Activation Of Mitogen-activated Protein Kinase Signaling Research Articles

Fas Apoptosis Inhibitory Molecule 2 Inhibits Pathological Cardiac Hypertrophy by Regulating the MAPK Signaling Pathway.

Pathological cardiac hypertrophy stands as a pivotal mechanism contributing to diverse cardiovascular diseases, ultimately leading to heart failure. Despite its clinical significance, the intricate molecular mechanisms instigating pathological cardiac hypertrophy remain inadequately understood. In this study, we aim to further reveal its complex pathogenesis by exploring the role of Fas apoptotic inhibitory molecule 2 (FAIM2) in modulating pathological cardiac hypertrophy. We used phenylephrine-induced hypertrophic cardiomyocytes and also generated cardiac-specific knockout mice and adeno-associated virus serotype 9-Faim2 mice to evaluate the function of FAIM2 in pathological myocardial hypertrophy. Furthermore, unbiased RNA-sequencing analysis was used to identify the direct target and corresponding molecular events contributing to FAIM2 function. Ultimately, our study revealed a downregulation of FAIM2 expression in phenylephrine-induced hypertrophic cardiomyocytes and pressure overload-induced hypertrophic hearts. FAIM2 exhibited a significant attenuation of phenylephrine-induced enlargement of primary neonatal rat cardiomyocytes, whereas FAIM2 knockdown aggravated the hypertrophic response. Furthermore, Faim2 gene knockout significantly exacerbated cardiac hypertrophy and heart fibrosis invivo. Mechanistic investigations unveiled that FAIM2 exerts its inhibitory effect by suppressing TAK1-JNK1/2-p38 MAPK signaling cascades, thereby mitigating cardiac hypertrophy. Our findings position FAIM2 as a novel negative regulator of pathological cardiac hypertrophy through its inhibitory action on mitogen-activated protein kinase signaling activation. This identification of FAIM2's role provides crucial insights that may pave the way for the development of effective therapeutic strategies aimed at mitigating pathological cardiac hypertrophy, addressing a critical need in cardiovascular disease management.

High-intensity interval training using electrical stimulation ameliorates muscle fatigue in chronic kidney disease-related cachexia by restoring mitochondrial respiratory dysfunction.

Exercise, especially high-intensity interval training (HIIT), can increase mitochondrial respiratory capacity and enhance muscular endurance, but its systemic burden makes it difficult to safely and continuously prescribe for patients with chronic kidney disease (CKD)-related cachexia who are in poor general condition. In this study, we examined whether HIIT using electrical stimulation (ES), which does not require whole-body exercise, improves muscle endurance in the skeletal muscle of 5/6 nephrectomized rats, a widely used animal model for CKD-related cachexia. Male Wistar rats (10weeks old) were randomly assigned to a group of sham-operated (Sham) rats and a group of 5/6 nephrectomy (Nx) rats. HIIT was performed on plantar flexor muscles in vivo with supramaximal ES every other day for 4weeks to assess muscle endurance, myosin heavy-chain isoforms, and mitochondrial respiratory function in Nx rats. A single session was also performed to identify upstream signaling pathways altered by HIIT using ES. In the non-trained plantar flexor muscles from Nx rats, the muscle endurance was significantly lower than that in plantar flexor muscles from Sham rats. The proportion of myosin heavy chain IIa/x, mitochondrial content, mitochondrial respiratory capacity, and formation of mitochondrial respiratory supercomplexes in the plantaris muscle were also significantly decreased in the non-trained plantar flexor muscles from Nx rats than compared to those in plantar flexor muscles from Sham rats. Treatment with HIIT using ES for Nx rats significantly improved these molecular and functional changes to the same degrees as those in Sham rats. Furthermore, a single session of HIIT with ES significantly increased the phosphorylation levels of AMP-activated protein kinase (AMPK) and p38 mitogen-activated protein kinase (MAPK), pathways that are essential for mitochondrial activation signaling by exercise, in the plantar muscles of both Nx and Sham rats. The findings suggest that HIIT using ES ameliorates muscle fatigue in Nx rats via restoration of mitochondrial respiratory dysfunction with activation of AMPK and p38 MAPK signaling. Our ES-based HIIT protocol can be performed without placing a burden on the whole body and be a promising intervention that is implemented even in conditions of reduced general performance status such as CKD-related cachexia.

