Antitumor activity of the ERK inhibitor SCH772984 [corrected] against BRAF mutant, NRAS mutant and wild-type melanoma

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.

Targeting the p90RSK/MDM2/p53 Pathway Is Effective in Blocking Tumors with Oncogenic Up-Regulation of the MAPK Pathway Such as Melanoma and Lung Cancer

In most human tumors, the MAPK pathway is constitutively activated. Since p90RSK is downstream of MAPK, it is often hyperactive and capable of phosphorylating oncogenic substrates. We have previously shown that p90RSK phosphorylates MDM2 at S166, promoting p53 degradation in follicular thyroid carcinomas. Thus, the inhibition of p90RSK restores p53 expression, which in turn inhibits cell proliferation and promotes apoptosis. In the present study, we demonstrated that the p90RSK/MDM2/p53 pathway proved to be an excellent target in the therapy of tumors with MAPK hyperactivation. For this purpose, we selected p53wt melanoma, lung and medullary thyroid carcinoma cell lines with high activation of p90RSK. In these cell lines, we demonstrated that the p90RSK/MDM2/p53 pathway is implicated in the regulation of the cell cycle and apoptosis through p53-dependent transcriptional control of p21 and Bcl-2. Furthermore, with an immunohistochemical evaluation of primary melanomas and lung tumors, which exhibit highly activated p90RSK compared to corresponding normal tissue, we demonstrated that MDM2 stabilization was associated with p90RSK phosphorylation. The results indicate that p90RSK is able to control the proliferative rate and induction of apoptosis through the regulation of p53wt levels by stabilizing MDM2 in selected tumors with constitutively activated MAPKs, making p90RSK a new attractive target for anticancer therapy.

MAPK/ERK activation in macrophages promotes Leishmania internalization and pathogenesis

The obligate intracellular parasite Leishmania binds several receptors to trigger uptake by phagocytic cells, ultimately resulting in visceral or cutaneous leishmaniasis. A series of signaling pathways in host cells, which are critical for establishment and persistence of infection, are activated during Leishmania internalization. Thus, preventing Leishmania uptake by phagocytes could be a novel therapeutic strategy for leishmaniasis. However, the host cellular machinery mediating promastigote and amastigote uptake is not well understood. Here, using small molecule inhibitors of Mitogen-activated protein/Extracellular signal regulated kinases (MAPK/ERK), we demonstrate that ERK1/2 mediates Leishmania amazonensis uptake and (to a lesser extent) phagocytosis of beads by macrophages. We find that inhibiting host MEK1/2 or ERK1/2 leads to inefficient amastigote uptake. Moreover, using inhibitors and primary macrophages lacking spleen tyrosine kinase (SYK) or Abl family kinases, we show that SYK and Abl family kinases mediate Raf, MEK, and ERK1/2 activity and are necessary for uptake. Finally, we demonstrate that trametinib, a MEK1/2 inhibitor used to treat cancer, reduces disease severity and parasite burden in Leishmania-infected mice, even if it is started after lesions develop. Our results show that maximal Leishmania infection requires MAPK/ERK and highlight potential for MAPK/ERK-mediated signaling pathways to be novel therapeutic targets for leishmaniasis.

Large-scale Pan-cancer Cell Line Screening Identifies Actionable and Effective Drug Combinations

Oncology drug combinations can improve therapeutic responses and increase treatment options for patients. The number of possible combinations is vast and responses can be context-specific. Systematic screens can identify clinically relevant, actionable combinations in defined patient subtypes. We present data for 109 anticancer drug combinations from AstraZeneca's oncology small molecule portfolio screened in 755 pan-cancer cell lines. Combinations were screened in a 7 × 7 concentration matrix, with more than 4 million measurements of sensitivity, producing an exceptionally data-rich resource. We implement a new approach using combination Emax (viability effect) and highest single agent (HSA) to assess combination benefit. We designed a clinical translatability workflow to identify combinations with clearly defined patient populations, rationale for tolerability based on tumor type and combination-specific "emergent" biomarkers, and exposures relevant to clinical doses. We describe three actionable combinations in defined cancer types, confirmed in vitro and in vivo, with a focus on hematologic cancers and apoptotic targets.

SIGNIFICANCE

We present the largest cancer drug combination screen published to date with 7 × 7 concentration response matrices for 109 combinations in more than 750 cell lines, complemented by multi-omics predictors of response and identification of "emergent" combination biomarkers. We prioritize hits to optimize clinical translatability, and experimentally validate novel combination hypotheses. This article is featured in Selected Articles from This Issue, p. 695.

Targeted therapy, immunotherapy, and small molecules and peptidomimetics as emerging immunoregulatory agents for melanoma

Primary cutaneous melanoma is the most lethal of all skin neoplasms and its incidence is increasing. Clinical management of advanced melanoma in the last decade has been revolutionised by the availability of immunotherapies and targeted therapies, used alone and in combination. This article summarizes advances in the treatment of late-stage melanoma including use of protein kinase inhibitors, antibody-based immune checkpoint inhibitors, adoptive immunotherapy, vaccines and more recently, small molecules and peptidomimetics as emerging immunoregulatory agents.

Melanocortin receptor 4 as a new target in melanoma therapy: Anticancer activity of the inhibitor ML00253764 alone and in association with B-raf inhibitor vemurafenib

The aim of our study is to investigate in vitro and in vivo MC4R as a novel target in melanoma using the selective antagonist ML00253764 (ML) alone and in combination with vemurafenib, a B-rafV600E inhibitor. The human melanoma B-raf mutated A-2058 and WM 266-4 cell lines were used. An MC4R null A-2058 cell line was generated using a CRISPR/Cas9 system. MC4R protein expression was analysed by western blotting, immunohistochemistry, and immunofluorescence. Proliferation and apoptotic assays were performed with ML00253764, whereas the synergism with vemurafenib was evaluated by the combination index (CI) and Loewe methods. ERK1/2 phosphorylation and BCL-XL expression were quantified by western blot. In vivo experiments were performed in Athymic Nude-Foxn1nu male mice, injecting subcutaneously melanoma cells, and treating animals with ML, vemurafenib and their concomitant combination. Comet and cytome assays were performed. Our results show that human melanoma cell lines A-2058 and WM 266-4, and melanoma human tissue, express functional MC4R receptors on their surface. MC4R receptors on melanoma cells can be inhibited by the selective antagonist ML, causing antiproliferative and proapoptotic activity through the inhibition of phosphorylation of ERK1/2 and a reduction of BCL-XL. The concomitant combination of vemurafenib and ML caused a synergistic effect on melanoma cells in vitro and inhibited in vivo tumor growth in a preclinical model, without causing mouse weight loss or genotoxicity. Our original research contributes to the landscape of pharmacological treatments for melanoma, providing MC4R antagonists as drugs that can be added to established therapies.

Computational Investigations on Reaction Mechanisms of the Covalent Inhibitors Ponatinib and Analogs Targeting the Extracellular Signal-Regulated Kinases

As an important cancer therapeutic target, extracellular signal-regulated kinases (ERK) are involved in triggering various cellular responses in tumors. Regulation of the ERK signaling pathway by the small molecular inhibitors is highly desired for the sake of cancer therapy. In contrast to the routine inhibitors targeting ERKs through long-range non-bonding interactions, Ponatinib, a covalent inhibitor to ERK2 with a macrocyclic structure characterized by the α,β-C=C unsaturated ketone, can form the stable -C(S)-C(H)-type complex via the four-center barrier due to the nucleophilic addition reaction of the thiol group of the Cys166 residue of ERK2 with the C=C double bond of Ponatinib with reaction free-energy barrier of 47.2 kcal/mol. Reaction mechanisms for the covalent binding were calculated using QM/MM methods and molecular dynamics simulations. The interaction modes and the corresponding binding free energies were obtained for the non-covalent and covalent complexation. The binding free energies of the non-covalent and covalent inhibitions are 14.8 kcal/mol and 33.4 kcal/mol, respectively. The mechanistic study stimulated a rational design on the modified Ponatinib structure by substituting the C=C bond with the C=N bond. It was demonstrated that the new compound exhibits better inhibition activity toward ERK2 in term of both thermodynamic and kinetic aspects through the covalent binding with a lower reaction free-energy barrier of 23.1 kcal/mol. The present theoretical work sheds new light on the development of the covalent inhibitors for the regulation of ERKs.

