ERK5 modulates IL-6 secretion and contributes to tumor-induced immune suppression

Interleukin-6 (IL-6)-associated tumor microenvironment remodelling and cancer immunotherapy

Interleukin-6 (IL-6) is a pro-inflammatory cytokine playing a pivotal role during inflammation and immune responses. In the recent years, the function of IL-6 in the tumor microenvironment (TME) for affecting tumorigenesis and immunotherapy response has been investigated. The genetic mutations are mainly responsible for the development of cancer, while interactions in TME are also important, involving both cancers and non-cancerous cells. IL-6 plays a significant role in these interactions, enhancing the proliferation, survival and metastasis of tumor cells through inflammatory pathways, highlighting its carcinogenic function. Multiple immune cells including macrophages, T cells, myeloid-derived suppressor cells, dendritic cells and natural killer cells can be affected by IL-6 to develop immunosuppressive TME. IL-6 can also participate in the immune evasion through increasing levels of PD-L1, compromising the efficacy of therapeutics. Notably, IL-6 exerts a double-edge sword function and it can dually increase or decrease cancer immunotherapy, providing a challenge for targeting this cytokine in cancer therapy. Highlighting the complicated function of IL-6 in TME can lead to the development of effective therapeutics for cancer immunity.

RSK1 and RSK2 as therapeutic targets: an up-to-date snapshot of emerging data

INTRODUCTION

The four members of the p90 ribosomal S6 kinase (RSK) family are serine/threonine protein kinases, which are phosphorylated and activated by ERK1/2. RSK1/2/3 are further phosphorylated by PDK1. Receiving inputs from two major signaling pathways places RSK as a key signaling node in numerous pathologies. A plethora of RSK1/2 substrates have been identified, and in the majority of cases the causative roles these RSK substrates play in the pathology are unknown.

AREAS COVERED

The majority of studies have focused on RSK1/2 and their functions in a diverse group of cancers. However, RSK1/2 are known to have important functions in cardiovascular disease and neurobiological disorders. Based on the literature, we identified substrates that are common in these pathologies with the goal of identifying fundamental physiological responses to RSK1/2.

EXPERT OPINION

The core group of targets in pathologies driven by RSK1/2 are associated with the immune response. However, there is a paucity of the literature addressing RSK function in inflammation, which is critical to know as the pan RSK inhibitor, PMD-026, is entering phase II clinical trials for metastatic breast cancer. A RSK inhibitor has the potential to be used in numerous diverse diseases and disorders.

In vitro T cell responses to PD-1 blockade are reduced by IFN-α but do not predict therapy response in melanoma patients

PD-1 blockade therapy has revolutionized melanoma treatment, but still not all patients benefit and pre-treatment identification of those patients is difficult. Increased expression of inflammatory markers such as interleukin (IL)-6 in blood of patients correlates with poor treatment response. We set out to study the effect of inflammatory cytokines on PD-1 blockade in vitro. For this, we studied the effect of IL-6 and type I interferon (IFN) in vitro on human T cells in a mixed leukocyte reaction (MLR) in the absence or presence of PD-1 blockade. While IL-6 reduced IFN-γ secretion by T cells in both the presence and absence of PD-1 blockade, IFN-α specifically reduced the IFN-γ secretion only in the presence of PD-1 blockade. IFN-α reduced T cell proliferation independent of PD-1 blockade and reduced the percentage of cells producing IFN-γ only in the presence of PD-1 blockade. Next we determined the type I IFN score in a cohort of 22 melanoma patients treated with nivolumab. In this cohort, we did not find a correlation between clinical response and type I IFN score, nor between clinical response and IFN-γ secretion in vitro in a MLR in the presence of PD-1 blockade. We conclude that IFN-α reduces the effectiveness of PD-1 blockade in vitro, but that in this cohort, type I IFN score in vivo, nor IFN-γ secretion in vitro in a MLR in the presence of PD-1 blockade correlated to decreased therapy responses in patients.

Bone and Extracellular Signal-Related Kinase 5 (ERK5)

Bones are vital for anchoring muscles, tendons, and ligaments, serving as a fundamental element of the human skeletal structure. However, our understanding of bone development mechanisms and the maintenance of bone homeostasis is still limited. Extracellular signal-related kinase 5 (ERK5), a recently identified member of the mitogen-activated protein kinase (MAPK) family, plays a critical role in the pathogenesis and progression of various diseases, especially neoplasms. Recent studies have highlighted ERK5's significant role in both bone development and bone-associated pathologies. This review offers a detailed examination of the latest research on ERK5 in different tissues and diseases, with a particular focus on its implications for bone health. It also examines therapeutic strategies and future research avenues targeting ERK5.

