Synthesis and biological evaluation of rhodanine derivatives as PRL-3 inhibitors

In silico identification of putative druggable pockets in PRL3, a significant oncology target

Protein tyrosine phosphatases (PTP) have emerged as targets in diseases characterized by aberrant phosphorylations such as cancers. The activity of the phosphatase of regenerating liver 3, PRL3, has been linked to several oncogenic and metastatic pathways, particularly in breast, ovarian, colorectal, and blood cancers. Development of small molecules that directly target PRL3, however, has been challenging. This is partly due to the lack of structural information on how PRL3 interacts with its inhibitors. Here, computational methods are used to bridge this gap by evaluating the druggability of PRL3. In particular, web-based pocket prediction tools, DoGSite3 and FTMap, were used to identify binding pockets using structures of PRL3 currently available in the Protein Data Bank. Druggability assessment by molecular dynamics simulations with probes was also performed to validate these results and to predict the strength of binding in the identified pockets. While several druggable pockets were identified, those in the closed conformation show more promise given their volume and depth. These two pockets flank the active site loops and roughly correspond to pockets predicted by molecular docking in previous papers. Notably, druggability simulations predict the possibility of low nanomolar affinity inhibitors in these sites implying the potential to identify highly potent small molecule inhibitors for PRL3. Putative pockets identified here can be leveraged for high-throughput virtual screening to further accelerate the drug discovery against PRL3 and development of PRL3-directed therapeutics.

Targeting Moonlighting Enzymes in Cancer

Moonlighting enzymes are multifunctional proteins that perform multiple functions beyond their primary role as catalytic enzymes. Extensive research and clinical practice have demonstrated their pivotal roles in the development and progression of cancer, making them promising targets for drug development. This article delves into multiple notable moonlighting enzymes, including GSK-3, GAPDH, and ENO1, and with a particular emphasis on an enigmatic phosphatase, PTP4A3. We scrutinize their distinct roles in cancer and the mechanisms that dictate their ability to switch roles. Lastly, we discuss the potential of an innovative approach to develop drugs targeting these moonlighting enzymes: target protein degradation. This strategy holds promise for effectively tackling moonlighting enzymes in the context of cancer therapy.

Targeting PRL phosphatases in hematological malignancies

INTRODUCTION

Phosphatase of regenerating liver (PRL) family proteins, also known as protein tyrosine phosphatase 4A (PTP4A), have been implicated in many types of cancers. The PRL family of phosphatases consists of three members, PRL1, PRL2, and PRL3. PRLs have been shown to harbor oncogenic potentials and are highly expressed in a variety of cancers. Given their roles in cancer progression and metastasis, PRLs are potential targets for anticancer therapies. However, additional studies are needed to be performed to fully understand the roles of PRLs in blood cancers.

AREAS COVERED

In this review, we will summarize recent studies of PRLs in normal and malignant hematopoiesis, the role of PRLs in regulating various signaling pathways, and the therapeutic potentials of targeting PRLs in hematological malignancies. We will also discuss how to improve current PRL inhibitors for cancer treatment.

EXPERT OPINION

Although PRL inhibitors show promising therapeutic effects in preclinical studies of different types of cancers, moving PRL inhibitors from bench to bedside is still challenging. More potent and selective PRL inhibitors are needed to target PRLs in hematological malignancies and improve treatment outcomes.

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.

Green design and synthesis of some novel thiazolidinone appended benzothiazole-triazole hybrids as antimicrobial agents

The global increase in bacterial resistance poses a significant threat, jeopardizing the effectiveness of antibiotics. Therefore, the development of new and efficient antimicrobial agents is pre-dominant. Taking this into consideration, in the present study, we designed and reported the facile synthesis of two novel series benzothiazole-triazole and thiazolidinone-appended benzothiazole-triazole hybrids using a molecular hybridization approach in a one-pot process. The synthesized compounds were tested for microbial growth inhibition against bacterial and fungal strains. Among all the synthetics, compounds derived from methoxyphenyl and heteroaromatic ring substitutions exhibited promising inhibitory activity. The current investigation has emphasized that benzothiazole-triazole hybrids incorporating thiazolidinone can be a promising and potent category of molecules with potential biological activities. This sustainable and eco-friendly protocol involves the metal-free, catalyst-free synthesis of bioactive scaffolds, which merges broad tolerance for functional groups with a short reaction time, resulting in good to excellent yields.

Recent advances in synthetic strategies and SAR of thiazolidin-4-one containing molecules in cancer therapeutics

Cancer is one of the life-threatening diseases accountable for millions of demises globally. The inadequate effectiveness of the existing chemotherapy and its harmful effects has resulted in the necessity of developing innovative anticancer agents. Thiazolidin-4-one scaffold is among the most important chemical skeletons that illustrate anticancer activity. Thiazolidin-4-one derivatives have been the subject of extensive research and current scientific literature reveals that these compounds have shown significant anticancer activities. This manuscript is an earnest attempt to review novel thiazolidin-4-one derivatives demonstrating considerable potential as anticancer agents along with a brief discussion of medicinal chemistry-related aspects of these compounds and structural activity relationship studies in order to develop possible multi-target enzyme inhibitors. Most recently, various synthetic strategies have been developed by researchers to get various thiazolidin-4-one derivatives. In this review, the authors highlight the various synthetic, green, and nanomaterial-based synthesis routes of thiazolidin-4-ones as well as their role in anticancer activity by inhibition of various enzymes and cell lines. The detailed description of the existing modern standards in the field presented in this article may be interesting and beneficial to the scientists for further exploration of these heterocyclic compounds as possible anticancer agents.

