Dual specific phosphatase 4 suppresses ferroptosis and enhances sorafenib resistance in hepatocellular carcinoma

AIMS

This investigation aims to elucidate the mechanism underlying sorafenib-induced ferroptosis in hepatocellular carcinoma (HCC).

METHODS

The role of dual specificity phosphatase 4 (DUSP4) in sorafenib-treated HCC was investigated using comprehensive assessments both in vitro and in vivo, including Western blotting, qRT-PCR, cell viability assay, lipid reactive oxygen species (ROS) assay, immunohistochemistry, and xenograft tumor mouse model. Additionally, label-free quantitative proteomics was employed to identify potential proteins associated with DUSP4.

RESULTS

Our study revealed that suppression of DUSP4 expression heightens the susceptibility of HCC cells to ferroptosis inducers, specifically sorafenib and erastin, in both in vitro and in vivo settings. Furthermore, we identified DUSP4-mediated regulation of key ferroptosis-related markers, such as ferritin light chain (FTL) and ferritin heavy chain 1 (FTH1). Notably, label-free quantitative proteomics unveiled the phosphorylation of threonine residue T148 on YTH Domain Containing 1 (YTHDC1) by DUSP4. Further investigations unraveled that YTHDC1, functioning as an mRNA nuclear export regulator, is a direct target of DUSP4, orchestrating the subcellular localization of FTL and FTH1 mRNAs. Significantly, our study highlights a strong correlation between elevated DUSP4 expression and sorafenib resistance in HCC.

CONCLUSIONS

Our findings introduce DUSP4 as a negative regulator of sorafenib-induced ferroptosis. This discovery opens new avenues for the development of ferroptosis-based therapeutic strategies tailored for HCC treatment.

Proteomic Signaling of Dual-Specificity Phosphatase 4 (DUSP4) in Alzheimer's Disease

DUSP4 is a member of the DUSP (dual-specificity phosphatase) subfamily that is selective to the mitogen-activated protein kinases (MAPK) and has been implicated in a range of biological processes and functions in Alzheimer's disease (AD). In this study, we utilized the stereotactic delivery of adeno-associated virus (AAV)-DUSP4 to overexpress DUSP4 in the dorsal hippocampus of 5xFAD and wildtype (WT) mice, then used mass spectrometry (MS)-based proteomics along with the label-free quantification to profile the proteome and phosphoproteome in the hippocampus. We identified protein expression and phosphorylation patterns modulated in 5xFAD mice and examined the sex-specific impact of DUSP4 overexpression on the 5xFAD proteome/phosphoproteome. In 5xFAD mice, a substantial number of proteins were up- or down-regulated in both male and female mice in comparison to age and sex-matched WT mice, many of which are involved in AD-related biological processes, such as activated immune response or suppressed synaptic activities. Many proteins in pathways, such as immune response were found to be suppressed in response to DUSP4 overexpression in male 5xFAD mice. In contrast, such a shift was absent in female mice. For the phosphoproteome, we detected an array of phosphorylation sites regulated in 5xFAD compared to WT and modulated via DUSP4 overexpression in each sex. Interestingly, 5xFAD- and DUSP4-associated phosphorylation changes occurred in opposite directions. Strikingly, both the 5xFAD- and DUSP4-associated phosphorylation changes were found to be mostly in neurons and play key roles in neuronal processes and synaptic functions. Site-centric pathway analysis revealed that both the 5xFAD- and DUSP4-associated phosphorylation sites were enriched for a number of kinase sets in females but only a limited number of sets of kinases in male mice. Taken together, our results suggest that male and female 5xFAD mice responded to DUSP4 overexpression via shared and sex-specific molecular mechanisms, which might underly similar reductions in amyloid pathology in both sexes while learning deficits were reduced in only females with DUSP4 overexpression. Finally, we validated our findings with the sex-specific AD-associated proteomes in human cohorts and further developed DUSP4-centric proteomic network models and signaling maps for each sex.

ARID1A loss activates MAPK signaling via DUSP4 downregulation

BACKGROUND

ARID1A, a tumor suppressor gene encoding BAF250, a protein participating in chromatin remodeling, is frequently mutated in endometrium-related malignancies, including ovarian or uterine clear cell carcinoma (CCC) and endometrioid carcinoma (EMCA). However, how ARID1A mutations alter downstream signaling to promote tumor development is yet to be established.

METHODS

We used RNA-sequencing (RNA-seq) to explore transcriptomic changes in isogenic human endometrial epithelial cells after deleting ARID1A. Chromatin immunoprecipitation sequencing (ChIP-seq) was employed to assess the active or repressive histone marks on DUSP4 promoter and regulatory regions. We validated our findings using genetically engineered murine endometroid carcinoma models, human endometroid carcinoma tissues, and in silico approaches.

RESULTS

RNA-seq revealed the downregulation of the MAPK phosphatase dual-specificity phosphatase 4 (DUSP4) in ARID1A-deficient cells. ChIP-seq demonstrated decreased histone acetylation marks (H3K27Ac, H3K9Ac) on DUSP4 regulatory regions as one of the causes for DUSP4 downregulation in ARID1A-deficient cells. Ectopic DUSP4 expression decreased cell proliferation, and pharmacologically inhibiting the MAPK pathway significantly mitigated tumor formation in vivo.

CONCLUSIONS

Our findings suggest that ARID1A protein transcriptionally modulates DUSP4 expression by remodeling chromatin, subsequently inactivating the MAPK pathway, leading to tumor suppression. The ARID1A-DUSP4-MAPK axis may be further considered for developing targeted therapies against ARID1A-mutated cancers.

Identification of DUSP4/6 overexpression as a potential rheostat to NRAS-induced hepatocarcinogenesis

BACKGROUND

Upregulation of the mitogen-activated protein kinase (MAPK) cascade is common in hepatocellular carcinoma (HCC). Neuroblastoma RAS viral oncogene homolog (NRAS) is mutated in a small percentage of HCC and is hitherto considered insufficient for hepatocarcinogenesis. We aimed to characterize the process of N-Ras-dependent carcinogenesis in the liver and to identify potential therapeutic vulnerabilities.

METHODS

NRAS V12 plasmid was delivered into the mouse liver via hydrodynamic tail vein injection (HTVI). The resulting tumours, preneoplastic lesions, and normal tissue were characterized by NanoString® gene expression analysis, Western Blot, and Immunohistochemistry (IHC). The results were further confirmed by in vitro analyses of HCC cell lines.

RESULTS

HTVI with NRAS V12 plasmid resulted in the gradual formation of preneoplastic and neoplastic lesions in the liver three months post-injection. These lesions mostly showed characteristics of HCC, with some exceptions of spindle cell/ cholangiocellular differentiation. Progressive upregulation of the RAS/RAF/MEK/ERK signalling was detectable in the lesions by Western Blot and IHC. NanoString® gene expression analysis of preneoplastic and tumorous tissue revealed a gradual overexpression of the cancer stem cell marker CD133 and Dual Specificity Phosphatases 4 and 6 (DUSP4/6). In vitro, transfection of HCC cell lines with NRAS V12 plasmid resulted in a coherent upregulation of DUSP4 and DUSP6. Paradoxically, this upregulation in PLC/PRF/5 cells was accompanied by a downregulation of phosphorylated extracellular-signal-regulated kinase (pERK), suggesting an overshooting compensation. Silencing of DUSP4 and DUSP6 increased proliferation in HCC cell lines.

CONCLUSIONS

Contrary to prior assumptions, the G12V NRAS mutant form is sufficient to elicit hepatocarcinogenesis in the mouse. Furthermore, the upregulation of the MAPK cascade was paralleled by the overexpression of DUSP4, DUSP6, and CD133 in vivo and in vitro. Therefore, DUSP4 and DUSP6 might fine-tune the excessive MAPK activation, a mechanism that can potentially be harnessed therapeutically.

