MEK1/2 dual-specificity protein kinases: Structure and regulation

Onychocolone A produced by the fungus Onychocola sp. targets cancer stem cells and stops pancreatic cancer progression by inhibiting MEK2-dependent cell signaling

Pancreatic cancer (PC) shows a high fatality rate that can only be faced with a combination of surgery and chemotherapy or palliative treatment in the case of advanced patients. Besides, PC tumors are enriched with subpopulations of cancer stem cells (CSCs) that are resistant to the existing chemotherapeutic agents, which raises an important need for the identification of new drugs. To fill this gap, we have tested the anti-tumoral activity of microbial extracts, which chemical diversity offers a broad spectrum of potential new bioactive compounds. Extracts derived from the fungus Onychocola sp. CF-107644 were assayed via high throughput screening followed by bioassay-guided fractionation and resulted in the identification and isolation of six benzophenone derivatives with antitumoral activity: onychocolones A-F (#1-6). The structures of the compounds were established by spectroscopic methods, including ESI-TOF MS, 1D and 2D NMR analyses and X-ray diffraction. Compounds #1-4 significantly inhibited the growth of the pancreas tumoral cell lines, with low-micromolar Median Effective Doses (ED50s). Compound #1 (onychocolone A) was prioritized for further profiling due to its pro-apoptotic effect, which was further validated on 3D spheroids and pancreatic CSCs. Protein expression assays showed that the effect was mechanistically linked to the inhibition of MEK onco-signaling pathway. The efficacy of onychocolone A was also demonstrated in vivo by the reduction of tumor growth in a pancreatic xenograft mouse model generated by CSCs. Altogether, the data support that onychocolone A is a promising new small molecule for hit-to-lead development of a new treatment for PC.

Molecular Dynamics Simulation on the Suppression Mechanism of Phosphorylation to Ser222 by Allosteric Inhibitors Targeting MEK1/2 Kinase

Allosteric inhibitors of mitogen-activated protein kinase 1 (MEK1) reveal distinct interactions with MEK1 activation loop residues. The structural analyses will determine whether, and how, distinct inhibitors suppress the phosphorylation of MEK1 and may guide future therapeutic development. In this study, we explored the suppression mechanism of the phosphorylation process in the presence of MEK allosteric inhibitors, such as selumetinib, trametinib, cobimetinib, and CH5126766, by employing molecular dynamics simulations accompanied by principal component analysis. The simulations of wildtype MEK1 show that Ser222 can come close to γ-phosphate but not Ser218. We have found the conformation where Ser222 is within 5 Å of distance, which makes Ser222 accessible for γ-phosphate. The conformation analysis from the simulations of MEK1 in the presence of allosteric inhibitors reveals that the inhibitor restricts the flexibility of Ser222 through strong interactions with the activation loop, Lys97, and water mediates interactions with amino acids in the vicinity. The results reveal that all the inhibitors act as screeners between the activation loop and Mg-ATP and restricting the flexibility of the activation loop through strong interaction causes the suppression of the phosphorylation process of MEK1. The results conclude that a strong interaction of allosteric inhibitors with the activation loop restricts the movement of Ser222 toward Mg-ATP, which could be the dominant factor for the suppression of phosphorylation in MEK1. This research will provide novel insights to design effective anticancer therapeutics for targeting MEK1 in the future.

Targeting the RAS upstream and downstream signaling pathway for cancer treatment

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

Properties of FDA-approved small molecule protein kinase inhibitors: A 2024 update

Owing to the dysregulation of protein kinase activity in many diseases including cancer, this enzyme family has become one of the most important drug targets in the 21st century. There are 80 FDA-approved therapeutic agents that target about two dozen different protein kinases and seven of these drugs were approved in 2023. Of the approved drugs, thirteen target protein-serine/threonine protein kinases, four are directed against dual specificity protein kinases (MEK1/2), twenty block nonreceptor protein-tyrosine kinases, and 43 inhibit receptor protein-tyrosine kinases. The data indicate that 69 of these drugs are prescribed for the treatment of neoplasms. Six drugs (abrocitinib, baricitinib, deucravacitinib, ritlecitinib, tofacitinib, upadacitinib) are used for the treatment of inflammatory diseases (atopic dermatitis, rheumatoid arthritis, psoriasis, alopecia areata, and ulcerative colitis). Of the 80 approved drugs, nearly two dozen are used in the treatment of multiple diseases. The following seven drugs received FDA approval in 2023: capivasertib (HER2-positive breast cancer), fruquintinib (metastatic colorectal cancer), momelotinib (myelofibrosis), pirtobrutinib (mantle cell lymphoma, chronic lymphocytic leukemia, small lymphocytic lymphoma), quizartinib (Flt3-mutant acute myelogenous leukemia), repotrectinib (ROS1-positive lung cancer), and ritlecitinib (alopecia areata). All of the FDA-approved drugs are orally effective with the exception of netarsudil, temsirolimus, and trilaciclib. This review summarizes the physicochemical properties of all 80 FDA-approved small molecule protein kinase inhibitors including the molecular weight, number of hydrogen bond donors/acceptors, polar surface area, potency, solubility, lipophilic efficiency, and ligand efficiency.

A review on the effect of COX-2-mediated mechanisms on development and progression of gastric cancer induced by nicotine

Smoking is a documented risk factor for cancer, e.g., gastric cancer. Nicotine, the principal tobacco alkaloid, would exert its role of contribution to gastric cancer development and progression through nicotinic acetylcholine receptors (nAChRs) and β-adrenergic receptors (β-ARs), which then promote cancer cell proliferation, migration and invasion. As a key isoenzyme in conversion of arachidonic acid to prostaglandins, cyclooxygenase-2 (COX-2) has been demonstrated to have a wide range of effects in carcinogenesis and tumor development. At present, many studies have reported the effect of nicotine on gastric cancer by binding to nAChR, as well as indirectly stimulating β-AR to mediate COX-2-related pathways. This review summarizes these studies, and also proposes more potential COX-2-mediated mechanisms. These events might contribute to the growth and progression of gastric cancer exposed to nicotine through tobacco smoke or cigarette substitutes. Also, this review article has therefore the potential not only to make a significant contribution to the treatment and prognosis of gastric cancer for smokers but also to the clinical application of COX-2 antagonists. In addition, this work also discusses the considerable challenges of this field with special reference to the future perspective of COX-2-mediated mechanisms in development and progression of gastric cancer induced by nicotine.

The Minimum Protein Staple? - Towards 'bio'-Baldwin's rules via inter-phosphosite linking in the MEK1 activation loop

In small molecule organic chemistry, the heuristic insight into ring-forming processes that was enabled by Baldwin's rules some 50 years ago proved a step-change in the role of mechanistically guided synthesis. It created a lens upon and marker of fundamental stereoelectronic and conformation-guided chemical processes. However, despite the widespread role of stereoelectronics and conformational control in Biology, no equivalent coherent exploitation of trapped, ring-forming processes yet exists in biomolecules. In the development of a minimal ring-closing process in intact proteins that might prove suitable in a coherent rule-set, we have tested endo-trig ring-closing conjugate thioether lanthionine (Lan) -CH2-S-CH2- formation as a limiting cyclization. Spontaneous Lan formation in proteins is rare if not non-existent and when found in natural product cyclic peptides it requires the mediation of corresponding biosynthetic enzymes as well as productive reactive conformations to guide it. Here, we show that within a conformationally flexible and functionally important protein loop - the MAPK kinase phosphorylation-targeted activation loop - Lan ring-closing is possible. Ring-closing proves to be critically dependent on the location of a trig electrophilic site in just one of two regioisomeric potential precursors to allow phosphosite-to-phosphosite 'stapling'. This first example of spontaneous protein thioether ring-closing/'stapling' and its accessibility from just one precursor (despite the potential for both to form an identical 'staple') now reveals the potential for Lan formation not only as an accessible form of minimal stapling in proteins but also as an exquisitely sensitive probe of associated protein geometries. We suggest that the use of this (as well as the development of other such, intramolecular protein traps that are dependent on inherent protein-controlled reactivity rather than forced crosslinking) may allow the broader trapping and mapping of relevant, even minor, protein states. In this way, protein ring formation may enable a form of extended 'bio-Baldwin's rules' that help to delineate relevant protein conformational space.

