The regulation of oncogenic Ras/ERK signalling by dual-specificity mitogen activated protein kinase phosphatases (MKPs)

Targeting the RAS upstream and downstream signaling pathway for Cancer treatment

Cancer often involves the overactivation of RAS/RAF/MEK/ERK (MAPK) and PI3K-Akt-mTOR pathways due to mutations in genes like RAS, RAF, PTEN, and PIK3CA. Various strategies are employed to address the overactivation of these pathways, among which targeted therapy emerges as a promising approach. Directly targeting specific proteins, leads to encouraging results in cancer treatment. For instance, RTK inhibitors such as imatinib and afatinib selectively target these receptors, hindering ligand binding and reducing signaling initiation. These inhibitors have shown potent efficacy against Non-Small Cell Lung Cancer. Other inhibitors, like lonafarnib targeting Farnesyltransferase and GGTI 2418 targeting geranylgeranyl Transferase, disrupt post-translational modifications of proteins. Additionally, inhibition of proteins like SOS, SH2 domain, and Ras demonstrate promising anti-tumor activity both in vivo and in vitro. Targeting downstream components with RAF inhibitors such as vemurafenib, dabrafenib, and sorafenib, along with MEK inhibitors like trametinib and binimetinib, has shown promising outcomes in treating cancers with BRAF-V600E mutations, including myeloma, colorectal, and thyroid cancers. Furthermore, inhibitors of PI3K (e.g., apitolisib, copanlisib), AKT (e.g., ipatasertib, perifosine), and mTOR (e.g., sirolimus, temsirolimus) exhibit promising efficacy against various cancers such as Invasive Breast Cancer, Lymphoma, Neoplasms, and hematological malignancies. This review offers an overview of small molecule inhibitors targeting specific proteins within the RAS upstream and downstream signaling pathways in cancer.

Alcohol Consumption During Adolescence Alters the Cognitive Function in Adult Male Mice by Persistently Increasing Levels of DUSP6

Binge alcohol drinking during adolescence has long-term effects on the adult brain that alter brain structure and behaviors, but the underlying mechanisms remain poorly understood. Extracellular signal-regulated kinase (ERK) is involved in the synaptic plasticity and pathological brain injury by regulating the expression of cyclic adenosine monophosphate response element binding protein (CREB) and brain-derived neurotrophic factor (BDNF). Dual-specificity phosphatase 6 (DUSP6) is a critical effector that dephosphorylates ERK1/2 to control the basal tone, amplitude, and duration of ERK signaling. To explore DUSP6 as a regulator of ERK signaling in the mPFC and its impact on long-term effects of alcohol, a male mouse model of adolescent intermittent alcohol (AIA) exposure was established. Behavioral experiments showed that AIA did not affect anxiety-like behavior or sociability in adulthood, but significantly damaged new object recognition and social recognition memory. Molecular studies further found that AIA reduced the levels of pERK-pCREB-BDNF-PSD95/NR2A involved in synaptic plasticity, while DUSP6 was significantly increased. Intra-mPFC infusion of AAV-DUSP6-shRNA restored the dendritic spine density and postsynaptic density thickness by reversing the level of p-ERK and its downstream molecular expression, and ultimately repaired adult cognitive impairment caused by chronic alcohol exposure during adolescence. These findings indicate that AIA exposure inhibits ERK-CREB-BDNF-PSD95/NR2A by increasing DUSP6 in the mPFC in adulthood that may be associated with long-lasting cognitive deficits.

Signaling pathways in liver cancer: pathogenesis and targeted therapy

Liver cancer remains one of the most prevalent malignancies worldwide with high incidence and mortality rates. Due to its subtle onset, liver cancer is commonly diagnosed at a late stage when surgical interventions are no longer feasible. This situation highlights the critical role of systemic treatments, including targeted therapies, in bettering patient outcomes. Despite numerous studies on the mechanisms underlying liver cancer, tyrosine kinase inhibitors (TKIs) are the only widely used clinical inhibitors, represented by sorafenib, whose clinical application is greatly limited by the phenomenon of drug resistance. Here we show an in-depth discussion of the signaling pathways frequently implicated in liver cancer pathogenesis and the inhibitors targeting these pathways under investigation or already in use in the management of advanced liver cancer. We elucidate the oncogenic roles of these pathways in liver cancer especially hepatocellular carcinoma (HCC), as well as the current state of research on inhibitors respectively. Given that TKIs represent the sole class of targeted therapeutics for liver cancer employed in clinical practice, we have particularly focused on TKIs and the mechanisms of the commonly encountered phenomena of its resistance during HCC treatment. This necessitates the imperative development of innovative targeted strategies and the urgency of overcoming the existing limitations. This review endeavors to shed light on the utilization of targeted therapy in advanced liver cancer, with a vision to improve the unsatisfactory prognostic outlook for those patients.

Reporter cell lines to screen for inhibitors or regulators of the KRAS-RAF-MEK1/2-ERK1/2 pathway

The RAS-regulated RAF-MEK1/2-ERK1/2 signalling pathway is activated in cancer due to mutations in RAS proteins (especially KRAS), BRAF, CRAF, MEK1 and MEK2. Whilst inhibitors of KRASG12C (lung adenocarcinoma) and BRAF and MEK1/2 (melanoma and colorectal cancer) are clinically approved, acquired resistance remains a problem. Consequently, the search for new inhibitors (especially of RAS proteins), new inhibitor modalities and regulators of this pathway, which may be new drug targets, continues and increasingly involves cell-based screens with small molecules or genetic screens such as RNAi, CRISPR or protein interference. Here we describe cell lines that exhibit doxycycline-dependent expression KRASG12V or BRAFV600E and harbour a stably integrated EGR1:EmGFP reporter gene that can be detected by flow cytometry, high-content microscopy or immunoblotting. KRASG12V or BRAFV600E-driven EmGFP expression is inhibited by MEK1/2 or ERK1/2 inhibitors (MEKi and ERKi). BRAFi inhibit BRAFV600E-driven EmGFP expression but enhance the response to KRASG12V, recapitulating paradoxical activation of wild type RAF proteins. In addition to small molecules, expression of iDab6, encoding a RAS-specific antibody fragment inhibited KRASG12V- but not BRAFV600E-driven EmGFP expression. Finally, substitution of EmGFP for a bacterial nitroreductase gene allowed KRASG12V or BRAFV600E to drive cell death in the presence of a pro-drug, which may allow selection of pathway inhibitors that promote survival. These cell lines should prove useful for cell-based screens to identify new regulators of KRAS- or BRAF-dependent ERK1/2 signalling (drug target discovery) as well as screening or triaging 'hits' from drug discovery screens.

Combined KRAS-MAPK pathway inhibitors and HER2-directed drug conjugate is efficacious in pancreatic cancer

Targeting the mitogen-activated protein kinase (MAPK) cascade in pancreatic ductal adenocarcinoma (PDAC) remains clinically unsuccessful. We aim to develop a MAPK inhibitor-based therapeutic combination with strong preclinical efficacy. Utilizing a reverse-phase protein array, we observe rapid phospho-activation of human epidermal growth factor receptor 2 (HER2) in PDAC cells upon pharmacological MAPK inhibition. Mechanistically, MAPK inhibitors lead to swift proteasomal degradation of dual-specificity phosphatase 6 (DUSP6). The carboxy terminus of HER2, containing a TEY motif also present in extracellular signal-regulated kinase 1/2 (ERK1/2), facilitates binding with DUSP6, enhancing its phosphatase activity to dephosphorylate HER2. In the presence of MAPK inhibitors, DUSP6 dissociates from the protective effect of the RING E3 ligase tripartite motif containing 21, resulting in its degradation. In PDAC patient-derived xenograft (PDX) models, combining ERK and HER inhibitors slows tumour growth and requires cytotoxic chemotherapy to achieve tumour regression. Alternatively, MAPK inhibitors with trastuzumab deruxtecan, an anti-HER2 antibody conjugated with cytotoxic chemotherapy, lead to sustained tumour regression in most tested PDXs without causing noticeable toxicity. Additionally, KRAS inhibitors also activate HER2, supporting testing the combination of KRAS inhibitors and trastuzumab deruxtecan in PDAC. This study identifies a rational and promising therapeutic combination for clinical testing in PDAC patients.

miR-483-5p orchestrates the initiation of protein synthesis by facilitating the decrease in phosphorylated Ser209eIF4E and 4E-BP1 levels

Eukaryotic initiation factor 4E (eIF4E) is a pivotal protein involved in the regulatory mechanism for global protein synthesis in both physiological and pathological conditions. MicroRNAs (miRNAs) play a significant role in regulating gene expression by targeting mRNA. However, the ability of miRNAs to regulate eIF4E and its phosphorylation remains relatively unknown. In this study, we predicted and experimentally verified targets for miR-483-5p, including eukaryotic translation initiation factor eIF4E and its binding proteins, 4E-BPs, that regulate protein synthesis. Using the Web of Science database, we identified 28 experimentally verified miR-483-5p targets, and by the TargetScan database, we found 1818 predicted mRNA targets, including EIF4E, EIF4EBP1, and EIF4EBP2. We verified that miR-483-5p significantly reduced ERK1 and MKNK1 mRNA levels in HEK293 cells. Furthermore, we discovered that miR-483-5p suppressed EIF4EBP1 and EIF4EBP2, but not EIF4E. Finally, we found that miR-483-5p reduced the level of phosphorylated eIF4E (pSer209eIF4E) but not total eIF4E. In conclusion, our study suggests that miR-483-5p's multi-targeting effect on the ERK1/ MKNK1 axis modulates the phosphorylation state of eIF4E. Unlike siRNA, miRNA can have multiple targets in the pathway, and thereby exploring the role of miR-483-5p in various cancer models may uncover therapeutic options.

