Mitogen-activated Protein Kinase Pathway Research Articles

BCR::ABL1-induced mitochondrial morphological alterations as a potential clinical biomarker in chronic myeloid leukemia.

The BCR::ABL1 oncogene plays a crucial role in the development of chronic myeloid leukemia (CML). Previous studies have investigated the involvement of mitochondrial dynamics in various cancers, revealing potential therapeutic strategies. However, the impact of BCR::ABL1 on mitochondrial dynamics remains unclear. In this study, we demonstrated that BCR::ABL1 is sufficient to induce excessive mitochondrial fragmentation by activating dynamin-related protein (DRP)1 through the mitogen-activated protein kinase (MAPK) pathway. Leukocytes obtained from patients with CML and the BCR::ABL1-positive cell lines exhibited increased mitochondrial fragmentation compared to leukocytes obtained from healthy donors and BCR::ABL1-negative cells. Furthermore, the analysis of BCR::ABL1-transduced cells showed increased phosphorylation of DRP1 at serine 616 and extracellular signal-regulated kinase (ERK) 1/2. Moreover, the inhibition of DRP1 and upstream mitogen-activated extracellular signal-regulated kinase (MEK) 1/2 suppressed mitochondrial fragmentation. Strikingly, DRP1 inhibition effectively reduced the viability of BCR::ABL1-positive cells and induced necrotic cell death. Additionally, a label-free artificial intelligence-driven flow cytometry successfully identified not only the BCR::ABL1-transduced cells but also peripheral leukocytes from CML patients by assessing mitochondrial morphological alterations. These findings suggested the crucial role of BCR::ABL1-induced mitochondrial fragmentation in driving BCR::ABL1-positive cell proliferation, and the potential use of mitochondrial morphological alterations as a clinical biomarker for the label-free detection of CML cells.

Exploring the In Vitro Effects of Zingerone on Differentiation and Signalling Pathways in Bone Cell Lines

Objective: Ensuring adequate bone health is crucial for preventing conditions such as osteoporosis and fractures. Zingerone, a phytonutrient isolated from cooked ginger, has gained attention for its potential benefits in bone health. This study evaluated the osteoprotective potential of zingerone and its effects on differentiation and signalling pathways in vitro using SAOS-2 osteosarcoma and RAW264.7 macrophage cell lines, aiming to elucidate its mechanism of action in bone remodelling. Methods: SAOS-2 osteosarcoma and RAW264.7 macrophage cells were treated with zingerone at concentrations of 200 µM. Osteoblast differentiation was assessed by alkaline phosphatase (ALP) activity, bone mineralisation via Alizarin Red S stain, and gene expression markers (ALP, runt-related transcription factor 2 (Runx2), and osteocalcin) via quantitative polymerase chain reaction (q-PCR). Osteoclast differentiation was evaluated by tartrate-resistant acid phosphatase (TRAP) staining, TRAP activity, and mitogen-activated protein kinase (MAPK) pathways. Results: Treatment with zingerone was non-toxic at 200 µM. Zingerone (200 µM) significantly stimulated the gene expression of ALP and Runx2 in SAOS-2 cells (p < 0.05) without statistically significantly enhancing SAOS-2 mineralisation via calcium deposits. Moreover, zingerone significantly inhibited osteoclast differentiation in RAW264.7 cells as evidenced by reduced TRAP staining and activity (p < 0.05). Conclusions: Zingerone shows promise in reducing osteoclast activity and supporting early osteoblast differentiation, suggesting its potential as a dietary supplement for bone health. Further in vivo and clinical studies are needed to confirm its role in managing osteoporosis.

A viral protein activates the MAPK pathway to promote viral infection by downregulating callose deposition in plants

Mitogen-activated protein kinase (MAPK) cascades are evolutionarily conserved in both plants and animals and play critical roles in activating innate immunity to defend against various pathogens. However, the role of MAPK cascades in positively regulating or enhancing viral infections in plants is unclear. In this study, we investigate the involvement of MAPK cascades in infection by the positive-strand RNA virus tomato chlorosis virus (ToCV). Our findings reveal that ToCV infection activates MAPK cascades, promoting virus spread within plants. Specifically, ToCV P7, a pathogenicity determinant protein, localizes to the plasma membrane and recruits NbMPK3/6 from the nucleus. Subsequently, P7 is directly phosphorylated on serine 59 by NbMPK3/6. Phosphorylated P7 interacts with NbREM1.1 and inhibits its ability to induce callose deposition at plasmodesmata. These results demonstrate that NbMPK3/6 directly phosphorylate ToCV P7, modulating antiviral defence mechanisms by downregulating callose deposition at plasmodesmata and thereby enhancing ToCV transmission in N. benthamiana. This study sheds light on the intricate arms race between host defence and viral counter-defence strategies.