Role of Mitogen-Activated Protein (MAP) Kinase Pathways in Metabolic Diseases

Physiological processes that govern the normal functioning of mammalian cells are regulated by a myriad of signalling pathways. Mammalian mitogen-activated protein (MAP) kinases constitute one of the major signalling arms and have been broadly classified into four groups that include extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), p38, and ERK5. Each signalling cascade is governed by a wide array of external and cellular stimuli, which play a critical part in mammalian cells in the regulation of various key responses, such as mitogenic growth, differentiation, stress responses, as well as inflammation. This evolutionarily conserved MAP kinase signalling arm is also important for metabolic maintenance, which is tightly coordinated via complicated mechanisms that include the intricate interaction of scaffold proteins, recognition through cognate motifs, action of phosphatases, distinct subcellular localisation, and even post-translational modifications. Aberration in the signalling pathway itself or their regulation has been implicated in the disruption of metabolic homeostasis, which provides a pathophysiological foundation in the development of metabolic syndrome. Metabolic syndrome is an umbrella term that usually includes a group of closely associated metabolic diseases such as hyperglycaemia, hyperlipidaemia, and hypertension. These risk factors exacerbate the development of obesity, diabetes, atherosclerosis, cardiovascular diseases, and hepatic diseases, which have accounted for an increase in the worldwide morbidity and mortality rate. This review aims to summarise recent findings that have implicated MAP kinase signalling in the development of metabolic diseases, highlighting the potential therapeutic targets of this pathway to be investigated further for the attenuation of these diseases.

The cardiac glycoside ZINC253504760 induces parthanatos-type cell death and G2/M arrest via downregulation of MEK1/2 phosphorylation in leukemia cells

Overcoming multidrug resistance (MDR) represents a major obstacle in cancer chemotherapy. Cardiac glycosides (CGs) are efficient in the treatment of heart failure and recently emerged in a new role in the treatment of cancer. ZINC253504760, a synthetic cardenolide that is structurally similar to well-known GCs, digitoxin and digoxin, has not been investigated yet. This study aims to investigate the cytotoxicity of ZINC253504760 on MDR cell lines and its molecular mode of action for cancer treatment. Four drug-resistant cell lines (P-glycoprotein-, ABCB5-, and EGFR-overexpressing cells, and TP53-knockout cells) did not show cross-resistance to ZINC253504760 except BCRP-overexpressing cells. Transcriptomic profiling indicated that cell death and survival as well as cell cycle (G2/M damage) were the top cellular functions affected by ZINC253504760 in CCRF-CEM cells, while CDK1 was linked with the downregulation of MEK and ERK. With flow cytometry, ZINC253504760 induced G2/M phase arrest. Interestingly, ZINC253504760 induced a novel state-of-the-art mode of cell death (parthanatos) through PARP and PAR overexpression as shown by western blotting, apoptosis-inducing factor (AIF) translocation by immunofluorescence, DNA damage by comet assay, and mitochondrial membrane potential collapse by flow cytometry. These results were ROS-independent. Furthermore, ZINC253504760 is an ATP-competitive MEK inhibitor evidenced by its interaction with the MEK phosphorylation site as shown by molecular docking in silico and binding to recombinant MEK by microscale thermophoresis in vitro. To the best of our knowledge, this is the first time to describe a cardenolide that induces parthanatos in leukemia cells, which may help to improve efforts to overcome drug resistance in cancer. A cardiac glycoside compound ZINC253504760 displayed cytotoxicity against different multidrug-resistant cell lines. ZINC253504760 exhibited cytotoxicity in CCRF-CEM leukemia cells by predominantly inducing a new mode of cell death (parthanatos). ZINC253504760 downregulated MEK1/2 phosphorylation and further affected ERK activation, which induced G2/M phase arrest.

Clinical, Morphologic, and Molecular Features of Benign and Intermediate-grade Melanocytic Tumors With Activating Mutations in MAP2K1

Activating mutations in MAP2K1 can be seen in benign and intermediate-grade melanocytic neoplasms with spitzoid morphology. We analyzed the clinical, histopathologic, and genetic features for 16 cases of benign and intermediate-grade melanocytic tumors harboring activating MAP2K1 mutations. We compared them to Spitz neoplasms with characteristic Spitz fusions or HRAS mutation. We also compared the mutational pattern of benign and intermediate-grade MAP2K1 -mutated neoplasms and melanomas with activating MAP2K1 mutations. Among the 16 cases, the favored morphologic diagnosis was Spitz nevus (8/16), atypical Spitz tumors (6/16), and deep penetrating nevus (2/16). The 2 most common architectural patterns seen included a plaque-like silhouette with fibroplasia around the rete reminiscent of a dysplastic nevus (n=7) or a wedge-shaped or nodular pattern with the plexiform arrangement of the nests aggregating around the adnexa or neurovascular bundle (n=8). The cases with dysplastic architecture and spitzoid cytology resembled dysplastic Spitz nevi. Compared with true Spitz neoplasms, MAP2K1 -mutated neoplasms occurred in older age groups and had more frequent pagetosis and a lower average mitotic count. The most common type of mutation in the benign and intermediate-grade cases in the literature involves an in-frame deletion, while, in melanomas, missense mutations are predominant. Benign and intermediate-grade melanocytic neoplasms with activating mutations in MAP2K1 can have morphologic overlap with Spitz neoplasms. A significant proportion of melanomas also have activating MAP2K1 mutations. In-frame deletions are predominantly seen in the benign and intermediate-grade cases, and missense mutations are predominantly seen in melanomas.

Advances in the extracellular signal-regulated kinase signaling pathway in silkworms, Bombyx mori (Lepidoptera)

Signaling pathways regulate the transmission of signals during organism growth and development, promoting the smooth and accurate completion of numerous physiological and biochemical reactions. The extracellular signal-regulated kinase (ERK) signaling pathway is an essential pathway involved in regulating various physiological processes, such as cell proliferation, differentiation, adhesion, migration, and more. This pathway also contributes to several important physiological processes in silkworms, including protein synthesis, reproduction, and immune defense against pathogens. Organizing related studies on the ERK signaling pathway in silkworms can provide a better understanding of its mechanism in Lepidopterans and develop a theoretical foundation for improving cocoon production and new strategies for pest biological control.

Phase plane dynamics of ERK phosphorylation

The extracellular signal-regulated kinase (ERK) controls multiple critical processes in the cell and is deregulated in human cancers, congenital abnormalities, immune diseases, and neurodevelopmental syndromes. Catalytic activity of ERK requires dual phosphorylation by an upstream kinase, in a mechanism that can be described by two sequential Michaelis-Menten steps. The estimation of individual reaction rate constants from kinetic data in the full mechanism has proved challenging. Here, we present an analytically tractable approach to parameter estimation that is based on the phase plane representation of ERK activation and yields two combinations of six reaction rate constants in the detailed mechanism. These combinations correspond to the ratio of the specificities of two consecutive phosphorylations and the probability that monophosphorylated substrate does not dissociate from the enzyme before the second phosphorylation. The presented approach offers a language for comparing the effects of mutations that disrupt ERK activation and function in vivo. As an illustration, we use phase plane representation to analyze dual phosphorylation under heterozygous conditions, when two enzyme variants compete for the same substrate.

Soloxolone Methyl Reduces the Stimulatory Effect of Leptin on the Aggressive Phenotype of Murine Neuro2a Neuroblastoma Cells via the MAPK/ERK1/2 Pathway

Despite the proven tumorigenic effect of leptin on epithelial-derived cancers, its impact on the aggressiveness of neural crest-derived cancers, notably neuroblastoma, remains largely unexplored. In our study, for the first time, transcriptome analysis of neuroblastoma tissue demonstrated that the level of leptin is elevated in neuroblastoma patients along with the severity of the disease and is inversely correlated with patient survival. The treatment of murine Neuro2a neuroblastoma cells with leptin significantly stimulated their proliferation and motility and reduced cell adhesion, thus rendering the phenotype of neuroblastoma cells more aggressive. Given the proven efficacy of cyanoenone-bearing semisynthetic triterpenoids in inhibiting the growth of neuroblastoma and preventing obesity in vivo, the effect of soloxolone methyl (SM) on leptin-stimulated Neuro2a cells was further investigated. We found that SM effectively abolished leptin-induced proliferation of Neuro2a cells by inducing G1/S cell cycle arrest and restored their adhesiveness to extracellular matrix (ECM) proteins to near control levels through the upregulation of vimentin, zonula occludens protein 1 (ZO-1), cell adhesion molecule L1 (L1cam), and neural cell adhesion molecule 1 (Ncam1). Moreover, SM significantly suppressed the leptin-associated phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and ribosomal protein S6 kinase A1 (p90RSK), which are key kinases that ensure the survival and proliferation of cancer cells. Further molecular modeling studies demonstrated that the inhibitory effect of SM on the mitogen-activated protein kinase (MAPK)/ERK1/2 signaling pathway can be mediated by its direct interaction with ERK2 and its upstream regulators, son of sevenless homolog 1 (SOS) and mitogen-activated protein kinase kinase 1 (MEK1). Taken together, our findings in murine Neuro2a cells provide novel evidence of the stimulatory effect of leptin on the aggressiveness of neuroblastoma, which requires further detailed studies in human neuroblastoma cells and relevant animal models. The obtained results indicate that SM can be considered a promising drug candidate capable of reducing the impact of adipokines on tumor progression.

