MEK Inhibitor Research Articles

MEK1/2 promote ROS production and deubiquitinate NLRP3 independent of ERK1/2 during NLRP3 inflammasome activation

Inflammasomes are cytosolic supramolecular complexes that play a key role in the innate immune response. Overactivation of NLR family pyrin domain containing 3 (NLRP3) inflammasome leads to multiple diseases. Post-translational modifications (PTMs) are essential modulators of inflammasomes especially in activation phase. Here we found that MEK1/2 kinase activity was indispensable in NLRP3 inflammasome activation both in vitro and in vivo. Inhibition of MEK1/2 resulted in reactive oxygen species (ROS) scavenging and ubiquitination of NLRP3, which further blocked NLRP3 inflammasome activation. These effects were independent of ERK1/2, which were classic downstream of MEK1/2. These investigations proposed a mechanism that MEK1/2 regulated inflammation via non-transcriptional regulation of NLRP3 inflammasome and might help better understanding the effects and side-effects of MEK inhibitors in clinical use.

Cdk8 and Hira mutations trigger X chromosome elimination in naive female hybrid mouse embryonic stem cells

Mouse embryonic stem cells (ESCs) possess a pluripotent developmental potential and a stable karyotype. An exception is the frequent loss of one X chromosome in female ESCs derived from inbred mice. In contrast, female ESCs from crosses between different Mus musculus subspecies often maintain two X chromosomes and can model X chromosome inactivation. Here we report that combined mutations of Hira and Cdk8 induce rapid loss of one X chromosome in a Mus musculus castaneus hybrid female ESC line that originally maintains two X chromosomes. We show that MEK1 inhibition, which is used for culturing naive pluripotent ESCs is sufficient to induce X chromosome loss. In conventional ESC media, Hira and Cdk8 mutant ESCs maintain both X chromosomes. Induction of X chromosome loss by switching to naive culture media allows us to perform kinetic measurements for calculating the chromosome loss rate. Our analysis shows that X chromosome loss is not explained by selection of XO cells, but likely driven by a process of chromosome elimination. We show that elimination of the X chromosome occurs with a rate of 0.3% per cell per division, which exceeds reported autosomal loss rates by 3 orders of magnitude. We show that chromosomes 8 and 11 are stably maintained. Notably, Xist expression from one of the two X chromosomes rescues X chromosomal instability in ΔHiraΔCdk8 ESCs. Our study defines mutations of Hira and Cdk8 as molecular drivers for X chromosome elimination in naive female ESCs and describes a cell system for elucidating the underlying mechanism.

CASPER: A Phase I trial combining calaspargase pegol-mnkl and cobimetinib in pancreatic cancer.

Asparagine synthetase (ASNS) catalyzes the biosynthesis of asparagine from aspartate and glutamine. Cells lacking ASNS, however, are auxotrophic for asparagine. Use of L-asparaginase to promote asparagine starvation in solid tumors with low ASNS levels, such as pancreatic ductal adenocarcinoma (PDAC), is a rationale treatment strategy. However, tumor cell resistance to L-asparaginase has limited its clinical utility. Our preclinical studies show that RAS/MAPK signaling circumvents L-asparaginase-induced tumor killing, but L-asparaginase and MEK inhibition potentiated tumor killing; suggesting that this combination may provide meaningful clinical benefit to patients with PDAC. This Phase I trial (NCT05034627) will evaluate the safety and tolerability of the MEK inhibitor, cobimetinib, in combination with pegylated L-asparaginase, L calaspargase pegol-mknl, in patients with locally-advanced or metastatic PDAC.