Anterior gradient 2 induces resistance to sorafenib via endoplasmic reticulum stress regulation in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) accounts for almost 80% of all liver cancer cases and is the sixth most common cancer and the second most common cause of cancer-related death worldwide. The survival rate of sorafenib-treated advanced HCC patients is still unsatisfactory. Unfortunately, no useful biomarkers have been verified to predict sorafenib efficacy in HCC.

RESULTS

We assessed a sorafenib resistance-related microarray dataset and found that anterior gradient 2 (AGR2) is highly associated with overall and recurrence-free survival and with several clinical parameters in HCC. However, the mechanisms underlying the role of AGR2 in sorafenib resistance and HCC progression remain unknown. We found that sorafenib induces AGR2 secretion via posttranslational modification and that AGR2 plays a critical role in sorafenib-regulated cell viability and endoplasmic reticulum (ER) stress and induces apoptosis in sorafenib-sensitive cells. In sorafenib-sensitive cells, sorafenib downregulates intracellular AGR2 and conversely induces AGR2 secretion, which suppresses its regulation of ER stress and cell survival. In contrast, AGR2 is highly intracellularly expressed in sorafenib-resistant cells, which supports ER homeostasis and cell survival. We suggest that AGR2 regulates ER stress to influence HCC progression and sorafenib resistance.

CONCLUSIONS

This is the first study to report that AGR2 can modulate ER homeostasis via the IRE1α-XBP1 cascade to regulate HCC progression and sorafenib resistance. Elucidation of the predictive value of AGR2 and its molecular and cellular mechanisms in sorafenib resistance could provide additional options for HCC treatment.

Roles of protein tyrosine phosphatases in hepatocellular carcinoma progression (Review)

Hepatocellular carcinoma (HCC) represents almost 80% of all liver cancers, is the sixth most common cancer and is the second‑highest cause of cancer‑related deaths worldwide. Protein tyrosine phosphatases (PTPs), which are encoded by the largest family of phosphatase genes, play critical roles in cellular responses and are implicated in various signaling pathways. Moreover, PTPs are dysregulated and involved in various cellular processes in numerous cancers, including HCC. Kinases and phosphatases are coordinators that modulate cell activities and regulate signaling responses. There are multiple interacting signaling networks, and coordination of these signaling networks in response to a stimulus determines the physiological outcome. Numerous issues, such as drug resistance and inflammatory reactions in the tumor microenvironment, are implicated in cancer progression, and the role of PTPs in these processes has not been well elucidated. Therefore, the present review focused on discussing the relationship of PTPs with inflammatory cytokines and chemotherapy/targeted drug resistance, providing detailed information on how PTPs can modulate inflammatory reactions and drug resistance to influence progression in HCC.

Cisplatin or Doxorubicin Reduces Cell Viability via the PTPIVA3-JAK2-STAT3 Cascade in Hepatocellular Carcinoma

Introduction

Hepatocellular carcinoma (HCC) accounts for 80% of all liver cancers and is the 2nd leading cause of cancer-related death in Taiwan. Various factors, including rapid cell growth, a high recurrence rate and drug resistance, make HCC difficult to cure. Moreover, the survival rate of advanced HCC patients treated with systemic chemotherapy remains unsatisfactory. Hence, the identification of novel molecular targets and the underlying mechanisms of chemoresistance in HCC and the development more effective therapeutic regimens are desperately needed.

Methods

An MTT assay was used to determine the cell viability after cisplatin or doxorubicin treatment. Western blotting, qRT‒PCR and immunohistochemistry were utilized to examine the protein tyrosine phosphatase IVA3 (PTP4A3) level and associated signaling pathways. ELISA was utilized to analyze the levels of the inflammatory cytokine IL-6 influenced by cisplatin, doxorubicin and PTP4A3 silencing.

Results

In this study, we found that PTP4A3 in the cisplatin/doxorubicin-resistant microarray was closely associated with the overall and recurrence-free survival rates of HCC patients. Cisplatin or doxorubicin significantly reduced cell viability and decreased PTP4A3 expression in hepatoma cells. IL-6 secretion increased with cisplatin or doxorubicin treatment and after PTP4A3 silencing. Furthermore, PTP4A3 was highly expressed in tumor tissues versus adjacent normal tissues from HCC patients. In addition, we evaluated the IL-6-associated signaling pathway involving STAT3 and JAK2, and the levels of p-STAT3, p-JAK2, STAT3 and JAK2 were obviously reduced with cisplatin or doxorubicin treatment in HCC cells using Western blotting and were also decreased after silencing PTP4A3. Collectively, we suggest that cisplatin or doxorubicin decreases HCC cell viability via downregulation of PTP4A3 expression through the IL-6R-JAK2-STAT3 cascade.

