Phosphatase Of Regenerating Liver Research Articles

Expression of Phosphatase of Regenerating Liver 1 and 3 mRNA in Esophageal Squamous Cell Carcinoma

Phosphatase of regenerating liver (PRL) 3 messenger RNA (mRNA) was reported to express in human colorectal, gastric, ovarian, breast, and hepatic cancers. To examine the expression of PRL-1 and PRL-3 mRNAs in human esophageal squamous cell carcinoma (ESCC). Expression of PRL-1 and PRL-3 mRNA was examined with reverse transcriptase-polymerase chain reaction in fresh tissue collected from 40 cases of ESCC with matched lymph node metastasis in 21 cases. The association of expression of PRL-1 and PRL-3 mRNAs with clinicopathologic parameters was analyzed. The frequencies of PRL-1 and PRL-3 mRNA expression were significantly higher in ESCC than in normal esophageal tissue (P = .001; P = .01) and also significantly higher in ESCC with lymph node metastasis than in those without lymph node metastasis (P = .01; P = .03). The levels of PRL-1 and PRL-3 mRNA expression were significantly higher in ESCC with lymph node metastasis than in those without lymph node metastasis (P = .04; P = .04). The frequencies and levels of PRL-1 and PRL-3 mRNA expression were correlated with the later stages but not with tumor differentiation, tumor location in the esophagus, patient's sex, and age. PRL-1 and PRL-3 mRNAs may be involved in and used to predict the metastasis of ESCC. The possibility of using PRL-1 and PRL-3 as the therapeutical target is also discussed.

Molecular biological character of PRL-3 and its relationship with colorectal cancer metastasis

The phosphatase of regenerating liver(PRL)families of phosphatases,consisting of PRL-1,PRL-2,and PRL-3,are individually overexpressed in a variety of cancer cell lines and tissues when eom-pared with their normal counterparts.Several recent studies have shown that PRL-3 is expressed at a higher lev-el and at a greater frequency in colorectal cancer with liver metastases compared with primary colorectal tumorsand normal colon tissue.Expression of PRL can enhance metastatic and invasive properties of cells and initiate tumor angiogenesis in experimental mice.However,the exact mechanism and in- teracting proteins of the PRL remain unclear.With further study,PRL-3 may server as an attractive target for therapeutic intervention and marker for colon cancer metastasis. Key words: Colonic neoplasms; Rectal neoplasms; PRL-3; Metastasis

Translational Control of C-terminal Src Kinase (Csk) Expression by PRL3 Phosphatase

Phosphatase of regenerating liver 3 (PRL3) is up-regulated in cancer metastases. However, little is known of PRL3-mediated cellular signaling pathways. We previously reported that elevated PRL3 expression increases Src kinase activity, which likely contributes to the increased tumorigenesis and metastasis potential of PRL3. PRL3-induced Src activation is proposed to be indirect through down-regulation of Csk, a negative regulator of Src. Given the importance of PRL3 in tumor metastasis and the role of Csk in controlling Src activity, we addressed the mechanism by which PRL3 mediates Csk down-regulation. PRL3 is shown to exert a negative effect on Csk protein synthesis, rather than regulation of Csk mRNA levels or protein turnover. Interestingly, the preferential decrease in Csk protein synthesis is a consequence of increased eIF2 phosphorylation resulting from PRL3 expression. Reduced Csk synthesis also occurs in response to cellular stress that induces eIF2 phosphorylation, indicating that this regulatory mechanism may occur in response to a wider spectrum of cellular conditions known to direct translational control. Thus, we have uncovered a previously uncharacterized role for PRL3 in the gene-specific translational control of Csk expression.

Discovery of novel PRL-3 inhibitors based on the structure-based virtual screening

The inhibitors of phosphatase of regenerating liver-3 (PRL-3) have been shown to be useful as therapeutics for the treatment of cancer. We have been able to identify 12 novel PRL-3 inhibitors by means of the virtual screening with docking simulations under the consideration of the effects of ligand solvation in the scoring function. Because the newly identified inhibitors are structurally diverse and reveal a significant potency with IC(50) values ranging from 10 to 50muM, all of them can be considered for further development by structure-activity relationship or de novo design methods. Structural features relevant to the interactions of the newly identified inhibitors with the amino acid residues in the active site and the peripheral binding site of PRL-3 are discussed in detail.