Proteomic signaling of dual specificity phosphatase 4 (DUSP4) in Alzheimer's disease

DUSP4 is a member of the DUSP (Dual-Specificity Phosphatase) subfamily that is selective to the mitogen-activated protein kinases (MAPK) and has been implicated in a range of biological processes and functions in Alzheimer's disease (AD). In this study, we utilized stereotactic delivery of adeno-associated virus (AAV)-DUSP4 to overexpress DUSP4 in the dorsal hippocampus of 5xFAD and wildtype (WT) mice, then used mass spectrometry (MS)-based proteomics along with label-free quantification to profile the proteome and phosphoproteome in the hippocampus. We identified patterns of protein expression and phosphorylation that are modulated in 5xFAD mice and examined the sex-specific impact of DUSP4 overexpression on the 5xFAD proteome/phosphoproteome. In 5xFAD mice, a substantial number of proteins were up- or down-regulated in both male and female mice in comparison to age and sex-matched WT mice, many of which are involved in AD-related biological processes, such as the activated immune response or suppression of synaptic activities. Upon DUSP4 overexpression, significantly regulated proteins were found in pathways that were suppressed, such as the immune response, in male 5xFAD mice. In contrast, such a shift was absent in female mice. For the phosphoproteome, we detected an array of phosphorylation sites that are regulated in 5xFAD compared to WT, and are modulated by DUSP4 overexpression in each sex. Interestingly, the changes in 5xFAD- and DUSP4-associated phosphorylation occurred in opposite directions. Strikingly, both the 5xFAD- and DUSP4-associated phosphorylation changes were found for the most part in neurons, and play key roles in neuronal processes and synaptic function. Site-centric pathway analysis revealed that both the 5xFAD- and DUSP4-associated phosphorylation sites were enriched for a number of kinase sets in female, but only a limited number of sets of kinases in male mice. Taken together, our results suggest that male and female 5xFAD mice respond to DUSP4 overexpression via shared and sex-specific molecular mechanisms, which might underly similar reductions in amyloid pathology in both sexes, while learning deficits were reduced in only females with DUSP4 overexpression. Finally, we validated our findings with the sex-specific AD-associated proteomes in human cohorts and further developed DUSP4-centric proteomic network models and signaling maps for each sex.

Inhibition of microRNA-122 alleviates pyroptosis by targeting dual-specificity phosphatase 4 in myocardial ischemia/reperfusion injury

Pyroptosis is a type of programmed cell death that induces myocardial ischemia-reperfusion injury (I/RI), which leads to cardiac dysfunction and even lethal reperfusion injury. MiR-122 is a liver-specific miRNA associated with coronary heart disease, but its role in pyroptosis activation in myocardial I/RI remains unclear. Thus, this study aimed to determine whether miR-122 inhibition exerts myocardial I/RI protection in in vivo and in vitro models. An I/RI model was established in vivo using C57BL/J6 male mice. MiR-122 expression was upregulated in the heart tissues from the I/RI group. Quantitative results of echocardiography parameters showed that miR-122 inhibition improved cardiac function and downregulated interleukin (IL)-1β, IL-18, caspase 1, and caspase 11. However, pretransfection with recombinant adeno-associated virus type 9 encoding a DUSP4-specific siRNA (AAV9-siDUSP4) blocked the protective effects of miR-122 inhibition. A hypoxia/reoxygenation (H/R) model was established to mimic the I/R condition in vitro using H9C2 cells. Results showed that miR-122 inhibition increased superoxide dismutase activity (SOD) and cell viability and decreased malondialdehyde (MDA) level, IL-1β, IL-18, caspase 1, caspase 11, and cell death. These protective effects were abolished by transfection with DUSP4-specific siRNA. In summary, miR-122 expression is upregulated in I/RI, and miR-122 inhibition alleviates I/RI by suppressing pyroptosis through targeting DUSP4. Thus, miR-122 may be a novel therapeutic target for treating myocardial I/RI.

TAT-Beclin 1 represses the carcinogenesis of DUSP4-positive PTC by enhancing autophagy

BACKGROUND

DUSP4 is a pro-tumorigenic molecule of papillary thyroid carcinoma (PTC). DUSP4 also exists as an autophagic regulator. Moreover, DUSP4, as a negative regulator of MAPK, can prevent Beclin 1 from participating in autophagic response. This study aimed to explore whether TAT-Beclin 1, a recombinant protein of Beclin 1, could inhibit the tumorigenesis of DUSP4-positive PTC by regulating autophagy.

METHODS

First, we divided PTC tissues into three groups according to DUSP4 expression levels by immunohistochemical analyses, and evaluated the relationship between autophagic molecules (Beclin 1 and LC3II) and DUSP4 using Western blotting assays. After overexpression of DUSP4 by lentiviral transduction, the in vitro and in vivo roles of TAT-Beclin 1 on DUSP4-overexpressed PTC cells were assessed (including autophagic activity, cell survival and function, and tumor growth). The roles of TAT-Beclin 1 in the survival of DUSP4-silenced PTC cells were also evaluated.

RESULTS

Our results showed that the expression levels of autophagic proteins decreased with the increase of DUSP4 expression in PTC tissues. In PTC cells, DUSP4 overexpression-inhibited autophagic activity (including Beclin 1 expression, LC3 conversion rate and LC3-puncta formation) and -promoted cell proliferation and migration were reversed by TAT-Beclin 1 administration. In vivo assays also showed that DUSP4-overexpressed PTC cells had stronger tumorigenic ability and weaker autophagic activity, which was blocked by TAT-Beclin 1 administration.

CONCLUSION

TAT-Beclin 1, as an autophagic promoter, could repress the carcinogenesis of DUSP4-positive PTC, which implies that the use of TAT-Beclin 1 for the PTC patients' treatment might be determined according to the DUSP4 level in their tumors.

DUSP4 inhibits autophagic cell death and apoptosis in colorectal cancer by regulating BCL2-Beclin1/Bax signaling

BACKGROUND

The DUSP4 gene plays an important role in the carcinogenesis of colorectal cancer (CRC). However, the underlying mechanism of DUSP4-regulated colorectal carcinogenesis is unknown. DUSP4 is a negative regulator of the MAP kinase (MAPK) JNK, and JNK-mediated BCL2 phosphorylation is associated with apoptosis and autophagic cell death. Our study aimed to explore the significance of BCL2 phosphorylation-dependent autophagy and apoptosis in DUSP4-promoted colorectal carcinogenesis.

METHODS

We first investigated the roles of DUSP4 in the survival of HCT116 and SW480 CRC cell lines using gene-silencing and -overexpression techniques. Next, we explored the effects of DUSP4 on the BCL2 phosphorylation, autophagy and apoptosis of HCT116 and SW480 cells. Ultimately, with the help of pharmacological inhibitors of Beclin1 and BCL2 (spautin-1 and ABT-737), the relationship between BCL2-Beclin1/Bax signaling and DUSP4-regulated autophagy, apoptosis, survival and migration in HCT116 cells was clarified.

RESULTS

Our results first confirmed the contribution of DUSP4 to the survival of HCT116 and SW480 cells. In addition, DUSP4 silencing resulted in BCL2 phosphorylation and the enhancement in autophagy and apoptosis in HCT116 and SW480 cells, while DUSP4 overexpression showed the opposite effect. Moreover, DUSP4 silencing inhibited the protein interaction between BCL2 and Beclin1 or Bax in HCT116 cells. Moreover, the survival and migration of HCT116 cells inhibited by DUSP4 silencing were blocked by autophagy inhibition with spautin-1. Notably, the survival and migration of HCT116 cells promoted by DUSP4 overexpression were reversed by ABT-737.