Discussion

Therefore, emerging evidence provides a deep understanding of the roles of PTP4A3 in HCC cisplatin/doxorubicin chemoresistance, which can be applied to develop early diagnosis strategies and reveal prognostic factors to establish novel targeted therapeutics to specifically treat HCC.

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.

Anticancer Profile of Rhodanines: Structure-Activity Relationship (SAR) and Molecular Targets-A Review

The rhodanine core is a well-known privileged heterocycle in medicinal chemistry. The rhodanines, as subtypes of thiazolidin-4-ones, show a broad spectrum of biological activity, including anticancer properties. This review aims to analyze the anticancer features of the rhodanines described over the last decade in the scientific literature. The structure–activity relationship of rhodanine derivatives, as well as some of the molecular targets, were discussed. The information contained in this review could be of benefit to the design of new, effective small molecules with anticancer potential among rhodanine derivatives or their related heterocycles.

The double lives of phosphatases of regenerating liver: A structural view of their catalytic and noncatalytic activities

Phosphatases of regenerating liver (PRLs) are protein phosphatases involved in the control of cell growth and migration. They are known to promote cancer metastasis but, despite over 20 years of study, there is still no consensus about their mechanism of action. Recent work has revealed that PRLs lead double lives, acting both as catalytically active enzymes and as pseudophosphatases. The three known PRLs belong to the large family of cysteine phosphatases that form a phosphocysteine intermediate during catalysis. Uniquely to PRLs, this intermediate is stable, with a lifetime measured in hours. As a consequence, PRLs have very little phosphatase activity. Independently, PRLs also act as pseudophosphatases by binding CNNM membrane proteins to regulate magnesium homeostasis. In this function, an aspartic acid from CNNM inserts into the phosphatase catalytic site of PRLs, mimicking a substrate–enzyme interaction. The delineation of PRL pseudophosphatase and phosphatase activities in vivo was impossible until the recent identification of PRL mutants defective in one activity or the other. These mutants showed that CNNM binding was sufficient for PRL oncogenicity in one model of metastasis, but left unresolved its role in other contexts. As the presence of phosphocysteine prevents CNNM binding and CNNM-binding blocks catalytic activity, these two activities are inherently linked. Additional studies are needed to untangle the intertwined catalytic and noncatalytic functions of PRLs. Here, we review the current understanding of the structure and biophysical properties of PRL phosphatases.

Review of anticancer potentials and structure-activity relationships (SAR) of rhodanine derivatives

Rhodanine has been recognized as a privileged scaffold in medicinal chemistry due to its well-known ability to demonstrate a broad range of biological activities. The possibility of structural diversification has contributed to the significance of rhodanine structure in effective drug discovery and design. Many studies have confirmed the potential of rhodanine-derived compounds in the treatment of different types of cancer through the apoptosis induction mechanism. Furthermore, most of the rhodanine derivatives exhibited remarkable anticancer activity in the micromolar range while causing negligible cytotoxicity to normal cells. This review critically describes the anticancer activity profile of reported rhodanine compounds and the structure-activity relationships (SAR) to highlight the value of rhodanine as the core structure for future cancer drug development as well as to assist the researchers in rational drug design.

The dual inhibition against the activity and expression of tyrosine phosphatase PRL-3 from a rhodanine derivative

Increasing evidences demonstrated that PRL-3 was associated with metastatic potential in a variety of cancers including CRC, gastric cancer, ovarian cancer and so on. PRL-3 knock down inhibited the development of metastasis by reducing the size of primary tumors and inhibiting the invasion and growth of cancer cells. Therefore, PRL-3 is a promising diagnostic marker and therapeutic target in tumors. So far, only several PRL-3 inhibitors have been reported. In this study, six rhodanine derivatives were synthesized and characterized. The compounds were evaluated against tyrosine phosphatase PRL-3. Among these compounds, 5-(5-chloro-2-(trifluoromethyl)benzylidene)-2-thioxothiazolidin-4-one (4) could effectively inhibit PRL-3 with IC₅₀ value of 15.22 μM. Fluorescent assays suggested compound 4 tightly bound to tyrosine phosphatase PRL-3 with the molar ratio of 1:1, and the binding constant of 1.74 × 10⁶ M^-1. Compound 4 entered into SW-480 cells, selectively inhibited the expression of PRL-3 and increased the phosphorylation of PRL-3 substrates, and decreased the survival rate of SW-480 cells with IC₅₀ of 6.64 μM and induced apoptosis. The results revealed that compound 4 is a dual functional inhibitor against the activity and expression of PRL-3 and a promising anti-cancer candidate targeting PRL-3.

