Phosphatase Of Regenerating Liver Research Articles

Protein Tyrosine Phosphatase PRL-3: A Key Player in Cancer Signaling.

Protein phosphatases are primarily responsible for dephosphorylation modification within signal transduction pathways. Phosphatase of regenerating liver-3 (PRL-3) is a dual-specific phosphatase implicated in cancer pathogenesis. Understanding PRL-3's intricate functions and developing targeted therapies is crucial for advancing cancer treatment. This review highlights its regulatory mechanisms, expression patterns, and multifaceted roles in cancer progression. PRL-3's involvement in proliferation, migration, invasion, metastasis, angiogenesis, and drug resistance is discussed. Regulatory mechanisms encompass transcriptional control, alternative splicing, and post-translational modifications. PRL-3 exhibits selective expressions in specific cancer types, making it a potential target for therapy. Despite advances in small molecule inhibitors, further research is needed for clinical application. PRL-3-zumab, a humanized antibody, shows promise in preclinical studies and clinical trials. Our review summarizes the current understanding of the cancer-related cellular function of PRL-3, its prognostic value, and the research progress of therapeutic inhibitors.

Exploiting frequent and specific expression of PRL3 in pediatric solid tumors for first-in-child use of PRL3-zumab humanized antibody

Phosphatase of regenerating liver 3 (PRL3) is a specific tumor antigen overexpressed in a broad range of adult cancer types. However, its physiological expression in pediatric embryonal and mesenchymal tumors and its association with clinical outcomes in children is unknown. We sought to profile the expression of PRL3 in pediatric tumors in relation to survival outcomes, expression of angiogenesis markers, and G-protein-coupled receptor (GPCR)-mitogen-activated protein kinase (MAPK) signaling targets. PRL3-zumab, a first-in-class humanized antibody, was administered in a dose escalation schedule in a first-in-child clinical trial to study toxicity, pharmacokinetics, and clinical outcomes. Among 64 pediatric tumors, PRL3 was most frequently expressed in neuroblastoma (100%), rhabdomyosarcoma and non-rhabdomyosarcoma soft tissue sarcomas (71%), and renal sarcomas (60%) but absent in paired normal tissues. PRL3 was expressed in 75% of relapsed tumors and associated with shorter median event-free survival. Microarray profiling of PRL3-positive tumors showed elevation of angiogenin, TIMP1 and TIMP2, and GPCR-MAPK signaling proteins that commonly interacted with PRL3. The first use of PRL3-zumab in a pediatric patient saw no adverse events. A 28.6% reduction in maximum target lesion diameter was achieved when PRL3-zumab was administered concurrently with hypofractionated radiation. These findings support wider exploration of PRL3 expression in embryonal and mesenchymal tumors and further clinical application of PRL3-zumab in pediatric patients.

Phosphatase and Pseudo-Phosphatase Functions of Phosphatase of Regenerating Liver 3 (PRL-3) Are Insensitive to Divalent Metals In Vitro.

Phosphatase of regenerating liver 3 (PRL-3) is associated with cancer metastasis and has been shown to interact with the cyclin and CBS domain divalent metal cation transport mediator (CNNM) family of proteins to regulate the intracellular concentration of magnesium and other divalent metals. Despite PRL-3's importance in cancer, factors that regulate PRL-3's phosphatase activity and its interactions with CNNM proteins remain unknown. Here, we show that divalent metal ions, including magnesium, calcium, and manganese, have no impact on PRL-3's structure, stability, phosphatase activity, or CNNM binding capacity, indicating that PRL-3 does not act as a metal sensor, despite its interaction with CNNM metal transporters. In vitro approaches found that PRL-3 is a broad but not indiscriminate phosphatase, with activity toward di- and tri-nucleotides, phosphoinositols, and NADPH but not other common metabolites. Although calcium, magnesium, manganese, and zinc-binding sites were predicted near the PRL-3 active site, these divalent metals did not specifically alter PRL-3's phosphatase activity toward a generic substrate, its transition from an inactive phospho-cysteine intermediate state, or its direct binding with the CBS domain of CNNM. PRL-3's insensitivity to metal cations negates the possibility of its role as an intracellular metal content sensor for regulating CNNM activity. Further investigation is warranted to define the regulatory mechanisms governing PRL-3's phosphatase activity and CNNM interactions, as these findings could hold potential therapeutic implications in cancer treatment.