CONCLUSIONS

It was indicated that DUSP4 can maintain the survival and function of CRC cells by inhibiting BCL2 phosphorylation-dependent autophagic cell death and apoptosis.

Genome-Wide CRISPR/Cas9 Library Screening Identified that DUSP4 Deficiency Induces Lenvatinib Resistance in Hepatocellular Carcinoma

Background: Lenvatinib is in a first-line therapy for advanced hepatocellular carcinoma (HCC). However, drug resistance is one of the principal obstacles for treatment failure. The molecular mechanism of Lenvatinib resistance has not been well investigated.

Materials and methods: A genome-wide CRISPR/Cas9 knockout screening system was established and bioinformatic analysis was used to identify critical genes associated with Lenvatinib resistance. Cell proliferation assays, colony formation assays and cell migration assays were performed to investigate the effect of drug resistance associated genes, particularly DUSP4, on cancer cell malignant behavior during Lenvatinib treatment. In vivo experiments were conducted by using a xenograft mouse model.

Results: We identified six genes that were associated with Lenvatinib resistance in HCC, including DUSP4, CCBL1, DHDH, CNTN2, NOS3 and TNF. DUSP4 was found to be significantly decreased at the mRNA and protein levels in Lenvatinib resistant HCC cells. DUSP4 knockout enhanced HCC cell survival, cell proliferation and migration during Lenvatinib treatment in vitro and in vivo, accompanied by regulation of p-ERK and p-MEK levels. This finding implied that DUSP4 deficiency induced Lenvatinib resistance. Interestingly, DUSP4 deficiency induced Lenvatinib resistance was abrogated by the MEK inhibitor Selumetinib, implying that MEK phosphorylation and DUSP4-inhibition dependent ERK activation were required for drug resistance. Finally, we found that DUSP4 deficiency was associated with HCC prognosis and response to Lenvatinib based on clinical data.

Conclusions: DUSP4 deficiency mediates Lenvatinib resistance by activating MAPK/ERK signaling and combination therapy using Lenvatinib and MEK inhibitors may be a promising therapeutic strategy for overcoming Lenvatinib resistance.

Loss of DUSP4 Expression as a Prognostic Biomarker in Clear Cell Renal Cell Carcinoma

Dual-specificity protein phosphatase 4 (DUSP4) is a negative regulator of mitogen-activated protein kinases. The prognostic impact of DUSP4 expression in renal cell carcinoma is not well studied. Therefore, we evaluated the clinicopathological implications of DUSP4 expression in clear cell renal cell carcinoma by performing immunohistochemistry (IHC). The clinical outcome according to DUSP4 expression was evaluated through survival analyses, and the association between mRNA expression and prognosis was confirmed by online analysis (Kaplan-Meier plotter). Loss of DUSP4 expression was noted in most histological subtypes of renal cell carcinoma. Loss of DUSP4 expression in clear cell renal cell carcinoma was significantly correlated with old age (p = 0.033), high histologic grade (p < 0.001), tumor necrosis (p < 0.001), and high pT category (p < 0.001). In survival analysis, loss of DUSP4 expression was associated with poor clinical outcomes in cancer-specific survival and recurrence-free survival (p = 0.010 and p = 0.007, respectively). Upon TCGA data analysis, patients with low DUSP4 mRNA expression showed a shorter overall survival (p = 0.023). These results suggest that loss of DUSP4 expression can be used as a potential biomarker for predicting clinical outcomes in clear cell renal cell carcinoma patients.

Long non-coding RNA AFAP1-AS1 promotes thyroid cancer progression by sponging miR-204-3p and upregulating DUSP4

Long non-coding RNA (lncRNA) actin filament-associated protein 1-antisense RNA 1 (AFAP1-AS1), shows crucial regulatory function in tumor progression. Nonetheless, the biological function and underlying mechanism of AFAP1-AS1 in the progression of thyroid cancer is still unclear. Expressions of AFAP1-AS1, miR-204-3p, and DUSP4 were quantified utilizing qRT-PCR and/or Western blot. In loss-of-function and gain-of-function assays, cell proliferation, migration and invasion were appraised by CCK-8 assay, wound healing assay, Transwell migration and invasion assays, respectively. Luciferase reporter assay was employed for validating the interaction between miR-204-3p and AFAP1-AS1 or the 3'UTR of dual specificity phosphatase 4 (DUSP4). AFAP1-AS1 was highly expressed in thyroid cancer tissues and cell lines. Highly expressed AFAP1-AS1 was in association with advanced TNM stage and positive lymph node metastasis. Knockdown of AFAP1-AS1 suppressed the proliferation, migration and invasion of thyroid cancer cells, and overexpression of AFAP1-AS1 induced a reversed effect. MiR-204-3p was targetedly repressed by AFAP1-AS1, and miR-204-3p could negatively regulate DUSP4 expression. AFAP1-AS1 augmented the expression of DUSP4 via repressing miR-204-3p, and the effects of AFAP1-AS1 overexpression on thyroid cancer cells were also partly abolished by miR-204-3p restoration. In summary, AFAP1-AS1 facilitates thyroid cancer cell proliferation, migration, and invasion by regulating miR-204-3p/DUSP4 axis.

Methylation of dual-specificity phosphatase 4 controls cell differentiation

Mitogen-activated protein kinases (MAPKs) are inactivated by dual-specificity phosphatases (DUSPs), the activities of which are tightly regulated during cell differentiation. Using knockdown screening and single-cell transcriptional analysis, we demonstrate that DUSP4 is the phosphatase that specifically inactivates p38 kinase to promote megakaryocyte (Mk) differentiation. Mechanistically, PRMT1-mediated methylation of DUSP4 triggers its ubiquitinylation by an E3 ligase HUWE1. Interestingly, the mechanistic axis of the DUSP4 degradation and p38 activation is also associated with a transcriptional signature of immune activation in Mk cells. In the context of thrombocytopenia observed in myelodysplastic syndrome (MDS), we demonstrate that high levels of p38 MAPK and PRMT1 are associated with low platelet counts and adverse prognosis, while pharmacological inhibition of p38 MAPK or PRMT1 stimulates megakaryopoiesis. These findings provide mechanistic insights into the role of the PRMT1-DUSP4-p38 axis on Mk differentiation and present a strategy for treatment of thrombocytopenia associated with MDS.

Transcriptional regulation of human DUSP4 gene by cancer-related transcription factors

Dual specificity phosphatase 4 (DUSP4), a member of the dual specificity phosphatase family, is responsible for the dephosphorylation and inactivation of ERK, JNK and p38, which are mitogen-activated protein kinases involved in cell proliferation, differentiation and apoptosis, but also in inflammation processes. Given its importance for cellular signalling, DUSP4 is subjected to a tight regulation and there is growing evidence that its expression is dysregulated in several tumours. However, the mechanisms underlying DUSP4 transcriptional regulation remain poorly understood. Here, we analysed the regulation of the human DUSP4 promoters 1 and 2, located upstream of exons 1 and 2, respectively, by the cancer-related transcription factors (TFs) STAT3, FOXA1, CTCF and YY1. The presence of binding sites for these TFs was predicted in both promoters through the in silico analysis of DUSP4, and their functionality was assessed through luciferase activity assays. Regulatory activity of the TFs tested was found to be promoter-specific. While CTCF stimulated the activity of promoter 2 that controls the transcription of variants 2 and X1, STAT3 stimulated the activity of promoter 1 that controls the transcription of variant 1. YY1 positively regulated both promoters, although to different extents. Through site-directed mutagenesis, the functionality of YY1 binding sites present in promoter 2 was confirmed. This study provides novel insights into the transcriptional regulation of DUSP4, contributing to a better comprehension of the mechanisms of its dysregulation observed in several types of cancer.