Human Blood Serum Can Diminish EGFR-Targeted Inhibition of Squamous Carcinoma Cell Growth through Reactivation of MAPK and EGFR Pathways

Regardless of the presence or absence of specific diagnostic mutations, many cancer patients fail to respond to EGFR-targeted therapeutics, and a personalized approach is needed to identify putative (non)responders. We found previously that human peripheral blood and EGF can modulate the activities of EGFR-specific drugs on inhibiting clonogenity in model EGFR-positive A431 squamous carcinoma cells. Here, we report that human serum can dramatically abolish the cell growth rate inhibition by EGFR-specific drugs cetuximab and erlotinib. We show that this phenomenon is linked with derepression of drug-induced G1S cell cycle transition arrest. Furthermore, A431 cell growth inhibition by cetuximab, erlotinib, and EGF correlates with a decreased activity of ERK1/2 proteins. In turn, the EGF- and human serum-mediated rescue of drug-treated A431 cells restores ERK1/2 activity in functional tests. RNA sequencing revealed 1271 and 1566 differentially expressed genes (DEGs) in the presence of cetuximab and erlotinib, respectively. Erlotinib- and cetuximab-specific DEGs significantly overlapped. Interestingly, the expression of 100% and 75% of these DEGs restores to the no-drug level when EGF or a mixed human serum sample, respectively, is added along with cetuximab. In the case of erlotinib, EGF and human serum restore the expression of 39% and 83% of DEGs, respectively. We further assessed differential molecular pathway activation levels and propose that EGF/human serum-mediated A431 resistance to EGFR drugs can be largely explained by reactivation of the MAPK signaling cascade.

Cetuximab-Conjugated Magnetic Poly(Lactic-co-Glycolic Acid) Nanoparticles for Dual-Targeted Delivery of Irinotecan in Glioma Treatment

A glioma is the most common malignant primary brain tumor in adults and is categorized according to its growth potential and aggressiveness. Within gliomas, grade 4 glioblastoma remains one of the most lethal malignant solid tumors, with a median survival time less than 18 months. By encapsulating CPT-11 and oleic acid-coated magnetic nanoparticles (OMNPs) in poly(lactic-co-glycolic acid) (PLGA) nanoparticles, we first prepared PLGA@OMNP@CPT-11 nanoparticles in this study. After conjugating cetuximab (CET) with PLGA@OMNP@CPT-11, spherical PLGA@OMNP@CPT-11-CET nanoparticles with 250 nm diameter, 33% drug encapsulation efficiency, and 22% drug loading efficiency were prepared in a single emulsion/evaporation step. The nanoparticles were used for dual-targeted delivery of CPT-11 to U87 primary glioblastoma cells by actively targeting the overexpressed epidermal growth factor receptor on the surface of U87 cells, as well as by magnetic targeting. The physicochemical properties of nanoparticles were characterized in detail. CET-mediated targeting promotes intracellular uptake of nanoparticles by U87 cells, which can release four times more drug at pH 5 than at pH 7.4 to facilitate drug release in endosomes after intracellular uptake. The nanovehicle PLGA@OMNP-CET is cytocompatible and hemocompatible. After loading CPT-11, PLGA@OMNP@CPT-11-CET shows the highest cytotoxicity toward U87 compared with free CPT-11 and PLGA@OMNP@CPT-11 by providing the lowest drug concentration for half-maximal cell death (IC50) and the highest rate of cell apoptosis. In orthotopic brain tumor-bearing nude mice with U87 xenografts, intravenous injection of PLGA@OMNP@ CPT-11-CET followed by guidance with a magnetic field provided the best treatment efficacy with the lowest tumor-associated signal intensity from bioluminescence imaging.

Inhibition of p90 ribosomal S6 kinases disrupts melanoma cell growth and immune evasion

BACKGROUND

The mitogen-activated protein kinase (MAPK) signaling pathway is frequently hyperactivated in malignant melanoma and its inhibition has proved to be an efficient treatment option for cases harboring BRAFV600 mutations (BRAFMut). However, there is still a significant need for effective targeted therapies for patients with other melanoma subgroups characterized by constitutive MAPK activation, such as tumors with NRAS or NF-1 alterations (NRASMut, NF-1LOF), as well as for patients with MAPK pathway inhibitor-resistant BRAFMut melanomas, which commonly exhibit a reactivation of this pathway. p90 ribosomal S6 kinases (RSKs) represent central effectors of MAPK signaling, regulating cell cycle progression and survival.

METHODS

RSK activity and the functional effects of its inhibition by specific small molecule inhibitors were investigated in established melanoma cell lines and patient-derived short-term cultures from different MAPK pathway-hyperactivated genomic subgroups (NRASMut, BRAFMut, NF-1LOF). Real-time qPCR, immunoblots and flow cytometric cell surface staining were used to explore the molecular changes following RSK inhibition. The effect on melanoma cell growth was evaluated by various two- and three-dimensional in vitro assays as well as with melanoma xenograft mouse models. Co-cultures with gp100- or Melan-A-specific cytotoxic T cells were used to assess immunogenicity of melanoma cells and associated T-cell responses.

RESULTS

In line with elevated activity of the MAPK/RSK signaling axis, growth and survival of not only BRAFMut but also NRASMut and NF-1LOF melanoma cells were significantly impaired by RSK inhibitors. Intriguingly, RSK inhibition was particularly effective in three-dimensional growth settings with long-term chronic drug exposure and suppressed tumor cell growth of in vivo melanoma models. Additionally, our study revealed that RSK inhibition simultaneously promoted differentiation and immunogenicity of the tumor cells leading to enhanced T-cell activation and melanoma cell killing.

CONCLUSIONS

Collectively, RSK inhibitors exhibited both multi-layered anti-tumor efficacy and broad applicability across different genomic melanoma subgroups. RSK inhibition may therefore represent a promising novel therapeutic strategy for malignant melanoma with hyperactivated MAPK signaling.

Enhanced Apoptosis and Loss of Cell Viability in Melanoma Cells by Combined Inhibition of ERK and Mcl-1 Is Related to Loss of Mitochondrial Membrane Potential, Caspase Activation and Upregulation of Proapoptotic Bcl-2 Proteins

Targeting of MAP kinase pathways by BRAF inhibitors has evolved as a key therapy for BRAF-mutated melanoma. However, it cannot be applied for BRAF-WT melanoma, and also, in BRAF-mutated melanoma, tumor relapse often follows after an initial phase of tumor regression. Inhibition of MAP kinase pathways downstream at ERK1/2, or inhibitors of antiapoptotic Bcl-2 proteins, such as Mcl-1, may serve as alternative strategies. As shown here, the BRAF inhibitor vemurafenib and the ERK inhibitor SCH772984 showed only limited efficacy in melanoma cell lines, when applied alone. However, in combination with the Mcl-1 inhibitor S63845, the effects of vemurafenib were strongly enhanced in BRAF-mutated cell lines, and the effects of SCH772984 were enhanced in both BRAF-mutated and BRAF-WT cells. This resulted in up to 90% loss of cell viability and cell proliferation, as well as in induction of apoptosis in up to 60% of cells. The combination of SCH772984/S63845 resulted in caspase activation, processing of poly (ADP-ribose) polymerase (PARP), phosphorylation of histone H2AX, loss of mitochondrial membrane potential, and cytochrome c release. Proving the critical role of caspases, a pan-caspase inhibitor suppressed apoptosis induction, as well as loss of cell viability. As concerning Bcl-2 family proteins, SCH772984 enhanced expression of the proapoptotic Bim and Puma, as well as decreased phosphorylation of Bad. The combination finally resulted in downregulation of antiapoptotic Bcl-2 and enhanced expression of the proapoptotic Noxa. In conclusion, combined inhibition of ERK and Mcl-1 revealed an impressive efficacy both in BRAF-mutated and WT melanoma cells, and may thus represent a new strategy for overcoming drug resistance.