A screen of FDA-approved drugs identifies inhibitors of protein tyrosine phosphatase 4A3 (PTP4A3 or PRL-3)

Protein tyrosine phosphatase 4A3 (PTP4A3 or PRL-3) is highly expressed in a variety of cancers, where it promotes tumor cell migration and metastasis leading to poor prognosis. Despite its clinical significance, small molecule inhibitors of PRL-3 are lacking. Here, we screened 1443 FDA-approved drugs for their ability to inhibit the activity of the PRL phosphatase family. We identified five specific inhibitors for PRL-3 as well as one selective inhibitor of PRL-2. Additionally, we found nine drugs that broadly and significantly suppressed PRL activity. Two of these broad-spectrum PRL inhibitors, Salirasib and Candesartan, blocked PRL-3-induced migration in human embryonic kidney cells with no impact on cell viability. Both drugs prevented migration of human colorectal cancer cells in a PRL-3 dependent manner and were selective towards PRLs over other phosphatases. In silico modeling revealed that Salirasib binds a putative allosteric site near the WPD loop of PRL-3, while Candesartan binds a potentially novel targetable site adjacent to the CX₅R motif. Inhibitor binding at either of these sites is predicted to trap PRL-3 in a closed conformation, preventing substrate binding and inhibiting function.

Targeting tubulin polymerization and DNA binding of 4-thiazolidinone–umbelliferone hybrids: synthesis and cytotoxicity evaluation

The discovery of a series of combretastatin A-4 inspired novel molecular hybrids of 4-thiazolidinone–umbelliferone as prominent cytotoxic agents was reported.

PRL3-DDX21 Transcriptional Control of Endolysosomal Genes Restricts Melanocyte Stem Cell Differentiation

Melanocytes, replenished throughout life by melanocyte stem cells (MSCs), play a critical role in pigmentation and melanoma. Here, we reveal a function for the metastasis-associated phosphatase of regenerating liver 3 (PRL3) in MSC regeneration. We show that PRL3 binds to the RNA helicase DDX21, thereby restricting productive transcription by RNAPII at master transcription factor (MITF)-regulated endolysosomal vesicle genes. In zebrafish, this mechanism controls premature melanoblast expansion and differentiation from MSCs. In melanoma patients, restricted transcription of this endolysosomal vesicle pathway is a hallmark of PRL3-high melanomas. Our work presents the conceptual advance that PRL3-mediated control of transcriptional elongation is a differentiation checkpoint mechanism for activated MSCs and has clinical relevance for the activity of PRL3 in regenerating tissue and cancer.

Pharmacological characterization of the cardiovascular effect of Nibethione: ex vivo, in vivo and in silico studies

OBJECTIVE

This work describes the vasorelaxant and antihypertensive effects and the mechanism of action on vascular smooth muscle cells of Nibethione, a synthetic thiazolidinedione derivative. Additionally, evidence of its cytotoxicity is assessed.

METHODS

Nibethione (NB) was synthesized, and its vasorelaxant effect and mechanism of action were assessed through ex vivo experiments. Molecular docking studies were used to predict the mode of interaction with L-type Ca²⁺ channel, and in vivo antihypertensive activity was assayed on spontaneously hypertensive rats (SHR). The cytotoxicity potential was evaluated in porcine aortic endothelial cells (PAECs) from primary explants.

KEY FINDINGS

Nibethione vasorelaxant effect was efficient on KCl (80 mm) and NE-contraction. This effect was deleteriously modified in the presence of potassium channel block drugs, while the maximal contraction induced with NE was significantly decreased by NB; the CaCl₂ -induced contraction was abolished entirely. In vivo experiments showed that NB decreased diastolic blood pressure in 20.3 % after its administration on SHR. The molecular docking showed that NB blocks L-type Ca²⁺ channel, and in vitro tests showed that NB did not produce cytotoxic activity on PAECs (IC₅₀ >1000 µm).

CONCLUSIONS

Nibethione showed in vivo antihypertensive and ex vivo vasorelaxant effects with implication of voltage-dependent L-type Ca²⁺ channel blocking, and this may contribute to the research of novel antihypertensive drugs.

Tapping the therapeutic potential of protein tyrosine phosphatase 4A with small molecule inhibitors

Protein tyrosine phosphatases (PTPs) are emerging new targets for drug discovery. PTPs and protein tyrosine kinases (PTKs) maintain cellular homeostasis through opposing roles: tyrosine O-dephosphorylation and -phosphorylation, respectively. An imbalance in the phosphorylation equilibrium results in aberrant protein signaling and pathophysiological conditions. PTPs have historically been considered 'undruggable', in part due to a lack of evidence defining their relationship to disease causality and a focus on purely competitive inhibitors. However, a better understanding of protein-protein interfaces and shallow active sites has recently renewed interest in the pursuit of allosteric and orthosteric modulators of targets outside the major druggable protein families. While their biological mechanism of action still remains to be clarified, PTP4A1-3 (also referred to as PRL1-3) are validated oncology targets and play an important role in cell proliferation, metastasis, and tumor angiogenesis. In this Digest, recent syntheses and structure-activity relationships (SAR) of small molecule inhibitors (SMIs) of PTP4A1-3 are summarized, and enzyme docking studies of the most potent chemotype are highlighted. In particular, the thienopyridone scaffold has emerged as a potent lead structure to interrogate the function and druggability of this dual-specificity PTP.