Dual-specificity phosphatase 1 inhibits Singapore grouper iridovirus replication via regulating apoptosis in Epinephelus coioides

The dual-specificity phosphatase (DUSP) family plays key roles in the maintenance of cellular homeostasis and apoptosis etc. In this study, the DUSP member DUSP1 of Epinephelus coioides was characterized: the length was 2371 bp including 281 bp 5' UTR, 911 bp 3' UTR, and a 1125 bp open reading frame encoding 374 amino acids. E. coioides DUSP1 has two conserved domains, a ROHD and DSPc along with a p38 MAPK phosphorylation site, localized at Ser308. E. coioides DUSP1 mRNA can be detected in all of the tissues examined, and the subcellular localization showed that DUSP1 was mainly distributed in the nucleus. Singapore grouper iridovirus (SGIV) infection could induce the differential expression of E. coioides DUSP1. Overexpression of DUSP1 could inhibit SGIV-induced cytopathic effect (CPE), the expressions of SGIV key genes, and the viral titers. Overexpression of DUSP1 could also regulate SGIV-induced apoptosis, and the expression of apoptosis-related factor caspase 3. The results would be helpful to further study the role of DUSP1 in viral infection.

An essential signaling cascade for avian auditory hair cell regeneration

Hearing loss is a chronic disease affecting millions of people worldwide, yet no restorative treatment options are available. Although non-mammalian species can regenerate their auditory sensory hair cells, mammals cannot. Birds retain facultative stem cells known as supporting cells that engage in proliferative regeneration when surrounding hair cells die. Here, we investigated gene expression changes in chicken supporting cells during auditory hair cell death. This identified a pathway involving the receptor F2RL1, HBEGF, EGFR, and ERK signaling. We propose a cascade starting with the proteolytic activation of F2RL1, followed by matrix-metalloprotease-mediated HBEGF shedding, and culminating in EGFR-mediated ERK signaling. Each component of this cascade is essential for supporting cell S-phase entry in vivo and is integral for hair cell regeneration. Furthermore, STAT3-phosphorylation converges with this signaling toward upregulation of transcription factors ATF3, FOSL2, and CREM. Our findings could provide a basis for designing treatments for hearing and balance disorders.

Targeting the RAS/RAF/MAPK pathway for cancer therapy: from mechanism to clinical studies

Metastatic dissemination of solid tumors, a leading cause of cancer-related mortality, underscores the urgent need for enhanced insights into the molecular and cellular mechanisms underlying metastasis, chemoresistance, and the mechanistic backgrounds of individuals whose cancers are prone to migration. The most prevalent signaling cascade governed by multi-kinase inhibitors is the mitogen-activated protein kinase (MAPK) pathway, encompassing the RAS-RAF-MAPK kinase (MEK)-extracellular signal-related kinase (ERK) pathway. RAF kinase is a primary mediator of the MAPK pathway, responsible for the sequential activation of downstream targets, such as MEK and the transcription factor ERK, which control numerous cellular and physiological processes, including organism development, cell cycle control, cell proliferation and differentiation, cell survival, and death. Defects in this signaling cascade are associated with diseases such as cancer. RAF inhibitors (RAFi) combined with MEK blockers represent an FDA-approved therapeutic strategy for numerous RAF-mutant cancers, including melanoma, non-small cell lung carcinoma, and thyroid cancer. However, the development of therapy resistance by cancer cells remains an important barrier. Autophagy, an intracellular lysosome-dependent catabolic recycling process, plays a critical role in the development of RAFi resistance in cancer. Thus, targeting RAF and autophagy could be novel treatment strategies for RAF-mutant cancers. In this review, we delve deeper into the mechanistic insights surrounding RAF kinase signaling in tumorigenesis and RAFi-resistance. Furthermore, we explore and discuss the ongoing development of next-generation RAF inhibitors with enhanced therapeutic profiles. Additionally, this review sheds light on the functional interplay between RAF-targeted therapies and autophagy in cancer.

Angelicin inhibits cell growth and promotes apoptosis in oral squamous cell carcinoma by negatively regulating DUSP6/cMYC signaling pathway

Angelicin has been reported to have antitumor effects on many types of cancer. However, few studies on angelicin in oral squamous cell carcinoma (OSCC) have been performed. We performed cell cycle and apoptosis analyses to assess the effect of angelicin on OSCC cells. We conducted RNA-seq studies to reveal differentially expressed genes (DEGs). Dual-specificity phosphatase 6 (DUSP6) and c-MYC were strongly down-regulated differential genes. Silencing RNA (siRNA) was used to knockdown DUSP6. The mouse xenograft model was used to mimic OSCC. Angelicin inhibited OSCC in vitro. We found that DUSP6 interacted with c-MYC. DUSP6 knockdown group and DUSP6 knockdown + angelicin group had similar effects of OSCC cells. Angelicin could reduce tumor formation, DUSP6, and c-MYC expression in vivo. Compared with paclitaxel, the tumor inhibition effect of the two drugs was similar. However, angelicin did not cause weight loss and had lower toxicity. In sum, Angelicin has antitumor effects on OSCC in vitro and vivo by negatively regulating the DUSP6 mediated c-MYC signaling pathway.

Loss of SETD2 aggravates colorectal cancer progression caused by SMAD4 deletion through the RAS/ERK signalling pathway

BACKGOUND

Colorectal cancer (CRC) is a complex, multistep disease that arises from the interplay genetic mutations and epigenetic alterations. The histone H3K36 trimethyltransferase SET domain-containing 2 (SETD2), as an epigenetic signalling molecule, has a 5% mutation rate in CRC. SETD2 expression is decreased in the development of human CRC and mice treated with Azoxymethane /Dextran sodium sulfate (AOM/DSS). Loss of SETD2 promoted CRC development. SMAD Family member 4 (SMAD4) has a 14% mutation rate in CRC, and SMAD4 ablation leads to CRC. The co-mutation of SETD2 and SMAD4 predicted advanced CRC. However, little is known on the potential synergistic effect of SETD2 and SMAD4.

METHODS

CRC tissues from mice and SW620 cells were used as research subjects. Clinical databases of CRC patients were analyzed to investigate the association between SETD2 and SMAD4. SETD2 and SMAD4 double-knockout mice were established to further investigate the role of SETD2 in SMAD4-deficient CRC. The intestinal epithelial cells (IECs) were isolated for RNA sequencing and chromatin immunoprecipitation sequencing (ChIP-seq) to explore the mechanism and the key molecules resulting in CRC. Molecular and cellular experiments were conducted to analyze the role of SETD2 in SMAD4-deficient CRC. Finally, rescue experiments were performed to confirm the molecular mechanism of SETD2 in the development of SMAD4-dificient CRC.

RESULTS

The deletion of SETD2 promotes the malignant progression of SMAD4-deficient CRC. Smad4Vil-KO ; Setd2Vil-KO mice developed a more severe CRC phenotype after AOM/DSS induction, with a larger tumour size and a more vigorous epithelial proliferation rate. Further mechanistic findings revealed that the loss of SETD2 resulted in the down-regulation of DUSP7, which is involved in the inhibition of the RAS/ERK signalling pathway. Finally, the ERK1/2 inhibitor SCH772984 significantly attenuated the progression of CRC in Smad4Vil-KO ;Setd2Vil-KO mice, and overexpression of DUSP7 significantly inhibited the proliferation rates of SETD2KO ; SMAD4KO SW620 cells.