LncRNA MIAT binding to GATA3 activates MAPK signaling pathway and influences bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) manifests in premature neonates with aberrant pulmonary function. Numerous long non-coding RNAs (lncRNAs) have been implicated in the pathogenesis of BPD. This study aims to elucidate the impact of the lncRNA myocardial infarction-associated transcript (MIAT) on the initiation and progression of BPD. Initially, BPD murine models were established through hyperoxia induction in newborn mice. Subsequently, MIAT and GATA binding protein 3 (GATA3) expression levels were assessed, and intravenous administration of short hairpin RNAs (shRNAs) targeting MIAT and GATA3 was performed. Pulmonary histological alterations were examined through histological staining. Levels of inflammatory mediators were quantified using enzyme-linked immunosorbent assay (ELISA) kits. The interaction between MIAT and GATA3 was scrutinized through RNA immunoprecipitation, RNA pull-down, and fluorescence in situ hybridization. The downstream mechanisms of GATA3 were explored using bioinformatics analysis. In summary, lncRNA MIAT exhibited elevated expression in the lung tissues of BPD-afflicted mice. MIAT localized to the nucleus and interacted with GATA3, thereby activating the mitogen-activated protein kinase (MAPK) pathway. Knockdown of MIAT or silencing of GATA3 attenuated the inflammatory response, deactivated the MAPK pathway, and ameliorated BPD symptoms in mice, on the other hand, p-Cresyl sulfate potassium can activate the MAPK signaling pathway and attenuates the effects of si-MIAT or si-GAT3. These improvements were characterized by enhanced alveolar differentiation and reduced glycogen and collagen deposition. In conclusion, lncRNA MIAT plays a pivotal role in activating the MAPK pathway and exacerbating hyperoxia-induced BPD in mice through the binding to GATA3. It's an important discovery for the pathogenesis of BPD and may provide some new treatment for infants diagnosed with BPD.

Cannabiorcol as a novel inhibitor of the p38/MSK-1/NF-κB signaling pathway, reducing matrix metalloproteinases in osteoarthritis

BackgroundThe bioactivity and potential medicinal applications of cannabiorcol, a lesser-known derivative of Cannabis sativa, require further investigation. Osteoarthritis (OA) is a chronic joint condition marked by gradual degradation of the cartilage and commonly associated with elevated levels of matrix metalloproteinases (MMPs). However, the influence of cannabiorcol on OA and its underlying mechanisms remains unclear. MethodsIn silico analysis investigated the key transcription factors that regulate MMP expression. A chondrocyte cell model [interleukin (IL)-1β and IL-1⍺-treated C20A4 cell line] was established and treated with cannabiorcol. Associated cytotoxicity was assessed using a WST-8 assay. A monoiodoacetate-induced OA rat model was established and treated with cannabiorcol. Protein translocation and transactivation analyses were conducted using immunofluorescence and dual-luciferase reporter assays, respectively. Western blotting and real-time PCR analyzed relevant markers to examine cannabiorcol's effects on OA and its fundamental mechanisms. ResultsCannabiorcol inhibits the expression of IL-1β-induced MMPs compared to other cannabis-related compounds. In silico analysis revealed that the nuclear factor-kappa β (NF-κβ) and mitogen-activated protein kinase (MAPK) pathways are associated with MMP expression as key regulators. In vitro, cannabiorcol inhibits the NF-κB and p38 MAPK pathways independently cannabinoid receptors and transient receptor potential vanilloids. In vivo, cannabiorcol reduces MMP expression and ameliorates monoiodoacetate-induced OA traits in rats. ConclusionCannabiorcol inhibits IL-1β-induced MMP expression in vitro and alleviates OA in an MIA-induced OA rat model by reducing MMP expression and inhibiting the p65/p38 axis.

Impact and Mechanisms of Action of BDNF on Neurological Disorders, Cancer, and Cardiovascular Diseases.