Uvaol alleviates oxidative stress induced human umbilical vein endothelial cell injury by suppressing mitogen-activated protein kinase signaling pathway.

Deep venous thrombosis (DVT) is a potentially life-threatening disorder with high morbidity. Uvaol is a natural pentacyclic triterpene possessing multiple pharmacological activities. Nevertheless, the role of uvaol in DVT is unclarified. Human umbilical vein endothelial cells (HUVECs) were treated with hydrogen peroxide (H 2 O 2 ) to mimic DVT in vitro . CCK-8 assay and flow cytometry were utilized for measuring cell viability and apoptosis, respectively. Levels of the cell injury marker, thrombosis-associated factors, inflammatory cytokines, and oxidative stress-related markers were examined by commercial assay kits. Western blotting was used for evaluating the expression of mitogen-activated protein kinase (MAPK) signaling-associated proteins. Uvaol treatment attenuated H 2 O 2 -induced HUVEC apoptosis and injury. Uvaol reduced the expression of pro-thrombotic factors and inflammatory cytokines and attenuated oxidative stress in H 2 O 2 -stimulated HUVECs. Uvaol inhibited MAPK signaling pathway in H 2 O 2 -stimulated HUVECs. Activating MAPK signaling reversed uvaol-mediated protective effects on H 2 O 2 -treated HUVECs. Uvaol treatment alleviates H 2 O 2 -induced HUVEC injury, apoptosis, and oxidative stress by inactivating MAPK signaling.

Role of MAPKs in TGF-β1-induced maturation and mineralization in human osteoblast-like cells

Objectives: Our study aimed to clarify the role of mitogen-activated protein kinases (MAPKs) in transforming growth factor (TGF)-β1-stimulated mineralization in the human osteoblast-like MG63 cells. MethodsThe viability of MG63 cells under TGF-β1 stimulation was assessed by MTS assay. Western blotting determined TGF-β1-mediated activation of extracellular signal-related protein kinase (ERK), p38, and c-Jun amino-terminal kinase (JNK). Mineralization-related gene expression was examined by quantitative real-time PCR, and mineral deposition levels were evaluated by alizarin red S staining. ResultsTGF-β1 had no effect on MG63 cell proliferation. Activation of p38 was observed at 3 h post TGF-β1 stimulation. Moreover, JNK phosphorylation was upregulated by TGF-β1 from 1 to 6 h post stimulation, but had no activation on ERK phosphorylation throughout the experimental period. Treatment with JNK inhibitor diminished the alizarin red S-stained area in a dose-dependent manner. Mineral deposition was unaffected by MEK inhibitor, whereas p38 inhibitor increased the red-stained area. Gene expression levels of ALP and BSP were significantly decreased under treatment with JNK inhibitor and p38 inhibitor. The MEK inhibitor had no effect on the TGF-β1–mediated upregulation of ALP and BSP. Although all three inhibitors suppressed expression of COL I, none were found to stimulate expression of OCN. ConclusionsHuman osteoblast-like MG63 cells maturation and mineralization are induced through JNK activation of MAPK signaling in response to TGF-β1.

Traditional Chinese medicine Pien-Tze-Huang ameliorates LPS-induced sepsis through bile acid-mediated activation of TGR5-STAT3-A20 signalling