CONCLUSIONS

Our results demonstrated that SETD2 inhibits the RAS/ERK signaling pathway by facilitating the transcription of DUSP7 in SMAD4-deficient CRC, which could provide a potential therapeutic target for the treatment of advanced CRC.

Epstein-Barr virus-encoded miR-BART11-3p modulates the DUSP6-MAPK axis to promote gastric cancer cell proliferation and metastasis

Epstein-Barr virus (EBV)-encoded miRNAs within the BamHI-A rightward transcript (BART) region are abundantly expressed in EBV-associated gastric cancer (EBVaGC), suggesting that they play roles in tumorigenesis. However, how these viral miRNAs contribute to the development of EBVaGC remains largely obscure. In this study, we found that EBV-encoded miR-BART11-3p targets 3' -UTR of dual-specificity phosphatase 6 (DUSP6) mRNA to upregulate ERK phosphorylation and downregulate JNK and p38 phosphorylation. By doing so, miR-BART11-3p promotes gastric cancer (GC) cell proliferation, migration, and invasion in vitro, and facilitates tumor growth in vivo. Restoration of DUSP6 expression reverses the tumor-promoting activity of miR-BART11-3p in AGS GC cells. Consistently, knockdown of DUSP6 ablates the antitumor effects of miR-BART11-3p inhibitors in EBV-positive GC cells. Furthermore, blocking ERK phosphorylation with trametinib inhibited the proliferation, migration, and invasion of miR-BART11-3p-expressing AGS cells. Administration of a miR-BART11-3p antagomir reduced the growth of EBV-positive xenograft tumors. Together, these findings reveal a novel mechanism by which EBV dysregulates MAPK pathways through an EBV-encoded microRNA to promote the development and progression of EBVaGC, which may be harnessed to develop new therapeutics to treat EBVaGC. IMPORTANCE The Epstein-Barr virus (EBV) is the first human tumor virus found to encode miRNAs, which within the BART region have been detected abundantly in EBV-associated gastric cancer (EBVaGC) and play various roles in promoting tumorigenesis. In our study, we observed that EBV-miR-BART11-3p promotes cell proliferation and induces migration and invasion in GC. Interestingly, we showed that miR-BART11-3p upregulates p-ERK and downregulates p-JNK and p-p38 by directly targeting 3'-UTR of dual-specificity phosphatase 6 (DUSP6). Restoration of DUSP6 rescues the effects generated by miR-BART11-3p in GC cells, and blocking ERK phosphorylation with Trametinib augments JNK and p38 phosphorylation and inhibits the effects of miR-BART11-3p-expressing AGS cells, suggesting that miR-BART11-3p promotes cell proliferation, migration, and invasion by modulating DUSP6-MAPK axis in EBVaGC. The findings presented in this study provide new mechanisms into the tumorigenesis in EBVaGC and new avenues for the development of therapeutic strategies to combat EBVaGC targeting miR-BART11-3p or phospho-ERK.

miR-101-5p suppresses trophoblast cell migration and invasion via modulating the DUSP6-ERK1/2 axis in preeclampsia

PURPOSE

Dysregulated behaviors of trophoblast cells leading to defective placentation are considered the main cause of preeclampsia (PE). Abnormal miRNA expression profiles have been observed in PE placental tissue, indicating the significant role of miRNAs in PE development. This study aimed to investigate the expression of miR-101-5p in PE placental tissue and its biological functions.

METHODS

The expression of miR-101-5p in placental tissue was detected by quantitative real-time PCR (qRT-PCR). The localization of miR-101-5p in term placental tissue and decidual tissue was determined by the fluorescence in situ hybridization (FISH)-immunofluorescence (IF) double labeling assay. The effect of miR-101-5p on the migration, invasion, proliferation, and apoptosis of the HTR8/SVneo trophoblast cells was investigated. Online databases combined with transcriptomics were used to identify potential target genes and related pathways of miR-101-5p. Finally, the interaction between miR-101-5p and the target gene was verified by qRT-PCT, WB, dual-luciferase reporter assay, and rescue experiments.

RESULTS

The study found that miR-101-5p was upregulated in PE placental tissue compared to normal controls and was mainly located in various trophoblast cell subtypes in placental and decidual tissues. Overexpression of miR-101-5p impaired the migration and invasion of HTR8/SVneo cells. DUSP6 was identified as a potential downstream target of miR-101-5p. The expression of miR-101-5p was negatively correlated with DUSP6 expression in HTR8/SVneo cells, and miR-101-5p directly bound to the 3' UTR region of DUSP6. DUSP6 upregulation rescued the migratory and invasive abilities of HTR8/SVneo cells in the presence of miR-101-5p overexpression. Additionally, miR-101-5p downregulated DUSP6, resulting in enhanced ERK1/2 phosphorylation.

CONCLUSION

This study revealed that miR-101-5p inhibits the migration and invasion of HTR8/SVneo cells by regulating the DUSP6-ERK1/2 axis, providing a new molecular mechanism for the pathogenesis of PE.

Enhanced Cerebral Hemodynamics and Cognitive Function Via Knockout of Dual-Specificity Protein Phosphatase 5

Alzheimer's Disease (AD) and Alzheimer's Disease-Related Dementias (ADRD) are neurodegenerative disorders. Recent studies suggest that cerebral hypoperfusion is an early symptom of AD/ADRD. Dual-specificity protein phosphatase 5 (DUSP5) has been implicated in several pathological conditions, including pulmonary hypertension and cancer, but its role in AD/ADRD remains unclear. The present study builds on our previous findings, demonstrating that inhibition of ERK and PKC leads to a dose-dependent dilation of the middle cerebral artery and penetrating arteriole, with a more pronounced effect in Dusp5 KO rats. Both ERK and PKC inhibitors resulted in a significant reduction of myogenic tone in vessels from Dusp5 KO rats. Dusp5 KO rats exhibited stronger autoregulation of the surface but not deep cortical cerebral blood flow. Inhibition of ERK and PKC significantly enhanced the contractile capacity of vascular smooth muscle cells from both strains. Finally, a significant improvement in learning and memory was observed in Dusp5 KO rats 24 hours after initial training. Our results suggest that altered vascular reactivity in Dusp5 KO rats may involve distinct mechanisms for different vascular beds, and DUSP5 deletion could be a potential therapeutic target for AD/ADRD. Further investigations are necessary to determine the effects of DUSP5 inhibition on capillary stalling, blood-brain barrier permeability, and neurodegeneration in aging and disease models.

New insights into signal transduction pathways in adrenal steroidogenesis: role of mitochondrial fusion, lipid mediators, and MAPK phosphatases

Hormone-receptor signal transduction has been extensively studied in adrenal gland. Zona glomerulosa and fasciculata cells are responsible for glucocorticoid and mineralocorticoid synthesis by adrenocorticotropin (ACTH) and angiotensin II (Ang II) stimulation, respectively. Since the rate-limiting step in steroidogenesis occurs in the mitochondria, these organelles are key players in the process. The maintenance of functional mitochondria depends on mitochondrial dynamics, which involves at least two opposite events, i.e., mitochondrial fusion and fission. This review presents state-of-the-art data on the role of mitochondrial fusion proteins, such as mitofusin 2 (Mfn2) and optic atrophy 1 (OPA1), in Ang II-stimulated steroidogenesis in adrenocortical cells. Both proteins are upregulated by Ang II, and Mfn2 is strictly necessary for adrenal steroid synthesis. The signaling cascades of steroidogenic hormones involve an increase in several lipidic metabolites such as arachidonic acid (AA). In turn, AA metabolization renders several eicosanoids released to the extracellular medium able to bind membrane receptors. This report discusses OXER1, an oxoeicosanoid receptor which has recently arisen as a novel participant in adrenocortical hormone-stimulated steroidogenesis through its activation by AA-derived 5-oxo-ETE. This work also intends to broaden knowledge of phospho/dephosphorylation relevance in adrenocortical cells, particularly MAP kinase phosphatases (MKPs) role in steroidogenesis. At least three MKPs participate in steroid production and processes such as the cellular cycle, either directly or by means of MAP kinase regulation. To sum up, this review discusses the emerging role of mitochondrial fusion proteins, OXER1 and MKPs in the regulation of steroid synthesis in adrenal cortex cells.