Drosophila Phosphatase of Regenerating Liver Is Critical for Photoreceptor Cell Polarity and Survival during Retinal Development.

Establishing apicobasal polarity, involving intricate interactions among polarity regulators, is key for epithelial cell function. Though phosphatase of regenerating liver (PRL) proteins are implicated in diverse biological processes, including cancer, their developmental role remains unclear. In this study, we explore the role of Drosophila PRL (dPRL) in photoreceptor cell development. We reveal that dPRL, requiring a C-terminal prenylation motif, is highly enriched in the apical membrane of developing photoreceptor cells. Moreover, dPRL knockdown during retinal development results in adult Drosophila retinal degeneration, caused by hid-induced apoptosis. dPRL depletion also mislocalizes cell adhesion and polarity proteins like Armadillo, Crumbs, and DaPKC and relocates the basolateral protein, alpha subunit of Na+/K+-ATPase, to the presumed apical membrane. Importantly, this polarity disruption is not secondary to apoptosis, as suppressing hid expression does not rescue the polarity defect in dPRL-depleted photoreceptor cells. These findings underscore dPRL's crucial role in photoreceptor cell polarity and emphasize PRL's importance in establishing epithelial polarity and maintaining cell survival during retinal development, offering new insights into PRL's role in normal epithelium.

Development and characterization of nanobodies that specifically target the oncogenic Phosphatase of Regenerating Liver-3 (PRL-3) and impact its interaction with a known binding partner, CNNM3.

Phosphatase of Regenerating Liver-3 (PRL-3) is associated with cancer progression and metastasis. The mechanisms that drive PRL-3's oncogenic functions are not well understood, partly due to a lack of research tools available to study this protein. We have begun to address these issues by developing alpaca-derived single domain antibodies, or nanobodies, targeting PRL-3 with a KD of 30-300 nM and no activity towards highly homologous family members PRL-1 and PRL-2. We found that longer and charged N-terminal tags on PRL-3, such as GFP and FLAG, changed PRL-3 localization compared to untagged protein, indicating that the nanobodies may provide new insights into PRL-3 trafficking and function. The nanobodies perform equally, if not better, than commercially available antibodies in immunofluorescence and immunoprecipitation. Finally, hydrogen-deuterium exchange mass spectrometry (HDX-MS) showed that the nanobodies bind partially within the PRL-3 active site and can interfere with PRL-3 phosphatase activity. Co-immunoprecipitation with a known PRL-3 active site binding partner, the CBS domain of metal transporter CNNM3, showed that the nanobodies reduced the amount of PRL-3:CBS inter-action. The potential of blocking this interaction is highly relevant in cancer, as multiple research groups have shown that PRL-3 binding to CNNM proteins is sufficient to promote metastatic growth in mouse models. The anti-PRL-3 nanobodies represent an important expansion of the research tools available to study PRL-3 function and can be used to define the role of PRL-3 in cancer progression.

Knockdown of phosphatases of regenerating liver-1 prolongs the lifespan of Caenorhabditis elegans via activating DAF-16/FOXO.

Phosphatases of regenerating liver (PRLs) are dual-specificity protein phosphatases. The aberrant expression of PRLs threatens human health, but their biological functions and pathogenic mechanisms are unclear yet. Herein, the structure and biological functions of PRLs were investigated using the Caenorhabditis elegans (C. elegans). Structurally, this phosphatase in C. elegans, named PRL-1, consisted of a conserved signature sequence WPD loop and a single C(X)5 R domain. Besides, by Western blot, immunohistochemistry and immunofluorescence staining, PRL-1 was proved to mainly express in larval stages and express in intestinal tissues. Afterward, by feeding-based RNA-interference method, knockdown of prl-1 prolonged the lifespan of C. elegans but also improved their healthspan, such as locomotion, pharyngeal pumping frequency, and defecation interval time. Furthermore, the above effects of prl-1 appeared to be taken without acting on germline signaling, diet restriction pathway, insulin/insulin-like growth factor 1 signaling pathway, and SIR-2.1 but through a DAF-16-dependent pathway. Moreover, knockdown of prl-1 induced the nuclear translocation of DAF-16, and upregulated the expression of daf-16, sod-3, mtl-1, and ctl-2. Finally, suppression of prl-1 also reduced the ROS. In conclusion, suppression of prl-1 enhanced the lifespan and survival quality of C. elegans, which provides a theoretical basis for the pathogenesis of PRLs in related human diseases.