HLTF promotes hepatocellular carcinoma progression by enhancing SRSF1 stability and activating ERK/MAPK pathway

Helicase-like transcription factor (HLTF) has been found to be involved in the progression of several tumors, but the role of HLTF in hepatocellular carcinoma (HCC) progression has not been studied. Here, our study explored the underlying mechanism of HLTF in HCC progression for the first time. Database analysis and clinical sample examination indicated that HLTF was upregulated in HCC tissues and was related to poor clinicopathological features in patients. Upregulation of HLTF accelerated the growth and metastasis of HCC cells both in vitro and in vivo. Bioinformatics analysis and subsequent experiments revealed that ERK/MAPK signaling pathway activation was vital to HLTF-mediated proliferation and metastasis in HCC cells. Moreover, HLTF was demonstrated to interact with SRSF1 and contribute to its protein stability to activate the ERK/MAPK signaling pathway and enhance HCC growth and metastasis. In addition, miR-511-5p was expressed at a low level in HCC tissues, was negatively correlated HLTF, and regulated HLTF expression. Our study shows that HLTF plays an oncogenic role in HCC progression and provides a novel biomarker and therapeutic target for the diagnosis and treatment of HCC.

Bioengineering of BRAF and COX2 inhibitor nanogels to boost the immunotherapy of melanoma via pyroptosis

Glutathione-responsive nanogels (CDNPs) crosslinked via crosslinker DBHD with the BRAF inhibitor dabrafenib and the COX2 inhibitor celecoxib were fabricated. The CDNPs can effectively induce tumor cell pyroptosis to activate robust antitumor immunity. Additionally, CDNPs combined with αPD-1 antibody greatly inhibited tumor growth in a melanoma mouse model with a prolonged survival time.

Targeting Extracellular Signal-Regulated Protein Kinase 1/2 (ERK1/2) in Cancer: An Update on Pharmacological Small-Molecule Inhibitors

Extracellular signal-regulated protein kinase 1/2 (ERK1/2), the only known substrate of MEK1/2, is located downstream of the RAS-RAF-MEK-ERK (MAPK) pathway and is associated with the abnormal activation and poor prognosis of cancer. To date, several small-molecule inhibitors of RAS, RAF, and MEK have been reported to make rapid advances in cancer therapy; however, acquired resistance still occurs, thereby weakening the therapeutic efficacy of these inhibitors. Recently, selective inhibition of ERK1/2 has been regarded as a potential cancer therapeutic strategy that can not only effectively block the MAPK pathway but also overcome drug resistance caused by upstream mutations in RAS, RAF, and MEK. Herein, we summarize the oncogenic roles, key signaling network, and the single- and dual-target inhibitors of ERK1/2 in preclinical and clinical trials. Together, these inspiring findings shed new light on the discovery of more small-molecule inhibitors of ERK1/2 as candidate drugs to improve cancer therapeutics.

The Anti-Proliferative Effect of PI3K/mTOR and ERK Inhibition in Monolayer and Three-Dimensional Ovarian Cancer Cell Models

Simple Summary

In ovarian cancer patients the PI3K/AKT/mTOR and RAS/RAF/MEK/ERK kinase signaling pathways are frequently dysregulated, making them potential targets of therapeutic inhibitors. In this study, we used four human ovarian cancer cell lines grown in two- and three-dimensional models to investigate the potential efficacy of combining two inhibitors, which target these pathways, against ovarian cancer. The inhibitor combination was found to have cell line- and model-dependent synergistic antiproliferative effect.

Abstract

Most ovarian cancer patients are diagnosed with advanced stage disease, which becomes unresponsive to chemotherapeutic treatments. The PI3K/AKT/mTOR and the RAS/RAF/MEK/ERK kinase signaling pathways are attractive targets for potential therapeutic inhibitors, due to the high frequency of mutations to PTEN, PIK3CA, KRAS and BRAF in several ovarian cancer subtypes. However, monotherapies targeting one of these pathways have shown modest effects in clinical trials. This limited efficacy of the agents could be due to upregulation and increased signaling via the adjacent alternative pathway. In this study, the efficacy of combined PI3K/mTOR (BEZ235) and ERK inhibition (SCH772984) was investigated in four human ovarian cancer cell lines, grown as monolayer and three-dimensional cell aggregates. The inhibitor combination reduced cellular proliferation in a synergistic manner in OV-90 and OVCAR8 monolayers and in OV-90, OVCAR5 and SKOV3 aggregates. Sensitivity to the inhibitors was reduced in three-dimensional cell aggregates in comparison to monolayers. OV-90 cells cultured in large spheroids were sensitive to the inhibitors and displayed a robust synergistic antiproliferative response to the inhibitor combination. In contrast, OVCAR8 spheroids were resistant to the inhibitors. These findings suggest that combined PI3K/mTOR and ERK inhibition could be a useful strategy for overcoming treatment resistance in ovarian cancer and warrants further preclinical investigation. Additionally, in some cell lines the use of different three-dimensional models can influence cell line sensitivity to PI3K/mTOR and RAS/RAF/MEK/ERK pathway inhibitors.

SIRT2 regulates mitochondrial dynamics and reprogramming via MEK1-ERK-DRP1 and AKT1-DRP1 axes

During somatic reprogramming, cellular energy metabolism fundamentally switches from predominantly mitochondrial oxidative phosphorylation toward glycolysis. This metabolic reprogramming, also called the Warburg effect, is critical for the induction of pluripotency, but its molecular mechanisms remain poorly defined. Notably, SIRT2 is consistently downregulated during the reprogramming process and regulates glycolytic switch. Here, we report that downregulation of SIRT2 increases acetylation of mitogen-activated protein kinase (MAPK) kinase-1 (MEK1) at Lys175, resulting in activation of extracellular signal-regulated kinases (ERKs) and subsequent activation of the pro-fission factor dynamin-related protein 1 (DRP1). In parallel, downregulation of SIRT2 hyperacetylates the serine/threonine protein kinase AKT1 at Lys20 in a non-canonical way, activating DRP1 and metabolic reprogramming. Together, our study identified two axes, SIRT2-MEK1-ERK-DRP1 and SIRT2-AKT1-DRP1, that critically link mitochondrial dynamics and oxidative phosphorylation to the somatic reprogramming process. These upstream signals, together with SIRT2’s role in glycolytic switching, may underlie the Warburg effect observed in human somatic cell reprogramming.

Mitochondrial remodeling has critical roles for the somatic cell reprogramming process. Cha et al. report the functional role of SIRT2 in mitochondrial dynamics and remodeling during the human somatic cell reprogramming process. They identify two axes, SIRT2-MEK1-ERK-DRP1 and SIRT2-AKT1-DRP1, that link SIRT2 downregulation to mitochondrial remodeling and somatic cell reprogramming.

Promising therapeutic targets of endometriosis obtained from microRNA studies

Endometriosis is a benign tumor that affect 6-10% women of reproductive age. To date, it is suggested that the aberrant microRNA (miRNA) expressions play important roles in the pathogenesis of endometriosis. Reviewing the literature, we found nine overexpressed miRNAs, which were thoroughly investigated in the context of endometriotic tissues and cells. Most of the overexpressed miRNAs induced endometriosis-specific characteristics including inhibition of apoptosis and decidualization, upregulation of fibrogenesis, invasion, migration, cell proliferation, attachment to extracellular matrix, inflammation, and angiogenesis in the endometriotic cells. Then, we found that the downstream target molecules of these miRNAs, such as early growth response protein-1, extracellular signal-regulated kinase, matrix metallopeptidase 1, signal transducer and activator of transcription 3, cyclooxygenase-2, phosphoinositide 3-kinase, AKT, mammalian target of rapamycin, and vascular endothelial growth factor-A are promising for the therapeutic targets of endometriosis. Recent findings suggest that complex molecular mechanisms leading to development and progression of endometriosis by miRNAs may exist in endometriosis. The meticulous balance between tumorigenic miRNAs and tumoristatic miRNAs may destine the natural course and response to the surgical, medical, and hormonal treatments of this disease. Further investigations into endometriosis-associated miRNAs may elucidate the pathogenesis of endometriosis and help to develop novel therapeutics.