DUSP6 Deficiency Attenuates Neurodegeneration after Global Cerebral Ischemia

Transient global cerebral ischemia (tGCI) resulting from cardiac arrest causes selective neurodegeneration in hippocampal CA1 neurons. Although the effect is clear, the underlying mechanisms directing this process remain unclear. Previous studies have shown that phosphorylation of Erk1/2 promotes cell survival in response to tGCI. DUSP6 (also named MKP3) serves as a cytosolic phosphatase that dephosphorylates Erk1/2, but the role of DUSP6 in tGCI has not been characterized. We found that DUSP6 was specifically induced in the cytoplasm of hippocampal CA1 neurons 4 to 24 h after tGCI. DUSP6-deficient mice showed normal spatial memory acquisition and retention in the Barnes maze. Impairment of spatial memory acquisition and retention after tGCI was attenuated in DUSP6-deficient mice. Neurodegeneration after tGCI, revealed by Fluoro-Jade C and H&E staining, was reduced in the hippocampus of DUSP6-deficient mice and DUSP6 deficiency enhanced the phosphorylation and nuclear translocation of Erk1/2 in the hippocampal CA1 region. These data support the role of DUSP6 as a negative regulator of Erk1/2 signaling and indicate the potential of DUSP6 inhibition as a novel therapeutic strategy to treat neurodegeneration after tGCI.

MiR-216a-3p inhibits the proliferation and invasion of fibroblast-like synoviocytes by targeting dual-specificity phosphatase 5

Dual-specificity phosphatase 5 (DUSP5) is a novel anti-inflammatory modulator in many inflammatory diseases. However, the role of DUSP5 in fibroblast-like synoviocytes (FLS) of rheumatoid arthritis (RA) remains unknown. In this study, we aimed to explore the biological function and regulation of DUSP5 in FLS. We found that lower DUSP5 expression level was detected in collagen-induced arthritis (CIA) and synoviocyte MH7A. Overexpression of DUSP5 markedly decreased the proliferation, migration, and invasion of MH7A, which correlated with suppressing the phosphorylation of extracellular signal-regulated kinase (ERK). Moreover, DUSP5 was identified as a novel target gene of miR-216a-3p, which was upregulated in FLS. Therefore, DUSP5 expression was negatively regulated by miR-216a-3p, and the effect of DUSP5 overexpression on FLS was reversed by miR-216a-3p mimics. Overall, our study demonstrates that DUSP5 is a miR-216a-3p target gene and its anti-inflammatory function in FLS via inactivation of ERK. These results revealed that the miR-216a-3p/DUSP5 pathway may play a crucial role in the malignant behavior of FLS, which may serve as a new target for the treatment of RA.

Mead acid inhibits retinol-induced irritant contact dermatitis via peroxisome proliferator-activated receptor alpha

Retinol is widely used in topical skincare products to ameliorate skin aging and treat acne and wrinkles; however, retinol and its derivatives occasionally have adverse side effects, including the induction of irritant contact dermatitis. Previously, we reported that mead acid (5,8,11-eicosatrienoic acid), an oleic acid metabolite, ameliorated skin inflammation in dinitrofluorobenzene-induced allergic contact hypersensitivity by inhibiting neutrophil infiltration and leukotriene B₄ production by neutrophils. Here, we showed that mead acid also suppresses retinol-induced irritant contact dermatitis. In a murine model, we revealed that mead acid inhibited keratinocyte abnormalities such as keratinocyte hyperproliferation. Consistently, mead acid inhibited p38 MAPK (mitogen-activated protein kinase) phosphorylation, which is an essential signaling pathway in the keratinocyte hyperplasia induced by retinol. These inhibitory effects of mead acid were associated with the prevention of both keratinocyte hyperproliferation and the gene expression of neutrophil chemoattractants, including Cxcl1 and Cxcl2, and they were mediated by a PPAR (peroxisome proliferator-activated receptor)-α pathway. Our findings identified the anti-inflammatory effects of mead acid, the use of which can be expected to minimize the risk of adverse side effects associated with topical retinoid application.

ABL1/2 and DDR1 Drive MEKi Resistance in NRAS-Mutant Melanomas by Stabilizing RAF/MYC/ETS1 and Promoting RAF Homodimerization

Melanomas harboring NRAS mutations are a particularly aggressive and deadly subtype. If patients cannot tolerate or the melanomas are insensitive to immune checkpoint blockade, there are no effective 2nd-line treatment options. Drugs targeting the RAF/MEK/ERK pathway, which are used for BRAF-mutant melanomas, do little to increase progression-free survival (PFS). Here, using both loss-of-function and gain-of-function approaches, we show that ABL1/2 and DDR1 are critical nodes during NRAS-mutant melanoma intrinsic and acquired MEK inhibitor (MEKi) resistance. In some acquired resistance cells, ABL1/2 and DDR1 cooperate to stabilize RAF proteins, activate ERK cytoplasmic and nuclear signaling, repress p27/KIP1 expression, and drive RAF homodimerization. In contrast, other acquired resistance cells depend solely on ABL1/2 for their survival, and are sensitive to highly specific allosteric ABL1/2 inhibitors, which prevent β-catenin nuclear localization and destabilize MYC and ETS1 in an ERK-independent manner. Significantly, targeting ABL1/2 and DDR1 with an FDA-approved anti-leukemic drug, reverses intrinsic MEKi resistance, delays acquisition of acquired resistance, and doubles the survival time in a NRAS-mutant mouse model. These data indicate that repurposing FDA-approved drugs targeting ABL1/2 and DDR1 may be a novel and effective strategy for treating patients with treatment-refractory NRAS-driven melanomas.

Pten associates with important gene regulatory network to fine-tune Müller glia-mediated zebrafish retina regeneration

Unlike mammals, zebrafish possess a remarkable ability to regenerate damaged retina after an acute injury. Retina regeneration in zebrafish involves the induction of Müller glia-derived progenitor cells (MGPCs) exhibiting stem cell-like characteristics, which are capable of restoring all retinal cell-types. The induction of MGPC through Müller glia-reprograming involves several cellular, genetic and biochemical events soon after a retinal injury. Despite the knowledge on the importance of Phosphatase and tensin homolog (Pten), which is a dual-specificity phosphatase and tumor suppressor in the maintaining of cellular homeostasis, its importance during retina regeneration remains unknown. Here, we explored the importance of Pten during zebrafish retina regeneration. The Pten gets downregulated upon retinal injury and is absent from the MGPCs, which is essential to trigger Akt-mediated cellular proliferation essential for retina regeneration. We found that the downregulation of Pten in the post-injury retina accelerates MGPCs formation, while its overexpression restricts the regenerative response. We observed that Pten regulates the proliferation of MGPCs not only through Akt pathway but also by Mmp9/Notch signaling. Mmp9-activity is essential to induce the proliferation of MGPCs in the absence of Pten. Lastly, we show that expression of Pten is fine-tuned through Mycb/histone deacetylase1 and Tgf-β signaling. The present study emphasizes on the stringent regulation of Pten and its crucial involvement during the zebrafish retina regeneration.

Gene-Function-Based Clusters Explore Intricate Networks of Gene Expression of Circulating Tumor Cells in Patients with Colorectal Cancer

Colorectal cancer (CRC) is a complex disease characterized by dynamically deregulated gene expression and crosstalk between signaling pathways. In this study, a new approach based on gene-function-based clusters was introduced to explore the CRC-associated networks of gene expression. Each cluster contained genes involved in coordinated regulatory activity, such as RAS signaling, the cell cycle process, transcription, or translation. A retrospective case-control study was conducted with the inclusion of 119 patients with histologically confirmed colorectal cancer and 308 controls. The quantitative expression data of 15 genes were obtained from the peripheral blood samples of all participants to investigate cluster-gene and gene-gene interactions. DUSP6, MDM2, and EIF2S3 were consistently selected as CRC-associated factors with high significance in all logistic models. CPEB4 became an insignificant factor only when combined with the clusters for cell cycle processes and for transcription. The CPEB4/DUSP6 complex was a prerequisite for the significance of MMD, whereas EXT2, RNF4, ZNF264, WEE1, and MCM4 were affected by more than two clusters. Intricate networks among MMD, RAS signaling factors (DUSP6, GRB2, and NF1), and translation factors (EIF2S3, CPEB4, and EXT2) were also revealed. Our results suggest that limited G1/S transition, uncontrolled DNA replication, and the cap-independent initiation of translation may be dominant and concurrent scenarios in circulating tumor cells derived from colorectal cancer. This gene-function-based cluster approach is simple and useful for revealing intricate CRC-associated gene expression networks. These findings may provide clues to the metastatic mechanisms of circulating tumor cells in patients with colorectal cancer.

Construction and validation of a cuproptosis-related prognostic model for glioblastoma

Background

Cuproptosis, a newly reported type of programmed cell death, takes part in the regulation of tumor progression, treatment response, and prognosis. But the specific effect of cuproptosis-related genes (CRGs) on glioblastoma (GBM) is still unclear.