Hybridized Quinoline Derivatives as Anticancer Agents: Design, Synthesis, Biological Evaluation and Molecular Docking

Objective:

Conjugating quinolones with different bioactive pharmacophores to obtain potent anticancer active agents.

Methods:

Fused pyrazolopyrimidoquinolines 3a-d, Schiff bases 5, 6a-e, two hybridized systems: pyrazolochromenquinoline 7 and pyrazolothiazolidinquinoline 8, different substituted thiazoloquinolines 13-15 and thiazolo[3,2-a]pyridine derivatives 16a-c were synthesized. Their chemical structures were characterized through spectral and elemental analysis, cytotoxic activity on five cancer cell lines, caspase-3 activation, tubulin polymerization inhibition and cell cycle analysis were evaluated.

Results:

Four compounds 3b, 3d, 8 and 13 showed potent activity than doxorubicin on HCT116 and three compounds 3b, 3d and 8 on HEPG2. These promising derivatives showed increase in the level of caspase-3. The trifloromethylphenyl derivatives of pyrazolopyrimidoquinolines 3b and 3d showed considerable tubulin polymerization inhibitory activity. Both compounds arrested cell cycle at G2/M phase and induced apoptosis.

Conclusion:

Compounds 3b and 3d can be considered as promising anticancer active agents with 70% of colchicine activity on tubulin polymerization inhibition and represent hopeful leads that deserve further investigation and optimization.

Cycloaddition reactions for antiviral compounds

Prominent in the current stage of drug development, antiviral compounds can be efficiently prepared through cycloaddition reactions. The chapter reports the use of classical Diels–Alder and their hetero version for the design and synthesis of compounds that were tested for their antiviral activities against a variety of viruses. Furthermore, 1,3-dipolar cycloaddition reactions of selected 1,3-dipoles, such as azides, nitrones, and nitrile oxides, are reviewed in the light of their application in the preparation of key intermediates for antiviral synthesis. A few examples of [2+2] cycloaddition reactions are also presented. The products obtained from these pericyclic reaction approaches were all tested for their activities in terms of blocking the virus replication, and the relevant biological data are highlighted.

Targeting phosphatases of regenerating liver (PRLs) in cancer

The phosphatase of regenerating liver (PRL) family, also known as protein tyrosine phosphatase 4A (PTP4A), are dual-specificity phosphatases with largely unknown cellular functions. However, accumulating evidence indicates that PRLs are oncogenic across a broad variety of human cancers. PRLs are highly expressed in advanced tumors and metastases compared to early stage cancers or matched healthy tissue, and high expression of PRLs often correlates with poor patient prognosis. Consequentially, PRLs have been considered potential therapeutic targets in cancer. Persistent efforts have been made to define their role and mechanism in cancer progression and to create specific PRL inhibitors for basic research and drug development. However, targeting PRLs with small molecules remains challenging due to the highly conserved active site of protein tyrosine phosphatases and a high degree of sequence similarity between the PRL protein families. Here, we review the current PRL inhibitors, including the strategies used for their identification, their biological efficacy, potency, and selectivity, with a special focus on how PRL structure can inform future efforts to develop specific PRL inhibitors.

Photooxygenation of an amino-thienopyridone yields a more potent PTP4A3 inhibitor

The phosphatase PTP4A3 is an attractive anticancer target, but knowledge of its exact role in cells remains incomplete. A potent, structurally novel inhibitor of the PTP4A family was obtained by photooxygenation of a less active, electron-rich thienopyridone (1). Iminothienopyridinedione 13 displays increased solution stability and is readily obtained by two new synthetic routes that converge in the preparation of 1. The late-stage photooxygenation of 1 to give 13 in high yield highlights the potential of this reaction to modify the structure and properties of a biological lead compound and generate value for expanding the scope of an SAR investigation. Analog 13 should become a valuable tool for further exploration of the role of PTP4A3 in tumor progression.

Design, synthesis and biological evaluation of novel pyridine-thiazolidinone derivatives as anticancer agents: Targeting human carbonic anhydrase IX

In order to obtain novel Human carbonic anhydrase IX (CAIX) inhibitors, a series of pyridine-thiazolidinone derivatives was synthesized and characterized by various spectroscopic techniques. The binding affinity of the compounds was measured by fluorescence binding studies and enzyme inhibition activity using esterase assay of CAIX. It was observed that compound 8 and 11 significantly inhibit the CAIX activity with the IC₅₀ value, 1.61 μM and 1.84 μM, respectively. The binding-affinity of compound 8 and 11 for CAIX was significantly high with their K_D values 11.21 μM and 2.32 μM, respectively. Docking studies revealed that compound 8 and 11 efficiently binds in the active site cavity of CA IX by forming sufficient numbers of H-bonds and van der Waals interactions with active side residues. All the compounds were further screened in vitro for anticancer activity and found that compound 8 and 11 exhibit considerable anticancer activity against MCF-7 and HepG-2 cell lines. All these findings suggest that compound 8 and 11 may be further exploited as a novel pharmacophore model for the development of anticancer agents.