Selective Extracellular Signal-Regulated Kinase 1/2 (ERK1/2) Inhibition by the SCH772984 Compound Attenuates In Vitro and In Vivo Inflammatory Responses and Prolongs Survival in Murine Sepsis Models

Sepsis is the leading cause of death in intensive care units worldwide. Current treatments of sepsis are largely supportive and clinical trials using specific pharmacotherapy for sepsis have failed to improve outcomes. Here, we used the lipopolysaccharide (LPS)-stimulated mouse RAW264.7 cell line and AlphaLisa assay for TNFa as a readout to perform a supervised drug repurposing screen for sepsis treatment with compounds targeting epigenetic enzymes, including kinases. We identified the SCH772984 compound, an extracellular signal-regulated kinase (ERK) 1/2 inhibitor, as an effective blocker of TNFa production in vitro. RNA-Seq of the SCH772984-treated RAW264.7 cells at 1, 4, and 24 h time points of LPS challenge followed by functional annotation of differentially expressed genes highlighted the suppression of cellular pathways related to the immune system. SCH772984 treatment improved survival in the LPS-induced lethal endotoxemia and cecal ligation and puncture (CLP) mouse models of sepsis, and reduced plasma levels of Ccl2/Mcp1. Functional analyses of RNA-seq datasets for kidney, lung, liver, and heart tissues from SCH772984-treated animals collected at 6 h and 12 h post-CLP revealed a significant downregulation of pathways related to the immune response and platelets activation but upregulation of the extracellular matrix organization and retinoic acid signaling pathways. Thus, this study defined transcriptome signatures of SCH772984 action in vitro and in vivo, an agent that has the potential to improve sepsis outcome.

Melanoma dedifferentiation induced by IFN-γ epigenetic remodeling in response to anti-PD-1 therapy

Melanoma dedifferentiation has been reported to be a state of cellular resistance to targeted therapies and immunotherapies as cancer cells revert to a more primitive cellular phenotype. Here, we show that, counterintuitively, the biopsies of patient tumors that responded to anti-programmed cell death 1 (anti-PD-1) therapy had decreased expression of melanocytic markers and increased neural crest markers, suggesting treatment-induced dedifferentiation. When modeling the effects in vitro, we documented that melanoma cell lines that were originally differentiated underwent a process of neural crest dedifferentiation when continuously exposed to IFN-γ, through global chromatin landscape changes that led to enrichment in specific hyperaccessible chromatin regions. The IFN-γ-induced dedifferentiation signature corresponded with improved outcomes in patients with melanoma, challenging the notion that neural crest dedifferentiation is entirely an adverse phenotype.

Melanoma genomics: a state-of-the-art review of practical clinical applications

Our collective understanding of melanoma genomics has rapidly expanded in the past decade, bringing great promise to patients affected with the most severe and aggressive cases of melanoma. In this review, we present the practical clinical impact of genetics and genomics on modern melanoma diagnosis and treatment. Characterization of somatic driver mutations, which can be used to distinguish different subtypes of melanoma such as nonacral cutaneous melanoma (NACM), desmoplastic melanoma (DM), acral melanoma (AM), mucosal melanoma (MM) and uveal melanoma (UM), has led to the development of many targeted therapies against these tumours. Although targeted therapies exist for certain mutations, such as BRAF and KIT, other genotypes respond to newer-generation immune therapies such as immune checkpoint inhibitors. Epigenetics also plays a critical role in melanoma pathogenesis and drug resistance, holding promise for new treatment avenues. In this review, special attention is placed on clinical trials and translational research, especially novel genomic tests aimed to benefit patients on an individualized level in the current emerging era of personalized therapy.

Downregulation of THRSP Promotes Hepatocellular Carcinoma Progression by Triggering ZEB1 Transcription in an ERK-dependent Manner

Background: Hepatocellular carcinoma (HCC) is a major leading cause of cancer mortality worldwide. Thyroid hormone responsive (THRSP) gene is primarily known for regulating responses to thyroid hormones, but its expression has been correlated with differential outcomes in some cancers. To date, however, its role in the progression of HCC remains unknown. Methods: The mRNA and protein expression of THRSP was measured in HCC tissues and cell lines via qPCR and western blot assays. Lentiviral transfection was used to establish stable cell lines overexpressing THRSP and shRNA was used to silence THRSP. The effects of THRSP on cell growth were then determined in vivo and in vitro. Cell migration and invasion of HCC cells were investigated using transwell and wound healing assays. Results: In tissue samples from patients, HCC tissues had decreased THRSP expression relative to adjacent healthy tissues. Further, patients with decreased THRSP protein and mRNA expression had worse outcomes. Knockdown of THRSP led to increased cell growth, migration, and invasion of HCC cells, and THRSP overexpression exerted an anti-tumor effect in vivo and in vitro. We found that increased expression of THRSP inhibited hepatocellular carcinogenesis by inhibiting the process of epithelial-to-mesenchymal transition through acting on the ERK/ZEB1 signaling pathway. Conclusion: THRSP may act as a functional tumor suppressor and was frequently reduced in HCC tissue samples. We identified a novel pathway for the THRSP/ERK/ZEB1-regulated suppression of HCC tumorigenesis and invasion. Restoring THRSP expression may represent a promising approach for HCC therapies.

Inhibition of BRAF and ERK1/2 has synergistic effects on thyroid cancer growth in vitro and in vivo

Mutations in the BRAF gene are highly prevalent in thyroid cancer. However, the response rate of thyroid tumors to BRAF-directed therapies has been mixed. Increasingly, combination therapies inhibiting the MAPK pathway at multiple nodes have shown promise. Recently developed ERK1/2 inhibitors are of interest for use in combination therapies as they have the advantage of inhibiting the most downstream node of the MAPK pathway, therefore preventing pathway reactivation. Here, we examined the effect of combined BRAF inhibition (dabrafenib) and ERK1/2 inhibition (SCH772984) on the growth and survival of a panel of BRAF-mutant thyroid cancer cell lines using in vitro and in vivo approaches. We found that resistance due to MAPK pathway reactivation occurs quickly with single-agent BRAF inhibition, but can be prevented with combined BRAF and ERK1/2 inhibition. Combined inhibition also results in synergistic growth inhibition, decreased clonogenic survival, and enhanced induction of apoptosis in a subset of BRAF-mutant thyroid cancer cells. Finally, combined inhibition of BRAF and ERK1/2 results in enhanced inhibition of tumor growth in an anaplastic thyroid cancer in vivo model. These results provide key rationale to pursue combined BRAF and ERK1/2 inhibition as an alternative therapeutic strategy for BRAF-mutant advanced thyroid cancer patients.

ERK and mTORC1 Inhibitors Enhance the Anti-Cancer Capacity of the Octpep-1 Venom-Derived Peptide in Melanoma BRAF(V600E) Mutations

Melanoma is the main cause of skin cancer deaths, with special emphasis in those cases carrying BRAF mutations that trigger the mitogen-activated protein kinases (MAPK) signaling and unrestrained cell proliferation in the absence of mitogens. Current therapies targeting MAPK are hindered by drug resistance and relapse that rely on metabolic rewiring and Akt activation. To identify new drug candidates against melanoma, we investigated the molecular mechanism of action of the Octopus Kaurna-derived peptide, Octpep-1, in human BRAF(V600E) melanoma cells using proteomics and RNAseq coupled with metabolic analysis. Fluorescence microscopy verified that Octpep-1 tagged with fluorescein enters MM96L and NFF cells and distributes preferentially in the perinuclear area of MM96L cells. Proteomics and RNAseq revealed that Octpep-1 targets PI3K/AKT/mTOR signaling in MM96L cells. In addition, Octpep-1 combined with rapamycin (mTORC1 inhibitor) or LY3214996 (ERK1/2 inhibitor) augmented the cytotoxicity against BRAF(V600E) melanoma cells in comparison with the inhibitors or Octpep-1 alone. Octpep-1-treated MM96L cells displayed reduced glycolysis and mitochondrial respiration when combined with LY3214996. Altogether these data support Octpep-1 as an optimal candidate in combination therapies for melanoma BRAF(V600E) mutations.

Beyond EGFR, ALK and ROS1: Current evidence and future perspectives on newly targetable oncogenic drivers in lung adenocarcinoma

Lung cancer is the leading cause of cancer death worldwide. In the past decade EGFR, ALK and ROS1 TKIs lead to an unprecedented survival improvement of oncogene-addicted NSCLC patients, with better toxicity profile compared to chemotherapy. In recent years the implementation of high-throughput sequencing platforms led to the identification of uncommon molecular alterations in oncogenic drivers, such as BRAF, MET, RET, HER2 and NTRK. Moreover, newly developed drugs have been found to be active against hard to target drivers, such as KRAS. Specific TKIs targeting these genomic alterations are currently in clinical development and showed impressive activity and survival improvement, leading to FDA-accelerated approval for some of them. However, virtually all patients develop resistance to TKIs by on-target or off-target mechanisms. Here we review the clinicopathological features, the emerging targeted therapies and mechanisms of resistance and strategies to overcome them of KRAS, BRAF, MET, RET, HER2 and NTRK-addicted advanced NSCLCs.