PRL3 as a therapeutic target for novel cancer immunotherapy in multiple cancer types.

Phosphatase of Regenerating Liver-3 (PRL3) was discovered in 1998 and was subsequently found to be correlated with cancer progression and metastasis in 2001. Extensive research in the past two decades has produced significant findings on PRL3-mediated cancer signaling and functions, as well as its clinical relevance in diverse types of cancer. PRL3 has been established to play a role in many cancer-related functions, including but not limited to metastasis, proliferation, and angiogenesis. Importantly, the tumor-specific expression of PRL3 protein in multiple cancer types has made it an attractive therapeutic target. Much effort has been made in developing PRL3-targeted therapy with small chemical inhibitors against intracellular PRL3, and notably, the development of PRL3-zumab as a novel cancer immunotherapy against PRL3. In this review, we summarize the current understanding of the role of PRL3 in cancer-related cellular functions, its prognostic value, as well as perspectives on PRL3 as a target for unconventional immunotherapy in the clinic with PRL3-zumab.

Abstract 1338: Investigating Drug Fragments, Substrate Mimics, and Metal Ions as Inhibitors and Regulators of the Oncogene Phosphatase Of Regenerating Liver 3 (PRL-3)

Abstract 1338: Investigating Drug Fragments, Substrate Mimics, and Metal Ions as Inhibitors and Regulators of the Oncogene Phosphatase Of Regenerating Liver 3 (PRL-3)

Phosphatase-independent role of phosphatase of regenerating liver in cancer progression.

Phosphatase of regenerating liver (PRL) is a family of protein tyrosine phosphatases (PTPs) that are anchored to the plasma membrane by prenylation. They are frequently overexpressed in various types of malignant cancers and their roles in cancer progression have received considerable attention. Mutational analyses of PRLs have shown that their intrinsic phosphatase activity is dispensable for tumor formation induced by PRL overexpression in a lung metastasis model using melanoma cells. Instead, PRLs directly bind to cyclin M (CNNM) Mg2+ exporters in the plasma membrane and potently inhibit their Mg2+ export activity, resulting in an increase in intracellular Mg2+ levels. Experiments using mammalian culture cells, mice, and C. elegans have collectively revealed that dysregulation of Mg2+ levels severely affects ATP and reactive oxygen species (ROS) levels as well as the function of Ca2+ -permeable channels. Moreover, PRL overexpression altered the optimal pH for cell proliferation from normal 7.5 to acidic 6.5, which is typically observed in malignant tumors. Here, we review the phosphatase-independent biological functions of PRLs, focusing on their interactions with CNNM Mg2+ exporters in cancer progression.

The Deubiquitinating Enzyme USP4 Functions as an Oncoprotein in Gastric Cancer and Mediates NF-κB Signaling by Regulating PRL-3 Expression.

It has been reported that ubiquitin specific peptidase 4 (USP4) was functional in several tumors, but its function and mechanism in gastric cancer were still unknown. Bioinformatic tools were used to predict the prognosis of gastric cancer patients and the expression levels of USP4 in gastric cancer. Quantitative real-time polymerase chain reaction (qRT-PCR) and immunoblotting were carried out to detect the messenger RNA (mRNA) and protein levels. Cell viability of gastric cancer was evaluated by Cell Counting Kit-8 (CCK-8) assay. Cell line-derived xenograft models were established to evaluate the tumor growth of gastric cancer. Luciferase assay and immunoblotting were used to determine the activation of nuclear factor kappa B (NF-κB) signaling. The public database Kaplan-Meier Plotter showed that gastric cancer patients with high USP4 expression had a shorter overall survival or post-progression survival than the patients with decreased USP4. Further studies indicated that USP4 was elevated in gastric cancer tumor tissues. In contrast, knockdown of USP4 markedly inhibited gastric cancer cell growth, and suppressed the tumor growth of gastric cancer. Further studies revealed that USP4 knockdown significantly suppressed NF-κB-driven luciferase activity, and inhibited the phosphorylation of NF-κB p65 in gastric cancer cells. Additionally, qRT-PCR analysis showed that USP4 knockdown significantly downregulated the expressions of cyclin D2 (CCND2) and B cell leukemia/lymphoma 2 (BCL2). We also found that USP4 knockdown decreased the expressions of phosphatase of regenerating liver-3 (PRL-3), in contrast, overexpression of PRL-3 attenuated the inhibitory effects of USP4 knockdown on NF-κB signaling and cell viability in gastric cancer cells. Finally, PR-619, which has been proven to inhibit the activities of USP4 and other deubiquitinases, could inhibit cell viability and NF-κB signaling in gastric cancer cells. This study indicated that elevated USP4 predicted a poor index for gastric cancer patients, and mediated gastric cancer cell growth by regulating PRL-3/NF-κB signaling, which suggested USP4 may be a novel therapeutic target for gastric cancer.