Aldo-keto reductase family 1 member C3 mediates radioresistance of esophageal cancer cells through suppressing MAPK and AKT signaling

BackgroundAldo-keto reductase family 1 member C3 (AKR1C3) is a radioresistance gene in esophageal cancer. This study aimed to investigate the signaling pathways that mediate the regulatory role of AKR1C3 in the radioresistance of esophageal cancer cells.MethodsThe protein levels of AKR1C3 in cancer tissue samples were compared between patients with radiosensitive and radioresistant esophageal cancer using immunohistochemical staining. AKR1C3-silenced stable KYSE170R esophageal cancer cells (KY170R-shAKR1C3) were established. Colony formation assay was employed to evaluate the radiosensitivity of cancer cells, while flow cytometry analysis was utilized to quantify reactive oxygen species (ROS) production in these cells. Additionally, Western blotting was conducted to determine protein expression levels.ResultsAKR1C3 protein exhibited significantly higher expression in radioresistant cancer tissue samples compared to radiosensitive samples. AKR1C3 silencing promoted radiosensitivity and ROS production of KYSE170R cells. At 32 h after X-ray radiation, the levels of total and phosphorylated ERK1/2, JNK, and AKT proteins were significantly elevated in KYSE170R-shAKR1C3 cells compared to untransfected KYSE170R cells. The inhibitor of AKR1C3 remarkably enhanced the radiosensitivity of KYSE170R cells. Conversely, treatment with either a MEK inhibitor or an AKT inhibitor significantly increased the radioresistance of KYSE170R-shAKR1C3 cells.ConclusionsOur results suggest that AKR1C3 mediates radioresistance of KYSE170R cells possibly through MAPK and AKT signaling.

Dual MAPK Inhibition Triggers Pro-inflammatory Signals and Sensitizes BRAF V600E Glioma to T Cell-Mediated Checkpoint Therapy.

BRAF V600E pediatric low-grade gliomas frequently transform into high-grade gliomas (HGG) and poorly respond to chemotherapy, resulting in high mortality. Although combined BRAF and MEK inhibition (BRAFi+MEKi) outperforms chemotherapy, ∼70% of BRAF V600E HGG patients are therapy resistant and undergo unbridled tumor progression. BRAF V600E glioma have an immune-rich microenvironment suggesting that they could be responsive to immunotherapy but effects of BRAFi+MEKi on anti-tumor immunity are unclear. Using patient tumor tissue before and after BRAFi+MEKi, two novel syngeneic murine models of BRAF V600E HGG, and patient-derived cell lines, we examined the effects of clinically relevant BRAFi+MEKi with dabrafenib and trametinib on tumor growth, cell states, and tumor-infiltrating T cells. We find that BRAFi+MEKi treatment: i) upregulated programmed cell death protein-1 (PD-1) signaling genes and PD-1 ligand (PD-L1) protein expression in murine BRAF V600E HGG by stimulating IFNγ and IL-27, ii) attenuated T cell activity by IL-23, IL-27 and IL-32 production, which can promote the expansion of regulatory T cells, and iii) induced glial differentiation linked to a therapy-resistant PD-L1+ compartment through Galectin-3 secretion by tumor cells. Murine BRAF V600E HGG shrinkage by BRAFi+MEKi is associated with the upregulation of interferon-gamma response genes, MHC class I/II expression, and antigen presentation and processing programs, indicative of increased anti-tumor immunity. Combined BRAFi+MEKi with therapeutic antibodies inhibiting the PD-1 and cytotoxic T-lymphocyte associated protein 4 (CTLA-4) immune checkpoints re-activate T cells and provide a survival benefit over single therapy in a T cell-dependent manner. The quadruple treatment overcame BRAFi+MEKi resistance by invigorating T cell-mediated anti-tumor immunity in murine BRAF V600E HGG. PD-L1 expression was elevated in human BRAF-mutant versus BRAF-wildtype glioblastoma clinical specimen, complementing experimental findings and suggesting translational relevance for patient care.