Methods

The transcriptome data and corresponding clinical data of GBM samples were downloaded from the TCGA and GEO databases. R software and R packages were used to perform statistical analysis, consensus cluster analysis, survival analysis, Cox regression analysis, Lasso regression analysis, and tumor microenvironment analysis. The mRNA and protein expression levels of model-related genes were detected by RT-qPCR and Western blot assays, respectively.

Results

The expression profile of CRGs in 209 GBM samples from two separate datasets was obtained. Two cuproptosis subtypes, CRGcluster A and CRGcluster B, were identified by consensus cluster analysis. There were apparent differences in prognosis, tumor microenvironment, and immune checkpoint expression levels between the two subtypes, and there were 79 prognostic differentially expressed genes (DEGs). According to the prognostic DEGs, two gene subtypes, geneCluster A and geneCluster B, were identified, and a prognostic risk score model was constructed and validated. This model consists of five prognostic DEGs, including PDIA4, DUSP6, PTPRN, PILRB, and CBLN1. Ultimately, to improve the applicability of the model, a nomogram was established. Patients with GBM in the low-risk cluster have a higher mutation burden and predict a longer OS than in the high-risk group. Moreover, the risk score was related to drug sensitivity and negatively correlated with the CSC index.

Conclusion

We successfully constructed a cuproptosis-related prognostic model, which can independently predict the prognosis of GBM patients. These results further complement the understanding of cuproptosis and provide new theoretical support for developing a more effective treatment strategy.

Mechanisms of ERK phosphorylation triggered via mouse formyl peptide receptor 2

Formyl peptide receptors (FPRs) are expressed in the cells of the innate immune system and provide binding with pathogen and damage-associated molecular patterns with subsequent activation of the phagocytes for defense reactions such as chemotaxis, secretory degranulation and ROS generation. Probably, FPR2 is one of the unique receptors in the organism; it is able to recognize numerous ligands of different chemical structure, and moreover, these ligands can trigger opposite phagocyte responses promoting either pro- or anti-inflammatory reactions. Therefore, FPR2 and its signaling pathways are of intense research interest. We found only slight activation of ERK1/2 in the response to peptide ligand WKYMVM in the accelerating phase of ROS generation and more intense ERK1/2 phosphorylation in the declining phase of it in mouse bone marrow granulocytes. Lipid agonist BML-111 did not induce significant ERK phosphorylation when applied for 10-1800 s. To some extent co-localization of ERK1/2 and NADPH oxidase subunits was observed even in the intact cells and didn't change under FPR2 stimulation by WKYMVM, while direct PKC activation by PMA resulted to more efficient interaction between ERK1/2 and p47phox/p67phox and their translocation to plasma membrane. We have shown that phosphorylation and activation of ERK1/2 in bone marrow granulocytes depended on FPR2-triggered activity of PI3K and PKC, phosphatase DUSP6, and, the most but not the least, on ROS generation. Since blocking of ROS generation led to a slowdown of ERK activation indicating a significant contribution of ROS to the secondary regulation of ERK activity.

Dusp6 deficiency attenuates neutrophil-mediated cardiac damage in the acute inflammatory phase of myocardial infarction

Dual-specificity phosphatase 6 (DUSP6) serves a specific and conserved function on the dephosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). We previously identified Dusp6 as a regenerative repressor during zebrafish heart regeneration, therefore we propose to investigate the role of this repressor in mammalian cardiac repair. Utilizing a rat strain harboring Dusp6 nonsense mutation, rat neutrophil-cardiomyocyte co-culture, bone marrow transplanted rats and neutrophil-specific Dusp6 knockout mice, we find that Dusp6 deficiency improves cardiac outcomes by predominantly attenuating neutrophil-mediated myocardial damage in acute inflammatory phase after myocardial infarction. Mechanistically, Dusp6 is transcriptionally activated by p38-C/EBPβ signaling and acts as an effector for maintaining p-p38 activity by down-regulating pERK and p38-targeting phosphatases DUSP1/DUSP16. Our findings provide robust animal models and novel insights for neutrophil-mediated cardiac damage and demonstrate the potential of DUSP6 as a therapeutic target for post-MI cardiac remodeling and other relevant inflammatory diseases.

A positive feedback loop of ARF6 activates ERK1/2 signaling pathway via DUSP6 silencing to promote pancreatic cancer progression

ERK1/2 are essential proteins mediating mitogen-activated protein kinase signaling downstream of RAS in pancreatic adenocarcinoma (PDAC). Our previous study reveals that ARF6 plays a positive regulatory role in ERK1/2 pathway in a feedback loop manner. A significant part of the literature on ARF6 has emphasized its oncogenic effect as an essential downstream molecule of ERK1/2, and no research has been done on the regulation mechanisms of the feedback loop between ARF6 and the ERK1/2 signaling pathway. In the present study, we explore the gene network downstream of ARF6 and find that DUSP6 may be the critical signal molecule in the positive feedback loop between ARF6 and ERK1/2. Specifically, to elucidate the negative correlations between ARF6 and DUSP6 in pancreatic cancer, we examine their expressions in pancreatic cancer tissues by immunohistochemical staining. Then the impact of DUSP6 on the proliferation and apoptosis of PDAC cells are investigated by gain-of-function and loss-of-function approaches. Mechanism explorations uncover that ARF6 suppresses the expression of DUSP6, which is responsible for the dephosphorylation of ERK1/2. Altogether, these results indicate that DUSP6 plays a tumor-suppressive role and acts as an intermediate molecule between ARF6 and ERK1/2 in PDAC cells, thereby forming a positive feedback loop.

Identification and validation of four photodynamic therapy related genes inhibiting MAPK and inducing cell cycle alteration in squamous cell carcinoma

Introduction

Cutaneous squamous cell carcinoma (cSCC) is the second most common skin cancer, and photodynamic therapy (PDT) is a promising modality against cSCC. This study investigated the impact of PDT on the MAPK pathway and cell cycle alternation of cSCC as well as the related molecular mechanisms.

Method

Expressing mRNA profile data sets GSE98767, GSE45216, and GSE84758 were acquired from the GEO database. The functions of differently expressed genes (DEGs) were enriched by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Least absolute shrinkage and selection operator (Lasso) analysis were used to establish a diagnosis model based on GSE98767. A correlation analysis and a protein–protein interaction (PPI) network were used to evaluate the relationship between cSCC-PDT-related genes and the MAPK pathway. Single-sample gene set enrichment analysis (ssGSEA) was performed on GSE98767 to estimate MAPK activation and cell cycle activity. Finally, the effect of MAPK activation on the cell cycle was explored in vitro.

Result

Four cSCC-PDT-related genes, DUSP6, EFNB2, DNAJB1, and CCNL1, were identified as diagnostic markers of cSCC, which were upregulated in cSCC or LC50 PDT-protocol treatment and negatively correlated with the MAPK promoter. Despite having a smaller MAPK activation score, cSCC showed higher cell cycle activity. The PDT treatment suppressed the G1 to G2/M phase in JNK overexpressed A431 cells.

Conclusion

CCNL1, DNAJB1, DUSP6, and EFNB2 were identified as potential PDT target genes in cSCC treatment, whose potential therapeutic mechanism was inhibiting the MAPK pathway and inducing cell cycle alternation.

Overexpression of dual-specificity phosphatases 4 and 13 attenuates transforming growth factor β1-induced migration and drug resistance in A549 cells in vitro

Transforming growth factor-beta (TGFβ) proteins induce an epithelial-mesenchymal transition (EMT) programme that is associated with increased invasive and drug-resistant phenotype of carcinoma cells. In addition to the canonical pathway involving SMAD proteins, the mitogen-activated kinase (MAPK) pathway via extracellular signal-regulated kinases ½ (ERK1/2) is also involved in promoting and maintaining a mesenchymal phenotype by tumor cells following TGFβ signal activation. As dual-specificity phosphatases (DUSPs) regulate ERK1/2 activity by dephosphorylation, we aimed to examine DUSPs' expression upon TGFβ stimulation and whether DUSPs play a role in the EMT and related phenotypes promoted by TGFβ1 in A549 cells. We found that TGFβ1 stimulation led to marked changes in several DUSP proteins, including significant decreases in DUSP4 and DUSP13 expressions. We then showed that the ectopic co-expression of DUSP4/13 suppresses TGFβ1-induced ERK1/2 phosphorylation and protein levels of the EMT transcription factors Snail and Slug proteins. We then demonstrated that DUSP4/13 co-expression partially inhibited TGFβ1-promoted migration, invasion, and chemoresistance in A549 cells. Collectively, this report provides data for the involvement of DUSP4/13 in malignant phenotypes regulated by TGFβ1 in A549 cells.