Pien Tze Huang (PZH), a class-1 nationally protected traditional Chinese medicine (TCM), has been used to treat liver diseases such as hepatitis; however, the effect of PZH on the progression of sepsis is unknown. Here, we reported that PZH attenuated lipopolysaccharide (LPS)-induced sepsis in mice and reduced LPS-induced production of proinflammatory cytokines in macrophages by inhibiting the activation of mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signalling. Mechanistically, PZH stimulated signal transducer and activator of transcription 3 (STAT3) phosphorylation to induce the expression of A20, which could inhibit the activation of NF-κB and MAPK signalling. Knockdown of the bile acid (BA) receptor G protein-coupled bile acid receptor 1 (TGR5) in macrophages abolished the effects of PZH on STAT3 phosphorylation and A20 induction, as well as the LPS-induced inflammatory response, suggesting that BAs in PZH may mediate its anti-inflammatory effects by activating TGR5. Consistently, deprivation of BAs in PZH by cholestyramine resin reduced the effects of PZH on the expression of phosphorylated-STAT3 and A20, the activation of NF-κB and MAPK signalling, and the production of proinflammatory cytokines, whereas the addition of BAs to cholestyramine resin-treated PZH partially restored the inhibitory effects on the production of proinflammatory cytokines. Overall, our study identifies BAs as the effective components in PZH that activate TGR5-STAT3-A20 signalling to ameliorate LPS-induced sepsis.

Regulation of anti-inflammatory and antioxidant responses by methanol extract of Mikania cordata (Burm. f.) B. L. Rob. leaves via the inactivation of NF-κB and MAPK signaling pathways and activation of Nrf2 in LPS-induced RAW 264.7 macrophages

Mikania cordata (Burm. f.) B.L. Rob. has been traditionally used in tropical countries throughout Asia and Africa to treat gastric ulcers, dyspepsia, and dysentery. However, the mechanisms responsible for its anti-inflammatory and antioxidant activities are not fully understood. Therefore, this study sought to investigate the anti-inflammatory and antioxidant effects of methanol extracts of M. cordata (MMC) on inflammation and oxidative stress in lipopolysaccharide (LPS)-stimulated murine RAW 264.7 macrophages and elucidate its underlying regulatory mechanism. MMC significantly suppressed the production of nitric oxide (NO) and prostaglandin E2 (PGE2) in LPS-stimulated RAW 264.7 macrophages by downregulating the expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) at both the mRNA and protein levels. Moreover, MMC effectively reduced the mRNA expression levels and production of pro-inflammatory cytokines, including interleukin-6 (IL-6), IL-1β, and tumor necrosis factor-α (TNF-α). These suppressive effects of MMC on pro-inflammatory mediators and cytokines were mediated through the inhibition of transforming growth factor beta-activated kinase 1 (TAK1), which subsequently blocked the activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPKs). MMC also upregulated the nuclear factor erythroid-2-related factor 2 (Nrf2) by inducing the degradation of Kelch-like ECH-related protein 1 (Keap1), an Nrf2-specific E3 ligase. Accordingly, MMC enhanced Nrf2 target gene expression of anti-oxidative regulators such as heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase 1 (NQO1). However, it had minimal effect on the DPPH radical scavenging capacity in vitro. Collectively, these findings demonstrate that MMC holds promise as a potential therapeutic agent for alleviating inflammation-related diseases and oxidative stress.

Negative feedback regulation of MAPK signaling is an important driver of chronic lymphocytic leukemia progression

Despite available targeted treatments for the disease, drug-resistant chronic lymphocytic leukemia (CLL) poses a clinical challenge. The objective of this study is to examine whether the dual-specific phosphatases DUSP1 and DUSP6 are required to negatively regulate mitogen-activated protein kinases (MAPKs) and thus counterbalance excessive MAPK activity. We show that high expression of DUSP6 in CLL correlates with poor clinical prognosis. Importantly, genetic deletion of the inhibitory phosphatase DUSP1 or DUSP6 and blocking DUSP1/6 function using a small-molecule inhibitor reduces CLL cell survival invitro and invivo. Using global phospho-proteome approaches, we observe acute activation of MAPK signaling by DUSP1/6 inhibition. This promotes accumulation of mitochondrial reactive oxygen species and, thereby, DNA damage and apoptotic cell death in CLL cells. Finally, we observe that DUSP1/6 inhibition is particularly effective against treatment-resistant CLL and therefore suggest transient DUSP1/6 inhibition as a promising treatment concept to eliminate drug-resistant CLL cells.