Targeting MELK improves PD-1 blockade efficiency in cervical cancer via enhancing antitumor immunity

The balance between T helper 1 (Th1) and T helper 2 (Th2) has a critical function in determining intratumoral immune response and anti-PD-1 immunotherapy. The level of maternal embryonic leucine zipper kinase (MELK) is reported to correlate with infiltration of immune cells in cancers, but the underlying molecular mechanism is not clarified. In the present study, we aimed to elucidate the potential function of MELK in cervical cancer. We found that MELK was upregulated and played an oncogenic role in cervical cancer. MELK overexpression shifted Th1/Th2 balance toward Th2 predisposition in mouse cervical tumors in vivo and naive T cells from human PBMCs in vitro, whereas MELK knockdown exhibited opposite effects. MELK overexpression activated NF-κB signaling and promoted IL-6 secretion by cervical cancer cells. Depletion of IL-6 by neutralization antibodies abrogated the influence of MELK on Th1/Th2 balance. In addition, MELK modulated the antitumor activity of cytotoxic CD8+ T cells in cervical tumors, but depletion of Th2 cells by IL-4 neutralization abrogated this effect. Finally, MELK overexpression conferred tolerance to PD-1 blockade in cervical tumors, whereas targeting MELK by OTSSP167 significantly enhanced PD-1 blockade efficiency. Our data elucidated a novel role of MELK in regulating Th1/Th2 balance and anti-PD-1 immunotherapy in cervical cancer.

Design, Synthesis, and Biological Evaluation of Proteolysis-Targeting Chimeras as Highly Selective and Efficient Degraders of Extracellular Signal-Regulated Kinase 5

Extracellular signal-regulated kinase 5 (ERK5) is recognized as a key member of the mitogen-activated protein kinase family and is involved in tumor growth, migration, and angiogenesis. However, the results of ERK5 inhibition in multiple studies are controversial, and a highly specific ERK5-targeting agent is required to confirm physiological functions. Using proteolysis-targeting chimera technology, we designed the selective ERK5 degrader PPM-3 and examined its biological effect on cancer cells. Interestingly, the selective degradation of ERK5 with PPM-3 did not influence tumor cell growth directly. Based on proteomics analysis, the ERK5 deletion may be associated with tumor immunity. PPM-3 influences tumor development by affecting the differentiation of macrophages. Therefore, PPM-3 is an effective small-molecule tool for studying ERK5 and a promising immunotherapy drug candidate.

The role of platelets in the regulation of tumor growth and metastasis: the mechanisms and targeted therapy

Platelets are a class of pluripotent cells that, in addition to hemostasis and maintaining vascular endothelial integrity, are also involved in tumor growth and distant metastasis. The tumor microenvironment is a complex and comprehensive system composed of tumor cells and their surrounding immune and inflammatory cells, tumor-related fibroblasts, nearby interstitial tissues, microvessels, and various cytokines and chemokines. As an important member of the tumor microenvironment, platelets can promote tumor invasion and metastasis through various mechanisms. Understanding the role of platelets in tumor metastasis is important for diagnosing the risk of metastasis and prolonging survival. In this study, we more fully elucidate the underlying mechanisms by which platelets promote tumor growth and metastasis by modulating processes, such as immune escape, angiogenesis, tumor cell homing, and tumor cell exudation, and further summarize the effects of platelet-tumor cell interactions in the tumor microenvironment and possible tumor treatment strategies based on platelet studies. Our summary will more comprehensively and clearly demonstrate the role of platelets in tumor metastasis, so as to help clinical judgment of the potential risk of metastasis in cancer patients, with a view to improving the prognosis of patients.