A Selective Phosphatase of Regenerating Liver Phosphatase Inhibitor Suppresses Tumor Cell Anchorage-Independent Growth by a Novel Mechanism Involving p130Cas Cleavage

The phosphatase of regenerating liver (PRL) family, a unique class of oncogenic phosphatases, consists of three members: PRL-1, PRL-2, and PRL-3. Aberrant overexpression of PRL-3 has been found in multiple solid tumor types. Ectopic expression of PRLs in cells induces transformation, increases mobility and invasiveness, and forms experimental metastases in mice. We have now shown that small interfering RNA-mediated depletion of PRL expression in cancer cells results in the down-regulation of p130Cas phosphorylation and expression and prevents tumor cell anchorage-independent growth in soft agar. We have also identified a small molecule, 7-amino-2-phenyl-5H-thieno[3,2-c]pyridin-4-one (thienopyridone), which potently and selectively inhibits all three PRLs but not other phosphatases in vitro. The thienopyridone showed significant inhibition of tumor cell anchorage-independent growth in soft agar, induction of the p130Cas cleavage, and anoikis, a type of apoptosis that can be induced by anticancer agents via disruption of cell-matrix interaction. Unlike etoposide, thienopyridone-induced p130Cas cleavage and apoptosis were not associated with increased levels of p53 and phospho-p53 (Ser(15)), a hallmark of genotoxic drug-induced p53 pathway activation. This is the first report of a potent selective PRL inhibitor that suppresses tumor cell three-dimensional growth by a novel mechanism involving p130Cas cleavage. This study reveals a new insight into the role of PRL-3 in priming tumor progression and shows that PRL may represent an attractive target for therapeutic intervention in cancer.

Targeting PTPs with small molecule inhibitors in cancer treatment

Protein tyrosine phosphorylation plays a major role in cellular signaling. The level of tyrosine phosphorylation is controlled by protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Disturbance of the normal balance between PTK and PTP activity results in aberrant tyrosine phosphorylation, which has been linked to the etiology of several human diseases, including cancer. A number of PTPs have been implicated in oncogenesis and tumor progression and therefore are potential drug targets for cancer chemotherapy. These include PTP1B, which may augment signaling downstream of HER2/Neu; SHP2, which is the first oncogene in the PTP superfamily and is essential for growth factor-mediated signaling; the Cdc25 phosphatases, which are positive regulators of cell cycle progression; and the phosphatase of regenerating liver (PRL) phosphatases, which promote tumor metastases. As PTPs have emerged as drug targets for cancer, a number of strategies are currently been explored for the identification of various classes of PTP inhibitors. These efforts have resulted many potent, and in some cases selective, inhibitors for PTP1B, SHP2, Cdc25 and PRL phosphatases. Structural information derived from these compounds serves as a solid foundation upon which novel anti-cancer agents targeted to these PTPs can be developed.

PRL PTPs: mediators and markers of cancer progression

Aberrant protein tyrosine phosphorylation resulting from the altered activity of protein tyrosine phosphatases (PTPs) is increasingly being implicated in the genesis and progression of human cancer. Accumulating evidence indicates that the dysregulated expression of members of the phosphatase of regenerating liver (PRL) subgroup of PTPs is linked to these processes. Enhanced expression of the PRLs, notably PRL-1 and PRL-3, promotes the acquisition of cellular properties that confer tumorigenic and metastatic abilities. Up-regulation of PRL-3 is associated with the progression and eventual metastasis of several types of human cancer. Indeed, PRL-3 shows promise as a biomarker and prognostic indicator in colorectal, breast, and gastric cancers. However, the substrates and molecular mechanisms of action of the PRLs have remained elusive. Recent findings indicate that PRLs may function in regulating cell adhesion structures to effect epithelial-mesenchymal transition. The identification of PRL substrates is key to understanding their roles in cancer progression and exploiting their potential as exciting new therapeutic targets for cancer treatment.

Phosphatase of regenerating liver-3 and tumor

肝再生磷酸酶-3(PRL-3)是最新发现的与肿瘤转移相关的蛋白质酪氨酸磷酸酶(PTP),较多证据表明,PRL-3在结直肠癌、胃癌、乳腺癌、卵巢癌等表达明显升高,其表达异常与肿瘤的浸润和转移密切相关,可能成为抗肿瘤浸润和肿瘤治疗的一个新靶点。