Immunohistochemical assessment of cannabinoid type-1 receptor (CB1R) and its correlation with clinicopathological parameters in glioma

Background

Glioma is the most frequent primary brain tumor and one of the most aggressive forms of cancer. Recently, numerous studies have focused on cannabinoids as a new therapeutic approach due to their antineoplastic effects through activation of the cannabinoid receptors. This study aimed to investigate the immunohistochemical expression level of cannabinoid type-1 receptors (CB1R) in human glioma samples and evaluate its clinicopathologic significance.

Materials and methods

We analyzed the expression of CB1R in 61 paraffin-embedded glioma and 4 normal brain tissues using automated immunohistochemical assay. CB1R expression was categorized into high versus low expression levels. Statistical analyses were performed to evaluate the association between CB1R and phosphorylated extracellular signal-related kinase (p-ERK) expression levels and the clinicopathologic features of glioma.

Results

Our results showed that CB1R immunopositivity was seen in 59 of 61 cases (96.7%). CB1R was down-expressed in glioma compared to normal brain tissues. However, CB1R expression was not correlated with clinicopathological parameters except for p-ERK.

Conclusion

Our findings indicate the down-expression of CB1R in glioma tissues when compared to non-cancerous brain tissues. This change in CB1R expression in gliomas should be further tested regardless of the clinicopathological findings to provide a therapeutic advantage in glioma patients.

BRD4 inhibitor MZ1 exerts anti-cancer effects by targeting MYCN and MAPK signaling in neuroblastoma

Neuroblastoma(NB) is a common childhood solid tumor, and most patients in the high-risk group with MYCN gene amplification have a poor prognosis. Inhibition of bromodomain and extra terminal (BET) proteins has shown considerable promise in the investigation of MYCN-driven malignancies in recent years. MZ1 is a novel BET inhibitor that employs proteolytic-targeting chimera (PROTAC) technology for proteasomal degradation of target proteins and has shown excellent effects in some tumors, but its role in neuroblastoma remains poorly understood. Herein, we observed that MZ1 suppressed MYC-amplified NB cell proliferation and normal cell cycle, while simultaneously boosting cell apoptosis. MZ1 also provides a significant therapeutic impact in vivo. Mechanistically, MZ1 exhibits anti-tumor effect in NB cells by suppressing the expression of N-Myc or C-Myc as well as the MAPK signaling pathway. Overall, our data imply that MZ1 might be exploited as a possible therapeutic method for NB therapy.

Cardiomyocyte BRAF and type 1 RAF inhibitors promote cardiomyocyte and cardiac hypertrophy in mice in vivo

The extracellular signal-regulated kinase 1/2 (ERK1/2) cascade promotes cardiomyocyte hypertrophy and is cardioprotective, with the three RAF kinases forming a node for signal integration. Our aims were to determine if BRAF is relevant for human heart failure, whether BRAF promotes cardiomyocyte hypertrophy, and if Type 1 RAF inhibitors developed for cancer (that paradoxically activate ERK1/2 at low concentrations: the 'RAF paradox') may have the same effect. BRAF was up-regulated in heart samples from patients with heart failure compared with normal controls. We assessed the effects of activated BRAF in the heart using mice with tamoxifen-activated Cre for cardiomyocyte-specific knock-in of the activating V600E mutation into the endogenous gene. We used echocardiography to measure cardiac dimensions/function. Cardiomyocyte BRAFV600E induced cardiac hypertrophy within 10 d, resulting in increased ejection fraction and fractional shortening over 6 weeks. This was associated with increased cardiomyocyte size without significant fibrosis, consistent with compensated hypertrophy. The experimental Type 1 RAF inhibitor, SB590885, and/or encorafenib (a RAF inhibitor used clinically) increased ERK1/2 phosphorylation in cardiomyocytes, and promoted hypertrophy, consistent with a 'RAF paradox' effect. Both promoted cardiac hypertrophy in mouse hearts in vivo, with increased cardiomyocyte size and no overt fibrosis. In conclusion, BRAF potentially plays an important role in human failing hearts, activation of BRAF is sufficient to induce hypertrophy, and Type 1 RAF inhibitors promote hypertrophy via the 'RAF paradox'. Cardiac hypertrophy resulting from these interventions was not associated with pathological features, suggesting that Type 1 RAF inhibitors may be useful to boost cardiomyocyte function.

CRAF dimerization with ARAF regulates KRAS-driven tumor growth

KRAS, which is mutated in ∼30% of all cancers, activates the RAF-MEK-ERK signaling cascade. CRAF is required for growth of KRAS mutant lung tumors, but the requirement for CRAF kinase activity is unknown. Here, we show that subsets of KRAS mutant tumors are dependent on CRAF for growth. Kinase-dead but not dimer-defective CRAF rescues growth inhibition, suggesting that dimerization but not kinase activity is required. Quantitative proteomics demonstrates increased levels of CRAF:ARAF dimers in KRAS mutant cells, and depletion of both CRAF and ARAF rescues the CRAF-loss phenotype. Mechanistically, CRAF depletion causes sustained ERK activation and induction of cell-cycle arrest, while treatment with low-dose MEK or ERK inhibitor rescues the CRAF-loss phenotype. Our studies highlight the role of CRAF in regulating MAPK signal intensity to promote tumorigenesis downstream of mutant KRAS and suggest that disrupting CRAF dimerization or degrading CRAF may have therapeutic benefit.

Dual-Specificity Phosphatases and Kidney Diseases

BACKGROUND

Dual-specificity phosphatases (DUSPs) belong to the family of protein tyrosine phosphatases, which can dephosphorylate both serine/threonine and tyrosine residues. During the past decades, DUSPs have been implicated in various physiological and pathological activities. Besides mitogen-activated protein kinases (MAPKs) as the main substrates, other protein and nonprotein substrates can also be dephosphorylated by DUSPs. Aberrant regulations of DUSPs have been found in various diseases such as cancer, neurological disorders, and kidney diseases, suggesting the involvement of DUSPs in the pathogenesis of diseases.

SUMMARY

In this review, we summarize the general characteristics of DUSPs and the research progress made in the field of kidney diseases, including diabetic nephropathy, hypertensive nephropathy, chronic kidney disease, acute kidney injury, and lupus nephritis. As the main biochemical function of DUSPs is to dephosphorylate MAPKs activity, decreased DUSPs are found in kidney disease models, whereas forced DUSPs expression reverses the disease presentation, which was proved by using transgenic or gene knockout model.

KEY MESSAGES

Mounting evidence demonstrates that DUSPs have essential physiological and pathological functions in kidney disease. Fully understanding the functions and mechanisms of DUSPs in kidney disease contributes to their clinical application in translation medicine.

Sustained experimental activation of FGF8/ERK in the developing chicken spinal cord models early events in ERK-mediated tumorigenesis

The MAPK/ERK pathway regulates a variety of physiological cellular functions, including cell proliferation and survival. It is abnormally activated in many types of human cancers in response to driver mutations in regulators of this pathway that trigger tumor initiation. The early steps of oncogenic progression downstream of ERK overactivation are poorly understood due to a lack of appropriate models. We show here that ERK1/2 overactivation in the trunk neural tube of the chicken embryo through expression of a constitutively active form of the upstream kinase MEK1 (MEK1ca), rapidly provokes a profound change in the transcriptional signature of developing spinal cord cells. These changes are concordant with a previously established role of the tyrosine kinase receptor ligand FGF8 acting via the ERK1/2 effectors to maintain an undifferentiated state. Furthermore, we show that MEK1ca-transfected spinal cord cells lose neuronal identity, retain caudal markers, and ectopically express potential effector oncogenes, such as AQP1. MEK1ca expression in the developing spinal cord from the chicken embryo is thus a tractable in vivo model to identify the mechanisms fostering neoplasia and malignancy in ERK-induced tumorigenesis of neural origins.

Signal pathways of melanoma and targeted therapy

Melanoma is the most lethal skin cancer that originates from the malignant transformation of melanocytes. Although melanoma has long been regarded as a cancerous malignancy with few therapeutic options, increased biological understanding and unprecedented innovations in therapies targeting mutated driver genes and immune checkpoints have substantially improved the prognosis of patients. However, the low response rate and inevitable occurrence of resistance to currently available targeted therapies have posed the obstacle in the path of melanoma management to obtain further amelioration. Therefore, it is necessary to understand the mechanisms underlying melanoma pathogenesis more comprehensively, which might lead to more substantial progress in therapeutic approaches and expand clinical options for melanoma therapy. In this review, we firstly make a brief introduction to melanoma epidemiology, clinical subtypes, risk factors, and current therapies. Then, the signal pathways orchestrating melanoma pathogenesis, including genetic mutations, key transcriptional regulators, epigenetic dysregulations, metabolic reprogramming, crucial metastasis-related signals, tumor-promoting inflammatory pathways, and pro-angiogenic factors, have been systemically reviewed and discussed. Subsequently, we outline current progresses in therapies targeting mutated driver genes and immune checkpoints, as well as the mechanisms underlying the treatment resistance. Finally, the prospects and challenges in the development of melanoma therapy, especially immunotherapy and related ongoing clinical trials, are summarized and discussed.