Stearyl palmitate a multi-target inhibitor against breast cancer: in-silico, in-vitro & in-vivo approach

Multi-target inhibitors are currently trending in the pharmaceutical research, as they possess increased efficacy and reduced toxicity. In this study multi-target inhibitors for breast cancer are explored from a curated list of natural products, i.e. 4,670 phytochemicals belonging to 360 medicinal plants. In-silico screening of phytochemicals using SeeSAR and AutoDock Vina resulted in identification of Stearyl Palmitate as a potential drug molecule that inhibits three drug targets, i.e. HER-2, MEK-1 and PARP-1 proteins. Molecular Dynamics Simulation for 100 ns each for these three protein-ligand complexes using Desmond, Maestro platform also confirmed the prediction of multi-target inhibition by Stearyl Palmitate. Further in-vitro MTT assay demonstrated that Stearyl Palmitate has a significant IC50 value of 40 µM against MCF-7 cells and >1000 µM against L929 cells. This confirmed that Stearyl Palmitate is having selective cytotoxicity towards breast cancer cells in comparison to non-cancerous cells. Fluorescence staining and flow cytometry analysis confirmed that, Stearyl Palmitate is inducing apoptosis in MCF-7 cells at IC50 concentration. Finally, in-vivo efficacy and toxicity studies were performed using zebrafishes (Danio rerio). It was observed that the fishes treated with IC50 concentration of Stearyl Palmitate demonstrated 2x folds reduction in tumour size, while double dose resulted in 4x folds reduction in tumour size. Stearyl Palmitate did not demonstrate any toxicity or side effects in the zebrafishes. It is concluded that, Stearyl Palmitate, a phytochemical reported to be present in Althea officinalis is a potential anti-breast cancer agent, with ability to inhibit multiple targets such as HER-2, MEK-1 and PARP-2 proteins.Communicated by Ramaswamy H. Sarma.

Small molecule protein kinase inhibitors approved by regulatory agencies outside of the United States

Owing to genetic alterations and overexpression, the dysregulation of protein kinases plays a significant role in the pathogenesis of many autoimmune and neoplastic disorders and protein kinase antagonists have become an important drug target. Although the efficacy of imatinib in the treatment of chronic myelogenous leukemia in the United States in 2001 was the main driver of protein kinase inhibitor drug discovery, this was preceded by the approval of fasudil (a ROCK antagonist) in Japan in 1995 for the treatment of cerebral vasospasm. There are 21 small molecule protein kinase inhibitors that are approved in China, Japan, Europe, and South Korea that are not approved in the United Sates and 75 FDA-approved inhibitors in the United States. Of the 21 agents, eleven target receptor protein-tyrosine kinases, eight inhibit nonreceptor protein-tyrosine kinases, and two block protein-serine/threonine kinases. All 21 drugs are orally bioavailable or topically effective. Of the non-FDA approved drugs, sixteen are prescribed for the treatment of neoplastic diseases, three are directed toward inflammatory disorders, one is used for glaucoma, and fasudil is used in the management of vasospasm. The leading targets of kinase inhibitors approved by both international regulatory agencies and by the FDA are members of the EGFR family, the VEGFR family, and the JAK family. One-third of the 21 internationally approved drugs are not compliant with Lipinski's rule of five for orally bioavailable drugs. The rule of five relies on four parameters including molecular weight, number of hydrogen bond donors and acceptors, and the Log of the partition coefficient.

RAS-targeted cancer therapy: Advances in drugging specific mutations

Rat sarcoma (RAS), as a frequently mutated oncogene, has been studied as an attractive target for treating RAS-driven cancers for over four decades. However, it is until the recent success of kirsten-RAS (KRAS)^G12C inhibitor that RAS gets rid of the title "undruggable". It is worth noting that the therapeutic effect of KRAS^G12C inhibitors on different RAS allelic mutations or even different cancers with KRAS^G12C varies significantly. Thus, deep understanding of the characteristics of each allelic RAS mutation will be a prerequisite for developing new RAS inhibitors. In this review, the structural and biochemical features of different RAS mutations are summarized and compared. Besides, the pathological characteristics and treatment responses of different cancers carrying RAS mutations are listed based on clinical reports. In addition, the development of RAS inhibitors, either direct or indirect, that target the downstream components in RAS pathway is summarized as well. Hopefully, this review will broaden our knowledge on RAS-targeting strategies and trigger more intensive studies on exploiting new RAS allele-specific inhibitors.

Deucravacitinib is an allosteric TYK2 protein kinase inhibitor FDA-approved for the treatment of psoriasis

Psoriasis is a heterogeneous, inflammatory, autoimmune skin disease that affects up to 2% of the world's population. There are many treatment modalities including topical medicines, ultraviolet light therapy, monoclonal antibodies, and several oral medications. Cytokines play a central role in the pathogenesis of this disorder including TNF-α, (tumor necrosis factor-α) IL-17A (interleukin-17A), IL-17F, IL-22, and IL-23. Cytokine signaling involves transduction mediated by the JAK-STAT pathway. There are four JAKS (JAK1/2/3 and TYK2) and six STATS (signal transducer and activators of transcription). Janus kinases contain an inactive JH2 domain that is aminoterminal to the active JH1 domain. Under basal conditions, the JH2 domain inhibits the activity of the JH1 domain. Deucravacitinib is an orally effective N-trideuteromethyl-pyridazine derivative that targets and stabilizes the TYK2 JH2 domain and thereby blocks TYK2 JH1 activity. Seven other JAK inhibitors, which target the JAK family JH1 domain, are prescribed for the treatment of neoplastic and other inflammatory diseases. The use of deuterium in the trimethylamide decreases the rate of demethylation and slows the production of a metabolite that is active against a variety of targets in addition to TYK2. A second unique aspect in the development of deucravacitinib is the targeting of a pseudokinase domain. Deucravacitinib is rather specific for TYK2 and its toxic effects are much less than those of the other FDA-approved JAK inhibitors. The successful development of deucravacitinib may stimulate the development of additional pseudokinase ligands for the JAK family and for other kinase families as well.

Chitosan targets PI3K/Akt/FoxO3a axis to up-regulate FAM172A and suppress MAPK/ERK pathway to exert anti-tumor effect in osteosarcoma

Osteosarcoma (OS) is a serve and the most frequent primary malignant tumor of bone. Chitosan was reported to have anti-tumor effect on human cancers including OS. However, the molecular mechanism by which chitosan suppresses tumor growth is not fully illustrated. In this study, human OS cell lines, including both Saos-2 and U2OS cells, were used to dissect the underlying mechanisms. RNA sequencing results show that a candidate biomarker family with sequence similarity 172 member A (FAM172A) was up-regulated in both of the two cell lines treated with chitosan. We observed that the mitogen-activated protein kinase (MAPK) signaling pathway could be inactivated by chitosan, and the MAPK inhibition caused by chitosan was reversed by FAM172A knockdown. Moreover, we uncovered a direct interaction between C-terminal domain of FAM172A (311-415) and mitogen-activated protein kinase kinase 1 (MEK1) (270-307) by immunoprecipitation assay. Finally, we also found that chitosan could bind with subunit p85 of PI3K to further inactivate the PI3K/Akt pathway. Taken together, our study demonstrates that chitosan binds with PI3K p85 subunit to suppress the activity of PI3K/Akt pathway to up-regulate the expression of FAM172A, and which exerts its function by suppressing phosphorylation of MEK1/2 and blocking the activity of MAPK/ERK signaling pathway. Taken together, our study deepens the understanding of the molecular mechanism of MAPK/ERK pathway inhibition induced by chitosan, and provides insights into the development of new targets to enhance the pharmacological effect of chitosan against OS.