Ezrin is a specific and direct target of protein tyrosine phosphatase PRL-3

Phosphatase of Regenerating Liver-3 (PRL-3) is a small protein tyrosine phosphatase considered an appealing therapeutic cancer target due to its involvement in metastatic progression. However, despite its importance, the direct molecular targets of PRL-3 action are not yet known. Here we report the identification of Ezrin as a specific and direct cellular substrate of PRL-3. In HCT116 colon cancer cell line, Ezrin was identified among the cellular proteins whose phosphorylation level decreased upon ectopic over-expression of wtPRL-3 but not of catalytically inactive PRL-3 mutants. Although PRL-3 over-expression in HCT116 cells appeared to affect Ezrin phosphorylation status at both tyrosine residues and Thr567, suppression of the endogenous protein by RNA interference pointed to Ezrin-Thr567 as the residue primarily affected by PRL-3 action. In vitro dephosphorylation assays suggested Ezrin-Thr567 as a direct substrate of PRL-3 also proving this enzyme as belonging to the dual specificity phosphatase family. Furthermore, the same effect on levels of pThr567, but not on pTyr residues, was observed in endothelial cells pointing to Ezrin-pThr567 dephosphorylation as a mean through which PRL-3 exerts its function in promoting tumor progression as well as in the establishment of the new vasculature needed for tumor survival and expansion.

Prokaryotic Expression and Polyclonal Antibody Preparation of PRL3

Abstract Phosphatase of regenerating liver 3 (PRL3), which belongs to the superfamily of protein tyrosine phosphatases (PTPs), represents a group of low molecular weight PTPs that participate in tumorigenesis and metastasis processes. Presented here are the results of cloning, prokaryotic expression, purification, and polyclonal antibody preparation of PRL3. To obtain a specific polyclonal antibody against PRL3, the authors have prepared GST-PRL3 to immunize rabbits and purify an anti-PRL3 polyclonal antibody by negative selection affinity columns. Western blot analysis shows that the anti-PRL3 polyclonal antibody has a specific binding ability with PRL3 protein. The anti-PRL3 polyclonal antibody provides a good tool to further study the function of PRL3.

The value and correlation between PRL‐3 expression and matrix metalloproteinase activity and expression in human gliomas

Local invasion of tumor cells is characteristic of most human glioma invasions. It is associated with increased motility and a potential to degrade the extracellular matrix. Matrix metalloproteinases (MMPs) have been proved to be a main process in local invasion of brain tumor. PRL-3 is a new protein tyrosine phosphatase which would also degrade the extracellular matrix and has been proved to be expressed in liver metastases derived from colorectal cancer. In this study, we sought to investigate the expression of PRL-3 in glioma tissues and investigate the relationship between MMPs (MMP2, MMP9, membrane-type matrix metalloproteinase 1 [MT1-MMP]) activity and expression in gliomas. The modifications of in situ hybridization of mRNA phosphatase of regenerating liver-3 (PRL-3) methods are preformed in the study of paraffin-embedded slides. The immunohistochemistry and gelatin zymography are used to detect the expression of PRL-3 and activity of MMPs. The results show that PRL-3 mRNA and antibody of PRL-3 are detected in glioma tissues mainly in grades IV and III, only a little in grade II, but not in normal brain tissue and glioma grade I. MMP2 and MMP9 are observed mainly in glioma tissues of grades IV and III in activity and expression. MT1-MMP protein is located in glioma tissues and vessel endothelial cells. This is the first report of detecting PRL-3 expression in gliomas, especially in grades III and IV, which may play an important role in progression of gliomas. PRL-3, MMP2 and MT1-MMP cooperatively contribute to gliomas invasion. Intermediate MMP2 (MT1-MMP, TIMP-2, MMP2 trimeric complex) is detected in high grades of glioma tissues by gelatin zymography and may be a marker indicating latent malignance of gliomas.

Phosphatase Activity, Trimerization, and the C-terminal Polybasic Region Are All Required for PRL1-mediated Cell Growth and Migration

The phosphatase of regenerating liver (PRL) phosphatases are implicated in a number of tumorigenesis and metastasis processes. The PRLs are unique among protein-tyrosine phosphatases in that they have extremely low phosphatase activity, a high propensity for trimer formation, and a polybasic region that precedes the C-terminal prenylation motif. To investigate the functional significance of these distinctive biochemical and structural features, we established a cell-based system in which ectopic PRL1 expression increased cell proliferation and migration, whereas knockdown of endogenous PRL1 abrogated these cellular activities. We showed that the intrinsic PRL1 phosphatase activity is obligatory for its biological function. We provided evidence that trimerization may be a general property for all PRL enzymes, and that PRL1 trimer formation is essential for the PRL1-mediated cell growth and migration. This finding indicates a novel mechanism for phosphatase regulation. We further demonstrated that the conserved C-terminal polybasic region is important for specific phosphoinositide recognition by PRL1. Both the polybasic residues and the adjacent prenylation motif are required for proper PRL1 subcellular localization and full biological activity.