Direct Targeting of CREB1 with Imperatorin Inhibits TGFβ2-ERK Signaling to Suppress Esophageal Cancer Metastasis

Metastasis accounts for 90% of cancer death worldwide, and effective therapeutic strategies are lacking. The aim of this work is to identify the key drivers in tumor metastasis and screen therapeutics for treatment of esophageal squamous cell carcinoma (ESCC). Gene Ontology analysis of The Cancer Genome Atlas (TCGA) gene expression datasets of ESCC patients with or without lympy metastasis identifies that TGFβ2 is highly enriched in the pathways essential for tumor metastasis and upregulates in the metastatic ESCC tumors. High TGFβ2 expression in ESCC correlates with metastasis and patient survival, and functionally contributes to tumor metastasis via activating extracellular signal-regulated kinases (ERK) signaling. By screening of a library consisting of 429 bioactive compounds, imperatorin is verified as a novel TGFβ2 inhibitor, with robustly suppressive effect on tumor metastasis in multiple mice models. Mechanistically, direct binding of imperatorin and CREB1 inhibits phosphorylation, nuclear translocation of CREB1, and its interaction with TGFβ2 promoter, represses TGFβ2 expression and fibroblasts-secreted CCL2, and then inactivates ERK signaling to block cancer invasion and abrogates the paracrine effects of fibroblasts on tumor angiogenesis and metastasis. Overall, the findings suggest the use of TGFβ2 as a diagnostic and prognostic biomarker and therapeutic target in ESCC, and supports the potential of imperatorin as a novel therapeutic strategy for cancer metastasis.

Current State of Target Treatment in BRAF Mutated Melanoma

Incidence of melanoma has been constantly growing during the last decades. Although most of the new diagnoses are represented by thin melanomas, the number of melanoma-related deaths in 2018 was 60,712 worldwide (Global Cancer Observatory, 2019). Until 2011, no systemic therapy showed to improve survival in patients with advanced or metastatic melanoma. At that time, standard of care was chemotherapy, with very limited results. The identification of BRAF V600 mutation, and the subsequent introduction of BRAF targeting drugs, radically changed the clinical practice and dramatically improved outcomes. In this review, we will retrace the development of molecular-target drugs and the current therapeutic scenario for patients with BRAF mutated melanoma, from the introduction of BRAF inhibitors as single agents to modern clinical practice. We will also discuss the resistance mechanisms identified so far, and the future therapeutic perspectives in BRAF mutated melanoma.

Semaphorin-5A downregulation is associated with enhanced migration and invasion of BRAF-positive melanoma cells under vemurafenib treatment in melanomas with heterogeneous BRAF status

Tumor heterogeneity affects the efficacy of anticancer treatment as tumor subclones with distinct molecular patterns may be present within one tumor, leading to differing sensitivities to chemotherapeutic agents. In the present study, six melanoma tissue fragments were obtained from different parts of tumor of four patients and then the effect of vemurafenib treatment on biological characteristics and molecular processes of cell cultures was estimated by using MTT-test, apoptosis, migration and invasion assays, PCR real time. There was different BRAF status determined between cells derived from the central and peripheral regions of primary melanoma tumors. BRAF-positive melanoma cells showed an increased apoptotic rate under vemurafenib treatment, as well as increased migration and invasion rates, whereas BRAF-negative melanoma cells did not exhibit such tendency. Furthermore, semaphorin-5A levels were diminished in BRAF-positive cells, but not in BRAF-negative ones, which could be related to increased migration and invasion. Melanoma cells derived from different regions of the same tumor may differ by mutations status, molecular processes and biological response to target therapy. The downregulation of semaphorin-5A may be involved in divergent effects of anticancer agents on tumor cell biology.

Melanoma Brain Metastases in the Era of Target Therapies: An Overview

Malignant melanoma is the third most common type of tumor that causes brain metastases. Patients with cerebral involvement have a dismal prognosis and their treatment is an unmet medical need. Brain involvement is a multistep process involving several signaling pathways such as Janus kinase/signal Transducer and Activator of Transcription (JAK/STAT), Phosphoinositide 3-kinase/Protein Kinase B (PI3K/AKT), Vascular Endothelial Growth Factor and Phosphatase and Tensin Homolog (PTEN). Recently therapy that targets the MAPK signaling (BRAF/MEK inhibitors) and immunotherapy (anti-CTLA4 and anti-PD1 agents) have changed the therapeutic approaches to stage IV melanoma. In contrast, there are no solid data about patients with brain metastases, who are usually excluded from clinical trials. Retrospective data showed that BRAF-inhibitors, alone or in combination with MEK-inhibitors have interesting clinical activity in this setting. Prospective data about the combinations of BRAF/MEK inhibitors have been recently published, showing an improved overall response rate. Short intracranial disease control is still a challenge. Several attempts have been made in order to improve it with combinations between local and systemic therapies. Immunotherapy approaches seem to retain promising activity in the treatment of melanoma brain metastasis as showed by the results of clinical trials investigating the combination of anti-CTL4 (Ipilimumab) and anti-PD1(Nivolumab). Studies about the combination or the sequential approach of target therapy and immunotherapy are ongoing, with immature results. Several clinical trials are ongoing trying to explore new approaches in order to overcome tumor resistance. At this moment the correct therapeutic choices for melanoma with intracranial involvement is still a challenge and new strategies are needed.

The MNK1/2-eIF4E Axis as a Potential Therapeutic Target in Melanoma

: Melanoma is a type of skin cancer that originates in the pigment-producing cells of the body known as melanocytes. Most genetic aberrations in melanoma result in hyperactivation of the mitogen activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) pathways. We and others have shown that a specific protein synthesis pathway known as the MNK1/2-eIF4E axis is often dysregulated in cancer. The MNK1/2-eIF4E axis is a point of convergence for these signaling pathways that are commonly constitutively activated in melanoma. In this review we consider the functional implications of aberrant mRNA translation in melanoma and other malignancies. Moreover, we discuss the consequences of inhibiting the MNK1/2-eIF4E axis on the tumor and tumor-associated cells, and we provide important avenues for the utilization of this treatment modality in combination with other targeted and immune-based therapies. The past decade has seen the increased development of selective inhibitors to block the action of the MNK1/2-eIF4E pathway, which are predicted to be an effective therapy regardless of the melanoma subtype (e.g., cutaneous, acral, and mucosal).

ABCA8 is regulated by miR-374b-5p and inhibits proliferation and metastasis of hepatocellular carcinoma through the ERK/ZEB1 pathway

Background

ATP binding cassette subfamily A member 8 (ABCA8) belongs to the ATP binding cassette (ABC) transporter superfamily. ABCA8 is a transmembrane transporter responsible for the transport of organics, such as cholesterol, and drug efflux. Some members of the ABC subfamily, such as ABCA1, may inhibit cancer development. However, the mechanism of ABCA8 in the process of cancer activation is still ambiguous.

Methods

The expression of ABCA8 in human hepatocellular carcinoma (HCC) tissues and cell lines was examined using qPCR, immunoblotting, and immunohistochemical staining. The effects of ABCA8 on the proliferation and metastasis of HCC were examined using in vitro and in vivo functional tests. A luciferase reporter assay was performed to explore the binding between microRNA-374b-5p (miR-374b-5p) and the ABCA8 3′-untranslated region (UTR).

Results

ABCA8 was frequently down-regulated in HCC and this down-regulation was negatively correlated with prognosis. The overexpression of ABCA8 inhibited growth and metastasis in HCC, whereas the knockdown of ABCA8 exerted the antithetical effects both in vivo and in vitro. ABCA8 was down-regulated by miR-374b-5p; this down-regulation can induce epithelial transformation to mesenchyme via the ERK/ZEB1 signaling pathway and promote HCC progression.

Conclusion

We exposed the prognostic value of ABCA8 in HCC, and illuminated a novel pathway in ABCA8-regulated inhibition of HCC tumorigenesis and metastasis. These findings may lead to a new targeted therapy for HCC through the regulation of ABCA8, and miR-374b-5p.