Investigating a Library of Flavonoids as Potential Inhibitors of a Cancer Therapeutic Target MEK2 Using in Silico Methods

The second leading cause of death in the world is cancer. Mitogen-activated protein kinase (MAPK) and extracellular signal-regulated protein kinase (ERK) 1 and 2 (MEK1/2) stand out among the different anticancer therapeutic targets. Many MEK1/2 inhibitors are approved and widely used as anticancer drugs. The class of natural compounds known as flavonoids is well-known for their therapeutic potential. In this study, we focus on discovering novel inhibitors of MEK2 from flavonoids using virtual screening, molecular docking analyses, pharmacokinetic prediction, and molecular dynamics (MD) simulations. A library of drug-like flavonoids containing 1289 chemical compounds prepared in-house was screened against the MEK2 allosteric site using molecular docking. The ten highest-scoring compounds based on docking binding affinity (highest score: -11.3 kcal/mol) were selected for further analysis. Lipinski's rule of five was used to test their drug-likeness, followed by ADMET predictions to study their pharmacokinetic properties. The stability of the best-docked flavonoid complex with MEK2 was examined for a 150 ns MD simulation. The proposed flavonoids are suggested as potential inhibitors of MEK2 and drug candidates for cancer therapy.

Properties of FDA-approved small molecule protein kinase inhibitors: A 2023 update

Owing to the dysregulation of protein kinase activity in many diseases including cancer, this enzyme family has become one of the most important drug targets in the 21st century. There are 72 FDA-approved therapeutic agents that target about two dozen different protein kinases and three of these drugs were approved in 2022. Of the approved drugs, twelve target protein-serine/threonine protein kinases, four are directed against dual specificity protein kinases (MEK1/2), sixteen block nonreceptor protein-tyrosine kinases, and 40 target receptor protein-tyrosine kinases. The data indicate that 62 of these drugs are prescribed for the treatment of neoplasms (57 against solid tumors including breast, lung, and colon, ten against nonsolid tumors such as leukemia, and four against both solid and nonsolid tumors: acalabrutinib, ibrutinib, imatinib, and midostaurin). Four drugs (abrocitinib, baricitinib, tofacitinib, upadacitinib) are used for the treatment of inflammatory diseases (atopic dermatitis, psoriatic arthritis, rheumatoid arthritis, Crohn disease, and ulcerative colitis). Of the 72 approved drugs, eighteen are used in the treatment of multiple diseases. The following three drugs received FDA approval in 2022 for the treatment of these specified diseases: abrocitinib (atopic dermatitis), futibatinib (cholangiocarcinomas), pacritinib (myelofibrosis). All of the FDA-approved drugs are orally effective with the exception of netarsudil, temsirolimus, and trilaciclib. This review summarizes the physicochemical properties of all 72 FDA-approved small molecule protein kinase inhibitors including lipophilic efficiency and ligand efficiency.

Signaling pathways, microenvironment, and targeted treatments in Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is an inflammatory myeloid malignancy in the "L-group" histiocytosis. Mitogen-activated protein kinase (MAPK) pathway activating mutations are detectable in nearly all LCH lesions. However, the pathogenic roles of MAPK pathway activation in the development of histiocytosis are still elusive. This review will summarize research concerning the landscape and pathogenic roles of MAPK pathway mutations and related treatment opportunities in Langerhans cell histiocytosis. Video abstract.

Customized synthesis of phosphoprotein bearing phosphoserine or its nonhydrolyzable analog

Studies on the mechanism of protein phosphorylation and therapeutic interventions of its related molecular processes are limited by the difficulty in the production of purpose-built phosphoproteins harboring site-specific phosphorylated amino acids or their nonhydrolyzable analogs. Here we address this limitation by customizing the cell-free protein synthesis (CFPS) machinery via chassis strain selection and orthogonal translation system (OTS) reconfiguration screening. The suited chassis strains and reconfigured OTS combinations with high orthogonality were consequently picked out for individualized phosphoprotein synthesis. Specifically, we synthesized the sfGFP protein and MEK1 protein with site-specific phosphoserine (O-pSer) or its nonhydrolyzable analog, 2-amino-4-phosphonobutyric acid (C-pSer). This study successfully realized building cell-free systems for site-specific incorporation of phosphonate mimics into the target protein. Our work lays the foundation for developing a highly expansible CFPS platform and the streamlined production of user-defined phosphoproteins, which can facilitate research on the physiological mechanism and potential interference tools toward protein phosphorylation.

MEKK-3 Acts Cooperatively with NSY-1 in SKN-1-Dependent Manner against Oxidative Stress and Aging in Caenorhabditis elegans

Oxidative stress resulting from reactive oxygen species and other toxic metabolites is involved in human diseases, and it plays an important role in aging. In Caenorhabditis elegans, SKN-1 is required for protection against oxidative stress and aging. As p38 mitogen-activated protein kinase signaling is activated in response to oxidative stress, SKN-1 accumulates in intestinal nuclei and induces phase II detoxification genes. However, NSY-1, a well-known mitogen-activated protein kinase kinase kinase (MAPKKK) of C. elegans, acts as a partial regulator of the SKN-1-induced oxidative stress signaling pathway, suggesting that the regulator for optimal activation of SKN-1 remains unknown. Here, we report a MAPKKK, MEKK-3, as a new regulator required for full activation of SKN-1-mediated resistance against oxidative stress and aging. In RNA-interference-based screening, we found that the simultaneous knockdown of mekk-3 and nsy-1 significantly decreased the oxidative stress resistance and survival of SKN-1 transgenic worms. MEKK-3 was induced in response to oxidative stress. Mechanistic analysis revealed that double knockdown of mekk-3 and nsy-1 completely suppressed the nuclear localization of SKN-1. These results were reproduced in mutant worms in which SKN-1 is constitutively localized to intestinal nuclei. In addition, mekk-3 and nsy-1 were required for optimal induction of SKN-1 target genes such as gcs-1 and trx-1. These data indicate that MEKK-3 plays an essential role in the SKN-1-dependent signaling pathway involved in oxidative stress resistance and longevity by cooperating with NSY-1.

BRAF Inhibitors in Non-Small Cell Lung Cancer

RAF family proteins are serine–threonine kinases that play a central role in the MAPK pathway which is involved in embryogenesis, cell differentiation, cell proliferation and death. Deregulation of this pathway is found in up to 30% of all human cancers and BRAF mutations can be identified in 1.5–3.5% of NSCLC patients. Following the positive results obtained through the combination of BRAF and MEK inhibitors in BRAF-mutant melanoma, the same combination was prospectively assessed in BRAF-mutant NSCLC. In cohort B of the BRF113928 trial, 57 pretreated NSCLC patients were treated with dabrafenib plus trametinib: an ORR of 68.4%, a disease control rate of 80.7%, a median PFS of 10.2 months and a median OS of 18.2 months were observed. Similar results were reported in the first-line setting (cohort C), with an ORR of 63.9%, a DCR of 75% and a median PFS and OS of 10.2 and 17.3 months, respectively. The combination was well tolerated: the main adverse events were pyrexia (64%), nausea (56%), diarrhoea (56%), fatigue (36%), oedema (36%) and vomiting (33%). These positive results led to the approval of the combination of dabrafenib and trametinib for the treatment of BRAF V600E metastatic NSCLC patients regardless of previous therapy. Ongoing research should better define the role of new generation RAF inhibitors for patients with acquired resistance, the activity of chemo-immunotherapy or the combination of TKIs with chemotherapy or with immunotherapy in patients with BRAF-mutated cancers.