Brain-derived neurotrophic factor (BDNF), which is primarily expressed in the brain and nervous tissues, is the most abundant neurotrophic factor in the adult brain. BDNF serves not only as a major neurotrophic signaling agent in the human body but also as a crucial neuromodulator. Widely distributed throughout the central nervous system (CNS), both BDNF and its receptors play a significant role in promoting neuronal survival and growth, thereby exerting neuroprotective effects. It is further considered as a guiding medium for the functionality and structural plasticity of the CNS. Increasingly, research has indicated the critical importance of BDNF in understanding human diseases. Activation of intracellular signaling pathways such as the mitogen-activated protein kinase pathway, phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin pathway, and phospholipase C γ pathway by BDNF can all potentially enhance the growth, survival, proliferation, and migration of cancer cells, influencing cancer development. The loss of BDNF and its receptor, tropomyosin receptor kinase B, in signaling pathways is also associated with increased susceptibility to brain and heart diseases. Additionally, reduced BDNF levels in both the central and peripheral systems have been closely linked to various neurogenic diseases, including neuropathic pain and psychiatric disorders. As such, this review summarizes and analyzes the impact of BDNF on neurogenic diseases, cancer, and cardiovascular diseases. This study thereby aimed to elucidate its effects on these diseases to provide new insights and approaches for their treatment.

Structure elucidation and molecular mechanism of an immunomodulatory polysaccharide from Nostoc commune

Nostoc commune Vaucher, a terrestrial and benthic blue-green alga, widely used in food and medicine worldwide. N. commune Polysaccharides (NCVP) have excellent biological activities, especially immunomodulatory, hypoglycemic and anti-tumor activities. However, the mechanism and structure-activity relationship of NCVP has been less studied. In this study, based on methylation and NMR results, a novel polysaccharide NCVP2 with 135 kDa, containing→4)-α-D-Galp-(1→, → 4)-β-D-Glcp-(1→, and →4)-α-D-Xylp-(1→ residues as the backbon, was sequentially purified from N.commune by DEAE-52 and Sephadex G-100 column. NCVP2 (50 μg/mL) exhibited the strong in vitro immunomodulatory activity by promoting the generation of nitric oxide (NO) and reactive oxygen species (ROS). A total of 2048 differentially expressed genes (DEGs) were identified by RNA-seq, including 1019 down-regulated genes and 1065 up-regulated genes. These DEGs were mainly enriched in the immune-related biological processes, involving in Mitogen-activated protein kinase (MAPK) and Toll-like receptor (TLR) signaling pathways by GO and KEGG enrichment analysis. Furthermore, Western blot results proved NCVP2 could recognize TLR2 and TLR4/MD2, and regulate TLR7/IRF7, MAPK and PI3K/AKT signaling pathways. In summary, a novel polysaccharide NCVP2 from N.commune was proposed to exhibit significant immunomodulatory effects with multiple-paths and targets, and has great potential in the development of healthy foods such as immunomodulators.

The sensor protein AaSho1 regulates infection structures differentiation, osmotic stress tolerance and virulence via MAPK module AaSte11-AaPbs2-AaHog1 in Alternaria alternata

The high-osmolarity-sensitive protein Sho1 functions as a key membrane receptor in phytopathogenic fungi, which can sense and respond to external stimuli or stresses, and synergistically regulate diverse fungal biological processes through cellular signaling pathways. In this study, we investigated the biological functions of AaSho1 in Alternaria alternata, the causal agent of pear black spot. Targeted gene deletion revealed that AaSho1 is essential for infection structure differentiation, response to external stresses and synthesis of secondary metabolites. Compared to the wild-type (WT), the ∆AaSho1 mutant strain showed no significant difference in colony growth, morphology, conidial production and biomass accumulation. However, the mutant strain exhibited significantly reduced levels of melanin production, cellulase (CL) and ploygalacturonase (PG) activities, virulence, resistance to various exogenous stresses. Moreover, the appressorium and infection hyphae formation rates of the ∆AaSho1 mutant strain were significantly inhibited. RNA-Seq results showed that there were four branches including pheromone, cell wall stress, high osmolarity and starvation in the Mitogen-activated Protein Kinase (MAPK) cascade pathway. Furthermore, yeast two-hybrid experiments showed that AaSho1 activates the MAPK pathway via AaSte11-AaPbs2-AaHog1. These results suggest that AaSho1 of A. alternata is essential for fungal development, pathogenesis and osmotic stress response by activating the MAPK cascade pathway via Sho1-Ste11-Pbs2-Hog1.