Current Advances in the Treatment of BRAF-Mutant Melanoma

Melanoma is the most lethal form of skin cancer. Melanoma is usually curable with surgery if detected early, however, treatment options for patients with metastatic melanoma are limited and the five-year survival rate for metastatic melanoma had been 15-20% before the advent of immunotherapy. Treatment with immune checkpoint inhibitors has increased long-term survival outcomes in patients with advanced melanoma to as high as 50% although individual response can vary greatly. A mutation within the MAPK pathway leads to uncontrollable growth and ultimately develops into cancer. The most common driver mutation that leads to this characteristic overactivation in the MAPK pathway is the B-RAF mutation. Current combinations of BRAF and MEK inhibitors that have demonstrated improved patient outcomes include dabrafenib with trametinib, vemurafenib with cobimetinib or encorafenib with binimetinib. Treatment with BRAF and MEK inhibitors has met challenges as patient responses began to drop due to the development of resistance to these inhibitors which paved the way for development of immunotherapies and other small molecule inhibitor approaches to address this. Resistance to these inhibitors continues to push the need to expand our understanding of novel mechanisms of resistance associated with treatment therapies. This review focuses on the current landscape of how resistance occurs with the chronic use of BRAF and MEK inhibitors in BRAF-mutant melanoma and progress made in the fields of immunotherapies and other small molecules when used alone or in combination with BRAF and MEK inhibitors to delay or circumvent the onset of resistance for patients with stage III/IV BRAF mutant melanoma.

The JAK2/STAT3 pathway is involved in the anti-melanoma effects of brevilin A

AIMS

Melanoma is lethal. Constitutively active signal transducer and activator of transcription 3 (STAT3) has been proposed as a pathogenic factor and a therapeutic target of melanoma. Brevilin A, a sesquiterpene lactone isolated from Centipeda minima (L.) A. Br. et Aschers., has been shown to exert antineoplastic effects and inhibit the STAT3 pathway in nasopharyngeal, lung, prostate and breast cancer cells. This study aimed to determine whether brevilin A has anti-melanoma effects, and whether STAT3 signaling is involved in the effects.

MAIN METHODS

A mouse A375 xenograft model, as well as A375 and A2058 cell models were employed to assess the in vivo and in vitro anti-melanoma effects of brevilin A. A375 cells stably expressing STAT3C, a constitutively active STAT3 mutant, were used to determine the role of STAT3 signaling in brevilin A's anti-melanoma effects.

KEY FINDINGS

Intraperitoneal injection of brevilin A dose-dependently inhibited melanoma growth in mice and suppressed STAT3 phosphorylation in the tumors. In cultured cells, brevilin A reduced cell viability, induced apoptosis, suppressed migration and invasion, decreased protein levels of phospho-JAK2 (Y1007/1008) and phospho-STAT3 (Tyr705), and restrained STAT3 nuclear localization. STAT3 over-activation diminished brevilin A's effects on cell viability and migration. Collectively, brevilin A exerts anti-melanoma effects and these effects are at least in part attributed to the inhibition of the JAK2/STAT3 pathway.

SIGNIFICANCE

Our findings provide a pharmacological basis for developing brevilin A as a new phytotherapeutic agent against melanoma.

Emerging Roles of 5-Lipoxygenase Phosphorylation in Inflammation and Cell Death

5-Lipoxygenase (ALOX5) is an iron-containing and nonheme dioxygenase that catalyzes the peroxidation of polyunsaturated fatty acids such as arachidonic acid. ALOX5 is the rate-limiting enzyme for the biosynthesis of leukotrienes, a family of proinflammatory lipid mediators derived from arachidonic acid. ALOX5 also make great contributions to mediating lipid peroxidation. In recent years, it has been discovered that ALOX5 plays a central role in cell death including apoptosis, pyroptosis, and ferroptosis, a newly discovered type of cell death. According to the previous studies, ALOX5 can regulate cell death in two ways: one is inflammation and the other is lipid peroxidation. Meanwhile, it has been shown that ALOX5 activity is regulated by several factors including protein phosphorylation, ALOX5-interactng protein, redox state, and metal ions such as iron and calcium. In this review, we aim to summarize the knowledge on the emerging roles of ALOX5 protein phosphorylation in the regulation of cell death and inflammation in order to explore a potential target for human diseases.

Development of ERK1/2 inhibitors as a therapeutic strategy for tumour with MAPK upstream target mutations

Extracellular signal-regulated kinases 1 and 2 (ERK1/2) phosphorylate a variety of substrates that play key roles in promoting cell survival and proliferation. Many inhibitors, acting on upstream of the ERK pathway, exhibit excellent antitumor activity. However, drug-resistant tumour cells invariably emerge after their use due to the reactivation of ERK1/2 signalling. ERK1/2 inhibitors have shown clinical efficacy as a therapeutic strategy for the treatment of tumours with mitogen-activated protein kinase (MAPK) upstream target mutations. These inhibitors may be effective against cancers with altered MAPK upstream pathway and may be used as a possible strategy to overcome acquired resistance to MAPK inhibitors. In this review, we describe the mechanism and types of ERK1/2 inhibitors, summarise the current development status of small-molecule ERK1/2 inhibitors, including the preclinical data and clinical study progress, and discuss the future research directions for the application of ERK1/2 inhibitors.

Phenformin as an Anticancer Agent: Challenges and Prospects

Currently, there is increasing evidence linking diabetes mellitus (especially type 2 diabetes mellitus) with carcinogenesis through various biological processes, such as fat-induced chronic inflammation, hyperglycemia, hyperinsulinemia, and angiogenesis. Chemotherapeutic agents are used in the treatment of cancer, but in most cases, patients develop resistance. Phenformin, an oral biguanide drug used to treat type 2 diabetes mellitus, was removed from the market due to a high risk of fatal lactic acidosis. However, it has been shown that phenformin is, with other biguanides, an authentic tumor disruptor, not only by the production of hypoglycemia due to caloric restriction through AMP-activated protein kinase with energy detection (AMPK) but also as a blocker of the mTOR regulatory complex. Moreover, the addition of phenformin eliminates resistance to antiangiogenic tyrosine kinase inhibitors (TKI), which prevent the uncontrolled metabolism of glucose in tumor cells. In this review, we evidence the great potential of phenformin as an anticancer agent. We thoroughly review its mechanism of action and clinical trial assays, specially focusing on current challenges and future perspectives of this promising drug.

Developments in the Space of New MAPK Pathway Inhibitors for BRAF-Mutant Melanoma

The characterization of the MAPK signaling pathway has led to the development of multiple promising targeted therapy options for a subset of patients with metastatic melanoma. The combination of BRAF and MEK inhibitors represents an FDA-approved standard of care in patients with metastatic and resected BRAF-mutated melanoma. There are currently three FDA-approved BRAF/MEK inhibitor combinations for the treatment of patients with BRAF-mutated melanoma. Although there have been significant advances in the field of targeted therapy, further exploration of new targets within the MAPK pathway will strengthen therapeutic options for patients. Important clinical and translational research focuses on mechanisms of resistance, predictive biomarkers, and challenging patient populations such as those with brain metastases or resected melanoma.

Design, synthesis, and DNA interaction studies of furo-imidazo[3.3.3]propellane derivatives: Potential anticancer agents

A large number of natural products containing the propellane scaffold have been reported to exhibit cytotoxicity against several cancers; however, their mechanism of action is still unknown. Anticancer drugs targeting DNA are mainly composed of small planar molecule/s that can interact with the DNA helix, causing DNA malfunction and cell death. The aim of this study was to design and synthesize propellane derivatives that can act as DNA intercalators and/or groove binders. The unique structure of the propellane derivatives and their ability to display planar ligands with numerous possible geometries, renders them potential starting points to design new drugs targeting DNA in cancer cells. New substituted furo-imidazo[3.3.3]propellanes were synthesized via the reaction of substituted alkenylidene-hydrazinecarbothioamides with 2-(1,3-dioxo-2,3-dihydro-1H-2-ylidene)propanedinitrile in tetrahydrofuran at room temperature. The structures of the products were confirmed by a combination of elemental analysis, NMR, ESI-MS, IR and single crystal X-ray analysis. Interestingly, 5c, 5d and 5f showed an ability to interact with Calf Thymus DNA (CT-DNA). Their DNA-binding mode was investigated using a combination of absorption spectroscopy, DNA melting, viscosity, CD spectroscopy measurements, as well as competitive binding studies with several dyes. Their cytotoxicity was evaluated against the NCI-60 panel of cancer cell lines. 5c, 5d and 5f exhibited similar anti-proliferative activity against the A549 non-small cell lung cancer (NSCLC) cell line. Further mechanistic studies revealed their ability to induce DNA damage in the A549 cell line, as well as apoptosis, evidenced by elevated Annexin V expression, enhanced caspase 3/7 activation and PARP cleavage. In this study, we present the potential for designing novel propellanes to provoke cytotoxic activity, likely through DNA binding-induced DNA damage and apoptosis.