Regulation of positive and negative selection and TCR signaling during thymic T cell development by capicua

Central tolerance is achieved through positive and negative selection of thymocytes mediated by T cell receptor (TCR) signaling strength. Thus, dysregulation of the thymic selection process often leads to autoimmunity. Here, we show that Capicua (CIC), a transcriptional repressor that suppresses autoimmunity, controls the thymic selection process. Loss of CIC prior to T-cell lineage commitment impairs both positive and negative selection of thymocytes. CIC deficiency attenuated TCR signaling in CD4⁺CD8⁺ double-positive (DP) cells, as evidenced by a decrease in CD5 and phospho-ERK levels and calcium flux. We identified Spry4, Dusp4, Dusp6, and Spred1 as CIC target genes that could inhibit TCR signaling in DP cells. Furthermore, impaired positive selection and TCR signaling were partially rescued in Cic and Spry4 double mutant mice. Our findings indicate that CIC is a transcription factor required for thymic T cell development and suggests that CIC acts at multiple stages of T cell development and differentiation to prevent autoimmunity.

Paralog knockout profiling identifies DUSP4 and DUSP6 as a digenic dependence in MAPK pathway-driven cancers

Although single-gene perturbation screens have revealed a number of new targets, vulnerabilities specific to frequently altered drivers have not been uncovered. An important question is whether the compensatory relationship between functionally redundant genes masks potential therapeutic targets in single-gene perturbation studies. To identify digenic dependencies, we developed a CRISPR paralog targeting library to investigate the viability effects of disrupting 3,284 genes, 5,065 paralog pairs and 815 paralog families. We identified that dual inactivation of DUSP4 and DUSP6 selectively impairs growth in NRAS and BRAF mutant cells through the hyperactivation of MAPK signaling. Furthermore, cells resistant to MAPK pathway therapeutics become cross-sensitized to DUSP4 and DUSP6 perturbations such that the mechanisms of resistance to the inhibitors reinforce this mechanism of vulnerability. Together, multigene perturbation technologies unveil previously unrecognized digenic vulnerabilities that may be leveraged as new therapeutic targets in cancer.

DUSP6 regulates radio-sensitivity in glioblastoma by modulating the recruitment of p-DNAPKcs at DNA double-strand breaks

Glioblastoma (GBM) has poor median survival due to its resistance to chemo-radiotherapy regimen, resulting in tumor recurrence. Recurrent GBMs currently lack effective treatments. DUSP6 is known to be pro-tumorigenic and is up-regulated in GBM. We show that DUSP6 expression is significantly higher in recurrent GBM patient biopsies (n=11) compared to primary biopsies (n=11). Importantly, although reported as cytoplasmic protein, we found nuclear localization of DUSP6 in primary and recurrent patient samples and in parent and relapse population of GBM cell lines generated from in vitro radiation survival model. DUSP6 inhibition using BCI resulted in decreased proliferation and clonogenic survival of parent and relapse cells. Pharmacological or genetic inhibition of DUSP6 catalytic activity radio-sensitized primary and importantly, relapse GBM cells by inhibiting the recruitment of p-DNAPKcs, subsequently down-regulating the recruitment of γH2AX and 53BP1. This resulted in decreased cell survival and prolonged growth arrest upon irradiation in vitro and significantly increased the progression-free survival in orthotopic mouse models of GBM. Our study highlights a non-canonical function of DUSP6, emphasizing the potential application of DUSP6 inhibitors in the treatment of recurrent GBM.

NKX2-1 controls lung cancer progression by inducing DUSP6 to dampen ERK activity

The RAS→RAF→MEK→ERK pathway is hyperactivated in the majority of human lung adenocarcinoma (LUAD). However, the initial activating mutations induce homeostatic feedback mechanisms that limit ERK activity. How ERK activation reaches the tumor-promoting levels that overcome the feedback and drive malignant progression is unclear. We show here that the lung lineage transcription factor NKX2-1 suppresses ERK activity. In human tissue samples and cell lines, xenografts, and genetic mouse models, NKX2-1 induces the ERK phosphatase DUSP6, which inactivates ERK. In tumor cells from late-stage LUAD with silenced NKX2-1, re-introduction of NKX2-1 induces DUSP6 and inhibits tumor growth and metastasis. We show that DUSP6 is necessary for NKX2-1-mediated inhibition of tumor progression in vivo and that DUSP6 expression is sufficient to inhibit RAS-driven LUAD. Our results indicate that NKX2-1 silencing, and thereby DUSP6 downregulation, is a mechanism by which early LUAD can unleash ERK hyperactivation for tumor progression.

Synergistic Antiproliferative Effects of All-Trans Retinoic Acid and Paclitaxel on Autosomal Dominant Polycystic Kidney Disease Epithelial Cells

Autosomal dominant polycystic kidney disease (ADPKD) is a genetic disorder characterized by uncontrollable epithelial cell growth, cyst formation, and kidney malfunction. In the present study, we investigated the antiproliferative effects of the treatment with the combination of paclitaxel (PAC) and all-trans retinoic acid (ATRA) on ADPKD epithelial cells. Our results show that the combined treatment with 1 nM PAC and 10 nM ATRA significantly suppressed ADPKD cell proliferation (20%), while the treatment with ATRA or PAC alone had no such effect. Treatment with PAC and ATRA induced cell cycle arrest at the G2/M phase and apoptosis by upregulating p53 and caspase-8 expression and increased the intracellular calcium (Ca²⁺) level possibly by enhancing Ca²⁺ uptake via plasma membrane channels. In addition, this treatment suppressed extracellular signal-regulated kinase signaling possibly through mitogen-activated protein kinase phosphatase-1 activation. Thus, the combination of PAC and ATRA can be explored as a potential treatment regimen for ADPKD.

Loss of FBXO31-mediated degradation of DUSP6 dysregulates ERK and PI3K-AKT signaling and promotes prostate tumorigenesis

FBXO31 is the substrate receptor of one of many CUL1-RING ubiquitin ligase (CRL1) complexes. Here, we show that low FBXO31 mRNA levels are associated with high pre-operative prostate-specific antigen (PSA) levels and Gleason grade in human prostate cancer. Mechanistically, the ubiquitin ligase CRL1FBXO31 promotes the ubiquitylation-mediated degradation of DUSP6, a dual specificity phosphatase that dephosphorylates and inactivates the extracellular-signal-regulated kinase-1 and -2 (ERK1/2). Depletion of FBXO31 stabilizes DUSP6, suppresses ERK signaling, and activates the PI3K-AKT signaling cascade. Moreover, deletion of FBXO31 promotes tumor development in a mouse orthotopic model of prostate cancer. Treatment with BCI, a small molecule inhibitor of DUSP6, suppresses AKT activation and prevents tumor formation, suggesting that the FBXO31 tumor suppressor activity is dependent on DUSP6. Taken together, our studies highlight the relevance of the FBXO31-DUSP6 axis in the regulation of ERK- and PI3K-AKT-mediated signaling pathways, as well as its therapeutic potential in prostate cancer.

The Downregulation of eIF3a Contributes to Vemurafenib Resistance in Melanoma by Activating ERK via PPP2R1B

Vemurafenib, a BRAF V600E inhibitor, provides therapeutic benefits for patients with melanoma, but the frequent emergence of drug resistance remains a challenge. An understanding of the mechanisms underlying vemurafenib resistance may generate novel therapeutic strategies for patients with melanoma. Here, we showed that eIF3a, a translational regulatory protein, was an important mediator involved in vemurafenib resistance. eIF3a was expressed at significantly lower levels in vemurafenib-resistant A375 melanoma cells (A375R) than in parental A375 cells. Overexpression of eIF3a enhanced the sensitivity to BRAF inhibitors by reducing p-ERK levels. Furthermore, eIF3a controlled ERK activity by regulating the expression of the phosphatase PPP2R1B via a translation mechanism, thus determining the sensitivity of melanoma cells to vemurafenib. In addition, a positive correlation between eIF3a and PPP2R1B expression was also observed in tumor samples from the Human Protein Atlas and TCGA databases. In conclusion, our studies reveal a previously unknown molecular mechanism of BRAF inhibitor resistance, which may provide a new strategy for predicting vemurafenib responses in clinical treatment.