Effects of Platycodon grandiflorus on doxorubicin resistance and epithelial-mesenchymal transition of breast cancer cells via the p38 mitogen-activated protein kinase pathway.

With the increase of chemotherapy frequency for breast cancer, the drug resistance rate of patients is rising, accompanied by cell invasion and metastasis, thus causing mortality. We aimed to explore the mechanism by which Platycodon grandiflorus affects breast cancer cells in terms of the doxorubicin (Dox) resistance and epithelial-mesenchymal transition (EMT) via the p38 mitogen-activated protein kinase (p38 MAPK) signaling pathway. MCF-7/R cell lines with resistance to Dox were established. After 24h of culture with DMEM (blank group), they were divided into Platycodon grandiflorus, Platycodon grandiflorus + Ophiopogon japonicus, Platycodon grandiflorus + Curcumae Rhizoma, Platycodon grandiflorus + Curcumae Rhizoma + U46619 groups. Flow cytometry, colony formation assay, as well as Transwell assay were performed to examine the cells for apoptosis, proliferation, and invasion, respectively. Western blotting was performed to measure the phosphorylated (p)-p38 MAPK-to-p38 MAPK ratio together with N-cadherin, vimentin, β-catenin, and E-cadherin protein expressions. Compared with the blank group, the half maximal inhibitory concentration (IC50), number of cell colonies, number of invading cells and expressions of proteins related to EMT (i.e. N-cadherin, vimentin, and β-catenin) significantly reduced, but increases in apoptosis rate, p-p38 MAPK/p38 MAPK ratio and E-cadherin protein expression were observed in different groups (P < 0.05). Compared with the Platycodon grandiflorus + Curcumae Rhizoma group, the Platycodon grandiflorus + Curcumae Rhizoma + U46619 group had significantly decreased IC50, cell colony count, invading cell count and β-catenin, N-cadherin, and vimentin expressions, in addition to elevated E-cadherin protein expression, apoptosis rate, and p-p38 MAPK/p38 MAPK ratio (P < 0.05). Platycodon grandiflorus can reverse the resistance of breast cancer cells to Dox and regulate their biological activities by activating the p38 MAPK signaling pathway.

Differential analysis of microRNAs in plasma exosomes in patients with cerebral ischemic stroke.

The high incidence, disability, mortality, and recurrence rates of cerebral infarction impose a heavy burden on both the Chinese and global populations. It is essential for the early diagnosis, prevention, and protection against brain cell injury. To identify differentially expressed microRNAs (miRNAs) in plasma exosomes of patients with cerebral ischemic stroke, determine relevant biomarkers, and explore their potential signaling pathways. High-throughput sequencing was used to detect the expression of plasma exosomal miRNAs in patients with cerebral ischemic stroke and in a control group. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes enrichment, and target gene network analyses were performed to investigate the target genes and signaling pathways of the differentially expressed miRNAs. The sequencing results identified 95 differentially expressed miRNAs, with 40 upregulated and 55 downregulated miRNAs. Among these, hsa-miR-1303, hsa-miR-125b-1-3p, and hsa-miR-548ab were significantly upregulated in the stroke group and downregulated in the normal control group, whereas hsa-miR-1289 was downregulated in the stroke group and upregulated in the normal group. Gene Ontology, Kyoto Encyclopedia of Genes, and genomes enrichment analyses indicated that the differentially expressed miRNAs and their target genes were mainly concentrated in the PI3K-AKt, mitogen-activated protein kinase, calcium, Ras, Rap1, and cAMP signaling pathways. The expression of plasma exosomal hsa-miR-1303, hsa-miR-125b-1-3p, and hsa-miR-1289 was significantly different in stroke patients than in the control group. These miRNAs may be involved in various signaling pathways related to cerebral infarction, providing a reference for further experimental research.

Durvalumab and T-DXd Synergistically Promote Apoptosis of Cholangiocarcinoma Cells by Downregulating EGR1 Expression Through Inhibiting P38 MAPK Pathway.