DUSP4 promotes the carcinogenesis of CCRCC via negative regulation of autophagic death

DUSP4 is considered as an oncogenic gene. However, the effect of DUSP4 on the carcinogenesis of clear cell Renal cell carcinoma (CCRCC) is still unclear. In this study, DUSP4 mRNA levels were significantly increased in CCRCC tissues and cell lines. Furthermore, DUSP4 overexpression promotes the proliferation, migration, and tumorigenicity of CCRCC cells while DUSP4 silencing showed the opposite effects. Importantly, both autophagic activity (LC3 conversion rate and LC3 puncta formation) and total death level promoted by DUSP4 silencing were reversed by treatment with 3-MA in CCRCC cells. Moreover, the proliferation and migration of CCRCC cells inhibited by DUSP4 silencing were also recovered by suppression of autophagy with 3-MA. In conclusion, DUSP4 serves as an oncogenic gene in CCRCC carcinogenesis due to its inhibitory effect on autophagic death, indicating the potential value of DUSP4 in the diagnosis and treatment of CCRCC.

Low DUSP4 Expression Is Associated With Aggressive Phenotypes and Poor Prognosis in Gastric Cancer

BACKGROUND/AIM

Dual-specificity protein phosphatase 4 (DUSP4) negatively regulates MAPK signaling and is involved in various cellular processes. We herein evaluated the relationship between DUSP4 expression and clinicopathological characteristics in a large series of gastric cancer samples.

MATERIALS AND METHODS

DUSP4 expression was examined by immunohistochemistry in 508 gastric cancer samples. Cases were classified according to the TCGA molecular classification and HER2 amplification. Kaplan-Meier plots were used to predict the relationship between mRNA expression of DUSP4 and survival.

RESULTS

Low expression of DUSP4 was significantly correlated with larger tumor size, higher pT category, positive nodal status, higher stage, lymphovascular invasion, perineural invasion, worse overall survival, and worse recurrence-free survival. No correlation was observed between DUSP4 expression and molecular characteristics. Bioinformatics analysis showed that low mRNA expression was associated with a poor prognosis.

CONCLUSION

Low expression of DUSP4 is associated with aggressive phenotypes of gastric cancer and a poor prognosis.

Nicotine-derived NNK induces the stemness enrichment of CRC cells through regulating the balance of DUSP4-ERK1/2 feedback loop

Cigarette smoking has been considered as an independent risk factor for colorectal cancer (CRC) initiation and progression. In this study, we found that cigarette smoking was significantly associated with poor CRC differentiation (P = 0.040). Since studies have indicated that poorly differentiated tumors are more aggressive and metastasize earlier, leading to poorer prognosis; and cancer stem cells (CSCs) are largely responsible for tumor differentiation state, here we observed that the exposure of nicotine-derived 4-(methylnitrosamino)- 1-(3-pyridyl)- 1-butanone (NNK) promoted cell sphere formation and the expression of the stem cell markers, CD44, OCT4, C-MYC and NANOG in HCT8 and DLD-1 cells. Further colony formation assay, CCK-8 assay and tumor-bearing experiment showed that NNK exposure significantly increased the proliferative and growth ability of CRC cells. In mechanism, we found that NNK-activated ERK1/2 played an important role in enrichment of CRC stem cells and the up-regulation of DUSP4, a major negative regulator of ERK1/2. Moreover, DUSP4 up-regulation was essential for maintaining NNK-activated ERK1/2 in an appropriate level, which was an required event for NNK-induced stemness enrichment of CRC cells. Taken together, our findings provided a possible mechanistic insight into cigarette smoking-induced CRC progression.

DUSP4 inhibits autophagic cell death in PTC by inhibiting JNK-BCL2-Beclin1 signaling

Dual specificity phosphatase 4 (DUSP4) is a prognostic marker and potential target of papillary thyroid carcinoma (PTC); however, the molecular mechanism underlying DUSP4-regulated PTC carcinogenesis is unknown. DUSP4 is a negative regulator of the autophagy promoter, JNK. This study explored the relationship between DUSP4 and JNK-mediated autophagic cell death in PTC, and the roles of DUSP4 in PTC using gain-of-function and loss-of-function assays. In addition, we further identified the significance of the JNK-BCL2-Beclin1-autophagy signaling pathway on DUSP4-regulated PTC carcinogenesis by combining knockdown of DUSP4 with a JNK-specific inhibitor (SP600125). We found that knockdown of DUSP4 promoted the phosphorylation of JNK and BCL2 in PTC cells, and enhanced the release of Beclin1 from the BCL2-Beclin1 complex. Knockdown of DUSP4 promoted autophagy and the death of PTC cells. The death and autophagy enhanced by knockdown of DUSP4 was reversed by the JNK inhibitor. We further extended the in-vitro experiments by subcutaneously injecting nude mice with K1 cells transfected with DUSP4-silencing vector. In-vivo assays showed that knockdown of DUSP4 not only inhibited tumor growth, but also promoted the phosphorylation of JNK and BCL2 and the expression of LC3II. In conclusion, DUSP4 inhibits BCL2-Beclin1-autophagy signaling by negatively regulating JNK activity, thus inhibiting PTC oncogenesis. The data from this study contribute to the prevention and cure of PTC.

The microRNA-429/DUSP4 axis regulates the sensitivity of colorectal cancer cells to nintedanib

Colorectal cancer (CRC) is recognized as one of the most common malignancies, which ranks third among all cancer-related deaths worldwide. Nintedanib is an orally available tyrosine kinase inhibitor that can treat CRC; however, drug resistance to nintedanib leads to unsatisfactory treatments for patients with CRC. The aim of the present study was to explore whether overexpression of miR-429 elevated the sensitivity of CRC cells to nintedanib by downregulating dual specificity protein phosphatase 4 (DUSP4). The nintedanib-resistant CRC cell model was established via the treatment of cells with nintedanib in a dose-dependent manner. Reverse transcription-quantitative PCR was used to detect the expression levels of miR-429 and DUSP4, and to confirm the transfection efficiency of miR-429 mimic and DUSP4 overexpression plasmid. Cell Counting Kit-8 assay was utilized to measure the inhibition rate of cells. Western blotting was conducted to observe the expression levels of DUSP4 protein, apoptosis-related proteins and proteins related to the JNK signaling pathway. Dual-luciferase reporter assay was performed to evaluate luciferase activity and TUNEL assay was conducted to detect the apoptosis of cells. The results revealed that miR-429 mimic elevated the sensitivity of CRC cells to nintedanib. Moreover, by ENCORI prediction, DUSP4 was identified as a target gene of miR-429, and overexpression of DUSP4 reversed the inducing effect of miR-429 overexpression on the sensitivity of CRC cells to nintedanib. In conclusion, overexpression of miR-429 may elevate the sensitivity of CRC cells to nintedanib through inhibition of the JNK signaling pathway by targeting DUSP4. These findings may aid in the prevention of drug resistance of CRC cells to nintedanib.

Analysis of CRISPR-Cas9 screens identifies genetic dependencies in melanoma

Targeting the MAPK signaling pathway has transformed the treatment of metastatic melanoma. CRISPR-Cas9 genetic screens provide a genome-wide approach to uncover novel genetic dependencies that might serve as therapeutic targets. Here, we analyzed recently reported CRISPR-Cas9 screens comparing data from 28 melanoma cell lines and 313 cell lines of other tumor types in order to identify fitness genes related to melanoma. We found an average of 1,494 fitness genes in each melanoma cell line. We identified 33 genes, inactivation of which specifically reduced the fitness of melanoma. This set of tumor type-specific genes includes established melanoma fitness genes as well as many genes that have not previously been associated with melanoma growth. Several genes encode proteins that can be targeted using available inhibitors. We verified that genetic inactivation of DUSP4 and PPP2R2A reduces the proliferation of melanoma cells. DUSP4 encodes an inhibitor of ERK, suggesting that further activation of MAPK signaling activity through its loss is selectively deleterious to melanoma cells. Collectively, these data present a resource of genetic dependencies in melanoma that may be explored as potential therapeutic targets.