Immune-related glycosylation genes based classification predicts prognosis and therapy options of osteosarcoma

Osteosarcoma is the most common primary bone malignancy, with a very poor prognosis. Aberrant glycosylation is close involvement in osteosarcoma. Accordingly, this study aimed at investigating the role of glycosylation genes in the prognosis and therapy options of osteosarcoma. The microenvironment of osteosarcoma was assessed using estimate algorithm. A total of 20 immune-related glycosylation genes (IRGGs) was identified using Pearson correlation analysis. Accordingly, osteosarcoma patients were divided into C1 and C2 type using consensus clustering. Multiple algorithms (Xcell, MCP-counter, ssGSEA, epic, quantiseq), cancer immune cycle analysis, and GSVA were applied to estimate the immune, molecule and metabolism characteristics of osteosarcoma, indicating that C1 type was featured with high immune infiltration, high glycosylation, enriched MEK signaling, and good prognosis, while C2 type was characterized by more metastasis, enriched immunotherapy-positive gene signatures, high tumor mutation burden, and poor prognosis. Results from TIDE algorithm and immunotherapy datasets suggested the C2 type’s preference of immune checkpoint inhibitors (ICIs), while data of GDSC, CMap analysis and cell experiments indicated that C1 type was sensitivity to MEK inhibitor PD0325901. In addition, univariate Cox and Lasso analysis was combined to establish an IRGGs’ risk score containing 6 genes (B3GNT8, FUT7, GAL3ST4, GALNT14, HS3ST2, and MFNG). The data of DCA and ROC indicated its well prediction of prognosis in osteosarcoma. Finally, cellular location analysis showed that the 6 genes not only distributed in tumor cells but also in immune cells. In summary, the classification and risk score based on IRGGs effectively predicted the prognosis and therapy options of osteosarcoma. Further studies on IRGGs may contribute to the understanding of cancer immunity in osteosarcoma.

Exploring immunotherapy efficacy in non-small cell lung cancer patients with BRAF mutations: a case series and literature review.

The use of immunotherapy in treatment of non-small cell lung cancer (NSCLC) patients with the BRAF gene mutations is an area of active research and is an item of clinical trials. While BRAF mutations are relatively infrequent in NSCLC patients, comprising approximately 1-3% of cases, the V600E substitution stands out as the most prevalent subtype of BRAF mutations. The presence of this mutation in cancer cells qualifies the patients for first-line therapy with BRAF and MEK inhibitors. This study aims to evaluate the efficacy of immunotherapy in NSCLC patients with BRAF mutations. We presented a series of seven NSCLC cases with BRAF mutations, four of whom received immunotherapy or chemoimmunotherapy. We observed benefit from immunotherapy in all patients, but its duration depended on comorbidities and the presence of brain metastases. Utilization of the next generation sequencing (NGS) technique causes high detection frequency of BRAF mutations (4.7% of patients), although mutations other than V600E may predominate (4 out of 7 patients). In patients receiving immune checkpoint inhibitors (ICIs)-based therapy, the median progression-free survival (PFS) was 17 months from the start of immunotherapy, the overall objective response rate (ORR) was 50%, and disease control was achieved in all patients. Immunotherapy can benefit NSCLC patients with BRAF mutations, though its efficacy is affected by comorbidities and brain metastases. The use of NGS enhances mutation detection, highlighting the need for personalized treatment approaches in NSCLC management. The varying responses to treatments among the patients emphasize the complexity of NSCLC management and the necessity for a personalized approach.

MAP kinase kinase 1 (MEK1) within extracellular vesicles inhibits tumour growth by promoting anti-tumour immunity.