Cholangiocarcinoma is a hepatobiliary system tumor with a high mortality rate. Although durvalumab and trastuzumab deruxtecan (T-DXd) have shown efficacy in treating cancers such as non-small cell lung cancer, their effects and regulatory mechanisms in cholangiocarcinoma remain unclear. In this study, we aimed to investigate the role and mechanism of durvalumab and T-DXd in inducing apoptosis in cholangiocarcinoma cells. Cholangiocarcinoma cells were treated with varying concentrations of durvalumab and T-DXd, either individually or in combination, to evaluate their effects. Apoptosis was quantified using flow cytometry. Quantitative real-time PCR (qPCR) and Western blotting were used to measure the mRNA expression and protein levels of genes associated with apoptosis and cell cycle regulation. The underlying mechanism was further explored through pathway enrichment analysis of differentially expressed genes (DEGs) and corroborated by qPCR and Western blotting. Xenotransplantation models using immune-deficient NOD-SCID/IL2Rγnull (NSG) mice were established to assess the in vivo effects of durvalumab and T-DXd. Our results showed that both durvalumab and T-DXd inhibited cholangiocarcinoma cell proliferation in a dose-dependent manner. Both agents promoted apoptosis and arrested the cell cycle of cholangiocarcinoma cells, with the combination treatment having the most significant effect. Furthermore, treatment with durvalumab, T-DXd, and the combination downregulated the protein levels of early growth response 1 (EGR1) by inactivating the p38 mitogen-activated protein kinase (MAPK) pathway. In vivo experiments indicated that durvalumab and T-DXd prolonged the survival of NSG mice bearing cholangiocarcinoma xenografts. In conclusion, our findings demonstrated that durvalumab and T-DXd synergistically promoted apoptosis in cholangiocarcinoma cells by inhibiting EGR1 expression through inactivation of the p38 MAPK pathway. This study confirmed the potential of durvalumab and T-DXd for the treatment of cholangiocarcinoma.

YY1 downregulation underlies therapeutic response to molecular targeted agents

During targeted treatment, oncogene-addicted tumor cells often evolve from an initial drug-sensitive state through a drug-tolerant persister bottleneck toward the ultimate emergence of drug-resistant clones. The molecular basis underlying this therapy-induced evolutionary trajectory has not yet been completely elucidated. Here, we employed a multifaceted approach and implicated the convergent role of transcription factor Yin Yang 1 (YY1) in the course of diverse targeted kinase inhibitors. Specifically, pharmacological perturbation of the receptor tyrosine kinase (RTK)/mitogen-activated protein kinase (MAPK) pathway resulted in the downregulation of YY1 transcription, which subsequently resumed upon therapeutic escape. Failure to decrease YY1 subverted cytotoxic effects, whereas elimination of residual YY1 maximized anticancer efficacy and forestalled the emergence of drug resistance. Mechanistically, YY1 was uncovered to dictate cell cycle and autophagic programs. Immunohistochemical analysis on a wide spectrum of clinical specimens revealed that YY1 was ubiquitously expressed across lung adenocarcinomas and exhibited anticipated fluctuation in response to corresponding RTK/MAPK inhibition. These findings advance our understanding of targeted cancer management by highlighting YY1 as a determinant node in the context of genotype-directed agents.

The Anti-Inflammatory Roles of Vitamin D for Improving Human Health

Vitamin D receptors (VDRs) are present in almost all cells of the immune system, including B cells, T cells, NK (Natural Killer) cells, dendritic cells, and monocytes, as well as the epithelial cells of many organs such as the intestine, pancreas, prostate, lungs, and cardiomyocytes. In addition, some immune cells, including dendritic cells, macrophages, and B and T cells, can synthesize calcitriol by expressing 1α-hydroxylase. Upon binding to VDRs, vitamin D (Vit D) regulates the expression of genes involved in immune responses, including those encoding for cytokines. It modulates the production of pro-inflammatory cytokines while promoting the synthesis of anti-inflammatory cytokines. Vit D also affects the differentiation and maturation of cells of the immune system. By inhibiting the nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways, Vit D reduces the expression of pro-inflammatory genes. These effects highlight the potential of Vit D as a therapeutic agent in the management of inflammatory diseases, including autoimmune disorders, cardiovascular diseases, diabetes, metabolic syndrome, cancer, neurological diseases, depression, and inflammatory bowel disease.