Transcriptome Profiling Reveals New Insights into the Immune Microenvironment and Upregulation of Novel Biomarkers in Metastatic Uveal Melanoma

Simple Summary

Uveal melanoma (UM) is a rare aggressive eye cancer. Although treatment of the eye tumour is successful, about 50% of UM patients develop a relapse of their cancer in the liver. At present, such advanced disease is not curable. A better understanding of the metastatic UM (mUM) in the liver is essential to improve patient survival. This study examines both the response of immune cells within the liver to the UM secondaries (metastases), as well as the expression of various proteins by the UM cells. Our study demonstrates that there is a limited immune response to the mUM, but reveals that a certain type of reactive immune cell: a protumourigenic subset of macrophage is dominant within the mUM. Our research also reveals novel proteins within the mUM, which are specific to these cells and therefore may be targetable in future therapies.

Abstract

Metastatic uveal melanoma (mUM) to the liver is incurable. Transcriptome profiling of 40 formalin-fixed paraffin-embedded mUM liver resections and 6 control liver specimens was undertaken. mUMs were assessed for morphology, nuclear BAP1 (nBAP1) expression, and their tumour microenvironments (TME) using an “immunoscore” (absent/altered/high) for tumour-infiltrating lymphocytes (TILs) and macrophages (TAMs). Transcriptomes were compared between mUM and control liver; intersegmental and intratumoural analyses were also undertaken. Most mUM were epithelioid cell-type (75%), amelanotic (55%), and nBAP1-ve (70%). They had intermediate (68%) or absent (15%) immunoscores for TILs and intermediate (53%) or high (45%) immunoscores for TAMs. M2-TAMs were dominant in the mUM-TME, with upregulated expression of ANXA1, CD74, CXCR4, MIF, STAT3, PLA2G6, and TGFB1. Compared to control liver, mUM showed significant (p < 0.01) upregulation of 10 genes: DUSP4, PRAME, CD44, IRF4/MUM1, BCL2, CD146/MCAM/MUC18, IGF1R, PNMA1, MFGE8/lactadherin, and LGALS3/Galectin-3. Protein expression of DUSP4, CD44, IRF4, BCL-2, CD146, and IGF1R was validated in all mUMs, whereas protein expression of PRAME was validated in 10% cases; LGALS3 stained TAMs, and MFGEF8 highlighted bile ducts only. Intersegmental mUMs show differing transcriptomes, whereas those within a single mUM were similar. Our results show that M2-TAMs dominate mUM-TME with upregulation of genes contributing to immunosuppression. mUM significantly overexpress genes with targetable signalling pathways, and yet these may differ between intersegmental lesions.

Aberrant expression of DUSP4 is a specific phenomenon in betel quid-related oral cancer

Oral cancer due to betel quid chewing habit is very common in South Asian countries. We attempted to detect the presence of a novel gene in epithelial cells stimulated with arecoline, a main component of betel quid. Human gingival epithelial progenitors were cultured and treated with a 3-day alternating regimen with/without 50 μg/ml arecoline for 1 month. DNA microarray and methylation arrays were analyzed to identify the candidate genes. Immunohistochemical staining was performed in the tissue samples. Genome-wide analyses, quantitative reverse transcription PCR and quantitative methylation-specific PCR revealed DUSP4 as the most significant and promising gene. The methylation levels of DUSP4 were significantly higher in the betel quid-related oral squamous cell carcinoma (OSCC) than those in the non-related OSCC and controls (Mann-Whitney U test, p < 0.05). The number of DUSP4 immunopositive cells in betel quid-related OSCC was significantly higher than those from the non-chewing patients and the controls (p < 0.05). Hypermethylation of DUSP4 may be considered as a specific event in betel quid-related oral cancer.

DUSP4 directly deubiquitinates and stabilizes Smad4 protein, promoting proliferation and metastasis of colorectal cancer cells

Colorectal cancer is a common health-threatening tumor within the gastrointestinal tract. The aim of this study was to test the biological role of DUSP4 in colorectal cancer cells. In our study, DUSP4 overexpression-treated HCT116 cells and DUSP4 knockdown-treated SW480 cells were selected to perform study. Quantitative real-time PCR test (qRT-PCR) and western blot were used to detect DUSP4 abundance in clinical tissues and six cell lines, as well as ubiquitin-related Smad4 degradation. Western blot, migration and invasion. were used to assess the relationships between DUSP4 and Smad4. Higher DUSP4 expression of functional significance was observed in colorectal cancer tissues and cells. The results showed that both treatments could affect the proliferation, colony formation, migration, invasion of tumor cells, and the expression of epithelial mesenchymal transformation (EMT)-associated biomarkers. Moreover, in colorectal cancer cells, DUSP4 could promote the Smad4 degradation by regulating ubiquitin-related Smad4 degradation, and promote the cell proliferation, migration and invasion by regulating Smad4 degradation via Smad4 gene. Meanwhile, DUSP4 can directly deubiquitinate and stabilize Smad4 protein, hence further promote proliferation and metastasis of colorectal cancer cells.

Dusp4 Contributes to Anesthesia Neurotoxicity via Mediated Neural Differentiation in Primates

Background

Children who are exposed to anesthesia multiple times may undergo cognitive impairment during development. The underlying mechanism has been revealed as anesthesia-induced cognitive deficiency in young rodents and monkeys. However, the molecular mechanism of sevoflurane-induced neural development toxicity is unclear.

Methods

By combining RNA sequencing analysis of macaques’ prefrontal cortex and human neural differentiation, this study investigates the mechanism of sevoflurane-induced neurotoxicity in primates.

Results

The level of dual specificity protein phosphatase 4 (Dusp4) was significantly downregulated in non-human primates after sevoflurane treatment. We further uncovered the dynamical expression of Dusp4 during the human neural differentiation of human embryonic stem cells and found that knockdown of Dusp4 could significantly inhibit human neural differentiation.

Conclusion

This study indicated that Dusp4 is critically involved in the sevoflurane-induced inhibition of neural differentiation in non-human primate and the regulation of human neural differentiation. It also suggested that Dusp4 is a potential therapeutic target for preventing the sevoflurane-induced neurotoxicity in primates.

DUSP4 is involved in the enhanced proliferation and survival of DUSP4-overexpressing cancer cells

Dual-specificity phosphatase 4 (DUSP4), a MAP kinase phosphatase, has been regarded as a tumor suppressor gene in several cancers. However, high-level expression of DUSP4 is occasionally observed in specific cancers and its functional significance in carcinogenesis is not fully understood. In the present study, we showed that downregulation of DUSP4 suppressed the proliferation of cancer cell lines exhibiting high expression of DUSP4 by inducing apoptosis and cell cycle arrest at G2/M phase. Expression microarray analyses and pathway analyses revealed that downregulation of DUSP4 activated the p53 signaling pathway, and might be involved in cell growth suppression. Aberrant accumulation of p53 and induction of p53 downstream target genes were further investigated. Furthermore, cell growth suppression following downregulation of DUSP4 was markedly attenuated in p53-deleted cells established using the CRISPR/Cas9 system. These findings suggest that constitutive expression of DUSP4 in cancer cells contributes to enhanced proliferation through escape from apoptosis and cell cycle arrest. We propose that DUSP4 could be a novel therapeutic target for cancers overexpressing it.