The Tyrosine Phosphatase PRL Regulates Attachment of Toxoplasma gondii to Host Cells and Is Essential for Virulence.

ABSTRACTThe pathogenesis of Toxoplasma gondii is mainly due to tissue damage caused by the repeating lytic cycles of the parasite. Many proteins localized to the pellicle of the parasite, particularly kinases, have been identified as critical regulators of the Toxoplasma lytic cycle. However, little is known about the associated protein phosphatases. Phosphatase of regenerating liver (PRL), a highly conserved tyrosine phosphatase, is an oncoprotein that plays pivotal roles in mammalian cells and typically associates with membranes via a conserved prenylation site. PRL in Toxoplasma has a predicted prenylation motif in the C terminus, like other homologs. We have determined that T. gondii PRL (TgPRL) localizes to the plasma membrane and that disruption of TgPRL results in a defect in the parasite’s ability to attach to host cells. This function is dependent on both TgPRL’s membrane localization and phosphatase activity. Importantly, in vivo experiments have shown that while mice infected with parental strain parasites die within days of infection, those infected with parasites lacking TgPRL not only survive but also develop immunity that confers protection against subsequent infection with wild-type parasites. Immunoprecipitation experiments revealed that the PRL-CNNM (cyclin M) complex, which regulates intracellular Mg2+ homeostasis in mammalian cells, is also present in Toxoplasma. Consistent with this interaction, parasites lacking TgPRL had higher intracellular Mg2+ levels than the parental or complemented strains, suggesting TgPRL is involved in regulating intracellular Mg2+ homeostasis. Thus, TgPRL is a vital regulator of the Toxoplasma lytic cycle and virulence, showing its potential as a target of therapeutic intervention.IMPORTANCE Infection with Toxoplasma gondii can lead to severe and even life-threatening diseases in people with compromised or suppressed immune systems. Unfortunately, drugs to combat the parasite are limited, highly toxic, and ineffective against the chronic stage of the parasite. Consequently, there is a strong demand for the discovery of new treatments. A comprehensive understanding of how the parasite propagates in the host cells and which proteins contribute to the parasite’s virulence will facilitate the discovery of new drug targets. Our study meets this objective and adds new insights to understanding the lytic cycle regulation and virulence of Toxoplasma by determining that the protein phosphatase TgPRL plays a vital role in the parasite’s ability to attach to host cells and that it is essential for parasite virulence.

A novel role for PRL in regulating epithelial cell density by inducing apoptosis at confluence.

Maintaining proper epithelial cell density is essential for the survival of multicellular organisms. Although regulation of cell density through apoptosis is well known, its mechanistic details remain elusive. Here, we report the involvement of membrane-anchored phosphatase of regenerating liver (PRL), originally known for its role in cancer malignancy, in this process. In epithelial Madin-Darby canine kidney cells, upon confluence, doxycycline-induced expression of PRL upregulated apoptosis, reducing cell density. This could be circumvented by artificially reducing cell density via stretching the cell-seeded silicon chamber. Moreover, small interfering RNA-mediated knockdown of endogenous PRL blocked apoptosis, leading to greater cell density. Mechanistically, PRL promoted apoptosis by upregulating the translation of E-cadherin and activating the TGF-β pathway. Morpholino-mediated inhibition of PRL expression in zebrafish embryos caused developmental defects, with reduced apoptosis and increased epithelial cell density during convergent extension. Overall, this study revealed a novel role for PRL in regulating density-dependent apoptosis in vertebrate epithelia. This article has an associated First Person interview with the first author of the paper.