Wenshen-Jianpi prescription, a Chinese herbal medicine, improves visceral hypersensitivity in a rat model of IBS-D by regulating the MEK/ERK signal pathway

The goal of the study was to analyze whether WJP can alleviate visceral hypersensitivity in IBS-D model rats. In this study, 36 Sprague–Dawley (SD) rats aged 4 weeks old were randomly divided into two groups: the model group (n = 27) and the control group (n = 9). The rat model of IBS-D was established by modified compound methods for 4 weeks. After the modification, IBS-D rats were randomly divided into three groups, namely, the IBS-D model group (n = 9), the positive drug group (n = 9), and the WJP group (n = 9), with different interventions, respectively. The control group was fed and allowed to drink water routinely. The Bristol stool scale scores were used to assess the severity of diarrhea. Abdominal withdrawal reflex (AWR) scores were used to assess visceral sensitivity. Expression of TNF-α was measured, and histopathological examinations were performed to assess colon inflammation in IBS-D model rats. Key factors of the MEK/ERK signal pathway in the tissue of the colon and hippocampus were measured to analyze the mechanism of WJP. Compared with the control group, the Bristol stool scale scores in the model group were significantly increased (p < 0.0001). The scores of the WJP group were significantly decreased compared with the model group (p = 0.0001). Compared with the control group, AWR scores in the model group at each pressure level were significantly increased (p = 0.0003, p < 0.0001, p = 0.0007, and p = 0.0009). AWR scores of the WJP group were significantly decreased compared with the model group (p = 0.0003, p = 0.0007, p = 0.0007, and p = 0.0009). Compared with the control group, the model group had significantly higher expression of TNF-α in the colon tissue (p < 0.0001). However, the WJP group had significantly lower level of TNF-α compared with the model group (p < 0.0001). Meanwhile, compared with the control group, the relative expression of the proteins of p-MEK1/2, p-ERK1, and p-ERK2 in the colon tissue was significantly increased in the model group (p < 0.0001). Compared with the model group, the relative expression of the proteins in the colon tissue were significantly decreased in the WJP group (p < 0.0001, p = 0.0019, and p = 0.0013). Compared with the control group, the relative expression of the proteins of p-MEK1/2, p-ERK1, and p-ERK2 in the hippocampus tissue were significantly increased in the model group (p < 0.0001). Compared with the model group, the relative expression of the proteins in the hippocampus tissue were significantly decreased in the WJP group (p = 0.0126, p = 0.0291, and p = 0.0145). The results indicated that WJP can alleviate visceral hypersensitivity in IBS-D model rats, possibly mediated by downregulating the expression of TNF-α, p-MEK1/2, p-ERK1, and p-ERK2 in the colon tissue. At the same time, WJP also affects downregulating the expression of p-MEK1/2, p-ERK1, and p-ERK2 in the hippocampus tissue.

Tegaserod Maleate Suppresses the Growth of Gastric Cancer In Vivo and In Vitro by Targeting MEK1/2

Gastric cancer (GC) ranks fifth in global incidence and fourth in mortality. The current treatments for GC include surgery, chemotherapy and radiotherapy. Although treatment strategies for GC have been improved over the last decade, the overall five-year survival rate remains less than 30%. Therefore, there is an urgent need to find novel therapeutic or preventive strategies to increase GC patient survival rates. In the current study, we found that tegaserod maleate, an FDA-approved drug, inhibited the proliferation of gastric cancer cells, bound to MEK1/2 and suppressed MEK1/2 kinase activity. Moreover, tegaserod maleate inhibited the progress of gastric cancer by depending on MEK1/2. Notably, we found that tegaserod maleate suppressed tumor growth in the patient-derived gastric xenograft (PDX) model. We further compared the effect between tegaserod maleate and trametinib, which is a clinical MEK1/2 inhibitor, and confirmed that tegaserod maleate has the same effect as trametinib in inhibiting the growth of GC. Our findings suggest that tegaserod maleate inhibited GC proliferation by targeting MEK1/2.

Janus kinase (JAK) inhibitors in the treatment of neoplastic and inflammatory disorders

The Janus kinase (JAK) family of nonreceptor protein-tyrosine kinases consists of JAK1, JAK2, JAK3, and TYK2 (Tyrosine Kinase 2). Each of these proteins contains a JAK homology pseudokinase (JH2) domain that interacts with and regulates the activity of the adjacent protein kinase domain (JH1). The Janus kinase family is regulated by numerous cytokines including interferons, interleukins, and hormones such as erythropoietin and thrombopoietin. Ligand binding to cytokine receptors leads to the activation of associated Janus kinases, which then catalyze the phosphorylation of the receptors. The SH2 domain of signal transducers and activators of transcription (STAT) binds to the cytokine receptor phosphotyrosines thereby promoting STAT phosphorylation and activation by the Janus kinases. STAT dimers are then translocated into the nucleus where they participate in the regulation and expression of dozens of proteins. JAK1/3 signaling participates in the pathogenesis of inflammatory disorders while JAK1/2 signaling contributes to the development of myeloproliferative neoplasms as well as several malignancies including leukemias and lymphomas. An activating JAK2 V617F mutation occurs in 95% of people with polycythemia vera and about 50% of cases of myelofibrosis and essential thrombocythemia. Abrocitinib, ruxolitinib, and upadacitinib are JAK inhibitors that are FDA-approved for the treatment of atopic dermatitis. Baricitinib is used for the treatment of rheumatoid arthritis and covid 19. Tofacitinib and upadacitinib are JAK antagonists that are used for the treatment of rheumatoid arthritis and ulcerative colitis. Additionally, ruxolitinib is approved for the treatment of polycythemia vera while fedratinib, pacritinib, and ruxolitinib are approved for the treatment of myelofibrosis.

The overview of Mitogen-activated extracellular signal-regulated kinase (MEK)-based dual inhibitor in the treatment of cancers

Mitogen-activated extracellular signal-regulated kinase 1 and 2 (MEK1/2) are the critical components of the mitogen-activated protein kinase/extracellular signal-regulated kinase 1 and 2 (MAPK/ERK1/2) signaling pathway which is one of the well-characterized kinase cascades regulating cell proliferation, differentiation, growth, metabolism, survival and mobility both in normal and cancer cells. The aberrant activation of MAPK/ERK1/2 pathway is a hallmark of numerous human cancers, therefore targeting the components of this pathway to inhibit its dysregulation is a promising strategy for cancer treatment. Enormous efforts have been done in the development of MEK1/2 inhibitors and encouraging advancements have been made, including four inhibitors approved for clinical use. However, due to the multifactorial property of cancer and rapidly arising drug resistance, the clinical efficacy of these MEK1/2 inhibitors as monotherapy are far from ideal. Several alternative strategies have been developed to improve the limited clinical efficacy, including the dual inhibitor which is a single drug molecule able to simultaneously inhibit two targets. In this review, we first introduced the activation and function of the MAPK/ERK1/2 components and discussed the advantages of MEK1/2-based dual inhibitors compared with the single inhibitors and combination therapy in the treatment of cancers. Then, we overviewed the MEK1/2-based dual inhibitors for the treatment of cancers and highlighted the theoretical basis of concurrent inhibition of MEK1/2 and other targets for development of these dual inhibitors. Besides, the status and results of these dual inhibitors in both preclinical and clinical studies were also the focus of this review.

Disentangling ERBB Signaling in Breast Cancer Subtypes-A Model-Based Analysis

Simple Summary

Breast cancer subtypes are characterized by the expression and activity of estrogen-, progesterone- and HER2-receptors and differ by the treatment as well as patient prognosis. Tumors of the HER2-subtype overexpress this receptor and are successfully targeted with anti-HER2 therapies. We wanted to know if the HER2-receptor and the downstream signaling network act similarly also in the other subtypes and if this network could potentially be a therapeutic target beyond the HER2-positive subtype. To this end, we quantitatively assessed the wiring of signaling events in the individual subtypes to unravel the characteristics of HER-signaling. Our data along with a model-based analysis suggest that major parts of the intracellular signal transduction network are unchanged between the different breast cancer subtypes and that the clinical differences mostly come from the different levels at which these receptors are present in tumor cells as well as from the particular mutations that are present in individual tumors.