Expression of MAC30 in Rectal Cancers with or without Preoperative Radiotherapy

Objective: Meningioma-associated protein (MAC30) is overexpressed in several types of cancers, but its therapeutic implication in the patients has not been studied. We examined the relationship of MAC30 with clinicopathological and biological factors in rectal cancer patients with or without radiotherapy (RT). Methods: MAC30 was immunohistochemically examined in 75 distant and 91 adjacent normal mucosa specimens, 132 primary tumours and 39 lymph node metastases from rectal cancer patients participating in a clinical trial of preoperative RT. Results: In the RT group, MAC30 was or tended to be positively correlated with infiltrated growth pattern (p = 0.02), PRL (phosphatase of regenerating liver, p = 0.01) and Ki-67 expression (p = 0.06). MAC30 at the invasive margin of the metastasis was related to poor survival (p = 0.02) in the whole group of patients. MAC30 in primary tumours was not related to recurrence and survival in the non-RT or RT group. Conclusions:MAC30 expression in metastasis was an indicator for poor survival. After RT, MAC30 seemed to be more related to aggressive morphological and biological factors; however, we did not find direct evidence that MAC30 expression was related to the outcome of patients with or without RT.

Expression of the human phosphatases of regenerating liver (PRLs) in colonic adenocarcinoma and its correlation with lymph node metastasis

Human phosphatases of regenerating liver (PRLs) can induce cell growth, differentiation, and malignant transformation. In this study, we used specific polyclonal antibodies against PRLs to investigate their expression in colonic adenocarcinomas and its correlation with patient gender, age, tumor differentiation, localization, invasion, and metastasis. The polyclonal antibodies against PRL-1, PRL-2, and PRL-3 were produced and purified. The expression of PRLs in human colorectal carcinoma cell lines (SW480 and SW620) was examined by Western blotting. We also examined their expression in normal and pathologic tissues from the human colon. The tissues included 49 primary colonic adenocarcinomas, 14 cases with lymph node metastases, 15 colonic adenomas, and 12 normal colon samples. Hematoxylin and eosin staining, immunohistochemistry, and semiquantitative morphological analysis were used to evaluate the sections. PRLs were widely expressed in SW480 and SW620. PRL-1, PRL-2, and PRL-3 were expressed, respectively, in 16, 10, and 16% of primary colonic adenocarcinomas. In contrast, PRLs were strongly expressed in all lymph node metastases. There were no significant correlations between the expression of PRLs and patient gender, age, tumor differentiation, depth of invasion, or localization of tumor within the different sections of the colon. PRLs were not expressed in normal colon tissues or in colonic adenomas. PRLs were mainly expressed in the cytoplasm and at the cytoplasmic membranes of the colonic adenocarcinoma cells as well as in the endothelial cells and the surrounding smooth muscle cells of larger vessels in the lymph node metastases. Colonic adenocarcinoma cells have the ability to produce PRLs, which may relate to the lymph node metastasis of colonic adenocarcinoma.

PRL-3 siRNA Inhibits the Metastasis of B16-BL6 Mouse Melanoma Cells In Vitro and In Vivo

Phosphatase of regenerating liver-3 (PRL-3) has been proposed to promote the invasion of tumor cells to metastasis sites. However, the effect of PRL-3 on spontaneous metastasis has not been clearly demonstrated, and whether PRL-3 could become a new therapeutic target in malignant tumor is still unknown. In this study, we used PRL-3 siRNA as a molecular medicine to specifically reduce the expression of PRL-3 in B16-BL6 cells, a highly metastatic melanoma cell line. In vitro, PRL-3 siRNA significantly inhibited cell adhesion and migration, but had no effect on cell proliferation. In the spontaneous metastatic tumor model in vivo, PRL-3 siRNA treatment remarkably inhibited the proliferation of primary tumor, prevented tumor cells from invading the draining lymph nodes, and prolonged the life span of mice. Therefore, our results indicate that PRL-3 plays a critical role in promoting the whole process of spontaneous metastasis and tumor growth initiation, and that inhibiting PRL-3 will improve malignant tumor therapy.

PRL-3 siRNA inhibits the metastasis of B16-BL6 mouse melanoma cells in vitro and in vivo.

Phosphatase of regenerating liver-3 (PRL-3) has been proposed to promote the invasion of tumor cells to metastasis sites. However, the effect of PRL-3 on spontaneous metastasis has not been clearly demonstrated, and whether PRL-3 could become a new therapeutic target in malignant tumor is still unknown. In this study, we used PRL-3 siRNA as a molecular medicine to specifically reduce the expression of PRL-3 in B16-BL6 cells, a highly metastatic melanoma cell line. In vitro, PRL-3 siRNA significantly inhibited cell adhesion and migration, but had no effect on cell proliferation. In the spontaneous metastatic tumor model in vivo, PRL-3 siRNA treatment remarkably inhibited the proliferation of primary tumor, prevented tumor cells from invading the draining lymph nodes, and prolonged the life span of mice. Therefore, our results indicate that PRL-3 plays a critical role in promoting the whole process of spontaneous metastasis and tumor growth initiation, and that inhibiting PRL-3 will improve malignant tumor therapy.

