findings demonstrate that PRL2 is important for hematopoietic stem cell self-renewal and proliferation. In addition, both PRL2 and PRL3 are highly expressed in some hematological malignancies, including acute myeloid leukemia (AML), chronic myeloid leukemia (CML), multiple myeloma (MM) and acute lymphoblastic leukemia (ALL). Moreover, PRL deficiency impairs the proliferation and survival of leukemia cells through regulating oncogenic signaling pathways. While PRLs are potential novel therapeutic targets in hematological malignancies, their exact biological function and cellular substrates remain unclear. This review will discuss how PRLs regulate hematopoietic stem cell behavior, what signaling pathways are regulated by PRLs, and how to target PRLs in hematological malignancies. An improved understanding of how PRLs function and how they are regulated may facilitate the development of PRL inhibitors that are effective in cancer treatment.

Biochemical evaluation of virtual screening methods reveals a cell-active inhibitor of the cancer-promoting phosphatases of regenerating liver.

Computationally supported development of small molecule inhibitors has successfully been applied to protein tyrosine phosphatases in the past, revealing a number of cell-active compounds. Similar approaches have also been used to screen for small molecule inhibitors for the cancer-related phosphatases of regenerating liver (PRL) family. Still, selective and cell-active compounds are of limited availability. Since especially PRL-3 remains an attractive drug target due to its clear role in cancer metastasis, such compounds are highly demanded. In this study, we investigated various virtual screening approaches for their applicability to identify novel small molecule entities for PRL-3 as target. Biochemical evaluation of purchasable compounds revealed ligand-based approaches as well suited for this target, compared to docking-based techniques that did not perform well in this context. The best hit of this study, a 2-cyano-2-ene-ester and hence a novel chemotype targeting the PRLs, was further optimized by a structure–activity-relationship (SAR) study, leading to a low micromolar PRL inhibitor with acceptable selectivity over other protein tyrosine phosphatases. The compound is active in cells, as shown by its ability to specifically revert PRL-3 induced cell migration, and exhibits similar effects on PRL-1 and PRL-2. It is furthermore suitable for fluorescence microscopy applications, and it is commercially available. These features make it the only purchasable, cell-active and acceptably selective PRL inhibitor to date that can be used in various cellular applications.

Structural studies of a novel phosphatase-transpoter interaction

The Phosphatase of Regenerating Liver (PRL) family, a subgroup of the protein tyrosine phosphatases, comprises three highly oncogenic members, PRL-1, -2 and -3, implicated in the progression of numerous cancer types. PRL-2 is overexpressed in breast cancer and was shown to promote mammary tumour growth in mice, but its full role in these oncogenic effects remains elusive. Recently, PRL-2 was found to interact with cyclin M3 (CNNM3), a magnesium transporter. To characterize this novel interaction, I crystallized PRL-2 in complex with the cytosolic cystathionine-β-synthase (CBS) domain of CNNM3. The binding surface consists of an elongated loop from CBS that makes contact close to the catalytic site of PRL-2. Site-directed CBS mutants confirmed the loop residues important for binding. PRL-2 and CBS bind particularly tightly, as determined by isothermal titration calorimetry, and PRL-2 enzyme assays revealed that CBS binding reduces the phosphatase's catalytic activity in vitro. The novel role of oncogenic PRL-2 as modulator of intracellular magnesium levels may represent the link between its overexpression and its effects on tumour growth. Small-molecule inhibitors of the PRL-2/CNNM3 complex formation are a potentially valuable tool for exploring the physiological function of this new interaction and may be used as future drug leads for the treatment of breast cancer.