PRL stimulates mitotic errors by suppressing kinetochore-localized activation of AMPK during mitosis.

Phosphatase of regenerating liver (PRL) is frequently overexpressed in various malignant cancers and is known to be a driver of malignancy. Here, we demonstrated that PRL overexpression causes mitotic errors that accompany spindle misorientation and aneuploidy, which are intimately associated with cancer progression. Mechanistic analyses of this phenomenon revealed dysregulation of the energy sensor kinase, AMP-activated protein kinase (AMPK), in PRL-induced mitotic errors. Specifically, immunofluorescence analysis showed that levels of phosphorylated AMPK (P-AMPK), an activated form of AMPK, at the kinetochore were reduced by PRL expression. Moreover, artificial activation of AMPK using chemical activators, such as A769662 and AICAR, in PRL-expressing cells restored P-AMPK signals at the kinetochore and normalized spindle orientation. Collectively, these results indicate the crucial importance of the activation of kinetochore-localized AMPK in the normal progression of mitosis, which is specifically perturbed by PRL overexpression.Key words: cancer, AMPK, PRL, kinetochore, mitotic errors.

CNNM proteins selectively bind to the TRPM7 channel to stimulate divalent cation entry into cells

Magnesium is essential for cellular life, but how it is homeostatically controlled still remains poorly understood. Here, we report that members of CNNM family, which have been controversially implicated in both cellular Mg2+ influx and efflux, selectively bind to the TRPM7 channel to stimulate divalent cation entry into cells. Coexpression of CNNMs with the channel markedly increased uptake of divalent cations, which is prevented by an inactivating mutation to the channel's pore. Knockout (KO) of TRPM7 in cells or application of the TRPM7 channel inhibitor NS8593 also interfered with CNNM-stimulated divalent cation uptake. Conversely, KO of CNNM3 and CNNM4 in HEK-293 cells significantly reduced TRPM7-mediated divalent cation entry, without affecting TRPM7 protein expression or its cell surface levels. Furthermore, we found that cellular overexpression of phosphatases of regenerating liver (PRLs), known CNNMs binding partners, stimulated TRPM7-dependent divalent cation entry and that CNNMs were required for this activity. Whole-cell electrophysiological recordings demonstrated that deletion of CNNM3 and CNNM4 from HEK-293 cells interfered with heterologously expressed and native TRPM7 channel function. We conclude that CNNMs employ the TRPM7 channel to mediate divalent cation influx and that CNNMs also possess separate TRPM7-independent Mg2+ efflux activities that contribute to CNNMs' control of cellular Mg2+ homeostasis.

Intertumoral Heterogeneity of Primary Breast Tumors and Synchronous Axillary Lymph Node Metastases Reflected in IHC-Assessed Expression of Routine and Nonstandard Biomarkers

Breast cancer (BC) remains a significant healthcare challenge. Routinely, the treatment strategy is determined by immunohistochemistry (IHC)-based assessment of the key proteins such as estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and Ki-67. However, it is estimated that over 75% of deaths result from metastatic tumors, indicating a need to develop more accurate protocols for intertumoral heterogeneity assessment and their consequences on prognosis. Therefore, the aim of this preliminary study was the identification of the expression profiles of routinely used biomarkers (ER, PR, HER2, Ki-67) and additional relevant proteins [Bcl-2, cyclin D1, E-cadherin, Snail+Slug, gross cystic disease fluid protein 15 (GCDFP-15), programmed death receptor 1 (PD-L1), and phosphatase of regenerating liver 3 (PRL-3)] in breast primary tumors (PTs) and paired synchronous axillary lymph node (ALN) metastases. A total of 67 tissue samples met the inclusion criteria for the study. The expression status of biomarkers was assessed in PTs and ALN metastases using tissue microarrays followed by IHC. In 11 cases, the shift of intrinsic molecular BC subtype was noticed between PTs and paired ALN metastases. Moreover, a significant disproportion in E-cadherin presence (p = 0.0002) was noted in both foci, and the expression status of all proteins except for HER2 demonstrated considerable variance (k = 1, p < 0.0001). Importantly, in around 30% of cases, the ALN metastases demonstrated discordance, i.e., loss/gain of expression, compared to the PTs. Intertumoral synchronous heterogeneity in both foci (primary tumor and node metastasis) is an essential phenomenon affecting the clinical subtype and characteristics of BC. Furthermore, a greater understanding of this event could potentially improve therapeutic efficacy.