Targeting the ERK Signaling Pathway in Melanoma

The discovery of the role of the RAS/RAF/MEK/ERK pathway in melanomagenesis and its progression have opened a new era in the treatment of this tumor. Vemurafenib was the first specific kinase inhibitor approved for therapy of advanced melanomas harboring BRAF-activating mutations, followed by dabrafenib and encorafenib. However, despite the excellent results of first-generation kinase inhibitors in terms of response rate, the average duration of the response was short, due to the onset of genetic and epigenetic resistance mechanisms. The combination therapy with MEK inhibitors is an excellent strategy to circumvent drug resistance, with the additional advantage of reducing side effects due to the paradoxical reactivation of the MAPK pathway. The recent development of RAS and extracellular signal-related kinases (ERK) inhibitors promises to add new players for the ultimate suppression of this signaling pathway and the control of pathway-related drug resistance. In this review, we analyze the pharmacological, preclinical, and clinical trial data of the various MAPK pathway inhibitors, with a keen interest for their clinical applicability in the management of advanced melanoma.

Nuclear ERK: Mechanism of Translocation, Substrates, and Role in Cancer

The extracellular signal-regulated kinases 1/2 (ERK) are central signaling components that regulate stimulated cellular processes such as proliferation and differentiation. When dysregulated, these kinases participate in the induction and maintenance of various pathologies, primarily cancer. While ERK is localized in the cytoplasm of resting cells, many of its substrates are nuclear, and indeed, extracellular stimulation induces a rapid and robust nuclear translocation of ERK. Similarly to other signaling components that shuttle to the nucleus upon stimulation, ERK does not use the canonical importinα/β mechanism of nuclear translocation. Rather, it has its own unique nuclear translocation signal (NTS) that interacts with importin7 to allow stimulated shuttling via the nuclear pores. Prevention of the nuclear translocation inhibits proliferation of B-Raf- and N/K-Ras-transformed cancers. This effect is distinct from the one achieved by catalytic Raf and MEK inhibitors used clinically, as cells treated with the translocation inhibitors develop resistance much more slowly. In this review, we describe the mechanism of ERK translocation, present all its nuclear substrates, discuss its role in cancer and compare its translocation to the translocation of other signaling components. We also present proof of principle data for the use of nuclear ERK translocation as an anti-cancer target. It is likely that the prevention of nuclear ERK translocation will eventually serve as a way to combat Ras and Raf transformed cancers with less side-effects than the currently used drugs.

Resistance to MAPK Inhibitors in Melanoma Involves Activation of the IGF1R-MEK5-Erk5 Pathway

Combined treatment of metastatic melanoma with BRAF and MEK inhibitors has improved survival, but the emergence of resistance represents an important clinical challenge. Targeting ERK is a suitable strategy currently being investigated in melanoma and other cancers. To anticipate possible resistance to ERK inhibitors (ERKi), we used SCH772984 (SCH) as a model ERKi to characterize resistance mechanisms in two BRAF V600E melanoma cell lines. The ERKi-resistant cells were also resistant to vemurafenib (VMF), trametinib (TMT), and combined treatment with either VMF and SCH or TMT and SCH. Resistance to SCH involved stimulation of the IGF1R-MEK5-Erk5 signaling pathway, which counteracted inhibition of Erk1/2 activation and cell growth. Inhibition of IGF1R with linsitinib blocked Erk5 activation in SCH-resistant cells and decreased their growth in 3D spheroid growth assays as well as in NOD scid gamma (NSG) mice. Cells doubly resistant to VMF and TMT or to VMF and SCH also exhibited downregulated Erk1/2 activation linked to stimulation of the IGF1R-MEK5-Erk5 pathway, which accounted for resistance. In addition, we found that the decreased Erk1/2 activation in SCH-resistant cells involved reduced expression and function of TGFα. These data reveal an escape signaling route that melanoma cells use to bypass Erk1/2 blockade during targeted melanoma treatment and offer several possible targets whose disruption may circumvent resistance. SIGNIFICANCE: Activation of the IGF1R-MEK5-Erk5 signaling pathway opposes pharmacologic inhibition of Erk1/2 in melanoma, leading to the reactivation of cell proliferation and acquired resistance.

Crizotinib enhances anti-CD30-LDM induced antitumor efficacy in NPM-ALK positive anaplastic large cell lymphoma

Combining antibody-drug conjugates (ADCs) with targeted small-molecule inhibitors can enhance antitumor effects beyond those attainable with monotherapy. In this study, we investigated the therapeutic combination of a CD30-targeting ADC (anti-CD30-lidamycin [LDM]) with a small-molecule inhibitor (crizotinib) of nucleophosmin-anaplastic lymphoma kinase NPM-ALK in CD30⁺/ALK⁺ anaplastic large cell lymphoma (ALCL). In vitro, anti-CD30-LDM showed strong synergistic antiproliferative activity when combined with crizotinib. Furthermore, treatment with anti-CD30-LDM plus crizotinib resulted in a stronger induction of cell apoptosis than monotherapy with either treatment. Western blot analysis revealed that ERK1/2 phosphorylation was increased in response to anti-CD30-LDM-induced DNA damage. Interestingly, the addition of crizotinib inhibited the expression of phosphorylated ERK1/2 and further augmented anti-CD30-LDM-mediated apoptosis, providing a potential synergistic mechanism for DNA-damaging agents combined with NPM-ALK inhibitors. In Karpas299 and SU-DHL-1 xenograft models, anti-CD30-LDM plus crizotinib was more effective in inhibiting tumor growth than either treatment alone. This research demonstrated for the first time that the combination of anti-CD30-LDM and crizotinib exhibits a synergistic inhibitory effect in tumor cells. These results provide scientific support for future clinical evaluations of anti-CD30-LDM, or other DNA-damaging agents, combined with NPM-ALK inhibitors.

EGFR/uPAR interaction as druggable target to overcome vemurafenib acquired resistance in melanoma cells

Background

BRAF inhibitor (BRAF-I) therapy for melanoma patients harboring the V600E mutation is initially highly effective, but almost all patients relapse within a few months. Understanding the molecular mechanisms behind BRAF-I responsiveness and acquired resistance is therefore an important issue. Here we assessed the role of urokinase type plasminogen activator receptor (uPAR) as a potentially valuable biomarker in the acquisition of BRAF-I resistance in V600E mutant melanoma cells.

Methods

We examined uPAR and EGFR levels by real time PCR and western blot analysis. uPAR loss of function was realized by knocking down uPAR by RNAi or using M25, a peptide that uncouples uPAR-integrin interaction. We investigated uPAR-β1integrin-EGFR association by co-immunoprecipitation and confocal immuno-fluorescence analysis. Acquired resistance to BRAF-I was generated by chronic exposure of cells to vemurafenib.

Findings

We proved that uPAR knockdown in combination with vemurafenib inhibits melanoma cell proliferation to greater extent than either treatment alone causing a decrease in AKT and ERK1/2 phosphorylation. Conversely, we demonstrated that uPAR enforced over-expression results in reduced sensitivity to BRAF inhibition. Moreover, by targeting uPAR and EGFR interaction with an integrin antagonist peptide we restored vemurafenib responsiveness in melanoma resistant cells. Furthermore, we found significant detectable uPAR and EGFR levels in tumor biopsies of 4 relapsed patients.

Interpretation

We disclosed an unpredicted mechanism of reduced sensitiveness to BRAF inhibition, driven by elevated levels of uPAR and identified a potential therapeutic strategy to overcome acquired resistance.

Funds

Associazione Italiana Ricerca sul Cancro (AIRC); Ente Cassa di Risparmio di Firenze.