MiR-122-5p protects against acute lung injury via regulation of DUSP4/ERK signaling in pulmonary microvascular endothelial cells

AIMS

The aim of this study was to explore the role of miR-122-5p in acute lung injury.

MATERIALS AND METHODS

Mice were subjected to intratracheal injection of lipopolysaccharide to establish an acute lung injury model. The mice also received miR-122-5p antagonist and mimic via injection to inhibit or overexpress miR-122-5p in the lung tissue, respectively. In an in vitro experiment, we isolated primary mouse lung microvascular endothelial cells and established a cell injury model via lipopolysaccharide treatment.

KEY FINDINGS

Mice injected with an miR-122-5p antagonist exhibited reduced lung injury, inflammation and oxidative stress, while mice injected with a miR-122-5p mimic exhibited exaggerated lung injury, inflammation and oxidative stress. In an in vitro experiment, we found that the miR-122-5p antagonist suppressed lipopolysaccharide-induced inflammation, apoptosis and oxidative stress. Moreover, miR-122-5p regulated the promoter activity of DUSP4, which negatively regulated ERK1/2 signaling. The use of DUSP4 siRNA counteracted the effects of the miR-122-5p antagonist.

SIGNIFICANCE

Taken together, these results show that miR-122-5p protected against acute lung injury via regulation of DUSP4/ERK signaling in pulmonary microvascular endothelial cells. MiR-122-5p antagonism may be a promising treatment method for acute lung injury.

Dual specificity phosphatase (DUSP)-4 is induced by platelet-derived growth factor -BB in an Erk1/2-, STAT3- and p53-dependent manner

Dual specificity phosphatase (DUSP) 4 has been described as a negative regulator of MAP kinase signaling, in particular for the ERK1/2 and JNK pathways. We found that DUSP4 expression was upregulated in response to prolonged platelet-derived growth factor (PDGF)-BB stimulation. The PDGF-BB-induced DUSP4 expression was dependent on ERK1/2, STAT3 and p53. We found that inhibition of ERK1/2 effectively reduced DUSP4 mRNA levels, whereas STAT3 was necessary for maintaining p53 expression. p53 has binding sites in the DUSP4 promoter and was found to promote DUSP4 expression.

miR-1226-3p Promotes Sorafenib Sensitivity of Hepatocellular Carcinoma via Downregulation of DUSP4 Expression

Background: Sorafenib appears to increase the survival rate of hepatocellular carcinoma (HCC) patients, but its response rate is seriously limited due to drug resistance. Molecular mechanisms underlying sorafenib resistance are still unknown. Herein, we explored the possible role of miR-1226-3p in sorafenib resistance of HCC.

Methods: The miR-1226-3p expression level in HCC cell lines was evaluated by qRT-PCR. Cell viabilities to sorafenib were measured by CCK-8 assay. Cell apoptosis and proliferation were detected by flow cytometry and EdU proliferation assay. A luciferase reporter of DUSP4 3'-UTR was used for validation as a target gene of miR-1226-3p. Finally, the effects of in vivo antitumor efficacy of miR-1226-3p combined with sorafenib were evaluated by HCC tumor xenografts in nude mice.

Results: Bioinformatics analysis from Gene Expression Omnibus (GEO) datasets GSE56059 suggested that miR-1226-3p expression was downregulated in HCC patients who showed progressive disease (PD) after sorafenib treatment. SK-HEP-1 cells expressed lower levels of miR-1226-3p than HepG2 cells. We confirmed that SK-HEP-1 cells were more resistant to sorafenib compared to HepG2 cells. In addition, miR-1226-3p mimic increased cell apoptosis of SK-HEP-1 cells, whereas miR-1226-3p inhibitor significantly impaired cell apoptosis of HepG2 cells after sorafenib treatment. Moreover, we validated that miR-1226-3p directly targeted dual specificity phosphatase 4 (DUSP4), and further demonstrated that knockdown of DUSP4 reduced sorafenib resistance by regulating the JNK-Bcl-2 axis.

Conclusions: miR-1226-3p promotes sorafenib sensitivity of HCC through downregulation of DUSP4 expression, and targeting miR-1226-3p may be a novel therapeutic strategy for overcoming sorafenib resistance.

Patterns of Dual-Specific Phosphatase 4 mRNA Expression Before and after Neoadjuvant Chemotherapy in Breast Cancer

Objective: Evaluation of the neoadjuvant chemotherapy response can be performed by comparing the breast cancer burden and pathobiology before and after treatment. This study was aimed to investigate the pattern of dualspecific phosphatase 4 (DUSP4) mRNA expression in breast cancer cells before and after neoadjuvant chemotherapy. Methods: This was a longitudinal study. Twenty samples of matched breast cancer tissue taken from biopsy before and after chemotherapy were subjected to qRT-PCR to detect DUSP4 mRNA expression. Results: The mean value of DUSP4 mRNA expression in prechemotherapy breast cancer patients was 9.906±0.333 and that in breast cancer patients postchemotherapy was 10.016±1.062. In the responsive group, the rate of DUSP4 mRNA expression increased by 0.476 after chemotherapy. In the nonresponsive group, the proportion of DUSP4 mRNA expression likely decreased by 1.012. Statistical analysis found no significant correlation between DUSP4 mRNA expression prechemotherapy and the clinical chemotherapeutic response with p-value = 0.994 (p ≥0.05). A significant correlation was found between the postchemotherapy DUSP4 mRNA expression and the clinical chemotherapeutic response with p-value = 0.003 (p < 0.5). Conclusion: No significant difference was found in the mRNA expression of DUSP4 in pre- and post-neoadjuvant chemotherapy specimens. High DUSP4 expression postchemotherapy shows a substantial correlation with the chemotherapeutic response.

MiR-122-5p inhibits cell migration and invasion in gastric cancer by down-regulating DUSP4

OBJECTIVE

To explore the relationship between miR-122-5p and DUSP4 and their effects on gastric cancer (GC) cell mobility and invasiveness.

METHODS

Abnormally expressed miRNAs and mRNAs were analyzed using microarrays. The miR-122-5p and DUSP4 mRNA expression levels in GC tissues and cells were determined by RT-qPCR. The target relationship between miR-122-5p and DUSP4 was validated by dual luciferase reporter assay. GC cell mobility and invasiveness were respectively observed by wound healing assay and transwell invasion assay. Western blot and immunohistochemistry were used for detection of the expressions of DUSP4 protein and MMP2 and MMP9 proteins related to cell invasion and migration. The migration and invasion abilities of gastric cancer cells in vivo were evaluated according to the number of lung metastatic nodules in mice.

RESULTS

The expression of miR-122-5p in GC tissues and cells was significantly down-regulated, whereas DUSP4 expression was up-regulated. Bioinformatics prediction strategies and dual luciferase reporter assay verified the binding sites of miR-122-5p on 3'UTR of DUSP4 and the target relationship between miR-122-5p and DUSP4. Overexpression of miR-122-5p and knockdown of DUSP4 in BGC-823 cells observantly suppressed GC cell mobility and invasiveness, whereas downregulation of miR-122-5p expression promoted cell metastasis. MiR-122-5p inhibited GC cell mobility and invasiveness and pulmonary tumor metastasis via downregulation of DUSP4.

CONCLUSION

MiR-122-5p restrained migration and invasion abilities of GC cells by repressing DUSP4.