Expression of phosphatase of regenerating liver (PRL)-3, is independently associated with biochemical failure, clinical failure and death in prostate cancer

Background

Prostate cancer (PC) stratification needs new prognostic tools to reduce overtreatment. Phosphatase of regenerating liver (PRL-3) is a phosphatase found at high levels in several cancer types, where its expression is associated with survival. A recent PC cell line study has shown it to be involved in PC growth and migration.

Methods

We used a monoclonal antibody to evaluate the expression of PRL-3 in PC tissue of patients in an unselected cohort of 535 prostatectomy patients. We analyzed associations between PRL-3 expression and biochemical failure-free survival (BFFS), clinical failure-free survival (CFFS) and PC death-free survival (PCDFS).

Results

Cytoplasmic PRL-3 staining in tumor cells was significantly correlated to expression of molecules in the VEGFR-axis, but not to the clinicopathological variables. High PRL-3 was not significantly associated with survival in the univariate analysis for BFFS (p = 0.131), but significantly associated with CFFS (p = 0.044) and PCDFS (p = 0.041). In multivariate analysis for the various end points, PRL-3 came out as an independent and significant indicator of poor survival for BFFS (HR = 1.53, CI95% 1.10–2.13, p = 0.012), CFFS (HR = 2.41, CI95% 1.17–4.98, p = 0.017) and PCDFS (HR = 3.99, CI95% 1.21–13.1, p = 0.023).

Conclusions

PRL-3 is independently associated with all PC endpoints in this study. Since high PRL-3 expression also correlates with poor prognosis in other cancers and functional studies in PC support these findings, PRL-3 emerges as a potential treatment target in PC.

5-Ene-4-thiazolidinones - An efficient tool in medicinal chemistry

The presented review is an attempt to summarize a huge volume of data on 5-ene-4-thiazolidinones being a widely studied class of small molecules used in modern organic and medicinal chemistry. The manuscript covers approaches to the synthesis of 5-ene-4-thiazolidinone derivatives: modification of the C5 position of the basic core; synthesis of the target compounds in the one-pot or multistage reactions or transformation of other related heterocycles. The most prominent pharmacological profiles of 5-ene derivatives of different 4-thiazolidinone subtypes belonging to hit-, lead-compounds, drug-candidates and drugs as well as the most studied targets have been discussed. Currently target compounds (especially 5-en-rhodanines) are assigned as frequent hitters or pan-assay interference compounds (PAINS) within high-throughput screening campaigns. Nevertheless, the crucial impact of the presence/nature of C5 substituent (namely 5-ene) on the pharmacological effects of 5-ene-4-thiazolidinones was confirmed by the numerous listed findings from the original articles. The main directions for active 5-ene-4-thiazolidinones optimization have been shown: i) complication of the fragment in the C5 position; ii) introduction of the substituents in the N3 position (especially fragments with carboxylic group or its derivatives); iii) annealing in complex heterocyclic systems; iv) combination with other pharmacologically attractive fragments within hybrid pharmacophore approach. Moreover, the utilization of 5-ene-4-thiazolidinones in the synthesis of complex compounds with potent pharmacological application is described. The chemical transformations cover mainly the reactions which involve the exocyclic double bond in C5 position of the main core and correspond to the abovementioned direction of the 5-ene-4-thiazolidinone modification.

Synthesis and anticancer activity of novel quinazolinone-based rhodanines

Background

Rhodanines and quinazolinones have been reported to possess various pharmacological activities.

Results

A novel series of twenty quinazolinone-based rhodanines were synthesized via Knoevenagel condensation between 4-[3-(substitutedphenyl)-3,4-dihydro-4-oxoquinazolin-2-yl)methoxy]substituted-benzaldehydes and rhodanine. Elemental and spectral analysis were used to confirm structures of the newly synthesized compounds. The newly synthesized compounds were biologically evaluated for in vitro cytotoxic activity against the human fibrosarcoma cell line HT-1080 as a preliminary screen using the MTT assay.

Conclusions

All the target compounds were active, displaying IC₅₀ values roughly in the range of 10–60 µM. Structure–activity relationship study revealed that bulky, hydrophobic, and electron withdrawing substituents at the para-position of the quinazolinone 3-phenyl ring as well as methoxy substitution on the central benzene ring, enhance cytotoxic activity. The four most cytotoxic compounds namely, 45, 43, 47, and 37 were further tested against two human leukemia cell lines namely, HL-60 and K-562 and showed cytotoxic activity in the low micromolar range with compound 45 being the most active, having IC₅₀ values of 1.2 and 1.5 μM, respectively. Interestingly, all four compounds were devoid of cytotoxicity against normal human fibroblasts strain AG01523, indicating that the synthesized rhodanines may be selectively toxic against cancer cells. Mechanistic studies revealed that the most cytotoxic target compounds exhibit pro-apoptotic activity and trigger oxidative stress in cancer cells.

