Stabilization of Motin family proteins in NF2-deficient cells prevents full activation of YAP/TAZ and rapid tumorigenesis

A Recent Overview of Molecular Pathways in Synthetic Lethality as a Proposed Valid Target in Oncology: Current Insights and Future Directions

Earlier conducted systematic reviews have focused on the important impact of synthetic lethality (SL) application in managing various types of tumors, classifying SL, methods for assessment, and technological advances in SL inhibitions and examining the preclinical and clinical landscape of SL cancer biology, and neither of those investigations presented the molecular pathway description of the recommended lethal target of SL in cancer. Out of 36 gene expression omnibus (GEO) database sets selected from 343 retrieved (2023 to 2024), 11 were excluded, and 25 were included in the study and presented in the review. Beyond the search, few interesting database sets comprising interesting molecular pathway were included in minority. Molecular pathways pictures of the proposed SL targets for the cancer condition were prepared for lucid understanding of the oncology disease fundamental mechanism behind the SL concept. SL approach benefits have been demonstrated in cancer. Thus, the current exploration suggests that SL approach of molecular investigations should be expanded to include other specialists including cardiovascular and nephrology to fully explore the benefits of society.

Targeting the PARylation-Dependent Ubiquitination Signaling Pathway for Cancer Therapies

Poly(ADP-ribosyl)ation (PARylation) is a dynamic protein post-translational modification (PTM) mediated by ADP-ribosyltransferases (ARTs), which regulates a plethora of essential biological processes, such as DNA repair, gene expression, and signal transduction. Among these, PAR-dependent ubiquitination (PARdU) plays a pivotal role in tagging PARylated substrates for subsequent ubiquitination and degradation events through the coordinated action of enzymes, including the E3 ligase RNF146 and the ADP-ribosyltransferase tankyrase. Notably, this pathway has emerged as a key regulator of tumorigenesis, immune modulation, and cell death. This review elucidates the molecular mechanisms of the PARdU pathway, including the RNF146-tankyrase interaction, substrate specificity, and upstream regulatory pathways. It also highlights the biological functions of PARdU in DNA damage repair, signaling pathways, and metabolic regulation, with a focus on its therapeutic potential in cancer treatment. Strategies targeting PARdU, such as tankyrase and RNF146 inhibitors, synthetic lethality approaches, and immune checkpoint regulation, offer promising avenues for precision oncology. These developments underscore the potential of PARdU as a transformative therapeutic target in combating various types of human cancer.

CRISPR-Cas9 screening identifies the role of FER as a tumor suppressor

It is important to systematically identify tumor suppressor genes (TSGs) to improve our understanding of tumorigenesis and develop strategies for early diagnosis and mitigating disease progression. In the present study, we used an in vivo genome-wide clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) screen and identified FPS/FES-related (FER) as a TSG. Single-cell RNA sequencing (scRNA-seq) revealed that normal cells with low FER expression exhibited elevated malignant transformation potential and stemness properties. FER knockout promoted the tumorigenic transformation, characterized by high colony-forming efficiency and suspension growth ability, acquired tumorigenicity in vivo, increased metabolic activity, dedifferentiation properties, and immune evasion. Moreover, analysis revealed that low FER expression tumors share molecular phenotypes with FER knockout cells, suggesting the consistent role of FER in tumor initiation and progression. Taken together, our findings not only provide insights into the essential role of FER as a tumor suppressor in tumor initiation and progression but also highlight its potential as a target for future clinical diagnosis. © 2024 The Pathological Society of Great Britain and Ireland.

WWC proteins-mediated compensatory mechanism restricts schwannomatosis driven by NF2 loss of function

NF2-related schwannomatosis, previously known as neurofibromatosis type 2, is a genetic disorder characterized by nerve tumors due to NF2 gene mutations. Mice with Nf2 deletion develop schwannomas slowly with low penetrance, hence inconvenient for preclinical studies. Here, we show that NF2, by recruiting E3 ubiquitin ligases β-TrCP1/2, promotes WWC1-3 ubiquitination and degradation. In NF2 mutated cells, WWC1-3 accumulation is a compensatory mechanism to prevent YAP/TAZ hyperactivation and rapid tumorigenesis. Accordingly, we generate a synthetic mouse model with complete penetrance and short latency by concurrently deleting Nf2 and Wwc1/2 in Schwann cells. This model closely resembles NF2-related schwannomatosis in patients, as confirmed by histological and single-cell transcriptome analysis. Moreover, a cell line from mouse schwannomas and a syngeneic tumor model in immune-competent mice are established. Furthermore, a screen using established models has identified candidate drugs that effectively suppress schwannoma progression. Hence, this work has developed rapid and transplantable models that will facilitate both basic and translational research on NF2-related schwannomatosis.