Extracellular vesicles (EVs) mediate intercellular communication in many physiologic processes and can modulate immune responses in individuals with cancer. Most studies of EVs in cancer have focused on their tumour promoting properties. Whether and how EVs might mediate tumour regression besides carrying antigens has not been well characterized. Using a mouse model of highly immunogenic regressor versus poorly immunogenic progressor tumour cells, we have characterized the role of EVs in activating macrophages and promoting tumour rejection. We found that the signalling molecule MAP2K1 (MEK1) is enriched in EVs secreted by regressor relative to progressor cells. Progressor EVs engineered to have levels of MEK1 similar to regressor EVs could inhibit tumour growth by indirectly promoting adaptive immunity in both syngeneic and 3rd party tumours. This effect required MEK1 activity and could occur by activating macrophages to promote adaptive immune responses against the tumour via the cytokine interferon-gamma. Our results suggest that MEK inhibition may be deleterious to cancer treatment, since MEK1 plays an important cell-extrinsic, tumour-suppressive role within EVs. Moreover, the delivery of MEK1 to tumour-associated macrophages, either by EVs, nanoparticles, or some other means, could be a useful strategy to treat cancer via the activation of anti-tumour immunity.

Dysregulation of RAS proteostasis by autosomal-dominant LZTR1 mutation induces Noonan syndrome-like phenotypes in mice.

Leucine-zipper-like post translational regulator 1 (LZTR1) is a member of the BTB-Kelch superfamily, which regulates the RAS proteostasis. Autosomal dominant (AD) mutations in LZTR1 have been identified in patients with Noonan syndrome (NS), a congenital anomaly syndrome. However, it remains unclear whether LZTR1 AD mutations regulate the proteostasis of the RAS subfamily molecules or cause NS-like phenotypes in vivo. To elucidate the pathogenesis of LZTR1 mutations, we generated two novel LZTR1 mutation knock-in mice (Lztr1G245R/+ and Lztr1R409C/+), which correspond to the human p.G248R and p.R412C mutations, respectively. LZTR1-mutant male mice exhibit low birth weight, distinctive facial features, and cardiac hypertrophy. Cardiomyocyte size and the expression of RAS subfamily members, including MRAS and RIT1, were significantly increased in the left ventricles (LVs) of mutant male mice. LZTR1 AD mutants did not interact with RIT1 and functioned as dominant-negative forms of wild-type LZTR1. Multi-omics analysis revealed that the MAPK signaling pathway was activated in the LVs of mutant mice. Treatment with the MEK inhibitor trametinib ameliorated cardiac hypertrophy in mutant male mice. These results suggest that MEK/ERK pathway is a therapeutic target for NS-like phenotype resulting from dysfunction of RAS proteostasis by LZTR1 AD mutations.

38 (PB026): The novel dual MEK inhibitor ABM-4095 for RAS-mutated lung cancer as a single agent or in combination with known therapies

38 (PB026): The novel dual MEK inhibitor ABM-4095 for RAS-mutated lung cancer as a single agent or in combination with known therapies

PPP3CB overexpression mediates EGFR TKI resistance in lung tumors via calcineurin/MEK/ERK signaling.

Despite initial high response rates to first-line EGFR TKI, all non-small-cell lung cancer (NSCLC) with EGFR-activating mutation will ultimately develop resistance to treatment. Identification of resistance mechanisms is critical to adapt treatment and improve patient outcomes. Here, we show that a PPP3CB transcript that encodes full-length catalytic subunit 2B of calcineurin accumulates in EGFR-mutant NSCLC cells with acquired resistance against different EGFR TKIs and in post-progression biopsies of NSCLC patients treated with EGFR TKIs. Neutralization of PPP3CB by siRNA or inactivation of calcineurin by cyclosporin A induces apoptosis in resistant cells treated with EGFR TKIs. Mechanistically, EGFR TKIs increase the cytosolic level of calcium and trigger activation of a calcineurin/MEK/ERK pathway that prevents apoptosis. Combining EGFR, calcineurin, and MEK inhibitors overcomes resistance to EGFR TKI in both in vitro and in vivo models. Our results identify PPP3CB overexpression as a new mechanism of acquired resistance to EGFR TKIs, and provide a promising therapeutic approach for NSCLC patients that progress under TKI treatment.

Extended 73-month survival in an elderly patient with BRAF V600E-mutated lung adenocarcinoma: A case report.