Downregulation of dual-specificity phosphatase 4 enhances cell proliferation and invasiveness in colorectal carcinomas

It is widely accepted that aberrant activation of the Wnt signaling pathway is responsible for the development of precursor lesions of colorectal cancer (CRC). However, the molecular mechanisms involved in the process of progression from these precursor lesions to invasive lesions of CRC are not fully understood. Recently, we reported that constitutive activation of MAPK accompanied by downregulation of dual‐specificity phosphatase 4 (DUSP4), a MAPK phosphatase, contributes to the progression of precursor lesions in the pancreas. In this study, we found that downregulation of DUSP4 was related to constitutive activation of ERKs in CRC cells. Restoration of DUSP4 resulted in inactivation of ERKs, leading to suppression of both proliferation and invasiveness, as shown by treatment with an MEK inhibitor. Furthermore, immunohistochemistry revealed that DUSP4 expression was upregulated in the superficial region of CRC tissue, whereas it was significantly downregulated in the deep region. In contrast, ERKs in the deep region were markedly hyperactivated compared to those in the superficial region. These results suggest that activation of the MAPK signaling pathway caused by downregulation of DUSP4 is responsible for progression of CRCs and would be a promising therapeutic target.

Convergence of BMI1 and CHD7 on ERK Signaling in Medulloblastoma

We describe molecular convergence between BMI1 and CHD7 in the initiation of medulloblastoma. Identified in a functional genomic screen in mouse models, a BMI1High;CHD7Low expression signature within medulloblastoma characterizes patients with poor overall survival. We show that BMI1-mediated repression of the ERK1/2 pathway leads to increased proliferation and tumor burden in primary human MB cells and in a xenograft model, respectively. We provide evidence that repression of the ERK inhibitor DUSP4 by BMI1 is dependent on a more accessible chromatin configuration in G4 MB cells with low CHD7 expression. These findings extend current knowledge of the role of BMI1 and CHD7 in medulloblastoma pathogenesis, and they raise the possibility that pharmacological targeting of BMI1 or ERK may be particularly indicated in a subgroup of MB with low expression levels of CHD7.

DUSP4 promotes doxorubicin resistance in gastric cancer through epithelial-mesenchymal transition

Chemoresistance limits treatment efficacy in gastric cancer and doxorubicin resistance is common in gastric cancer cells. Dual specificity phosphatase 4 (DUSP4) has been associated with tumor progression. This study aimed to investigate the mechanism of DUSP4 regulating doxorubicin resistance in gastric cancer cells. Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay were used to measure cell viability and proliferation in gastric cancer cells treated with doxorubicin. The expression of DUSP4, E-cadherin and Vimentin protein was detected by Western blotting. Overexpression of DUSP4 was more resistant to doxorubicin in gastric cancer cells. Knockdown of DUSP4 increased the sensitivity of gastric cancer cells to doxorubicin. Moreover, up-regulation of DUSP4 promoted the Epithelial-Mesenchymal Transition (EMT) in gastric cancer cells, but blocking the EMT using a Twist siRNA increased the sensitivity of gastric cancer cells to doxorubicin and confirmed the EMT was involved in DUSP4-mediated doxorubicin resistance. These findings demonstrated that DUSP4 could enhance doxorubicin resistance by promoting EMT in gastric cancer cells.

DUSP4 is associated with increased resistance against anti-HER2 therapy in breast cancer

The majority of patients develop resistance against suppression of HER2-signaling mediated by trastuzumab in HER2 positive breast cancer (BC). HER2 overexpression activates multiple signaling pathways, including the mitogen-activated protein kinase (MAPK) cascade. MAPK phosphatases (MKPs) are essential regulators of MAPKs and participate in many facets of cellular regulation, including proliferation and apoptosis. We aimed to identify whether differential MKPs are associated with resistance to targeted therapy in patients previously treated with trastuzumab. Using gene chip data of 88 HER2-positive, trastuzumab treated BC patients, candidate MKPs were identified by Receiver Operator Characteristics analysis performed in R. Genes were ranked using their achieved area under the curve (AUC) values and were further restricted to markers significantly associated with worse survival. Functional significance of the two strongest predictive markers was evaluated in vitro by gene silencing in HER2 overexpressing, trastuzumab resistant BC cell lines SKTR and JIMT-1. The strongest predictive MKPs were DUSP4/MKP-2 (AUC=0.75, p=0.0096) and DUSP6/MKP-3 (AUC=0.77, p=5.29E-05). Higher expression for these correlated to worse survival (DUSP4: HR=2.05, p=0.009 and DUSP6: HR=2, p=0.0015). Silencing of DUSP4 had significant sensitization effects – viability of DUSP4 siRNA transfected, trastuzumab treated cells decreased significantly compared to scramble-siRNA transfected controls (SKTR: p=0.016; JIMT-1: p=0.016). In contrast, simultaneous treatment with DUSP6 siRNA and trastuzumab did not alter cell proliferation. Our findings suggest that DUSP4 may represent a new potential target to overcome trastuzumab resistance.

Nimbolide suppresses non-small cell lung cancer cell invasion and migration via manipulation of DUSP4 expression and ERK1/2 signaling

Nimbolide plays an important role in treating human diseases. In these years, the anticancer property of nimbolide has been paid more and more attention. However, the role of nimbolide in non-small cell lung cancer (NSCLC) remains unclear. In this study, we found that nimbolide treatment suppressed the invasion and migration of NSCLC cells, in a dose-dependent manner. Moreover, nimbolide treatment dose-dependently inhibited ERK1/2 activation, decreased Snail and MMP-3 expression, and increased E-cadherin expression. Further, we found that nimbolide treatment upregulated DUSP4 expression. DUSP4 knockdown attenuated nimbolide-mediated inhibition of cell invasion, migration and ERK1/2 activation. We also found that DUSP4 knockdown suppressed the effect of nimbolide on MMP-3, Snail and E-cadherin expression. Taken together, our study demonstrates that nimbolide treatment can upregulate the expression of DUSP4, thus inhibiting ERK1/2 activation. Inhibition of ERK1/2 pathway by nimbolide decreases MMP-3 and Snail expression, and increases E-cadherin expression, which finally inhibits NSCLC cell invasion and migration. Therefore, nimbolide may act as a novel drug to inhibit NSCLC invasion and metastasis through manipulation of ERK1/2 signaling and DUSP4 expression.

ERBB activation modulates sensitivity to MEK1/2 inhibition in a subset of driver-negative melanoma

Melanomas are characterized by activating “driver” mutations in BRAF, NRAS, KIT, GNAQ, and GNA11. Resultant mitogen-activated protein kinase (MAPK) pathway signaling makes some melanomas susceptible to BRAF (BRAF V600 mutations), MEK1/2 (BRAF V600, L597, fusions; NRAS mutations), or other kinase inhibitors (KIT), respectively. Among driver-negative (“pan-negative”) patients, an unexplained heterogeneity of response to MEK1/2 inhibitors has been observed. Analysis of 16 pan-negative melanoma cell lines revealed that 8 (50%; termed Class I) are sensitive to the MEK1/2 inhibitor, trametinib, similar to BRAF V600E melanomas. A second set (termed Class II) display reduced trametinib sensitivity, paradoxical activation of MEK1/2 and basal activation of ERBBs 1, 2, and 3 (4 lines, 25%). In 3 of these lines, PI3K/AKT and MAPK pathway signaling is abrogated using the ERBB inhibitor, afatinib, and proliferation is even further reduced upon the addition of trametinib. A potential mechanism of ERBB activation in Class II melanomas is minimal expression of the ERK1/2 phosphatase, DUSP4, as ectopic restoration of DUSP4 attenuated ERBB signaling through potential modulation of the ERBB ligand, amphiregulin (AREG). Consistent with these data, immunohistochemical analysis of patient melanomas revealed a trend towards lower overall DUSP4 expression in pan-negative versus BRAF- and NRAS-mutant tumors. This study is the first to demonstrate that differential ERBB activity in pan-negative melanoma may modulate sensitivity to clinically-available MEK1/2 inhibitors and provides rationale for the use of ERBB inhibitors, potentially in combination with MEK1/2 inhibitors, in subsets of this disease.