Loss of function of ENT3 drives histiocytosis and inflammation through TLR-MAPK signaling

AbstractHistiocytoses are inflammatory myeloid neoplasms often driven by somatic activating mutations in mitogen-activated protein kinase (MAPK) cascade genes. H syndrome is an inflammatory genetic disorder caused by germ line loss-of-function mutations in SLC29A3, encoding the lysosomal equilibrative nucleoside transporter 3 (ENT3). Patients with H syndrome are predisposed to develop histiocytosis, yet the mechanism is unclear. Here, through phenotypic, molecular, and functional analysis of primary cells from a cohort of patients with H syndrome, we reveal the molecular pathway leading to histiocytosis and inflammation in this genetic disorder. We show that loss of function of ENT3 activates nucleoside-sensing toll-like receptors (TLR) and downstream MAPK signaling, inducing cytokine secretion and inflammation. Importantly, MEK inhibitor therapy led to resolution of histiocytosis and inflammation in a patient with H syndrome. These results demonstrate a yet-unrecognized link between a defect in a lysosomal transporter and pathological activation of MAPK signaling, establishing a novel pathway leading to histiocytosis and inflammation.

RAS-dependent RAF-MAPK hyperactivation by pathogenic RIT1 is a therapeutic target in Noonan syndrome-associated cardiac hypertrophy.

RIT1 is a RAS guanosine triphosphatase (GTPase) that regulates different aspects of signal transduction and is mutated in lung cancer, leukemia, and in the germline of individuals with Noonan syndrome. Pathogenic RIT1 proteins promote mitogen-activated protein kinase (MAPK) hyperactivation; however, this mechanism remains poorly understood. Here, we show that RAF kinases are direct effectors of membrane-bound mutant RIT1 necessary for MAPK activation. We identify critical residues in RIT1 that facilitate interaction with membrane lipids and show that these are necessary for association with RAF kinases and MAPK activation. Although mutant RIT1 binds to RAF kinases directly, it fails to activate MAPK signaling in the absence of classical RAS proteins. Consistent with aberrant RAF/MAPK activation as a driver of disease, we show that pathway inhibition alleviates cardiac hypertrophy in a mouse model of RIT1 mutant Noonan syndrome. These data shed light on the function of pathogenic RIT1 and identify avenues for therapeutic intervention.

Regulation of PD-L1 expression in non-small cell lung cancer by interleukin-1β.

Programmed cell death-ligand 1 (PD-L1) is a biomarker for prediction of the clinical efficacy of immune checkpoint inhibitors in various cancer types. The role of cytokines in regulation of PD-L1 expression in tumor cells has not been fully characterized, however. Here we show that interleukin-1β (IL-1β) plays a key role in regulation of PD-L1 expression in non-small cell lung cancer (NSCLC). We performed comprehensive screening of cytokine gene expression in NSCLC tissue using available single-cell RNA-Sequence data. Then we examined the role of IL-1β in vitro to elucidate its induction of PD-L1 on NSCLC cells. The IL-1β gene is highly expressed in the tumor microenvironment, particularly in macrophages. The combination of IL-1β and interferon-γ (IFN-γ) induced a synergistic increase in PD-L1 expression in NSCLC cell lines. IL-1β and IFN-γ also cooperatively activated mitogen-activated protein kinase (MAPK) signaling and promoted the binding of downstream transcription factors to the PD-L1 gene promoter. Furthermore, inhibitors of MAPK signaling blocked upregulation of PD-L1 by IL-1β and IFN-γ. Our study reports high levels of IL-1β in the tumor microenvironment may cooperate with IFN-γ to induce maximal PD-L1 expression in tumor cells via activation of MAPK signaling, with the IL-1β-MAPK axis being a promising therapeutic target for attenuation of PD-L1-mediated suppression of antitumor immunity.