Acupoint injection inhibiting abnormal secretion of mucin and inflammatory reaction of nasal mucosa in rats with allergic rhinitis through the p38 mitogen-activated protein kinase pathway

To observe the effects of acupoint injection on the expression of p38 mitogen-activated protein kinase (MAPK), phosphorylated (p)-p38 MAPK, mucin 5 subtype AC (MUC5AC) in the nasal mucosa, and serum inflammatory factors of rats with allergic rhinitis, so as to explore the mechanism of acupoint injection in improving inflammatory reactions in the nasal mucosa of rats with allergic rhinitis. SD rats were randomly divided into the normal group, model group, acupoint injection group, and non-acupoint group, with 7 rats in each group. The allergic rhinitis rat model was established using ovalbumin sensitization. Intervention was performed by injecting dexamethasone and 1% lidocaine mixture (0.05 mL) into the bilateral "Yingxiang"(LI20) and "Yintang"(GV24+) acupoints, with injection at non-acupoints for non-acupoint group as the control, once every 3 days for a total of 4 times. Allergic symptoms in the rat nose were evaluated using a cumulative scoring method；histopathological changes in the nasal mucosa were observed after HE staining；serum histamine (HA), interleukin (IL)-6, IL-8, and tumor necrosis factor-alpha (TNF-α) contents were detected using ELISA；real-time fluorescent quantitative PCR was used to detect the expression of MUC5AC mRNA in the nasal mucosa；Western blot was used to detect the expression of p38 MAPK, p-p38 MAPK, and MUC5AC protein in the nasal mucosa. Compared with the normal group, nasal allergic symptom score, serum HA, IL-6, IL-8, and TNF-α contents, nasal mucosal p38 MAPK, p-p38 MAPK proteins expression, MUC5AC mRNA and protein expression were significantly increased(P<0.01) in the model group. Compared with the model group and non-acupoint group, nasal allergic symptom score, serum HA, IL-6, IL-8, and TNF-α contents, nasal mucosal p38 MAPK and p-p38 MAPK proteins expression, MUC5AC mRNA and protein expression were significantly reduced (P<0.01, P<0.05) in the acupoint injection group. Acupoint injection can reduce nasal allergic symptom, and MUC5AC secretion in rats with allergic rhinitis, alleviate nasal mucosal inflammatory reactions, and its mechanism of action may be related to the inhibition of p38 MAPK phosphorylation, thereby reducing the release of inflammatory factors.

PDE4D drives rewiring of the MAPK pathway in BRAF-mutated melanoma resistant to MAPK inhibitors

BackgroundPhosphodiesterase type 4D (PDE4D) breaks down cyclic AMP (cAMP) reducing the signaling of this intracellular second messenger which plays a major role in melanocyte pathophysiology. In advanced melanoma, expression of PDE4D is increased, plays a role in tumor invasion and is negatively associated with survival. In the current work, we investigated the role of PDE4D in the resistance of BRAF-mutated melanoma to mitogen-activated protein kinase (MAPK) pathway-targeted therapy.MethodsEstablished human melanoma cell line sensitive and resistant to BRAF and MEK inhibitors and tumor tissues from melanoma patients were used in this study. Immunoblotting was used to analyze protein expression and quantitative reverse transcription-PCR was used to analyze mRNA expression. DNA methylation analysis was evaluated via bisulfite treatment followed by quantitative PCR. Cell viability was measured by clonogenic assays or spheroid cultures. Cell xenograft experiments in immunodeficient mice were used to validate the results in vivo.ResultsAnalysis of baseline tumors from patients with BRAFV600E-mutated melanoma treated with MAPK inhibitors showed that higher PDE4D expression in situ predicted worse survival in patients. Furthermore, acquired resistance to BRAF and MEK inhibitors was associated with overexpression of PDE4D in situ and ex vivo. The overexpression of the PDE4D5 isoform in melanoma cells resistant to targeted therapies was explained by demethylation or deletion of a CpG island located upstream of the PDE4D5 promoter. We further showed that PDE4D overexpression allowed RAF1 activation, promoting a switch from BRAF to RAF1 isoform in BRAF-mutated melanoma, favoring resistance to BRAF and MEK inhibitors. As a result, pharmacological inhibition of PDE4 activity impeded the proliferation of resistant cells ex vivo and in vivo. The anti-tumorigenic activity of PDE4 inhibitor was achieved via inhibition of the Hippo pathway which plays an important role in resistance to targeted therapies.ConclusionsIn summary, our research showed that PDE4D drives rewiring of the MAPK pathway in BRAF-mutated melanoma resistant to MAPK inhibitors and suggests that PDE4 inhibition is a novel therapeutic option for treatment of BRAF-mutated melanoma patients.

Inhibition of PA28γ expression can alleviate osteoarthritis by inhibiting endoplasmic reticulum stress and promoting STAT3 phosphorylation.