Angiomotin cleavage promotes leader formation and collective cell migration

Collective cell migration (CCM) is involved in multiple biological processes, including embryonic morphogenesis, angiogenesis, and cancer invasion. However, the molecular mechanisms underlying CCM, especially leader cell formation, are poorly understood. Here, we show that a signaling pathway regulating angiomotin (AMOT) cleavage plays a role in CCM, using mammalian epithelial cells and mouse models. In a confluent epithelial monolayer, full-length AMOT localizes at cell-cell junctions and limits cell motility. After cleavage, the C-terminal fragment of AMOT (AMOT-CT) translocates to the cell-matrix interface to promote the maturation of focal adhesions (FAs), generate traction force, and induce leader cell formation. Meanwhile, decreased full-length AMOT at cell-cell junctions leads to tissue fluidization and coherent migration of cell collectives. Hence, the cleavage of AMOT serves as a molecular switch to generate polarized contraction, promoting leader cell formation and CCM.

Yap methylation-induced FGL1 expression suppresses anti-tumor immunity and promotes tumor progression in KRAS-driven lung adenocarcinoma

BACKGROUND

Despite significant strides in lung cancer immunotherapy, the response rates for Kirsten rat sarcoma viral oncogene homolog (KRAS)-driven lung adenocarcinoma (LUAD) patients remain limited. Fibrinogen-like protein 1 (FGL1) is a newly identified immune checkpoint target, and the study of related resistance mechanisms is crucial for improving the treatment outcomes of LUAD patients. This study aimed to elucidate the potential mechanism by which FGL1 regulates the tumor microenvironment in KRAS-mutated cancer.

METHODS

The expression levels of FGL1 and SET1 histone methyltransferase (SET1A) in lung cancer were assessed using public databases and clinical samples. Lentiviruses were constructed for transduction to overexpress or silence FGL1 in lung cancer cells and mouse models. The effects of FGL1 and Yes-associated protein (Yap) on the immunoreactivity of cytotoxic T cells in tumor tissues were evaluated using immunofluorescence staining and flow cytometry. Chromatin immunoprecipitation and dual luciferase reporter assays were used to study the SET1A-directed transcriptional program.

RESULTS

Upregulation of FGL1 expression in KRAS-mutated cancer was inversely correlated with the infiltration of CD8+ T cells. Mechanistically, KRAS activated extracellular signal-regulated kinase 1/2 (ERK1/2), which subsequently phosphorylated SET1A and increased its stability and nuclear localization. SET1A-mediated methylation of Yap led to Yap sequestration in the nucleus, thereby promoting Yap-induced transcription of FGL1 and immune evasion in KRAS-driven LUAD. Notably, dual blockade of programmed cell death-1 (PD-1) and FGL1 further increased the therapeutic efficacy of anti-PD-1 immunotherapy in LUAD patients.

CONCLUSION

FGL1 could be used as a diagnostic biomarker of KRAS-mutated lung cancer, and targeting the Yap-FGL1 axis could increase the efficacy of anti-PD-1 immunotherapy.

Gene therapy for diffuse pleural mesotheliomas in preclinical models by concurrent expression of NF2 and SuperHippo

Diffuse pleural mesothelioma (DPM) is a lethal cancer with a poor prognosis and limited treatment options. The Hippo signaling pathway genes, such as NF2 and LATS1/2, are frequently mutated in DPM, indicating a tumor suppressor role in the development of DPM. Here, we show that in DPM cell lines lacking NF2 and in mice with a conditional Nf2 knockout, downregulation of WWC proteins, another family of Hippo pathway regulators, accelerates DPM progression. Conversely, the expression of SuperHippo, a WWC-derived minigene, effectively enhances Hippo signaling and suppresses DPM development. Moreover, the adeno-associated virus serotype 6 (AAV6) has been engineered to deliver both NF2 and SuperHippo genes into mesothelial cells, which substantially impedes tumor growth in xenograft and genetic DPM models and prolongs the median survival of mice. These findings serve as a proof of concept for the potential use of gene therapy targeting the Hippo pathway to treat DPM.