The significance of ERK5 catalytic-independent functions in disease pathways

Extracellular signal-regulated kinase 5 (ERK5), also known as BMK1 or MAPK7, represents a recent addition to the classical mitogen-activated protein kinase (MAPK) family. This family includes well-known members such as ERK1/2, c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (p38 MAPK), as well as atypical MAPKs such as ERK3, ERK4, ERK7 (ERK8), and Nemo-like kinase (NLK). Comprehensive reviews available elsewhere provide detailed insights into ERK5, which interested readers can refer to for in-depth knowledge (Nithianandarajah-Jones et al., 2012; Monti et al., Cancers (Basel), 2022, 14). The primary aim of this review is to emphasize the essential characteristics of ERK5 and shed light on the intricate nature of its activation, with particular attention to the catalytic-independent functions in disease pathways.

Immune Checkpoint Inhibitors, Small-Molecule Immunotherapies and the Emerging Role of Neutrophil Extracellular Traps in Therapeutic Strategies for Head and Neck Cancer

Immune checkpoint inhibitor (ICI) therapy has revolutionized the treatment of many cancer types, including head and neck cancers (HNC). When checkpoint and partner proteins bind, these send an "off" signal to T cells, which prevents the immune system from destroying tumor cells. However, in HNC, and indeed many other cancers, more people do not respond and/or suffer from toxic effects than those who do respond. Hence, newer, more effective approaches are needed. The challenge to durable therapy lies in a deeper understanding of the complex interactions between immune cells, tumor cells and the tumor microenvironment. This will help develop therapies that promote lasting tumorlysis by overcoming T-cell exhaustion. Here we explore the strengths and limitations of current ICI therapy in head and neck squamous cell carcinoma (HNSCC). We also review emerging small-molecule immunotherapies and the growing promise of neutrophil extracellular traps in controlling tumor progression and metastasis.

Etiopathogenic role of ERK5 signaling in sarcoma: prognostic and therapeutic implications

Sarcomas constitute a heterogeneous group of rare and difficult-to-treat tumors that can affect people of all ages, representing one of the most common forms of cancer in childhood and adolescence. Little is known about the molecular entities involved in sarcomagenesis. Therefore, the identification of processes that lead to the development of the disease may uncover novel therapeutic opportunities. Here, we show that the MEK5/ERK5 signaling pathway plays a critical role in the pathogenesis of sarcomas. By developing a mouse model engineered to express a constitutively active form of MEK5, we demonstrate that the exclusive activation of the MEK5/ERK5 pathway can promote sarcomagenesis. Histopathological analyses identified these tumors as undifferentiated pleomorphic sarcomas. Bioinformatic studies revealed that sarcomas are the tumors in which ERK5 is most frequently amplified and overexpressed. Moreover, analysis of the impact of ERK5 protein expression on overall survival in patients diagnosed with different sarcoma types in our local hospital showed a 5-fold decrease in median survival in patients with elevated ERK5 expression compared with those with low expression. Pharmacological and genetic studies revealed that targeting the MEK5/ERK5 pathway drastically affects the proliferation of human sarcoma cells and tumor growth. Interestingly, sarcoma cells with knockout of ERK5 or MEK5 were unable to form tumors when engrafted into mice. Taken together, our results reveal a role of the MEK5/ERK5 pathway in sarcomagenesis and open a new scenario to be considered in the treatment of patients with sarcoma in which the ERK5 pathway is pathophysiologically involved.

TLR7 Agonists Modulate the Activation of Human Conjunctival Epithelial Cells Induced by IL-1β via the ERK1/2 Signaling Pathway

Conjunctival epithelia cells play an important role in the development of allergic reactions. TLR7 agonists have been shown in studies to increase the body's immunological tolerance by controlling the proportion of Th1/Th2 cells, although it is still unknown what impact this has on conjunctival epithelial cells. In this study, we examined the effect of TLR7 agonists on the inflammatory-activation of conjunctival epithelial cells induced by IL-1β. Quantitative PCR and ELISA analysis confirmed that TLR7 agonists could impair the proinflammatory cytokines released by the epithelia cells, whereas pro-inflammatory cytokines led to subsequent reactive oxygen species and neutrophil chemotaxis. Phosphorylation analysis and nucleocytoplasmic separation further confirmed that TLR7 agonists inhibit IL-1β-induced epithelia cells activation and ATP depletion via modulating the cytoplasmic residence of ERK1/2. Our finding indicated that TLR7 of conjunctival epithelia cells could be as a potent anti-inflammatory target for the ocular surface. And TLR7 agonists may become potential new drug for the treatment of allergic conjunctivitis.