Osteoarthritis (OA) is a common degenerative disease. PA28γ is a member of the 11S proteasome activator and is involved in the regulation of several important cellular processes, including cell proliferation, apoptosis, and inflammation. This study aimed to explore the role of PA28γ in the occurrence and development of OA and its potential mechanism. A total of 120 newborn male mice were employed for the isolation and culture of primary chondrocytes. OA-related indicators such as anabolism, catabolism, inflammation, and apoptosis were detected. Effects and related mechanisms of PA28γ in chondrocyte endoplasmic reticulum (ER) stress were studied using western blotting, real-time polymerase chain reaction (PCR), and immunofluorescence. The OA mouse model was established by destabilized medial meniscus (DMM) surgery, and adenovirus was injected into the knee cavity of 15 12-week-old male mice to reduce the expression of PA28γ. The degree of cartilage destruction was evaluated by haematoxylin and eosin (HE) staining, safranin O/fast green staining, toluidine blue staining, and immunohistochemistry. We found that PA28γ knockdown in chondrocytes can effectively improve anabolism and catabolism and inhibit inflammation, apoptosis, and ER stress. Moreover, PA28γ knockdown affected the phosphorylation of IRE1α and the expression of TRAF2, thereby affecting the mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) signalling pathways, and finally affecting the inflammatory response of chondrocytes. In addition, we found that PA28γ knockdown can promote the phosphorylation of signal transducer and activator of transcription 3 (STAT3), thereby inhibiting ER stress in chondrocytes. The use of Stattic (an inhibitor of STAT3 phosphorylation) enhanced ER stress. In vivo, we found that PA28γ knockdown effectively reduced cartilage destruction in a mouse model of OA induced by the DMM surgery. PA28γ knockdown in chondrocytes can inhibit anabolic and catabolic dysregulation, inflammatory response, and apoptosis in OA. Moreover, PA28γ knockdown in chondrocytes can inhibit ER stress by promoting STAT3 phosphorylation.

The regulatory role of tRNA-derived small RNAs in the prognosis of gastric cancer

In recent years, tRNA-derived small RNAs (tsRNAs) including tRNA-derived stress-induced RNAs (tiRNAs) and tRNA-derived fragments (tRFs), with specific structure and enriched in body fluids, have been found to have specific biological functions. In this paper, the biogenesis, classification, subcellular localization, and biological functions of tsRNAs were summarized. It has been proved that tsRNAs affected tumor cells in proliferation, apoptosis, migration and invasion, and played roles in regulating the occurrence and development of various tumors. In gastric cancer (GC), the imbalance of tsRNAs, such as tRF-33-P4R8YP9LON4VDP, tRF-17-WS7K092, tRF-23-Q99P9P9NDD and others, was closely related to the clinicopathological characteristics of GC patients. Some tsRNAs, such as tRF-23-Q99P9P9NDD, tRF-31-U5YKFN8DYDZDD, and tRF-27-FDXXE6XRK45 promoted the proliferation, migration and invasion of GC cells. Other tsRNAs, such as tRF-41-YDLBRY73W0K5KKOVD, tRF-18-79MP9PO4, and tRF-Glu-TTC-027 inhibited the proliferation, migration and invasion of GC cells. The tsRNAs played roles in the occurrence of GC were through several signaling pathways, such as phosphoinositide 3-kinase (PI3K)-AKT serine/threonine kinase (AKT), Wnt-β-Catenin, and mitogen-activated protein kinase (MAPK) pathways. These findings may provide new strategies for the diagnosis and treatment of GC.

Retinoic acid ameliorates rheumatoid arthritis by attenuating inflammation and modulating macrophage polarization through MKP-1/MAPK signaling pathway.

Macrophages are innate immune cells connected with the development of inflammation. Retinoic acid has previously been proved to have anti-inflammatory and anti-arthritic properties. However, the exact mechanism through which retinoic acid modulates arthritis remains unclear. This study aimed to investigate whether retinoic acid ameliorates rheumatoid arthritis by modulating macrophage polarization. This study used retinoic acid to treat mice with adjuvant arthritis and evaluated anti-inflammatory effects by arthritis score, thermal nociceptive sensitization test, histopathologic examination and immunofluorescence assays. In addition, its specific anti-arthritic mechanism was investigated by flow cytometry, cell transfection and inflammatory signaling pathway assays in RAW264.7 macrophages in vitro. Retinoic acid significantly relieved joint pain and attenuated inflammatory cell infiltration in mice. Furthermore, this treatment modulated peritoneal macrophage polarization, increased levels of arginase 1, as well as decreased inducible nitric oxide synthase expression. In vitro, we verified that retinoic acid promotes macrophage transition from the M1 to M2 type by upregulating mitogen-activated protein kinase (MAPK) phosphatase 1 (MKP-1) expression and inhibiting P38, JNK and ERK phosphorylation in lipopolysaccharide-stimulated RAW264.7 cells. Notably, the therapeutic effects of retinoic acid were inhibited by MKP-1 knockdown. Retinoic acid exerts a significant therapeutic effect on adjuvant arthritis in mice by regulating macrophage polarization through the MKP-1/MAPK pathway, and play an important role in the treatment of rheumatic diseases.