Design, synthesis and biological evaluation of fused naphthofuro[3,2-c] quinoline-6,7,12-triones and pyrano[3,2-c]quinoline-6,7,8,13-tetraones derivatives as ERK inhibitors with efficacy in BRAF-mutant melanoma

Approximately 60% of human cancers exhibit enhanced activity of ERK1 and ERK2, reflecting their multiple roles in tumor initiation and progression. Acquired drug resistance, especially mechanisms associated with the reactivation of the MAPK (RAF/MEK/ERK) pathway represent a major challenge to current treatments of melanoma and several other cancers. Recently, targeting ERK has evolved as a potentially attractive strategy to overcome this resistance. Herein, we report the design and synthesis of novel series of fused naphthofuro[3,2-c]quinoline-6,7,12-triones 3a-f and pyrano[3,2-c]quinoline-6,7,8,13-tetraones 5a,b and 6, as potential ERK inhibitors. New inhibitors were synthesized and identified by different spectroscopic techniques and X-ray crystallography. They were evaluated for their ability to inhibit ERK1/2 in an in vitro radioactive kinase assay. 3b and 6 inhibited ERK1 with IC50s of 0.5 and 0.19 µM, and inhibited ERK2 with IC50s of 0.6 and 0.16 µM respectively. Kinetic mechanism studies revealed that the inhibitors are ATP-competitive inhibitors where 6 inhibited ERK2 with a K_i of 0.09 µM. Six of the new inhibitors were tested for their in vitro anticancer activity against the NCI-60 panel of tumor cell lines. Compound 3b and 6 were the most potent against most of the human tumor cell lines tested. Moreover, 3b and 6 inhibited the proliferation of the BRAF mutant A375 melanoma cells with IC50s of 3.7 and 0.13 µM, respectively. In addition, they suppressed anchorage-dependent colony formation. Treatment of the A375 cell line with 3b and 6 inhibited the phosphorylation of ERK substrates p-90RSK and ELK-1 and induced apoptosis in a dose dependent manner. Finally, a molecular docking study showed the potential binding mode of 3b and 6 within the ATP catalytic binding site of ERK2.

Molecular subtypes of colorectal cancer in pre-clinical models show differential response to targeted therapies: Treatment implications beyond KRAS mutations

Molecular subtypes of colorectal tumors are associated with prognosis and prediction for treatment benefit from chemotherapy. The purpose of this study was two-fold: 1) to determine the association of colorectal (CRC) molecular subtypes with response to targeted therapies in pre-clinical models and 2) to identify treatments for CRC stem-like subtype because these tumors are associated with a very poor patient prognosis. Eleven CRC cell lines were classified into molecular subtypes and tested for their response to pan-ERBB, MEK, and ERK inhibitors as single agents and in combination. All six inflammatory or TA cell lines were exquisitely sensitive to the combination of MEK and neratinib whereas all five stem-like cell lines were resistant. Growth inhibition in sensitive cell lines was greater with the combination than with either drug alone even in cell lines with KRAS mutations. The combination inhibited pERK in inflammatory cell lines but not in four out of five stem-like cell lines. MEK162 plus neratinib were synergistic in cell culture and xenograft models in inflammatory cell lines. The ERK inhibitor, SCH772984, down-regulated pERK, decreased cell viability, and was synergistic with neratinib in both inflammatory and stem-like subtypes. These results suggest that inhibition of pERK is a critical node in decreasing cell viability of stem-like CRC tumors. Our results also suggest that CRC molecular subtypes may yield predictive information and may help to identify patients who may respond to targeted inhibitors.

Protein-Protein Interactions: Emerging Oncotargets in the RAS-ERK Pathway

Given the implication of aberrant RAS-extracellular signal-regulated kinase (ERK) signaling in the development of a large number of tumor types, this route is under intense scrutiny to identify new anticancer drugs. Most avenues in that direction have been primarily focused on the inhibition of the catalytic activity of the kinases that participate in this pathway. Although promising, the efficacy of these therapies is short lived due to undesired toxicity and/or drug resistance problems. As an alternative path, new efforts are now being devoted to the targeting of protein-protein interactions (PPIs) involved in the flow of RAS-ERK signals. Many of these efforts have shown promising results in preclinical models. In this review, we summarize recent progress made in this area.

Immunotherapy Resistance by Inflammation-Induced Dedifferentiation

A promising arsenal of targeted and immunotherapy treatments for metastatic melanoma has emerged over the last decade. With these therapies, we now face new mechanisms of tumor-acquired resistance. We report here a patient whose metastatic melanoma underwent dedifferentiation as a resistance mechanism to adoptive T-cell transfer therapy (ACT) to the MART1 antigen, a phenomenon that had been observed only in mouse studies to date. After an initial period of tumor regression, the patient presented in relapse with tumors lacking melanocytic antigens (MART1, gp100) and expressing an inflammation-induced neural crest marker (NGFR). We demonstrate using human melanoma cell lines that this resistance phenotype can be induced in vitro by treatment with MART1 T cell receptor-expressing T cells or with TNFα, and that the phenotype is reversible with withdrawal of inflammatory stimuli. This supports the hypothesis that acquired resistance to cancer immunotherapy can be mediated by inflammation-induced cancer dedifferentiation.Significance: We report a patient whose metastatic melanoma underwent inflammation-induced dedifferentiation as a resistance mechanism to ACT to the MART1 antigen. Our results suggest that future melanoma ACT protocols may benefit from the simultaneous targeting of multiple tumor antigens, modulating the inflammatory response, and inhibition of inflammatory dedifferentiation-inducing signals. Cancer Discov; 8(8); 935-43. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 899.

ERK Mutations and Amplification Confer Resistance to ERK-Inhibitor Therapy

Purpose: MAPK pathway inhibitors targeting BRAF and MEK have shown clinical efficacy in patients with RAF- and/or RAS-mutated tumors. However, acquired resistance to these agents has been an impediment to improved long-term survival in the clinic. In such cases, targeting ERK downstream of BRAF/MEK has been proposed as a potential strategy for overcoming acquired resistance. Preclinical studies suggest that ERK inhibitors are effective at inhibiting BRAF/RAS-mutated tumor growth and overcome BRAF or/and MEK inhibitor resistance. However, as observed with other MAPK pathway inhibitors, treatment with ERK inhibitors is likely to cause resistance in the clinic. Here, we aimed to model the mechanism of resistance to ERK inhibitors.Experimental Design: We tested five structurally different ATP-competitive ERK inhibitors representing three different scaffolds on BRAF/RAS-mutant cancer cell lines of different tissue types to generate resistant lines. We have used in vitro modeling, structural biology, and genomic analysis to understand the development of resistance to ERK inhibitors and the mechanisms leading to it.Results: We have identified mutations in ERK1/2, amplification and overexpression of ERK2, and overexpression of EGFR/ERBB2 as mechanisms of acquired resistance. Structural analysis of ERK showed that specific compounds that induced on-target ERK mutations were impaired in their ability to bind mutant ERK. We show that in addition to MEK inhibitors, ERBB receptor and PI3K/mTOR pathway inhibitors are effective in overcoming ERK-inhibitor resistance.Conclusions: These findings suggest that combination therapy with MEK or ERBB receptor or PI3K/mTOR and ERK inhibitors may be an effective strategy for managing the emergence of resistance in the clinic. Clin Cancer Res; 24(16); 4044-55. ©2018 AACR.

BRAF in non-small cell lung cancer (NSCLC): Pickaxing another brick in the wall

Molecular characterization of non-small cell lung cancer (NSCLC) marked an historical turning point for the treatment of lung tumors harboring kinase alterations suitable for specific targeted drugs inhibition, translating into major clinical improvements. Besides EGFR, ALK and ROS1, BRAF represents a novel therapeutic target for the treatment of advanced NSCLC. BRAF mutations, found in 1.5-3.5% of NSCLC, are responsible of the constitutive activation of mitogen activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway. Clinical trials evaluating the efficacy of the BRAF inhibitor dabrafenib in combination with the downstream MEK inhibitor trametinib in metastatic BRAF^V600E-mutated NSCLC guaranteed FDA and EMA rapid approval of the combination regimen in this clinical setting. In line with the striking results observed in metastatic melanoma harboring the same molecular alteration, BRAF and MEK inhibition should be considered a new standard of care in this molecular subtype of NSCLC. In the present review, we propose an overview of the available evidence about BRAF in NSCLC mutations (V600E and non-V600E), from biological significance to emerging clinical implications of BRAF mutations detection. Focusing on the current strategies to act against the mutated kinase, we moreover approach additional strategies to overcome treatment resistance.