Rag GTPases suppress PRL-3 degradation and predict poor clinical diagnosis of cancer patients with low PRL-3 mRNA expression

Ras-related GTP binding (Rag) GTPases are required to activate mechanistic target of rapamycin complex 1 (mTORC1), which plays a central role in cell growth and metabolism and is considered as one of the most important oncogenic pathways. Therefore, Rag GTPases have been speculated to play a pro-cancer role via mTOR induction. However, aside from stimulation of mTOR signaling, firm links connecting Rag GTPase activity and their downstream effectors with cancer progression, remain largely unreported. In this study, we reported a novel link between RagB/C and a known oncoprotein phosphatase of regenerating liver-3 (PRL-3) by screening 22 pairs of tumors and their adjacent normal tissues from gastric, liver and lung cancers, and validating our findings in cancer cell lines with ectopic RagB/C expression. RagB/C was found to enhance PRL-3 stability by modulating two major cellular protein degradation pathways: lysosomal-autophagy and ubiquitin-proteasome system (UPS). Functionally, we identified the correlation between RagB/C expression with poor clinical outcomes in breast or colon cancer patients who also showed low PRL-3 mRNA expression from data retrieved from TCGA datasets, highlighting the potential relevance of Rag GTPase and PRL-3 mRNA in combination as a prognostic clinical biomarker.

PRL-3 induces a positive signaling circuit between glycolysis and activation of STAT1/2.

Multiple myeloma (MM) is an incurable hematologic malignancy resulting from the clonal expansion of plasma cells. MM cells are interacting with components of the bone marrow microenvironment such as cytokines to survive and proliferate. Phosphatase of regenerating liver (PRL)-3, a cytokine-induced oncogenic phosphatase, is highly expressed in myeloma patients and is a mediator of metabolic reprogramming of cancer cells. To find novel pathways and genes regulated by PRL-3, we characterized the global transcriptional response to PRL-3 overexpression in two MM cell lines. We used pathway enrichment analysis to identify pathways regulated by PRL-3. We further confirmed the hits from the enrichment analysis with in vitro experiments and investigated their function. We found that PRL-3 induced expression of genes belonging to the type 1 interferon (IFN-I) signaling pathway due to activation of signal transducer and activator of transcription (STAT) 1 and STAT2. This activation was independent of autocrine IFN-I secretion. The increase in STAT1 and STAT2 did not result in any of the common consequences of increased IFN-I or STAT1 signaling in cancer. Knockdown of STAT1/2 did not affect the viability of the cells, but decreased PRL-3-induced glycolysis. Interestingly, glucose metabolism contributed to the activation of STAT1 and STAT2 and expression of IFN-I-stimulated genes in PRL-3-overexpressing cells. In summary, we describe a novel signaling circuit where the key IFN-I-activated transcription factors STAT1 and STAT2 are important drivers of the increase in glycolysis induced by PRL-3. Subsequently, increased glycolysis regulates the IFN-I-stimulated genes by augmenting the activation of STAT1/2.

The phosphatase PRL-3 affects intestinal homeostasis by altering the crypt cell composition