TRIM22 promotes the proliferation of glioblastoma cells by activating MAPK signaling and accelerating the degradation of Raf-1

The tripartite motif (TRIM) 22 and mitogen-activated protein kinase (MAPK) signaling pathways play critical roles in the growth of glioblastoma (GBM). However, the molecular mechanism underlying the relationship between TRIM22 and MAPK signaling remains unclear. Here, we found that TRIM22 binds to exon 2 of the sphingosine kinase 2 (SPHK2) gene. An ERK1/2-driven luciferase reporter construct identified TRIM22 as a potential activator of MAPK signaling. Knockout and overexpression of TRIM22 regulate the inhibition and activation of MAPK signaling through the RING-finger domain. TRIM22 binds to Raf-1, a negative regulator of MAPK signaling, and accelerates its degradation by inducing K48-linked ubiquitination, which is related to the CC and SPRY domains of TRIM22 and the C1D domain of Raf-1. In vitro and in vivo, an SPHK2 inhibitor (K145), an ERK1/2 inhibitor (selumetinib), and the nonphosphorylated mutant Raf-1S338A inhibited GBM growth. In addition, deletion of the RING domain and the nuclear localization sequence of TRIM22 significantly inhibited TRIM22-induced proliferation of GBM cells in vivo and in vitro. In conclusion, our study showed that TRIM22 regulates SPHK2 transcription and activates MAPK signaling through posttranslational modification of two critical regulators of MAPK signaling in GBM cells.

Role of p38 MAPK, Akt and NFκB in renoprotective effects of nebivolol on renal ischemia-reperfusion injury in rats

ABSTRACT Renal ischemia-reperfusion (I-R) injury is a complex pathophysiologic condition characterized by oxidative stress, inflammation and apoptosis. We investigated the potential renoprotective effect of nebivolol, a β1 adrenergic receptor blocker, against renal I-R injury. We focused on the role of nebivolol in activating p38 mitogen-activated protein kinase (MAPK) signaling, Akt (protein kinase B) and nuclear factor-κB (NFκB) transcription factors, which contribute to oxidative stress, inflammation and apoptosis during renal I-R. We divided 20 adult male Wistar albino rats into three experimental groups. Group 1 was a sham control in which only laparotomy was performed. Group 2 was the I-R group in which both kidneys were made ischemic for 45 min, then reperfused for 24 h. Group 3 was the I-R + nebivolol group in which 10 mg/kg nebivolol was administrated by gavage for 7 days before I-R. We measured Inflammation, oxidative stress and active caspase-3 as well as activation of p38 MAPK, Akt (protein kinase B) and NFκB transcription factor. Nebivolol significantly reduced oxidative stress and increased superoxide dismutase levels during renal I-R. We found that nebivolol significantly decreased interstitial inflammation, and TNF-α and interleukin-1β mRNA expression. Nebivolol significantly reduced active caspase-3 and kidney injury molecule-1 (KIM-1) expressions. Nebivolol also significantly decreased activation of p38 MAPK signaling and NFκB, and induced Akt activation during renal I-R. Our findings suggest that nebivolol may be useful for management of renal I-R injury.

Glabridin ameliorates DNFB induced atopic dermatitis by suppressing MAPK/NF κB signaling pathways in mice

Purpose: To investigate the anti-inflammatory mechanism of action of glabridin (GBD) isolated from glycyrrhizae radix et rhizoma (Glycyrrhiza glabra L.) using atopic dermatitis (AD) mouse model. Methods: Nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways were investigated. The dorsal skin and serum of 2,4-dinitrofluorobenzene (DNFB)-induced AD mice were used to determine the levels of various inflammatory cytokines, including interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-4, IL-5, IL-6, IL-13, and immunoglobulin E (IgE) by enzyme-linked immunosorbent assay (ELISA). The relative levels of inflammation-associated mRNA and signaling pathways were determined by real time-polymerase chain reaction (RT-PCR) and western blotting, respectively. Hematoxylin and eosin (H&E) staining was used to assess the effect of GBD on tissue thickening and inflammatory cell infiltration in mice with AD. Results: Glabridin significantly relieved dorsal skin thickening, scabbing, and bleeding, and reduced the infiltration of inflammatory cells in mice with AD (p < 0.05). The levels of IFN-γ, TNF-α, IL-4, IL-5, IL-6, IL-13, and IgE were significantly reduced (p < 0.05 or 0.01). Moreover, the relative levels of IL-6 and IFN-γ mRNA showed a significant decrease (p < 0.01). Furthermore, GBD inhibited phosphorylation of MAPK signaling pathway and activation of NF-κB (p < 0.05 or 0.01). Conclusion: Glabridin exerts an inhibitory effect on AD by blocking MAPK and NF-κB signaling pathways. This finding highlights the relationship between traditional Chinese medicine and modern AD therapeutic methods, which should be further investigated for its potential to be developed as an external anti-AD medicine.