Angiomotin family proteins in the Hippo signaling pathway

The Motin family proteins (Motins) are a class of scaffolding proteins consisting of Angiomotin (AMOT), AMOT-like protein 1 (AMOTL1), and AMOT-like protein 2 (AMOTL2). Motins play a pivotal role in angiogenesis, tumorigenesis, and neurogenesis by modulating multiple cellular signaling pathways. Recent findings indicate that Motins are components of the Hippo pathway, a signaling cascade involved in development and cancer. This review discusses how Motins are integrated into the Hippo signaling network, as either upstream regulators or downstream effectors, to modulate cell proliferation and migration. The repression of YAP/TAZ by Motins contributes to growth inhibition, whereas subcellular localization of Motins and their interactions with actin fibers are critical in regulating cell migration. The net effect of Motins on cell proliferation and migration may contribute to their diverse biological functions.

NF2-Related Schwannomatosis (NF2): Molecular Insights and Therapeutic Avenues

NF2-related schwannomatosis (NF2) is a genetic syndrome characterized by the growth of benign tumors in the nervous system, particularly bilateral vestibular schwannomas, meningiomas, and ependymomas. This review consolidates the current knowledge on NF2 syndrome, emphasizing the molecular pathology associated with the mutations in the gene of the same name, the NF2 gene, and the subsequent dysfunction of its product, the Merlin protein. Merlin, a tumor suppressor, integrates multiple signaling pathways that regulate cell contact, proliferation, and motility, thereby influencing tumor growth. The loss of Merlin disrupts these pathways, leading to tumorigenesis. We discuss the roles of another two proteins potentially associated with NF2 deficiency as well as Merlin: Yes-associated protein 1 (YAP), which may promote tumor growth, and Raf kinase inhibitory protein (RKIP), which appears to suppress tumor development. Additionally, this review discusses the efficacy of various treatments, such as molecular therapies that target specific pathways or inhibit neomorphic protein-protein interaction caused by NF2 deficiency. This overview not only expands on the fundamental understanding of NF2 pathophysiology but also explores the potential of novel therapeutic targets that affect the clinical approach to NF2 syndrome.

The Hippo signaling pathway in development and regeneration

The Hippo signaling pathway is a central growth control mechanism in multicellular organisms. By integrating diverse mechanical, biochemical, and stress cues, the Hippo pathway orchestrates proliferation, survival, differentiation, and mechanics of cells, which in turn regulate organ development, homeostasis, and regeneration. A deep understanding of the regulation and function of the Hippo pathway therefore holds great promise for developing novel therapeutics in regenerative medicine. Here, we provide updates on the molecular organization of the mammalian Hippo signaling network, review the regulatory signals and functional outputs of the pathway, and discuss the roles of Hippo signaling in development and regeneration.

RNF166 promotes colorectal cancer progression by recognizing and destabilizing poly-ADP-ribosylated angiomotins

Activation of the Hippo pathway by angiomotins to limit colorectal cancer progression is prevalent, whereas the regulation of angiomotins remains elusive. In this study, we uncover the involvement of an upregulated E3 ubiquitin ligase called RNF166, which destabilizes angiomotins, activates YAP, and is associated with a poor prognosis in colorectal cancer patients. Mechanistically, RNF166 specifically recognizes PARsylated angiomotin, a modification mediated by tankyrase at specific amino acid residues (D506, E513, E516, and E528). The tankyrase inhibitor XAV939, effectively prevents RNF166-dependent destabilization of angiomotins and subsequent activation of YAP. Additionally, YAP-5SA, a constitutively active form of YAP, rescues colorectal cancer progression following knockdown of RNF166. Importantly, the C-terminus of RNF66, particularly the Di19-ZF domain, is the crucial region responsible for recognizing ADP-ribosylated angiomotins. Together, this work not only sheds light on the regulation of the Hippo pathway in colorectal cancer but also uncovers a novel poly(ADP-ribose)-binding domain, which may serve as a potential therapeutic target for intervention.

miR-3133 inhibits gastrointestinal cancer progression through activation of Hippo and p53 signalling pathways via multi-targets

BACKGROUND

Malignant cell growth and chemoresistance, the main obstacles in treating gastrointestinal cancer (GIC), rely on the Hippo and p53 signalling pathways. However, the upstream regulatory mechanisms of these pathways remain complex and poorly understood.

METHODS

Immunohistochemistry (IHC), western blot and RT-qPCR were used to analyse the expression of RNF146, miR-3133 and key components of Hippo and p53 pathway. CCK-8, colony formation, drug sensitivity assays and murine xenograft models were used to investigate the effect of RNF146 and miR-3133 in GIC. Further exploration of the upstream regulatory mechanism was performed using bioinformatics analysis, dual-luciferase reporter gene, immunoprecipitation assays and bisulfite sequencing PCR (BSP).