Expression of the phosphatase of regenerating liver-3 (PRL-3) is known to promote tumor growth in gastrointestinal adenocarcinomas, and the incidence of tumor formation upon inflammatory events correlates with PRL-3 levels in mouse models. These carcinomas and their onset are associated with the impairment of intestinal cell homeostasis, which is regulated by a balanced number of Paneth cells and Lgr5 expressing intestinal stem cells (Lgr5+ ISCs). Nevertheless, the consequences of PRL-3 overexpression on cellular homeostasis and ISC fitness in vivo are unexplored. Here, we employ a doxycycline-inducible PRL-3 mouse strain to show that aberrant PRL-3 expression within a non-cancerous background leads to the death of Lgr5+ ISCs and to Paneth cell expansion. A higher dose of PRL-3, resulting from homozygous expression, led to mice dying early. A primary 3D intestinal culture model obtained from these mice confirmed the loss of Lgr5+ ISCs upon PRL-3 expression. The impaired intestinal organoid formation was rescued by a PRL inhibitor, providing a functional link to the observed phenotypes. These results demonstrate that elevated PRL-3 phosphatase activity in healthy intestinal epithelium impairs intestinal cell homeostasis, which correlates this cellular mechanism of tumor onset with PRL-3-mediated higher susceptibility to tumor formation upon inflammatory or mutational events.Key messages• Transgenic mice homozygous for PRL-3 overexpression die early.• PRL-3 heterozygous mice display disrupted intestinal self-renewal capacity.• PRL-3 overexpression alone does not induce tumorigenesis in the mouse intestine.• PRL-3 activity leads to the death of Lgr5+ ISCs and Paneth cell expansion.• Impairment of cell homeostasis correlates PRL-3 action with tumor onset mechanisms.

The combination of PRL-3 inhibitor with sorafenib synergistically promotes AML apoptosis.

Phosphatase of regenerating liver-3 (PRL-3) is recognized as a novel independent crucial driver for AML progression. Thus, the specific inhibitor of PRL-3 would be a potential therapeutic agent to AML in clinics, but there are not enough preclinical applications reported yet. Here we evaluated the cytotoxicity of PRL-3 inhibitor, BR-1, against AML cells ML-1 and MOLM-13. Meanwhile, the effect of BR-1 on the biological characteristics of AML cells and the underlying mechanism was investigated along with the combination of BR-1 and sorafenib on the AML cell viability. Our results show that BR-1 promotes apoptosis by inactivation of the JAK/STAT5 and PI3K/AKT pathways, while inhibits cell proliferation through arresting cell cycle in the S phase. In addition, a combination of BR-1 with sorafenib can further improve the therapeutic effect on AML. Thus, our results demonstrated that BR-1 would be a novel and potent therapeutic agent to AML, and its combination with other anti-AML drugs would be a promising strategy for AML therapy.

Mesenchymal and Phosphatase of Regenerating Liver-3 Status in Circulating Tumor Cells May Serve as a Crucial Prognostic Marker for Assessing Relapse or Metastasis in Postoperative Patients With Colorectal Cancer

INTRODUCTION:Circulating tumor cells (CTCs) and phosphatase of regenerating liver-3 (PRL-3) have been considered to be significant prognostic indicators in metastatic colorectal cancer (CRC). This study discusses the prognostic significance of mesenchymal CTCs with PRL-3 (M+ PRL-3+ CTCs) in postoperative patients with CRC.METHODS:We detected CTC subtypes (including epithelial CTCs, biphenotypic epithelial/mesenchymal CTCs, and mesenchymal CTCs) and PRL-3 in CTCs from the peripheral blood samples of 156 patients. Receiver operating characteristic curve analysis, Kaplan-Meier analysis, and Cox proportional hazards regression analysis were performed to identify the prognostic value of mesenchymal CTCs with PRL-3+. Immunohistochemistry was used to detect the expression of PRL-3 in tumor tissues from some of the patients to explore the connection between CTCs and tissues.RESULTS:All CTCs were positive in all samples, both mesenchymal CTCs and PRL-3–positive cells. The count of mesenchymal and PRL-3+ CTCs was significantly associated with recurrence, and the optimal cutoff value was 2 (area under the curve = 0.690, P < 0.001). In addition, these patients had a significantly shorter median disease-free survival than those who did not fulfill the criteria (8.5 vs 24 months, P < 0.001) according to multivariable and multinomial logistic regression. Immunohistochemistry was applied to explore the associations between PRL-3 expression and significant prognostic risk factors, including recurrence (R = 0.566; P < 0.001), and M+ PRL-3+ status in CTCs (R = 0.452; P = 0.001).DISCUSSION:The status of M+ PRL-3+ in CTCs may serve as a crucial prognostic marker for assessing clinical outcomes in CRC.