Multi-Platform Classification of IDH-Wild-Type Glioblastoma Based on ERK/MAPK Pathway: Diagnostic, Prognostic and Therapeutic Implications

Glioblastoma is the most aggressive and frequent glioma in the adult population. Because current therapy regimens confer only minimal survival benefit, molecular subgrouping to stratify patient prognosis and therapy design is warranted. This study presents a multi-platform classification of glioblastoma by analyzing a large, ethnicity-inclusive 101-adult-patient cohort. It defines seven non-redundant IDH-wild-type glioblastoma molecular subgroups, G1-G7, corresponding to the upstream receptor tyrosine kinase (RTK) and RAS-RAF segment of the ERK/MAPK signal transduction pathway. These glioblastoma molecular subgroups are classified as G1/EGFR, G2/FGFR3, G3/NF1, G4/RAF, G5/PDGFRA, G6/Multi-RTK, and G7/Other. The comprehensive genomic analysis was refined by expression landscaping of all RTK genes, as well as of the major associated growth pathway mediators, and used to hierarchically cluster the subgroups. Parallel demographic, clinical, and histologic pattern analyses were merged with the molecular subgrouping to yield the first inclusive multi-platform classification for IDH-wild-type glioblastoma. This straightforward classification with diagnostic and prognostic significance may be readily used in neuro-oncological practice and lays the foundation for personalized targeted therapy approaches.

Current Insights of Inhibitors of p38 Mitogen-Activated Protein Kinase in Inflammation

BACKGROUND

The inflammatory process is one of the mechanisms by which our body upholds us from pathogens such as parasites, bacteria, viruses, and other harmful microorganisms. Inflammatory stimuli activate many intracellular signaling pathways such as the nuclear factor-kB (NF-kB) pathway and three mitogen-activated protein kinase (MAPK) pathways, which are mediated through extracellular-signal regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and p38. The p38 has evolved as an enticing target in treating many persistent inflammatory diseases. Hence, designing novel p38 inhibitors targeting MAPK pathways has acquired significance.

OBJECTIVE

Peruse to identify the lead target to discover novel p38MAPK inhibitors with different scaffolds having improved selectivity over the prototype drugs.

METHODS

Structure and the binding sites of p38MAPK were focused. Various scaffolds designed for inhibition and the molecules which have entered the clinical trials are discussed.

RESULTS

This review aspires to present the available information on the structure and the 3D binding sites of p38MAPK, various scaffolds designed for imidazole, urea, benzamide, azoles, quinoxaline, chromone, ketone as a potent p38MAPK inhibitors and their SAR studies and the molecules which have entered the clinical trials.

CONCLUSION

The development of successful selective p38MAPK inhibitors in inflammatory diseases is in progress despite all challenges. It was speculated that p38MAPK also plays an important role in treating diseases such as neuroinflammation, arterial inflammation, vascular inflammation, cancer and so on, which are posing the world with treatment challenges. In this review, clinical trials of drugs are discussed related to inflammatory and its related diseases. Research is in progress to design and develop novel p38MAPK inhibitors with minimal side effects.

Role of Protein Tyrosine Phosphatase in Regulation of Cell Signaling Cascades Affecting Tumor Cell Growth: A Future Perspective as Anti- Cancer Drug Target

Protein Tyrosine Phosphatase (PTP) superfamily is a key enzyme involved in the regulation of growth-related cell signaling cascades, such as the RAS/MAPK pathway, that directly affect cancer cell growth and metastasis. Several studies have indicated that the drug resistance observed in several late-stage tumors might also be affected by the levels of PTP in the cell. Hence, these phosphatases have been in the limelight for the past few decades as potential drug-targets and several promising drug candidates have been developed, even though none of these drugs have reached the market yet. In this review, we explore the potential of PTP as a viable anti-cancer drug target by studying PTPs, their regulation of several key cancer cell signaling pathways and how their levels affect various types of cancer. Furthermore, we present the current scenario of PTP as a molecular target and the various challenges faced in the development of PTP-targeting anti-cancer drugs.

Cancer stem cell phosphatases

Cancer stem cells (CSCs) are involved in the initiation and progression of human malignancies by enabling cancer tissue self-renewal capacity and constituting the therapy-resistant population of tumor cells. However, despite the exhausting characterization of CSC genetics, epigenetics, and kinase signaling, eradication of CSCs remains an unattainable goal in most human malignancies. While phosphatases contribute equally with kinases to cellular phosphoregulation, our understanding of phosphatases in CSCs lags severely behind our knowledge about other CSC signaling mechanisms. Many cancer-relevant phosphatases have recently become druggable, indicating that further understanding of the CSC phosphatases might provide novel therapeutic opportunities. This review summarizes the current knowledge about fundamental, but yet poorly understood involvement of phosphatases in the regulation of major CSC signaling pathways. We also review the functional roles of phosphatases in CSC self-renewal, cancer progression, and therapy resistance; focusing particularly on hematological cancers and glioblastoma. We further discuss the small molecule targeting of CSC phosphatases and their therapeutic potential in cancer combination therapies.

The Biology of Classic Hairy Cell Leukemia

Classic hairy cell leukemia (HCL) is a rare mature B-cell malignancy associated with pancytopenia and infectious complications due to progressive infiltration of the bone marrow and spleen. Despite tremendous therapeutic advances achieved with the implementation of purine analogues such as cladribine into clinical practice, the culprit biologic alterations driving this fascinating hematologic disease have long stayed concealed. Nearly 10 years ago, BRAF V600E was finally identified as a key activating mutation detectable in almost all HCL patients and throughout the entire course of the disease. However, additional oncogenic biologic features seem mandatory to enable HCL transformation, an open issue still under active investigation. This review summarizes the current understanding of key pathogenic mechanisms implicated in HCL and discusses major hurdles to overcome in the context of other BRAF-mutated malignancies.

Druggable cancer phosphatases

The phosphorylation status of oncoproteins is regulated by both kinases and phosphatases. Kinase inhibitors are rarely sufficient for successful cancer treatment, and phosphatases have been considered undruggable targets for cancer drug development. However, innovative pharmacological approaches for targeting phosphatases have recently emerged. Here, we review progress in the therapeutic targeting of oncogenic Src homology region 2 domain-containing phosphatase-2 (SHP2) and tumor suppressor protein phosphatase 2A (PP2A) and select other druggable oncogenic and tumor suppressor phosphatases. We describe the modes of action for currently available small molecules that target phosphatases, their use in drug combinations, and advances in clinical development toward future cancer therapies.

Dual-Specificity Phosphatase 9 Regulates Cellular Proliferation and Predicts Recurrence After Surgery in Hepatocellular Carcinoma

Hepatocellular carcinoma (CC) is a common and deadly cancer with complex molecular pathogenesis. Little is known about dual-specificity phosphatases (DUSPs) in HCC. We investigated DUSP9 expression in human HCC, associations between DUSP9 and patient outcomes, and effects of altered DUSP9 expression on HCC biology. We studied public data sets as well as 196 patients at our institution who had HCC resections. Quantitative real-time reverse transcription polymerase chain reaction and western blot demonstrated that DUSP9 expression was increased >10-fold in HCC compared to adjacent liver and healthy controls (P = 0.005). Kaplan-Meier and multivariable regression analyses revealed that higher DUSP9 expression was associated with shorter disease-free survival (high DUSP9, 1.6; 95% confidence interval, 0.9-2.3 vs. low DUSP9, 3.4; 95% confidence interval, 1.8-5.0 years; P = 0.04) and increased risk of recurrence (hazard ratio 1.55; 95% confidence interval, 1.01-2.67; P = 0.05) after resection. DUSP9 complementary DNA (cDNA) was cloned using rapid amplification of cDNA ends, revealing two DUSP9 isoforms in human HCC cells. Studies of transcriptional regulation using promoter-luciferase reporter constructs suggested that DUSP9 transcription is regulated by E26 transformation-specific transcription factors. Proliferation of hepatic cells in vitro was enhanced by lentiviral-mediated overexpression of DUSP9. In contrast, DUSP9 knockout HCC cells generated using clustered regularly interspaced short palindromic repeats (CRISPR) demonstrated decreased HCC proliferation and doxorubicin resistance in vitro and impaired xenograft growth in vivo. RNA sequencing, gene set enrichment, and network/pathway analysis revealed that DUSP9 knockout is associated with activation of protein kinase activity and apoptosis. Conclusion: DUSP9 regulates cell proliferation and predicts recurrence after surgery in HCC. DUSP9 may represent a novel prognostic candidate and therapeutic target. Additional studies are warranted to further explore the role and regulation of DUSP9 in HCC.