Small molecule targeting of PTPs in cancer

Protein tyrosine phosphatases (PTPs) undeniably have a central role in the development and progression of human cancers. Historically, however, PTPs have not been viewed as privileged drug targets, and progress on identifying potent, selective, and cell-active small molecule PTP inhibitors has suffered accordingly. This situation is rapidly changing, however, due to biochemical advances in the study of PTPs and recent small molecule screening campaigns, which have identified potent and mechanistically diverse lead structures. These compounds are facilitating the exploration of the fundamental cellular processes controlled by PTPs in cancers, and could form the inflection point for new therapeutic paradigms for the treatment of a range of cancers. Herein, we review recent advances in the discovery and biological annotation of cancer-relevant small molecule PTP inhibitors.

Critical Roles of Dual-Specificity Phosphatases in Neuronal Proteostasis and Neurological Diseases

Protein homeostasis or proteostasis is a fundamental cellular property that encompasses the dynamic balancing of processes in the proteostasis network (PN). Such processes include protein synthesis, folding, and degradation in both non-stressed and stressful conditions. The role of the PN in neurodegenerative disease is well-documented, where it is known to respond to changes in protein folding states or toxic gain-of-function protein aggregation. Dual-specificity phosphatases have recently emerged as important participants in maintaining balance within the PN, acting through modulation of cellular signaling pathways that are involved in neurodegeneration. In this review, we will summarize recent findings describing the roles of dual-specificity phosphatases in neurodegeneration and offer perspectives on future therapeutic directions.

Testing the ability of rhodanine and 2, 4-thiazolidinedione to interact with the human pancreatic alpha-amylase: electron-density descriptors complement molecular docking, QM, and QM/MM dynamics calculations

A combined molecular docking, QM, and QM/MM dynamics modeling complemented with electron-density based descriptors computed at the B3LYP/6-311G++(d,p) level of theory have been carried out in order to understand the ability of the drugs rhodanine (RD) and 2,4-thiazolidinedione (TZD) in the effective treatment of type 2 diabetes mellitus. The global HOMO/LUMO descriptors provided just a very rough estimate of the chemical reactivity of both molecules, while the features of electron density studied in terms of its Laplacian and electrostatic potential allowed identifying the local electron rich/poor sites which were associated with the regions of electrophilic/nucleophilic attacks in RD and TZD. These results were thoroughly checked using the novel physically-grounded functional descriptors such as the phase-space Fisher information density and the internal kinetic electronic pressure density, which confirmed the information on bonding and lone electron pair details. The molecular docking, QM, and QM/MM dynamics analyses revealed the detailed picture of interactions of the drugs with the amino acid residues of the active site of the human pancreatic alpha-amylase protein (hPAA). The main difference in behavior of RD and TZD molecules is related to the hydrogen bond between the NH group of the ligand and Asp197. In hPAA complex with RD the proton from the NH group, which carries large positive charge (~ +0.45 e), spontaneously transfers to the carboxyl group of Asp197 and stays there, while in complex with TZD this proton frequently changes its position with the more preferable formation of covalent bond with the N atom. Upon deprotonation of the ligand, its hydrogen bonds with Arg195 and His299 become stronger. This process influences the binding with the difference of the binding constants of RD and TZD about 200 times with the higher value corresponding to the RD molecule. Thus, the cumulative results lead to the conclusion that rhodanine would have a higher binding affinity than the 2,4-thiazolidinedione molecule in the active site of human pancreatic alpha-amylase.

Sulfamic acid catalyzed one-pot, three-component green approach: synthesis and cytotoxic evaluation of pyrazolyl-thiazole congeners

A one-pot multi-component protocol has been developed for the synthesis of biologically important pyrazolyl-thiazoles using sulfamic acid as a green catalyst in water.

Discovery and Evaluation of PRL Trimer Disruptors for Novel Anticancer Agents

Overexpression of PRL phosphatases (PRL1, PRL2, and PRL3) has been found in a variety of late-stage tumors and their distant metastatic sites. Therefore, the oncogenic PRL phosphatases represent intriguing targets for cancer therapy. There is considerable interest in identifying small molecule inhibitors targeting PRLs as novel anticancer agents. However, it has been difficult to acquire phosphatase activity-based PRL inhibitors due to the unusual wide and shallow catalytic pockets of PRLs revealed by crystal structure studies. Here, we present a novel method to identify PRL1 inhibitors by targeting the PRL1 trimer interface and the procedure to characterize their biochemical and cellular activity.

Molecular modeling, in silico screening and molecular dynamics of PfPRL-PTP of P. falciparum for identification of potential anti-malarials

Millions of deaths occur every year due to malaria. Growing resistance against existing drugs for treatment of malaria has exaggerated the problem further. There is an intense demand of identifying drug targets in malaria parasite. PfPRL-PTP protein is PRL group of phosphatase, and one of the interesting drug targets being involved in three important pathways of malaria parasite (secretion, phosphorylation, and prenylation). Therefore, in this study, we have modeled three-dimensional structure of PfPRL-PTP followed by validation of 3D structure using RAMPAGE, verify3D, and other structure validation tools. We could identify 12 potential inhibitory compounds using in silico screening of NCI library against PfPRL-PTP with Glide. The molecular dynamics simulation was also performed using GROMACS on PfPRL-PTP model alone and PfPRL-PTP-inhibitor complex. This study of identifying potential drug-like molecules would add up to the process of drug discovery against malaria parasite.