PRL3 Promotes Cell Invasion and Proliferation by Down-regulation of Csk Leading to Src Activation

Phosphatase of regenerating liver 3 (PRL3) is overexpressed in a variety of tumors, and high levels of PRL3 expression are associated with tumorigenesis and metastasis. Consistent with an oncogenic role for PRL3, we show that ectopic PRL3 expression promotes cell proliferation and invasion. However, little is known about the molecular basis for PRL3 function. Obtaining this knowledge is vital for understanding PRL3-mediated disease processes and for the development of novel anticancer therapies targeted to PRL3. Here we report that up-regulation of PRL3 activates the Src kinase, which initiates a number of signal pathways culminating in the phosphorylation of ERK1/2, STAT3, and p130(Cas). The activation of these pathways likely contributes to the increased cell growth and motility of PRL3 cells. We provide evidence that PRL3 induces Src activation through down-regulation of Csk, a negative regulator of Src. Importantly, Src activation and Csk down-regulation are also observed in colon cancer cells expressing a higher level of PRL3. Thus, we have revealed a biochemical mechanism for the PRL3-mediated cell invasion and proliferation in which elevated PRL3 expression causes a reduction in Csk level, leading to Src activation.

High PRL-3 expression in human gastric cancer is a marker of metastasis and grades of malignancies: an in situ hybridization study

Phosphatase of regenerating liver (PRL)-3, encoding a 22-kD low molecular weight tyrosine phosphatase, has been reported to be associated with metastasis of colorectal carcinoma. We assessed the levels of PRL-3 mRNA expression to know whether its up-regulation was involved in progression and metastasis of gastric carcinoma. Levels of PRL-3 expression in 94 human gastric adenocarcinomas and 54 matched lymph node metastases were detected by in situ hybridization and compared with clinicopathological characteristics including prognosis. High PRL-3 expression was detected in 36.2% of primary gastric carcinoma (with nodal metastasis, 55.6%; without nodal metastasis, 10%; P < 0.001) and in 74.1% of lymph node metastases. The incidence of high PRL-3 expression in lymph node metastasis was significantly higher than in primary tumors (P < 0.044). Moreover, high expression of PRL-3 was closely associated with tumor size, lymphatic invasion, venous invasion, extent of lymph node metastasis, and tumor stage. These results suggest that high PRL-3 expression may participate in the progression and metastasis of gastric carcinoma. PRL-3 might be a novel molecular marker for aggressive gastric cancer.

Biflavonoids inhibited phosphatase of regenerating liver-3 (PRL-3)

Two biflavonoids, ginkgetin (1) and sciadopitysin (2), were isolated from the MeOH extract of the young branches of Taxus cuspidata, which inhibited phosphatase of regenerating liver-3 (PRL-3) with IC50 values of 25.8 and 46.2 μM, respectively. This is the first report on PRL-3 inhibitors, isolated from natural sources.

Overexpression of phosphatase of regenerating liver-3 in breast cancer: association with a poor clinical outcome

Increasing evidence has suggested that phosphatase of regenerating liver-3 (PRL-3) plays an important role in cancer cell migration, invasion and metastasis. However, the correlation between the PRL-3 expression and clinical outcome in breast cancer has not been investigated. Using a PRL-3-specific monoclonal antibody 3B6, PRL-3 expression was assessed by immunohistochemistry in tumor tissues from 382 breast cancer patients with a median follow-up of 65 months. We found that 34.8% patients expressed a high level of PRL-3 protein in their tumors. Patients with a high level of PRL-3 in the tumor had a worse disease-specific survival (DSS) rate than those with a low level of PRL-3 (74.0% versus 84.9%, P = 0.011), and PRL-3 remained an independent prognostic marker for DSS (HR 1.8, 95% CI 1.1-2.9, P = 0.019) in multivariate analysis. More importantly, in 219 node-negative patients, PRL-3 showed a significant correlation with DSS in univariate analysis (P = 0.014) and retained a borderline significance (HR 2.65, 95% CI 0.92-7.64, P = 0.071) in multivariate analysis. Our results suggest that PRL-3 may serve as an unfavorable prognostic marker in breast cancer, especially for patients with node-negative diseases. Thus, our findings may provide useful information for individualized therapy in the clinical setting.