RESULTS

Clinical samples, in vitro and in vivo experiments demonstrated that RNF146 exerts oncogenic effects in GIC by regulating the Hippo pathway. Bioinformatics analysis identified a novel miRNA, miR-3133, as an upstream regulatory factor of RNF146. fluorescence in situ hybridization and RT-qPCR assays revealed that miR-3133 was less expressed in gastrointestinal tumour tissues and was associated with adverse pathological features. Functional assays and animal models showed that miR-3133 promoted the proliferation and chemotherapy sensitivity of GIC cells. miR-3133 affected YAP1 protein expression by targeting RNF146, AGK and CUL4A, thus activating the Hippo pathway. miR-3133 inhibited p53 protein degradation and extended p53's half-life by targeting USP15, SPIN1. BSP experiments confirmed that miR-3133 promoter methylation is an important reason for its low expression.

CONCLUSION

miR-3133 inhibits GIC progression by activating the Hippo and p53 signalling pathways via multi-targets, including RNF146, thereby providing prognostic factors and valuable potential therapeutic targets for GIC.

Proteolytic activation of angiomotin by DDI2 promotes angiogenesis

The scaffolding protein angiomotin (AMOT) is indispensable for vertebrate embryonic angiogenesis. Here, we report that AMOT undergoes cleavage in the presence of lysophosphatidic acid (LPA), a lipid growth factor also involved in angiogenesis. AMOT cleavage is mediated by aspartic protease DNA damage-inducible 1 homolog 2 (DDI2), and the process is tightly regulated by a signaling axis including neurofibromin 2 (NF2), tankyrase 1/2 (TNKS1/2), and RING finger protein 146 (RNF146), which induce AMOT membrane localization, poly ADP ribosylation, and ubiquitination, respectively. In both zebrafish and mice, the genetic inactivation of AMOT cleavage regulators leads to defective angiogenesis, and the phenotype is rescued by the overexpression of AMOT-CT, a C-terminal AMOT cleavage product. In either physiological or pathological angiogenesis, AMOT-CT is required for vascular expansion, whereas uncleavable AMOT represses this process. Thus, our work uncovers a signaling pathway that regulates angiogenesis by modulating a cleavage-dependent activation of AMOT.

WWC1/2 regulate spinogenesis and cognition in mice by stabilizing AMOT

WWC1 regulates episodic learning and memory, and genetic nucleotide polymorphism of WWC1 is associated with neurodegenerative diseases such as Alzheimer's disease. However, the molecular mechanism through which WWC1 regulates neuronal function has not been fully elucidated. Here, we show that WWC1 and its paralogs (WWC2/3) bind directly to angiomotin (AMOT) family proteins (Motins), and recruit USP9X to deubiquitinate and stabilize Motins. Deletion of WWC genes in different cell types leads to reduced protein levels of Motins. In mice, neuron-specific deletion of Wwc1 and Wwc2 results in reduced expression of Motins and lower density of dendritic spines in the cortex and hippocampus, in association with impaired cognitive functions such as memory and learning. Interestingly, ectopic expression of AMOT partially rescues the neuronal phenotypes associated with Wwc1/2 deletion. Thus, WWC proteins modulate spinogenesis and cognition, at least in part, by regulating the protein stability of Motins.

Two Hippo signaling modules orchestrate liver size and tumorigenesis

The Hippo pathway is a central regulator of organ size and tumorigenesis and is commonly depicted as a kinase cascade, with an increasing number of regulatory and adaptor proteins linked to its regulation over recent years. Here, we propose that two Hippo signaling modules, MST1/2-SAV1-WWC1-3 (HPO1) and MAP4K1-7-NF2 (HPO2), together regulate the activity of LATS1/2 kinases and YAP/TAZ transcriptional co-activators. In mouse livers, the genetic inactivation of either HPO1 or HPO2 module results in partial activation of YAP/TAZ, bile duct hyperplasia, and hepatocellular carcinoma (HCC). On the contrary, inactivation of both HPO1 and HPO2 modules results in full activation of YAP/TAZ, rapid development of intrahepatic cholangiocarcinoma (iCCA), and early lethality. Interestingly, HPO1 has a predominant role in regulating organ size. HPO1 inactivation causes a homogenous YAP/TAZ activation and cell proliferation across the whole liver, resulting in a proportional and rapid increase in liver size. Thus, this study has reconstructed the order of the Hippo signaling network and suggests that LATS1/2 and YAP/TAZ activities are finetuned by HPO1 and HPO2 modules to cause different cell fates, organ size changes, and tumorigenesis trajectories.