Abstract

Targeted therapies have shown striking success in the treatment of cancer over the last years. However, their specific effects on an individual tumor appear to be varying and difficult to predict. Using an integrative modeling approach that combines mechanistic and regression modeling, we gained insights into the response mechanisms of breast cancer cells due to different ligand–drug combinations. The multi-pathway model, capturing ERBB receptor signaling as well as downstream MAPK and PI3K pathways was calibrated on time-resolved data of the luminal breast cancer cell lines MCF7 and T47D across an array of four ligands and five drugs. The same model was then successfully applied to triple negative and HER2-positive breast cancer cell lines, requiring adjustments mostly for the respective receptor compositions within these cell lines. The additional relevance of cell-line-specific mutations in the MAPK and PI3K pathway components was identified via L₁ regularization, where the impact of these mutations on pathway activation was uncovered. Finally, we predicted and experimentally validated the proliferation response of cells to drug co-treatments. We developed a unified mathematical model that can describe the ERBB receptor and downstream signaling in response to therapeutic drugs targeting this clinically relevant signaling network in cell line that represent three major subtypes of breast cancer. Our data and model suggest that alterations in this network could render anti-HER therapies relevant beyond the HER2-positive subtype.

The mechanism of activation of MEK1 by B-Raf and KSR1

MEK1 interactions with B-Raf and KSR1 are key steps in Ras/Raf/MEK/ERK signaling. Despite this, vital mechanistic details of how these execute signal transduction are still enigmatic. Among these is why, despite B-Raf and KSR1 kinase domains similarity, the B-Raf/MEK1 and KSR1/MEK1 complexes have distinct contributions to MEK1 activation, and broadly, what is KSR1's role. Our molecular dynamics simulations clarify these still unresolved ambiguities. Our results reveal that the proline-rich (P-rich) loop of MEK1 plays a decisive role in MEK1 activation loop (A-loop) phosphorylation. In the inactive B-Raf/MEK1 heterodimer, the collapsed A-loop of B-Raf interacts with the P-rich loop and A-loop of MEK1, minimizing MEK1 A-loop fluctuation and preventing it from phosphorylation. In the active B-Raf/MEK1 heterodimer, the P-rich loop moves in concert with the A-loop of B-Raf as it extends. This reduces the number of residues interacting with MEK1 A-loop, allowing increased A-loop fluctuation, and bringing Ser222 closer to ATP for phosphorylation. B-Raf αG-helix Arg662 promotes MEK1 activation by orienting Ser218 towards ATP. In KSR1/MEK1, the KSR1 αG-helix has Ala826 in place of B-Raf Arg662. This difference results in much fewer interactions between KSR1 αG-helix and MEK1 A-loop, thus a more flexible A-loop. We postulate that if KSR1 were to adopt an active configuration with an extended A-loop as seen in other protein kinases, then the MEK1 P-rich loop would extend in a similar manner, as seen in the active B-Raf/MEK1 heterodimer. This would result in highly flexible MEK1 A-loop, and KSR1 functioning as an active, B-Raf-like, kinase.

MAP2K2 Delays Recovery in Murine Models of Acute Lung Injury and Associates with Acute Respiratory Distress Syndrome Outcome

Acute respiratory distress syndrome (ARDS) remains a significant problem in need of new pharmaceutical approaches to improve its resolution. Studies comparing gene expression signatures in rodents and humans with lung injury reveal conserved pathways, including MAPK (mitogen-activated protein kinase)/ERK (extracellular signal-related protein kinase) activation. In preclinical acute lung injury (ALI) models, inhibition of MAP2K1 (MAPK kinase 1)/MAP2K2 (MAPK kinase 2) improves measures of ALI. Myeloid cell deletion of MAP2K1 results in sustained MAP2K2 activation and nonresolving ALI, suggesting that MAP2K2 deactivation may be a key driver of ALI resolution. We used human genomic data from the iSPAAR (Identification of SNPs Predisposing to Altered Acute Lung Injury Risk) Consortium to assess genetic variants in MAP2K1 and MAP2K2 for association with mortality from ARDS. To determine the role of MAP2K2 in ALI recovery, we studied mice deficient in Map2k2 (Mek2-/-) and wild-type control mice in ALI models. We identified a MAP2K2 variant that was associated with death in ARDS and MAP2K2 expression. In Pseudomonas aeruginosa ALI, Mek2-/- mice had similar early alveolar neutrophilic recruitment but faster resolution of alveolar neutrophilia and vascular leak. Gene expression analysis revealed a role for MAP2K2 in promoting and sustaining select proinflammatory pathway activation in ALI. Bone marrow chimera studies indicate that leukocyte MAP2K2 is the key regulator of ALI duration. These studies implicate a role for MAP2K2 in ALI duration via transcriptional regulation of inflammatory programming with potential relevance to ARDS. Targeting leukocyte MAP2K2 may be an effective strategy to promote ALI resolution.

Membrane repair triggered by cholesterol-dependent cytolysins is activated by mixed lineage kinases and MEK

Repair of plasma membranes damaged by bacterial pore-forming toxins, such as streptolysin O or perfringolysin O, during septic cardiomyopathy or necrotizing soft tissue infections is mediated by several protein families. However, the activation of these proteins downstream of ion influx is poorly understood. Here, we demonstrate that following membrane perforation by bacterial cholesterol-dependent cytolysins, calcium influx activates mixed lineage kinase 3 independently of protein kinase C or ceramide generation. Mixed lineage kinase 3 uncouples mitogen-activated kinase kinase (MEK) and extracellular-regulated kinase (ERK) signaling. MEK signals via an ERK-independent pathway to promote rapid annexin A2 membrane recruitment and enhance microvesicle shedding. This pathway accounted for 70% of all calcium ion-dependent repair responses to streptolysin O and perfringolysin O, but only 50% of repair to intermedilysin. We conclude that mixed lineage kinase signaling via MEK coordinates microvesicle shedding, which is critical for cellular survival against cholesterol-dependent cytolysins.

Exploring the Natural Compounds in Flavonoids for Their Potential Inhibition of Cancer Therapeutic Target MEK1 Using Computational Methods

The Mitogen-Activated Protein Kinase (MAPK) signaling pathway plays an important role in cancer cell proliferation and survival. MAPKs' protein kinases MEK1/2 serve as important targets in drug designing against cancer. The natural compounds' flavonoids are known for their anticancer activity. This study aims to explore flavonoids for their inhibition ability, targeting MEK1 using virtual screening, molecular docking, ADMET prediction, and molecular dynamics (MD) simulations. Flavonoids (n = 1289) were virtually screened using molecular docking and have revealed possible inhibitors of MEK1. The top five scoring flavonoids based on binding affinity (highest score for MEK1 is -10.8 kcal/mol) have been selected for further protein-ligand interaction analysis. Lipinski's rule (drug-likeness) and absorption, distribution, metabolism, excretion, and toxicity predictions were followed to find a good balance of potency. The selected flavonoids of MEK1 have been refined with 30 (ns) molecular dynamics (MD) simulation. The five selected flavonoids are strongly suggested to be promising potent inhibitors for drug development as anticancer therapeutics of the therapeutic target MEK1.

The RASopathies: from pathogenetics to therapeutics

The RASopathies are a group of disorders caused by a germline mutation in one of the genes encoding a component of the RAS/MAPK pathway. These disorders, including neurofibromatosis type 1, Noonan syndrome, cardiofaciocutaneous syndrome, Costello syndrome and Legius syndrome, among others, have overlapping clinical features due to RAS/MAPK dysfunction. Although several of the RASopathies are very rare, collectively, these disorders are relatively common. In this Review, we discuss the pathogenesis of the RASopathy-associated genetic variants and the knowledge gained about RAS/MAPK signaling that resulted from studying RASopathies. We also describe the cell and animal models of the RASopathies and explore emerging RASopathy genes. Preclinical and clinical experiences with targeted agents as therapeutics for RASopathies are also discussed. Finally, we review how the recently developed drugs targeting RAS/MAPK-driven malignancies, such as inhibitors of RAS activation, direct RAS inhibitors and RAS/MAPK pathway inhibitors, might be leveraged for patients with RASopathies.

Precision medicine for metastatic colorectal cancer in clinical practice

Globally, metastatic colorectal cancer is one of the leading causes for cancer-related death. Treatment limited to conventional chemotherapeutics extended life for only a few months. However, advances in surgical approaches and medical treatment regimens have greatly increased survival, even leading to long-term remission in selected patients. Advances in multiomics analysis of tumors have built a foundation for molecular-targeted therapies. Furthermore, immunotherapies are on the edge of revolutionizing oncological practice. This review summarizes recent advances in the growing toolbox of personalized treatment for patients with metastatic colorectal cancer. We provide an overview of current multimodal therapy and explain novel immunotherapy and targeted therapy approaches in detail. We emphasize clinically relevant therapies, such as inhibitors of MAPK signaling, and give recommendations for clinical practice. Finally, we describe the potential predictive impact of molecular subtypes and provide an outlook on novel concepts, such as functional precision medicine.