BRAF is a mediator that activates the mitogen-activated protein kinase pathway. A mutation in BRAF can cause abnormal pathway activation, leading to cell proliferation. In a Phase II study, the combination therapy of the BRAF inhibitor dabrafenib and the MEK inhibitor trametinib was found to be effective in non-small cell lung cancer (NSCLC) patients with the BRAF mutation. However, this study has limited efficacy and safety data for elderly patients. We present a case of a patient who started treatment at 87 years old and showed a good prognosis, remaining alive 73 months from the start of treatment with no significant adverse events. The patient also maintained a partial response (PR) according to RECIST 1.1 at the last follow-up. This case suggests that the dabrafenib and trametinib combination therapy is safe and effective for elderly NSCLC patients with the BRAF mutation.

234 (PB222): Rational combination of pan-TEAD inhibitor SW-682 and MEK inhibitor mirdametinib in head and neck squamous cell carcinomas leads to synergistic response

234 (PB222): Rational combination of pan-TEAD inhibitor SW-682 and MEK inhibitor mirdametinib in head and neck squamous cell carcinomas leads to synergistic response

229 (PB217): Evaluation of the combined antiproliferative effects of Pan-RAF Inhibitor AZ-628 and MEK1 Inhibitor AZD-6244 across a diverse range of tumor cell lines

229 (PB217): Evaluation of the combined antiproliferative effects of Pan-RAF Inhibitor AZ-628 and MEK1 Inhibitor AZD-6244 across a diverse range of tumor cell lines

ERK signaling promotes resistance to TRK kinase inhibition in NTRK fusion-driven glioma mouse models

Pediatric-type high-grade gliomas frequently harbor gene fusions involving receptor tyrosine kinase genes, including neurotrophic tyrosine kinase receptor (NTRK) fusions. Clinically, these tumors show high initial response rates to tyrosine kinase inhibition but ultimately recur due to the accumulation of additional resistance-conferring mutations. Here, we develop a series of genetically engineered mouse models of treatment-naive and -experienced NTRK1/2/3 fusion-driven gliomas. All tested NTRK fusions are oncogenic invivo. The NTRK variant, N-terminal fusion partners, and resistance-associated point mutations all influence tumor histology and aggressiveness. Additional tumor suppressor losses greatly enhance tumor aggressiveness. Treatment with TRK kinase inhibitors significantly extends the survival of NTRK fusion-driven glioma mice, but fails to fully eradicate tumors, leading to recurrence upon treatment discontinuation. Finally, we show that ERK activation promotes resistance to TRK kinase inhibition and identify MEK inhibition as a potential combination therapy. These models will be invaluable tools to study therapy resistance of NTRK fusion tumors.

237 (PB225): Targeting NOS sensitizes the NRAS-mutant melanomas to MEK inhibition and induces Immunogenic Cell Death

237 (PB225): Targeting NOS sensitizes the NRAS-mutant melanomas to MEK inhibition and induces Immunogenic Cell Death

Novel biomarkers and drug correlations of non-canonical WNT signaling in prostate and breast cancer

Prostate cancer (PCa) and breast cancer (BC) present formidable challenges in global cancer-related mortality, necessitating effective management strategies. The present study explores non-canonical Wnt signaling in PCa and BC, aiming to identify biomarkers and assess their clinical and therapeutic implications. Co-expression analyses reveal distinct gene patterns, with five overlapping genes (SULF1, ALG3, IL16, PLXNA2 and RASGFR2) exhibiting divergent expression in both cancers. Clinical relevance investigations demonstrate correlations with TNM stages and biochemical recurrence. Drug correlation analyses unveil potential therapeutic avenues, indicating that Wnt5a and ROR2 expressions are related to MEK inhibitor sensitivity in cancers. Meanwhile, further correlation analyses were conducted between drugs and the other novel non-canonical WNT genes (ALG3, IL16, SULF1, PLXNA2, and RASGRF2). Our findings contribute to understanding non-canonical Wnt signaling, offering insights into cancer progression and potential personalized treatment approaches.