Abstract B009: The RNA binding activity of the BRAF Kinase

Abstract Multiprotein complexes are key molecular switches of oncogenic signal transduction pathways that relay the flux of information coming from transmembrane receptors and distribute signals to a myriad of effectors. As such the regulation of protein-protein interactions is crucial in signal transduction pathways. For instance, activation of the mitogen-activated protein kinases pathway (MAPK) occurs through a cascade of phosphorylation and protein-protein interactions (PPIs) and is often deregulated in cancer. RNA-protein interactions play key roles in biological processes. More than a thousand RNA binding proteins (RBPs) influence the fate of mRNAs and non-coding RNAs in different ways. It is however less described how RNAs can in turn influence the functions of proteins to which they bind. Here we propose that RNAs scaffold PPIs in the MAPK pathway, thereby fine-tuning oncogenic signaling. We focused our study on cutaneous melanoma for which the MAPK is activated in more than 70% of the cases due to activating mutations in BRAF and NRAS. Using UV-CrossLinking ImmunoPrecipitation (CLIP) experiments, we found that several proteins of the MAPK pathway, including BRAF (but not MEK and ERK) interact with RNAs in RAS-activated melanoma cells. In addition, using a PLA- based imaging technique that allows the visualisation of the proximity of two given proteins, we showed that RNAs promote the stabilisation of BRAF-PPIs, suggesting a scaffolding role of RNAs in the MAPK pathway. Loss of BRAF RNA binding activity (achieved with a single point mutation) is associated with decreased BRAF dimerization and signaling. The oncogenic mutant protein BRAF (V600E) also interacts with RNA in a variety of melanoma cell lines including a BRAF inhibitor-resistant melanoma cell line in which the dimerization of BRAF and CRAF is partly dependent on RNA. Identifying BRAF-bound RNAs will open new therapeutic strategies targeting RNA-protein interactions. We also envision that the level of BRAF-RNA interactions could serve as a predictive marker of response to BRAF (V600E) inhibitors. Citation Format: Alexia Le Barch, Sabrina Mennour, Patricia Uguen, Stephan Vagner. The RNA binding activity of the BRAF Kinase [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: RNAs as Drivers, Targets, and Therapeutics in Cancer; 2024 Nov 14-17; Bellevue, Washington. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(11_Suppl):Abstract nr B009.

Expression levels of some genes in the MAPK pathway (DUSP1, DUSP2, DUSP4, DUSP6 and DUSP10) in eyelid tumor tissue

Abstract Objectives To control mitogen-activated protein kinases (MAPK) signaling pathways involved in the onset and progression of cancer, dual specificity phosphatases (DUSPs/MKP) are essential. This study seeks to detect the correlation between eyelid tumors and the genes DUSPs, known for their influence on MAPK signaling pathways. Additionally, we aim to juxtapose our findings with analyses from various bioinformatics databases. Methods Expression levels of relevant genes in cDNA samples were determined by quantitative PCR method. Open-access databases were used for mutation analysis of relevant genes, mRNA expression changes, and survival analyses, and the STRING database was used for protein-protein interactions. Results It was found that the expression of DUSP1 and DUSP2 showed a significant decrease in the tumor tissue, while a significant increase was detected in the DUSP4 and DUSP6 genes. Additionally, when we compared the study genes with the Cancer Genome Atlas program cancer cohorts, it was found that the DUSP1 and DUSP10 gene expression profiles were downregulated in uveal melanoma compared to other cancer cohorts. Conclusions Significant and obvious changes were observed in the DUSP genes we studied in eyelid tumors. However, the relationship between these genes and cancer must be studied more. Considering that these enzymes are effective in cell proliferation, differentiation, and apoptosis, it would be appropriate to plan comprehensive studies on their interactions with other proteins they interact with in the MAPK pathway.