The role of T-LAK cell-originated protein kinase in targeted cancer therapy

Targeted therapy has gradually become the first-line clinical tumor therapy due to its high specificity and low rate of side effects. TOPK (T-LAK cell-originated protein kinase), a MAP kinase, is highly expressed in various tumor tissues, while it is rarely expressed in normal tissues, with the exceptions of testicular germ cells and some fetal tissues. It can promote cancer cell proliferation and migration and is also related to drug resistance. Therefore, TOPK is considered a good therapeutic target. Moreover, a number of studies have shown that targeting TOPK can inhibit the proliferation of cancer cells and promote their apoptosis. Here, we discussed the biological functions of TOPK in cancer and summarized its tumor-related signaling network and known TOPK inhibitors. Finally, the role of TOPK in targeted cancer therapy was concluded, and future research directions for TOPK were assessed.

Fine-tuning of MEK signaling is pivotal for limiting B and T cell activation

MEK1 and MEK2, the only known activators of ERK, are attractive therapeutic candidates for both cancer and autoimmune diseases. However, how MEK signaling finely regulates immune cell activation is only partially understood. To address this question, we specifically delete Mek1 in hematopoietic cells in the Mek2 null background. Characterization of an allelic series of Mek mutants reveals the presence of distinct degrees of spontaneous B cell activation, which are inversely proportional to the levels of MEK proteins and ERK activation. While Mek1 and Mek2 null mutants have a normal lifespan, 1Mek1 and 1Mek2 mutants retaining only one functional Mek1 or Mek2 allele in hematopoietic cell lineages die from glomerulonephritis and lymphoproliferative disorders, respectively. This establishes that the fine-tuning of the ERK/MAPK pathway is critical to regulate B and T cell activation and function and that each MEK isoform plays distinct roles during lymphocyte activation and disease development.

Injury-induced Erk1/2 signaling tissue-specifically interacts with Ca2+ activity and is necessary for regeneration of spinal cord and skeletal muscle

The transition of stem cells from quiescence to proliferation enables tissues to self-repair. The signaling mechanisms driving these stem-cell-status decisions are still unclear. Ca²⁺ and the extracellular signal-regulated kinase (Erk1/2) are two signaling pathways that have the potential to coordinate multiple signals to promote a specific cellular response. They both play important roles during nervous system development but their roles during spinal cord and muscle regeneration are not fully deciphered. Here we show in Xenopus laevis larvae that both Ca²⁺ and Erk1/2 signaling pathways are activated after tail amputation. In response to injury, we find that Erk1/2 signaling is activated in neural and muscle stem cells and is necessary for spinal cord and skeletal muscle regeneration. Finally, we show in vivo that Erk1/2 activity is necessary for an injury-induced increase in intracellular store-dependent Ca²⁺ dynamics in skeletal muscle-associated tissues but that in spinal cord, injury increases Ca²⁺ influx-dependent Ca²⁺ activity independent of Erk1/2 signaling. This study suggests that precise temporal and tissue-specific activation of Ca²⁺ and Erk1/2 pathways is essential for regulating spinal cord and muscle regeneration.

In Silico Screening of Available Drugs Targeting Non-Small Cell Lung Cancer Targets: A Drug Repurposing Approach

The RAS-RAF-MEK-ERK pathway plays a key role in malevolent cell progression in many tumors. The high structural complexity in the upstream kinases limits the treatment progress. Thus, MEK inhibition is a promising strategy since it is easy to inhibit and is a gatekeeper for the many malignant effects of its downstream effector. Even though MEK inhibitors are under investigation in many cancers, drug resistance continues to be the principal limiting factor to achieving cures in patients with cancer. Hence, we accomplished a high-throughput virtual screening to overcome this bottleneck by the discovery of dual-targeting therapy in cancer treatment. Here, a total of 11,808 DrugBank molecules were assessed through high-throughput virtual screening for their activity against MEK. Further, the Glide docking, MLSF and prime-MM/GBSA methods were implemented to extract the potential lead compounds from the database. Two compounds, DB012661 and DB07642, were outperformed in all the screening analyses. Further, the study results reveal that the lead compounds also have a significant binding capability with the co-target PIM1. Finally, the SIE-based free energy calculation reveals that the binding of compounds was majorly affected by the van der Waals interactions with MEK receptor. Overall, the in silico binding efficacy of these lead compounds against both MEK and PIM1 could be of significant therapeutic interest to overcome drug resistance in the near future.

Properties of FDA-approved small molecule protein kinase inhibitors: A 2022 update

Owing to the dysregulation of protein kinase activity in many diseases including cancer, this enzyme family has become one of the most important drug targets in the 21st century. There are 68 FDA-approved therapeutic agents that target about two dozen different protein kinases and six of these drugs were approved in 2021. Of the approved drugs, twelve target protein-serine/threonine protein kinases, four are directed against dual specificity protein kinases (MEK1/2), thirteen block nonreceptor protein-tyrosine kinases, and 39 target receptor protein-tyrosine kinases. The data indicate that 58 of these drugs are prescribed for the treatment of neoplasms (49 against solid tumors including breast, lung, and colon, five against nonsolid tumors such as leukemias, and four against both solid and nonsolid tumors: acalabrutinib, ibrutinib, imatinib, and midostaurin). Three drugs (baricitinib, tofacitinib, upadacitinib) are used for the treatment of inflammatory diseases including rheumatoid arthritis. Of the 68 approved drugs, eighteen are used in the treatment of multiple diseases. The following six drugs received FDA approval in 2021 for the treatment of these specified diseases: belumosudil (graft vs. host disease), infigratinib (cholangiocarcinomas), mobocertinib and tepotinib (specific forms of non-small cell lung cancer), tivozanib (renal cell carcinoma), and trilaciclib (to decrease chemotherapy-induced myelosuppression). All of the FDA-approved drugs are orally effective with the exception of netarsudil, temsirolimus, and the newly approved trilaciclib. This review summarizes the physicochemical properties of all 68 FDA-approved small molecule protein kinase inhibitors including lipophilic efficiency and ligand efficiency.

Specific genomic alterations and prognostic analysis of perihilar cholangiocarcinoma and distal cholangiocarcinoma

BACKGROUND

Cholangiocarcinoma (CCA), which consists of intrahepatic CCA (iCCA), perihilar CCA (pCCA), and distal CCA (dCCA), is an aggressive malignancy worldwide. PCCA and dCCA are often classified as extrahepatic CCA (exCCA). However, the differences in mutational characteristics between pCCA and dCCA remain unclear.

METHODS

Deep sequencing targeting of 450 cancer genes was performed for genomic alteration detection. The tumor mutational burden (TMB) was measured by an algorithm developed in-house. Correlation analysis was conducted using Fisher's exact test.

RESULTS

FGFR2 and ERBB2 mutations mainly occurred in iCCA and exCCA, respectively. In exCCA, the frequencies of PIK3CA, FAT4, KDM6A, MDM2, and TCF7L2 mutations were significantly higher in pCCA compared to dCCA, while the frequencies of TP53 and KRAS mutations were markedly lower in pCCA than those in dCCA. The prognosis-related mutations were different among the CCA subtypes. NF1 mutation was associated with short disease-free survival (DFS) and overall survival (OS), and ERBB2 mutation was associated with short DFS in dCCA patients. Meanwhile, MAP2K4 mutation was associated with long DFS and OS, and TERT mutation was associated with short DFS in pCCA. A series of mutations in genes, including ARID1A, ARID2, SMAD4, TERT, TP53, and KRAS, were found to be associated with the TMB.

CONCLUSIONS

In this study, we investigated the comprehensive genomic characterizations of CCA patients, identified the significant alterations in each subtype, and identified potential biomarkers for prognosis prediction. These results provide molecular evidence for the heterogeneity of CCA subtypes and evidence for further precision targeted therapy of CCA patients.