Inhibition of YAP/TAZ-driven TEAD activity prevents growth of NF2-null schwannoma and meningioma

Schwannoma tumours typically arise on the eighth cranial nerve and are mostly caused by loss of the tumour suppressor Merlin (NF2). There are no approved chemotherapies for these tumours and the surgical removal of the tumour carries a high risk of damage to the eighth or other close cranial nerve tissue. New treatments for schwannoma and other NF2-null tumours such as meningioma are urgently required. Using a combination of human primary tumour cells and mouse models of schwannoma, we have examined the role of the Hippo signalling pathway in driving tumour cell growth. Using both genetic ablation of the Hippo effectors YAP and TAZ as well as novel TEAD palmitoylation inhibitors, we show that Hippo signalling may be successfully targeted in vitro and in vivo to both block and, remarkably, regress schwannoma tumour growth. In particular, successful use of TEAD palmitoylation inhibitors in a preclinical mouse model of schwannoma points to their potential future clinical use. We also identify the cancer stem cell marker aldehyde dehydrogenase 1A1 (ALDH1A1) as a Hippo signalling target, driven by the TAZ protein in human and mouse NF2-null schwannoma cells, as well as in NF2-null meningioma cells, and examine the potential future role of this new target in halting schwannoma and meningioma tumour growth.

The Regulation and Double-Edged Roles of the Deubiquitinase OTUD5

OTUD5 (OTU Deubiquitinase 5) is a functional cysteine protease with deubiquitinase activity and is a member of the ovarian tumor protease (OTU) family. OTUD5 is involved in the deubiquitination of many key proteins in various cellular signaling pathways and plays an important role in maintaining normal human development and physiological functions. Its dysfunction can affect physiological processes, such as immunity and DNA damage repair, and it can even lead to tumors, inflammatory diseases and genetic disorders. Therefore, the regulation of OTUD5 activity and expression has become a hot topic of research. A comprehensive understanding of the regulatory mechanisms of OTUD5 and its use as a therapeutic target for diseases is of great value. Herein, we review the physiological processes and molecular mechanisms of OTUD5 regulation, outline the specific regulatory processes of OTUD5 activity and expression, and link OTUD5 to diseases from the perspective of studies on signaling pathways, molecular interactions, DNA damage repair and immune regulation, thus providing a theoretical basis for future studies.

Single-Cell RNA-Seq Reveals Heterogeneity of Cell Communications between Schwann Cells and Fibroblasts within Vestibular Schwannoma Microenvironment

Vestibular schwannomas (VSs), which develop from Schwann cells (SCs) of the vestibular nerve, are the most prevalent benign tumors of the cerebellopontine angle and internal auditory canal. Despite advances in treatment, the cellular components and mechanisms of VS tumor progression remain unclear. Herein, single-cell RNA-sequencing was performed on clinically surgically isolated VS samples and their cellular composition, including the heterogeneous SC subtypes, was determined. Advanced bioinformatics analysis revealed the associated biological functions, pseudotime trajectory, and transcriptional network of the SC subgroups. A tight intercellular communication between SCs and tumor-associated fibroblasts via integrin and growth factor signaling was observed and the gene expression differences in SCs and fibroblasts were shown to determine the heterogeneity of cellular communication in different individuals. These findings suggest a microenvironmental mechanism underlying the development of VS.

Transmembrane protein KIRREL1 regulates Hippo signaling via a feedback loop and represents a therapeutic target in YAP/TAZ-active cancers

The Hippo tumor-suppressor pathway is frequently dysregulated in human cancers and represents a therapeutic target. However, strategies targeting the mammalian Hippo pathway are limited because of the lack of a well-established cell-surface regulator. Here, we show that transmembrane protein KIRREL1, by interacting with both SAV1 and LATS1/2, promotes LATS1/2 activation by MST1/2 (Hippo kinases), and LATS1/2 activation, in turn, inhibits activity of YAP/TAZ oncoproteins. Conversely, YAP/TAZ directly induce the expression of KIRREL1 in a TEAD1-4-dependent manner. Indeed, KIRREL1 expression positively correlates with canonical YAP/TAZ target gene expression in clinical tumor specimens and predicts poor prognosis. Moreover, transgenic expression of KIRREL1 effectively blocks tumorigenesis in a mouse intrahepatic cholangiocarcinoma model, indicating a tumor-suppressor role of KIRREL1. Hence, KIRREL1 constitutes a negative feedback mechanism regulating the Hippo pathway and serves as a cell-surface marker and potential drug target in cancers with YAP/TAZ dependency.