Role of apigenin in high glucose-induced retinal microvascular endothelial cell dysfunction via regulating NOX4/p38 MAPK pathway in vitro.

To investigate the retinoprotective role of Apigenin (Api) against high glucose (HG)-induced human retinal microvascular endothelial cells (HRMECs), and to explore its regulatory mechanism. HRMECs were stimulated by HG for 48h to establish the in vitro cell model. Different concentrations of Api (2.5, 5, and 10 µmol/L) were applied for treatment. Cell counting kit-8 (CCK-8), Transwell, and tube formation assays were performed to examine the effects of Api on the viability, migration, and angiogenesis in HG-induced HRMECs. Vascular permeability was evaluated by Evans blue dye. The inflammatory cytokines and oxidative stress-related factors were measured using their commercial kits. Protein expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4) and p38 mitogen-activated protein kinase (MAPK) was measured by Western blot. Api prevented HG-induced HRMECs viability, migration, angiogenesis, and vascular permeability in a concentration-dependent manner. Meanwhile, Api also concentration-dependently inhibited inflammation and oxidative stress in HRMECs exposed to HG. In addition, HG caused an elevated expression of NOX4, which was retarded by Api treatment. HG stimulation facilitated the activation of p38 MAPK signaling in HRMECs, and Api could weaken this activation partly via downregulating NOX4 expression. Furthermore, overexpression of NOX4 or activation of p38 MAPK signaling greatly weakened the protective role of Api against HG-stimulated HRMECs. Api might exert a beneficial role in HG-stimulated HRMECs through regulating NOX4/p38 MAPK pathway.

Abstract 1632: MDM2 inhibitor alrizomadlin (APG-115) promotes antitumor activity of mitogen-activated protein kinase (MAPK) inhibitors in uveal melanoma

Abstract Uveal melanoma (UM) is the commonest primary intraocular malignancy, yet its molecular pathogenesis is poorly understood. Most UM cases have activating mutations in genes encoding G protein subunits alpha Q or 11, leading to activation of downstream effectors. These include protein kinase C, mitogen-activated protein kinases (MAPK1/3; also termed extracellular signal-regulated kinase 2/1 [ERK2⁄ERK1], respectively), and yes-associated protein, suggesting a rationale for therapeutically targeting these related pathways. Genetic analyses show that TP53 is infrequently mutated in UM, but associated pathways may be functionally inactivated. Ubiquitination-mediated degradation of p53 activates MAPK signaling, such that, active p53 may promote suppression of MAPK signaling. Alrizomadlin (APG-115) is a small molecule targeting p53/MDM2 that is in clinical development for solid and hematologic cancers. This study evaluated the antitumor effect of alrizomadlin, alone or combined with other targeted therapies, in preclinical models of UM. In cell-based antiproliferation assays of many UM cell lines, alrizomadlin exerted moderate growth inhibitory effects (IC50 = 0.151-1.857μM). When combined with inhibitors against mitogen-activated protein kinase kinase (MEK) [trametinib and selumetinib], mammalian target of rapamycin (mTOR) [rapamycin], focal adhesion kinase (FAK) [defactinib and Ascentage’s APG-2449, which targets FAK/ALK/ROS1], and MEK/rapidly accelerated fibrosarcoma [RAF] [VS-6766], alrizomadlin demonstrated enhanced antiproliferative activity. In a UM xenograft model (MP41), alrizomadlin showed dose-dependent antitumor activity when administered at 25, 50, and 100 mg/kg, with tumor growth inhibition (TGI) rates of 24.8%, 38%, and 39.1%, respectively. In this model, synergistic antitumor effects were observed when alrizomadlin was combined with selumetinib or APG-2449, with TGI rates of 65.4% and 47.5%, respectively. Mechanistically, alrizomadlin likely increased p53, MDM2, and downstream p21 in MP41 cells. Importantly, alrizomadlin inhibited ERK phosphorylation and enhanced selumetinib inhibition in a dose- and time-dependent manner. Prior studies indicated that FAK can suppress p53 by enhancing MDM2-dependent p53 ubiquitination. In this study, APG-2449 showed dose-dependent inhibition of FAK phosphorylation and upregulation of p53. Alrizomadlin also inhibited phosphorylation of FAK and downstream ERK. Therefore, the combination of alrizomadlin and APG-2449 was synergistic. Combining MEK and FAK inhibitors also markedly augmented caspase-3 and poly (ADP-ribose) polymerase 1 (PARP-1) cleavage (apoptosis hallmarks) and enhanced observed antitumor effects. In conclusion, our results demonstrate the potential utility of combining alrizomadlin with MAPK pathway inhibitors to treat patients with UM. Citation Format: Guangfeng Wang, Eric Liang, Ping Min, Dajun Yang, Yifan Zhai. MDM2 inhibitor alrizomadlin (APG-115) promotes antitumor activity of mitogen-activated protein kinase (MAPK) inhibitors in uveal melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1632.