A novel EGR-1 dependent mechanism for YB-1 modulation of paclitaxel response in a triple negative breast cancer cell line

Chemotherapy with taxanes such as paclitaxel (PTX) is a key component of triple negative breast cancer (TNBC) treatment. PTX is used in combination with other drugs in both the adjuvant setting and in advanced breast cancer. Because a proportion of patients respond poorly to PTX or relapse after its use, a greater understanding of the mechanisms conferring resistance to PTX is required. One protein shown to be involved in drug resistance is Y-box binding protein 1 (YB-1). High levels of YB-1 have previously been associated with resistance to PTX in TNBCs. In this study, we aimed to determine mechanisms by which YB-1 confers PTX resistance. We generated isogenic TNBC cell lines that differed by YB-1 levels and treated these with PTX. Using microarray analysis, we identified EGR1 as a potential target of YB-1. We found that low EGR1 mRNA levels are associated with poor breast cancer patient prognosis, and that EGR1 and YBX1 mRNA expression was inversely correlated in a TNBC line and in a proportion of TNBC tumours. Reducing the levels of EGR1 caused TNBC cells to become more resistant to PTX. Given that PTX targets cycling cells, we propose a model whereby high YB-1 levels in some TNBC cells can lead to reduced levels of EGR1, which in turn promotes slow cell cycling and resistance to PTX. Therefore YB-1 and EGR1 levels are biologically linked and may provide a biomarker for TNBC response to PTX.

Molecular signatures of sanguinarine in human pancreatic cancer cells: A large scale label-free comparative proteomics approach

Pancreatic cancer remains one of the most lethal of all human malignancies with its incidence nearly equaling its mortality rate. Therefore, it's crucial to identify newer mechanism-based agents and targets to effectively manage pancreatic cancer. Plant-derived agents/drugs have historically been useful in cancer therapeutics. Sanguinarine is a plant alkaloid with anti-proliferative effects against cancers, including pancreatic cancer. This study was designed to determine the mechanism of sanguinarine's effects in pancreatic cancer with a hope to obtain useful information to improve the therapeutic options for the management of this neoplasm. We employed a quantitative proteomics approach to define the mechanism of sanguinarine's effects in human pancreatic cancer cells. Proteins from control and sanguinarine-treated pancreatic cancer cells were digested with trypsin, run by nano-LC/MS/MS, and identified with the help of Swiss-Prot database. Results from replicate injections were processed with the SIEVE software to identify proteins with differential expression. We identified 37 differentially expressed proteins (from a total of 3107), which are known to be involved in variety of cellular processes. Four of these proteins (IL33, CUL5, GPS1 and DUSP4) appear to occupy regulatory nodes in key pathways. Further validation by qRT-PCR and immunoblot analyses demonstrated that the dual specificity phosphatase-4 (DUSP4) was significantly upregulated by sanguinarine in BxPC-3 and MIA PaCa-2 cells. Sanguinarine treatment also caused down-regulation of HIF1α and PCNA, and increased cleavage of PARP and Caspase-7. Taken together, sanguinarine appears to have pleotropic effects, as it modulates multiple key signaling pathways, supporting the potential usefulness of sanguinarine against pancreatic cancer.

Modulation of p38 kinase by DUSP4 is important in regulating cardiovascular function under oxidative stress

Over-activation of p38 is implicated in many cardiovascular diseases (CVDs), including myocardial infarction, hypertrophy, heart failure, and ischemic heart disease. Numerous therapeutic interventions for CVDs have been directed toward the inhibition of the p38 mitogen-activated protein kinase activation that contributes to the detrimental effect after ischemia/reperfusion (I/R) injuries. However, the efficacy of these treatments is far from ideal, as they lack specificity and are associated with high toxicity. Previously, we demonstrated that N-acetyl cysteine (NAC) pretreatment up-regulates DUSP4 expression in endothelial cells, regulating p38 and ERK1/2 activities, and thus providing a protective effect against oxidative stress. Here, endothelial cells under hypoxia/reoxygenation (H/R) insult and isolated heart I/R injury were used to investigate the role of DUSP4 in the modulation of the p38 pathway. In rat endothelial cells, DUSP4 is time-dependently degraded by H/R (0.25 ± 0.07-fold change of control after 2h H/R). Its degradation is closely associated with hyperphosphorylation of p38 (2.1 ± 0.36-fold change) and cell apoptosis, as indicated by the increase in cells immunopositive for cleaved caspase-3 (12.59 ± 3.38%) or TUNEL labeling (29.46 ± 3.75%). The inhibition of p38 kinase activity with 20 µM SB203580 during H/R prevents H/R-induced apoptosis, assessed via TUNEL (12.99 ± 1.89%). Conversely, DUSP4 gene silencing in endothelial cells augments their sensitivity to H/R-induced apoptosis (45.81 ± 5.23%). This sensitivity is diminished via the inhibition of p38 activity (total apoptotic cells drop to 17.47 ± 1.45%). Interestingly, DUSP4 gene silencing contributes to the increase in superoxide generation from cells. Isolated Langendorff-perfused mouse hearts were subjected to global I/R injury. DUSP4(-/-) hearts had significantly larger infarct size than WT. The increase in I/R-induced infarct in DUSP4(-/-) mice significantly correlates with reduced functional recovery (assessed by RPP%, LVDP%, HR%, and dP/dtmax) as well as lower CF% and a higher initial LVEDP. From immunoblotting analysis, it is evident that p38 is significantly overactivated in DUSP4(-/-) mice after I/R injury. The activation of cleaved caspase-3 is seen in both WT and DUSP4(-/-) I/R hearts. Infusion of a p38 inhibitor prior to ischemia and during the reperfusion improves both WT and DUSP4(-/-) cardiac function. Therefore, the identification of p38 kinase modulation by DUSP4 provides a novel therapeutic target for oxidant-induced diseases, especially myocardial infarction.

Redox activation of DUSP4 by N-acetylcysteine protects endothelial cells from Cd²⁺-induced apoptosis

Redox imbalance is a primary cause of endothelial dysfunction (ED). Under oxidant stress, many critical proteins regulating endothelial function undergo oxidative modifications that lead to ED. Cellular levels of glutathione (GSH), the primary reducing source in cells, can significantly regulate cell function via reversible protein thiol modification. N-acetylcysteine (NAC), a precursor for GSH biosynthesis, is beneficial for many vascular diseases; however, the detailed mechanism of these benefits is still not clear. From HPLC analysis, NAC significantly increases both cellular GSH and tetrahydrobiopterin levels. Immunoblotting of endothelial NO synthase (eNOS) and DUSP4, a dual-specificity phosphatase with a cysteine as its active residue, revealed that both enzymes are upregulated by NAC. EPR spin trapping further demonstrated that NAC enhances NO generation from cells. Long-term exposure to Cd(2+) contributes to DUSP4 degradation and the uncontrolled activation of p38 and ERK1/2, leading to apoptosis. Treatment with NAC prevents DUSP4 degradation and protects cells against Cd(2+)-induced apoptosis. Moreover, the increased DUSP4 expression can redox-regulate the p38 and ERK1/2 pathways from hyperactivation, providing a survival mechanism against the toxicity of Cd(2+). DUSP4 gene knockdown further supports the hypothesis that DUSP4 is an antioxidant gene, critical in the modulation of eNOS expression, and thus protects against Cd(2+)-induced stress. Depletion of intracellular GSH by buthionine sulfoximine makes cells more susceptible to Cd(2+)-induced apoptosis. Pretreatment with NAC prevents p38 overactivation and thus protects the endothelium from this oxidative stress. Therefore, the identification of DUSP4 activation by NAC provides a novel target for future drug design.