Structure of mitogen-activated protein kinase kinase 1 in the DFG-out conformation

Eukaryotic protein kinases contain an Asp-Phe-Gly (DFG) motif, the conformation of which is involved in controlling the catalytic activity, at the N-terminus of the activation segment. The motif can be switched between active-state (DFG-in) and inactive-state (DFG-out) conformations: however, the mechanism of conformational change is poorly understood, partly because there are few reports of the DFG-out conformation. Here, a novel crystal structure of nonphosphorylated human mitogen-activated protein kinase kinase 1 (MEK1; amino acids 38-381) complexed with ATP-γS is reported in which MEK1 adopts the DFG-out conformation. The crystal structure revealed that the structural elements (the αC helix and HRD motif) surrounding the active site are involved in the formation/stabilization of the DFG-out conformation. The ATP-γS molecule was bound to the canonical ATP-binding site in a different binding mode that has never been found in previously determined crystal structures of MEK1. This novel ATP-γS binding mode provides a starting point for the design of high-affinity inhibitors of nonphosphorylated inactive MEK1 that adopts the DFG-out conformation.

Integrative pan-cancer analysis of MEK1 aberrations and the potential clinical implications

Alterations of mitogen-activated protein kinase kinase 1 (MEK1) are commonly associated with tumorigenesis, and MEK1 is thought to be a suitable targeted therapy for various cancers. However, abnormal MEK1 alterations and their relevant clinical implications are unknown. Our research comprehensively analyzed the MEK1 alteration spectrum and provided novel insight for targeted therapies. There were 7694 samples covering 32 types of cancer from The Cancer Genome Atlas (TCGA) database. They were used to conduct an integrative analysis of MEK1 expression, alterations, functional impacts and clinical significance. There was a dramatic difference in the alteration frequency and distribution and clinical implications in 32 types of cancer from the TCGA. Skin cutaneous melanoma (SKCM) has the most alterations and has therapeutic targets located in the protein kinase domain, and the growing expression of SKCM is positively related to patient prognosis. MEK1 expression in lung adenocarcinoma (LUAD), kidney renal papillary cell carcinoma (KIRP), esophageal carcinoma (ESCA) and liver hepatocellular carcinoma (LIHC) is decreased, which is associated with better prognosis, while MEK1 expression in thymoma (THYM), stomach adenocarcinoma (STAD), kidney renal clear cell carcinoma (KIRC), testicular germ cell tumors (TGCTs) and head and neck squamous cell carcinoma (HNSC) is increased, which is associated with better prognosis. Mesothelioma (MESO) has the second highest alterations but has no therapy targets. This study provided a great and detailed interpretation of MEK1 expression, alterations and clinical implications in 32 types of cancer and reminded us to fill the gap in MEK1 research from a new perspective.

Blockade of mutant RAS oncogenic signaling with a special emphasis on KRAS

RAS proteins (HRAS, KRAS, NRAS) participate in many physiological signal transduction processes related to cell growth, division, and survival. The RAS proteins are small (188/189 amino acid residues) and they function as GTPases. These proteins toggle between inactive and functional forms; the conversion of inactive RAS-GDP to active RAS-GTP as mediated by guanine nucleotide exchange factors (GEFs) turns the switch on and the intrinsic RAS-GTPase activity stimulated by the GTPase activating proteins (GAPs) turns the switch off. RAS is upstream to the RAS-RAF-MEK-ERK and the PI3-kinase-AKT signaling modules. Importantly, the overall incidence of RAS mutations in all cancers is about 19% and RAS mutants have been a pharmacological target for more than three decades. About 84% of all RAS mutations involve KRAS. Except for the GTP/GDP binding site, the RAS proteins lack other deep surface pockets thereby hindering efforts to identify high-affinity antagonists; thus, they have been considered to be undruggable. KRAS mutations frequently occur in lung, colorectal, and pancreatic cancers, the three most deadly cancers in the United States. Studies within the last decade demonstrated that the covalent modification of KRAS C12, which accounts for about 10% of all RAS mutations, led to the discovery of an adjacent pocket (called the switch II pocket) that accommodated a portion of the drug. This led to the development of sotorasib as a second-line treatment of KRAS^G12C-mutant non-small cell lung cancer. Considerable effort also has been expended to develop MAP kinase and PI3-kinase pathway inhibitors as indirect RAS antagonists.

The newly identified MEK1 tyrosine phosphorylation target MACC1 is druggable by approved MEK1 inhibitors to restrict colorectal cancer metastasis

Cancer metastasis causes >90% of cancer deaths and remains a major treatment challenge. Here we deciphered the impact of tyrosine phosphorylation of MACC1, a causative driver for cancer metastasis, for cancer cell signaling and novel interventions to restrict cancer metastasis. We identified MACC1 as new MEK1 substrate. MEK1 directly phosphorylates MACC1, leading to accelerated and increased ERK1 activation. Mutating in silico predicted hierarchical MACC1 tyrosine phosphorylation sites abrogates MACC1-induced migration, invasion, and MET expression, a transcriptional MACC1 target. Targeting MEK1 by RNAi or clinically applicable MEK1 inhibitors AZD6244 and GSK1120212 reduces MACC1 tyrosine phosphorylation and restricts MACC1-induced metastasis formation in mice. Although MEK1 levels, contrary to MACC1, are not of prognostic relevance for CRC patients, MEK1 expression was found indispensable for MACC1-induced metastasis. This study identifies MACC1 as new MEK1 substrate for tyrosine phosphorylation decisively impacting cell motility, tumor growth, and metastasis. Thus, MAP kinase signaling is not linear leading to ERK activation, but branches at the level of MEK1. This fundamental finding opens new therapeutic options for targeting the MEK1/MACC1 axis as novel vulnerability in patients at high risk for metastasis. This might be extended from CRC to further solid tumor entities.

Mek1 and Mek2 Functional Redundancy in Erythropoiesis

Several studies have established the crucial role of the extracellular signal–regulated kinase (ERK)/mitogen-activated protein kinase pathway in hematopoietic cell proliferation and differentiation. MEK1 and MEK2 phosphorylate and activate ERK1 and ERK2. However, whether MEK1 and MEK2 differentially regulate these processes is unknown. To define the function of Mek genes in the activation of the ERK pathway during hematopoiesis, we generated a mutant mouse line carrying a hematopoietic-specific deletion of the Mek1 gene function in a Mek2 null background. Inactivation of both Mek1 and Mek2 genes resulted in death shortly after birth with a severe anemia revealing the essential role of the ERK pathway in erythropoiesis. Mek1 and Mek2 functional ablation also affected lymphopoiesis and myelopoiesis. In contrast, mice that retained one functional Mek1 (1Mek1) or Mek2 (1Mek2) allele in hematopoietic cells were viable and fertile. 1Mek1 and 1Mek2 mutants showed mild signs of anemia and splenomegaly, but the half-life of their red blood cells and the response to erythropoietic stress were not altered, suggesting a certain level of Mek redundancy for sustaining functional erythropoiesis. However, subtle differences in multipotent progenitor distribution in the bone marrow were observed in 1Mek1 mice, suggesting that the two Mek genes might differentially regulate early hematopoiesis.

Conformational Dynamics Analysis of MEK1 Using Hydrogen/Deuterium Exchange Mass Spectrometry

BACKGROUND

Activation of mitogen-activated protein kinases (MAPKs) is regulated by a phosphorylation cascade comprising three kinases, MAPK kinase kinase (MAP3K), MAPK kinase (MAP2K), and MAPK. MAP2K1 and MAPK2K2, also known as MEK1 and MEK2, activate ERK1 and ERK2. The structure of the MAPK signaling cascade has been studied, but high-resolution structural studies of MAP2Ks have often focused on kinase domains or docking sites, but not on full-length proteins.

OBJECTIVE

To understand the conformational dynamics of MEK1.

METHODS

Full-length MEK1 was purified from Escherichia coli (BL21), and its conformational dynamics were analyzed using hydrogen/deuterium exchange mass spectrometry (HDX-MS). The effects of ATP binding were examined by co-incubating MEK1 and adenylyl-imidodiphosphate (AMP- PNP), a non-hydrolysable ATP analog.

RESULTS

MEK1 exhibited mixed EX1/EX2 HDX kinetics within the N-terminal tail through β1, αI, and the C-terminal helix. AMP-PNP binding was found to reduce conformational dynamics within the glycine-rich loop and regions near the DFG motif, along with the activation lip.

CONCLUSION

We report for the first time that MEK1 has regions that slowly change its folded and unfolded states (mixed EX1/EX2 kinetics) and also report the conformational effects of ATP-binding to MEK1.