Autocrine activation of MAPK signaling mediates intrinsic tolerance to androgen deprivation in LY6D prostate cancer cells

The emergence of castration-resistant prostate cancer remains an area of unmet clinical need. We recently identified a subpopulation of normal prostate progenitor cells, characterized by an intrinsic resistance to androgen deprivation and expression of LY6D. We here demonstrate that conditional deletion of PTEN in the murine prostate epithelium causes an expansion of transformed LY6D+ progenitor cells without impairing stem cell properties. Transcriptomic analyses of LY6D+ luminal cells identified an autocrine positive feedback loop, based on the secretion of amphiregulin (AREG)-mediated activation of mitogen-activated protein kinase (MAPK) signaling, increasing cellular fitness and organoid formation. Pharmacological interference with this pathway overcomes the castration-resistant properties of LY6D+ cells with a suppression of organoid formation and loss of LY6D+ cells invivo. Notably, LY6D+ tumor cells are enriched in high-grade and androgen-resistant prostate cancer, providing clinical evidence for their contribution to advanced disease. Our data indicate that early interference with MAPK inhibitors can prevent progression of castration-resistant prostate cancer.

S100A7 promotes endometrial carcinoma progression by activating the MAPK signaling pathway

S100 calcium binding protein A7 (S100A7) has been proofed to play a carcinogenic role in several cancers. However, its role and the regulatory mechanism in Endometrial carcinoma (EC) was unknown. Western blot was applied to determine the expression of S100A7 and Mitogen-activated protein kinase (MAPK) pathway-related protein in EC cells. Functional in vitro experiments were conducted to explore the effects of S100A7 on cell proliferation, apoptosis, migration, invasion and angiogenesis in EC. As a result, S100A7 expression was dramatically up-regulated in EC cells. Overexpression of S100A7 enhanced EC cells proliferation, migration, invasion and angiogenesis, and suppressed cell apoptosis, as well as activated MAPK signaling pathway. Whereas, knockdown of S100A7 exerted the opposite effects. Our finding suggested that S100A7 may promote the malignant progression of EC by activating MAPK pathway, implying S100A7 has significant potential to be used as an emerging therapeutic target for EC treatment.

BOP1 Promotes Prostate Cancer through the DUSP6/MAPK Pathway.

Nucleolar prominence is a biomarker of prostate cancer (CaP), and the nucleolar protein block of proliferation 1 (BOP1) participates in the development of CaP, which has great significance for CaP therapy. Thus, this study explored the mechanism of BOP1 in CaP development. BOP1 expression levels in the tumor tissues of CaP patients and in PC3 tumor cells were determined. The viability, apoptosis rate of PC3 cells, and apoptosis-related proteins levels were determined to explore the effect of BOP1 on tumor-cell growth in vitro. BOP1 function in the metastasis of PC3 cells was further assessed by Transwell experiment. We also studied the influence of BOP1 on the expression of mitogen-activated protein kinase (MAPK) pathway-related proteins and investigated the regulatory effect of BOP1 on dual-specificity phosphatase 6 (DUSP6). BOP1 expression was upregulated in the tumor tissues and PC3 cells of CaP patients. BOP1 knockout reduced the activity of PC3 cells and induced apoptosis, significantly inhibiting the metastasis of PC3 cells. DUSP6 was overexpressed in tumor tissues and PC3 cells. BOP1 knockout inhibited DUSP6 expression and the MAPK pathway. DUSP6 overexpression reversed the inhibition of BOP1 siRNA (si-BOP1) on PC3 cells and the activated MAPK signaling pathway. This finding demonstrated that BOP1 promoted CaP progression by regulating the DUSP6/MAPK pathway.