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.

Design, synthesis and biological evaluation of novel diphenylthiazole-based cyclooxygenase inhibitors as potential anticancer agents

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely used medications as analgesics and antipyretics. Currently, there is a growing interest in their antitumor activity and their ability to reduce the risk and mortality of several cancers. While several studies revealed the ability of NSAIDs to induce apoptosis and inhibit angiogenesis in cancer cells, their exact anticancer mechanism is not fully understood. However, both cyclooxygenase (COX)-dependent and -independent pathways were reported to have a role. In an attempt to develop new anticancer agents, a series of diphenylthiazole substituted thiazolidinone derivatives was synthesized and evaluated for their anticancer activity against a panel of cancer cell lines. Additionally, the inhibitory activity of the synthesized derivatives against COX enzymes was investigated as a potential mechanism for the anticancer activity. Cytotoxicity assay results showed that compounds 15b and 16b were the most potent anticancer agents with half maximal inhibitory concentrations (IC50) between 8.88 and 19.25μM against five different human cancer cell lines. Interestingly, COX inhibition assay results were in agreement with that of the cytotoxicity assays where the most potent anticancer compounds showed good COX-2 inhibition comparable to that of celecoxib. Further support to our results were gained by the docking studies which suggested the ability of compound 15b to bind into COX-2 enzyme with low energy scores. Collectively, these results demonstrated the promising activity of the newly designed compounds as leads for subsequent development into potential anticancer agents.

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.

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Computational ligand- and docking-based approaches were tested for PRL-3 as a target.

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Ligand-based screening was proven a feasible approach for PRL-3 inhibitor discovery.

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A low micromolar, non-competitive inhibitor with novel chemotype for PRLs was discovered.

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The inhibitor efficiently blocks PRL induced cell migration.

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The inhibitor is non-cytotoxic, commercially available and suitable for fluorescence microscopy applications.

Synthesis and biological evaluation of new rhodanine analogues bearing 2-chloroquinoline and benzo[h]quinoline scaffolds as anticancer agents

Several rhodanine derivatives (9-39) were synthesized for evaluation of their potential as anticancer agents. Villsmeier cyclization to synthesize aza-aromatic aldehydes, rhodanine derivatives preparation and Knoevenagel type of condensation between the rhodanines and aza-aromatic aldehydes are key steps used for the synthesis of 31 compounds. In vitro antiproliferative activity of the synthesized rhodanine derivatives (9-39) was studied on a panel of six human tumor cell lines viz. HGC, MNK-74, MCF-7, MDAMB-231, DU-145 and PC-3 cell lines. Some of the compounds were capable of inhibiting the proliferation of cancer cell lines at a micromolar concentration. Six compounds are found to be potent against HGC cell lines; compound 15 is found to be active against HGC - Gastric, MCF7 - Breast Cancer and DU145 - Prostate Cancer cell lines; compound 39 is potent against MNK-74; four compounds are found to be potent against MCF-7 cell lines; three compounds are active against MDAMB-231; nine compounds are found to be potent against DU-145; three compounds are active against PC-3 cell lines. These compounds constitute a promising starting point for the development of novel and more potent anticancer agents in future.

Dual-specificity phosphatases as molecular targets for inhibition in human disease

SIGNIFICANCE

The dual-specificity phosphatases (DUSPs) constitute a heterogeneous group of cysteine-based protein tyrosine phosphatases, whose members exert a pivotal role in cell physiology by dephosphorylation of phosphoserine, phosphothreonine, and phosphotyrosine residues from proteins, as well as other non-proteinaceous substrates.

RECENT ADVANCES

A picture is emerging in which a selected group of DUSP enzymes display overexpression or hyperactivity that is associated with human disease, especially human cancer, making feasible targeted therapy approaches based on their inhibition. A panoply of molecular and functional studies on DUSPs have been performed in the previous years, and drug-discovery efforts are ongoing to develop specific and efficient DUSP enzyme inhibitors. This review summarizes the current status on inhibitory compounds targeting DUSPs that belong to the MAP kinase phosphatases-, small-sized atypical-, and phosphatases of regenerating liver subfamilies, whose inhibition could be beneficial for the prevention or mitigation of human disease.

CRITICAL ISSUES

Achieving specificity, potency, and bioavailability are the major challenges in the discovery of DUSP inhibitors for the clinics. Clinical validation of compounds or alternative inhibitory strategies of DUSP inhibition has yet to come.

FUTURE DIRECTIONS

Further work is required to understand the dual role of many DUSPs in human cancer, their function-structure properties, and to identify their physiologic substrates. This will help in the implementation of therapies based on DUSPs inhibition.