Modulation of ERK5 Activity as a Therapeutic Anti-Cancer Strategy

The extracellular signal-regulated kinase 5 (ERK5) signaling pathway is one of four conventional mitogen-activated protein (MAP) kinase pathways. Genetic perturbation of ERK5 has suggested that modulation of ERK5 activity may have therapeutic potential in cancer chemotherapy. This Miniperspective examines the evidence for ERK5 as a drug target in cancer, the structure of ERK5, and the evolution of structurally distinct chemotypes of ERK5 kinase domain inhibitors. The emerging complexities of ERK5 pharmacology are discussed, including the confounding phenomenon of paradoxical ERK5 activation by small-molecule ERK5 inhibitors. The impact of the recent development and biological evaluation of potent and selective bifunctional degraders of ERK5 and future opportunities in ERK modulation are also explored.

Histone methyltransferase KMT2D promotes prostate cancer progression through paracrine IL-6 signaling

Histone methyltransferase KMT2D plays a critical role as a human oncogene in prostate cancer (PCa). Dysregulated inflammatory responses and cytokine signaling are implicated in cancer progression. Furthermore, interleukin 6 (IL-6) is a pleiotropic cytokine that contributes to PCa progression; however, the association between KMT2D and IL-6 in PCa remains unclear. PCa cell proliferative potential, migratory potential, and apoptosis in vitro were determined using cell counting kit-8 (CCK-8), EdU incorporation, wound healing, and apoptosis assays. Proliferation and migratory potential were impaired and apoptosis was induced in PCa cells cultured with the conditioned medium from KMT2D-depleted cells. Cytokine array analysis showed that IL-6 was the most affected cytokine in the conditioned media. KMT2D knockdown significantly downregulated the expression of IL-6 in PCa cells. What's more, proliferation and migration were also impaired and apoptosis was also induced by silencing IL-6R expression. Immunohistochemistry (IHC) and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) were performed to validate the positive correlation between KMT2D and IL-6 in PCa tissue samples. Chromatin immunoprecipitation (ChIP)-PCR demonstrated that KMT2D and H3K4me1 occupied IL-6 enhancer regions and therefore, directly regulated IL-6 expression. The present study revealed that the KMT2D knockdown suppressed prostate cancer progression through the downregulation of paracrine IL-6 signaling. These results suggest that KMT2D could be regarded as a potential new target for PCa therapy.

Title: p38δ Regulates IL6 Expression Modulating ERK Phosphorylation in Preadipocytes

IL6 is an essential cytokine in metabolism regulation and for intercommunication among different organs and tissues. IL6 produced by different tissues has different functions and therefore it is very important to understand the mechanism of its expression in adipose tissue. In this work we demonstrated that IL6 expression in mouse preadipocytes, like in human, is partially dependent on Wnt5a and JNK. Using mouse preadipocytes lacking each one of the p38 SAPK family members, we have shown that IL6 expression is also p38γ and p38δ dependent. In fact, the lack of some of these two kinases increases IL6 expression without altering that of Wnt5a. Moreover, we show that the absence of p38δ promotes greater ERK1/2 phosphorylation in a MEK1/2 independent manner, and that this increased ERK1/2 phosphorylation state is contributing to the higher IL6 expression in p38δ^−/- preadipocytes. These results suggest a new crosstalk between two MAPK signaling pathway, p38δ and ERK1/2, where p38δ modulates the phosphorylation state of ERK1/2.

Clinical Significance and Regulation of ERK5 Expression and Function in Cancer

Extracellular signal-regulated kinase 5 (ERK5) is a unique kinase among MAPKs family members, given its large structure characterized by the presence of a unique C-terminal domain. Despite increasing data demonstrating the relevance of the ERK5 pathway in the growth, survival, and differentiation of normal cells, ERK5 has recently attracted the attention of several research groups given its relevance in inflammatory disorders and cancer. Accumulating evidence reported its role in tumor initiation and progression. In this review, we explore the gene expression profile of ERK5 among cancers correlated with its clinical impact, as well as the prognostic value of ERK5 and pERK5 expression levels in tumors. We also summarize the importance of ERK5 in the maintenance of a cancer stem-like phenotype and explore the major known contributions of ERK5 in the tumor-associated microenvironment. Moreover, although several questions are still open concerning ERK5 molecular regulation, different ERK5 isoforms derived from the alternative splicing process are also described, highlighting the potential clinical relevance of targeting ERK5 pathways.