Mangiferin Protects Against Angiotensin-II-Enhanced Hypertrophic Markers and Apoptosis in H9c2 Cardiomyocytes.

Hypertrophic cardiomyopathy accompanies numerous cardiovascular diseases, and the intervention of cardiac hypertrophy is an important issue to prevent detrimental consequences. Mangiferin (MGN) is a glucosylxanthone found in Mangifera indica, which exhibits anti-oxidant and anti-inflammatory properties. Various studies have demonstrated the cardioprotective potential of MGN, but the mechanisms behind its beneficial effects have not been fully revealed. Here, angiotensin-II (Ang-II) was used to induce cardiac hypertrophy, and we examined cell size, expression of hypertrophy markers (e.g., ANP, BNP, and [Formula: see text]-MHC), and oxidative stress (e.g., the ratio of NADPH/NADP[Formula: see text], the expression of p22phox and p67phox, and ROS and SOD production) of cardiomyocytes. Moreover, we assessed the activation of mitogen-activated protein kinase (MAPK) signaling (e.g., p38 and ERK) and the NF-[Formula: see text]Bp65/iNOS axis. Additionally, an annexin V/PI assay was employed to evaluate whether MGN administration can attenuate Ang-II-elicited apoptosis. Lastly, the expression of Ang-II type 1 receptor (AT1) was measured to confirm its involvement in MGN-mediated protection. Our results showed that treatment with MGN attenuated the Ang-II-induced cell size, expression of hypertrophy markers, and oxidative stress in cardiomyocytes. MGN also abrogated the activation of MAPK signaling and the NF-[Formula: see text]Bp65/iNOS axis. Additionally, MGN prevented apoptosis and downregulated the elevation of AT1 in cardiomyocytes that had been exposed to Ang-II. Altogether, these results demonstrated the potential of using MGN to ameliorate the Ang-II-associated cardiac hypertrophy, which may be due to its anti-oxidant and anti-inflammatory effects through suppression of MAPK signaling and the NF-[Formula: see text]Bp65/iNOS axis.

Chronic Inhalation Exposure to Antimony Trioxide Exacerbates the MAPK Signaling in Alveolar Bronchiolar Carcinomas in B6C3F1/N Mice.

Antimony trioxide (AT) is used as a flame retardant in fabrics and plastics. Occupational exposure in miners and smelters is mainly through inhalation and dermal contact. Chronic inhalation exposure to AT particulates in B6C3F1/N mice and Wistar Han rats resulted in increased incidences and tumor multiplicities of alveolar/bronchiolar carcinomas (ABCs). In this study, we demonstrated Kras (43%) and Egfr (46%) hotspot mutations in mouse lung tumors (n = 80) and only Egfr (50%) mutations in rat lung tumors (n = 26). Interestingly, there were no differences in the incidences of these mutations in ABCs from rats and mice at exposure concentrations that did and did not exceed the pulmonary overload threshold. There was increased expression of p44/42 mitogen-activated protein kinase (MAPK) (Erk1/2) protein in ABCs harboring mutations in Kras and/or Egfr, confirming the activation of MAPK signaling. Transcriptomic analysis indicated significant alterations in MAPK signaling such as ephrin receptor signaling and signaling by Rho-family GTPases in AT-exposed ABCs. In addition, there was significant overlap between transcriptomic data from mouse ABCs due to AT exposure and human pulmonary adenocarcinoma data. Collectively, these data suggest chronic AT exposure exacerbates MAPK signaling in ABCs and, thus, may be translationally relevant to human lung cancers.