Risk Stratification, Screening and Treatment of BRAF/MEK Inhibitors-Associated Cardiotoxicity.

In this review article we describe the cardiovascular adverse events associated with BRAF and MEK inhibitors as well as their pathophysiologic mechanisms and provide up to date guidance for risk stratified surveillance of patients on treatment and the optimal management of emergent cardiotoxicities. Combination BRAF/MEK inhibition has become an established standard treatment option for patients with a wide variety of BRAF mutant haematological and solid organ cancers, its use is most commonly associated with stage three and metastatic melanoma. The introduction of these targeted drugs has significantly improved the prognosis of previously treatment resistant cancers. It is increasingly recognised that these drugs have a number of cardiovascular toxicities including left ventricular systolic dysfunction, hypertension and QTc interval prolongation. Whilst cardiotoxicity is largely reversible and manageable with medical therapy, it does limit the effective use of these highly active agents.

Marmoset and human trophoblast stem cells differ in signaling requirements and recapitulate divergent modes of trophoblast invasion

Early human trophoblast development has remained elusive due to the inaccessibility of the early conceptus. Non-human primate models recapitulate many features of human development and allow access to early postimplantation stages. Here, we tracked the pre- to postimplantation transition of the trophoblast lineage in superficially implanting marmoset embryos invivo. We differentiated marmoset naive pluripotent stem cells into trophoblast stem cells (TSCs), which exhibited trophoblast-specific transcriptome, methylome, differentiation potential, and long-term self-renewal. Notably, human TSC culture conditions failed to support marmoset TSC derivation, instead inducing an extraembryonic mesoderm-like fate in marmoset cells. We show that combined MEK, TGF-β/NODAL, and histone deacetylase inhibition stabilizes a periimplantation trophoblast-like identity in marmoset TSCs. By contrast, these conditions differentiated human TSCs toward extravillous trophoblasts. Our work presents a paradigm to harness the evolutionary divergence in implantation strategies to elucidate human trophoblast development and invasion.

RNA sequencing identifies lung cancer lineage and facilitates drug repositioning.

Recent breakthrough therapies have improved survival rates in non-small cell lung cancer (NSCLC), but a paradigm for prospective confirmation is still lacking. Patientdatasets were mainly downloaded from TCGA, CPTAC and GEO. We conducted downstream analysis by collecting metagenes and generated 42-gene subtype classifiers to elucidate biological pathways. Subsequently, scRNA, eRNA, methylation, mutation, and copy number variation were depicted from a phenotype perspective. Enhancing the clinical translatability of molecular subtypes, preclinical models including CMAP, CCLE, and GDSC were utilized for drug repositioning. Importantly, we verified the presence of previously described three phenotypes including bronchioid, neuroendocrine, and squamoid. Poor prognosis was seen in squamoid and neuroendocrine clusters for treatment-naive and immunotherapy populations. The neuroendocrine cluster was dominated by STK11 mutations and 14q13.3 amplifications, whose related methylated loci are predictive of immunotherapy. And the greatest therapeutic potential lies in the bronchioid cluster. We further estimated the relative cell abundance of the tumor microenvironment (TME), specific cell types could be reflected among three clusters. Meanwhile, the higher portion of immune cell infiltration belonged to bronchioid and squamoid, not the neuroendocrine cluster. In drug repositioning, MEK inhibitors resisted bronchioid but were squamoid-sensitive. To conceptually validate compounds/targets, we employed RNA-seq and CCK-8/western blot assays. Our results indicated that dinaciclib and alvocidib exhibited similar activity and sensitivity in the neuroendocrine cluster. Also, a lineage factor named KLF5 recognized by inferred transcriptional factors activity could be suppressed by verteporfin.