Inhibition Of MAPK Pathway Research Articles

Abstract 5902: Targeting MAPK-driven tumors via inhibition of MAP2K4

Abstract MAPK pathway activation is a feature of multiple tumor types. Drugging KRAS and BRAF, the two main oncogenic drivers in the MAPK pathway, has proven successful in the clinic. Inhibition of the downstream effectors, MEK and ERK, can also induce tumor regression. Despite this, many tumors are intrinsically resistant to MAPK pathway inhibitors, or acquire resistance under selective pressure to drug treatment. This creates a need for combination treatments to improve clinical responses. A synthetic lethal (SL) interaction between inhibition of the MAPK pathway and blockade of JNK-JUN signaling has recently been described1. Specifically, data from yeast genetics and CRISPR knockout experiments in human cells have identified MAP2K4 as a potential therapeutic target that could be combined with MAPK inhibitors. To date, however, no potent MAP2K4 inhibitors with in vitro and cellular selectivity against key anti-targets have been reported. Here, we describe the development of potent covalent inhibitors of MAP2K4 kinase activity. Biochemical and cell-based assays show that the compound(s) are selective for MAP2K4 versus anti-targets including MAP2K7 and ERK kinases. The combination of MAP2K4 and MEK/ERK inhibitors was effective in cell lines driven by MAPK signaling. These data provide the rationale for further development of MAP2K4 inhibitors to advance our understanding of this novel drug combination.

Abstract 7268: The SOS1 inhibitor MRTX0902 demonstrates activity across cancer models with mutations in proximal components of the RAS-MAPK pathway

Abstract Genetic alterations in the RAS-MAPK pathway are one of the most frequent causes of human cancers. While targeted therapies are approved for patients harboring mutations in KRAS G12C in advanced or metastatic non-small cell lung cancer, there remains a need for an effective therapy for cancers characterized by additional RAS-MAPK pathway mutations across cancer types. Previous studies have shown that genetic or pharmacological inhibition of Son of Sevenless homolog 1 (SOS1) demonstrates antiproliferative activity in cancer cells addicted to KRAS signaling, including cell lines with oncogenic mutations in KRAS, SOS1, PTPN11, or EGFR or a loss-of-function mutation in NF1. These genetic alterations each function to increase SOS1-mediated GTP-loading of KRAS and increase signaling flux through the MAPK pathway. Inhibition of SOS1 by MRTX0902 is anticipated to shift the tumor cell equilibrium of KRAS towards the inactive GDP-bound KRAS, leading to MAPK pathway inhibition. MRTX0902 is a selective inhibitor of SOS1 under evaluation in clinical trials for the treatment of advanced, unresectable, or metastatic cancers with mutations in the KRAS-MAPK pathway. In the present studies, we have shown that MRTX0902 demonstrates single-agent anti-proliferative activity and modulates ERK1/2 phosphorylation (pERK) across a panel of human tumor cell lines harboring oncogenic mutations in SOS1, PTPN11, BRAF (class III) and NF1. Furthermore, oral administration of MRTX0902 as a monotherapy in preclinical human tumor cell-derived xenograft models harboring these oncogenic mutations results in significant tumor growth inhibition. Additionally, combination with the RAF/MEK clamp avutometinib demonstrated greater antitumor activity versus either monotherapy treatment. These data support the clinical utility of MRTX0902 as a single agent or combination partner of avutometinib for the treatment of human cancers harboring oncogenic mutations implicated in dysregulation of RAS-dependent signaling including SOS1, PTPN11, NF1, and BRAF (class III). Citation Format: Niranjan Sudhakar, Larry Yan, Fadia Qiryaqos, Jade Laguer, David Briere, Allan Hebbert, Andrew Calinisan, Silvia Coma, Jonathan Pachter, James G. Christensen, Peter Olson, Shilpi Khare. The SOS1 inhibitor MRTX0902 demonstrates activity across cancer models with mutations in proximal components of the RAS-MAPK pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7268.

Clinical, radiological and molecular responses to combination chemotherapy with MAPK pathway inhibition in relapsed and refractory Langerhans cell histiocytosis.

Optimal therapeutic approaches for advanced Langerhans cell histiocytosis (LCH) are not known. We assessed the safety and efficacy of combined chemotherapy with MAPK pathway inhibition in 10 patients with refractory systemic disease and/or LCH-associated neurodegeneration. Overall response rate was 9/10 (90%) for the entire cohort: 5/5 (100%) for patients with systemic disease and 6/7 (86%) for patients with central nervous system disease. BRAFV600E+ peripheral blood fraction decreased in 5/6 (83%). Toxicities included fever, skin rash, myalgias, neuropathy, cytopenias and hypocalcaemia. Prospective trials are required to optimize combination strategies, determine potential to achieve cure and compare outcomes to chemotherapy or MAPK inhibitor monotherapy.

Paeonol interferes with lupus nephritis by regulating M1/M2 polarization of macrophages

Systemic lupus erythematosus (SLE) is a complex autoimmune disease of unknown etiology. It is marked by the production of pathogenic autoantibodies and the deposition of immune complexes. Lupus nephritis (LN) is a prevalent and challenging clinical complications of SLE. Cortex Moutan contains paeonol as its main effective component. In this study, using the animal model of SLE induced by R848, it was found that paeonol could alleviate the lupus-like symptoms of lupus mouse model induced by R848 activating TLR7, reduce the mortality and ameliorate the renal damage of mice. In order to explore the mechanism of paeonol on lupus nephritis, we studied the effect of paeonol on the polarization of Raw264.7 macrophages in vitro. The experimental results show that paeonol can inhibit the polarization of macrophages to M1 and promote their polarization to M2, which may be related to the inhibition of MAPK and NF-κB signaling pathways. Our research provides a new insight into paeonol in the treatment of lupus nephritis, which is of great importance for the treatment of systemic lupus erythematosus and its complications.

Deoxycholic acid inhibits ASFV replication by inhibiting MAPK signaling pathway

African swine fever (ASF) is an acute, febrile, highly contagious infection of pigs caused by the African swine fever virus (ASFV). The purpose of this study is to understand the molecular mechanism of ASFV infection and evaluate the effect of DCA on MAPK pathway, so as to provide scientific basis for the development of new antiviral drugs. The transcriptome analysis found that ASFV infection up-regulated the IL-17 and MAPK signaling pathways to facilitate viral replication. Metabolome analysis showed that DCA levels were up-regulated after ASFV infection, and that exogenous DCA could inhibit activation of the MAPK pathway by ASFV infection and thus inhibit viral replication. Dual-luciferase reporter assays were used to screen the genes of ASFV and revealed that I73R could significantly up-regulate the transcription level of AP-1 transcription factor in the MAPK pathway. Confocal microscopy demonstrated that I73R could promote AP-1 entry into the nucleus, and that DCA could inhibit the I73R-mediated nuclear entry of AP-1, inhibiting MAPK pathway, and I73R interacts with AP-1. These results indicated that DCA can inhibit ASFV-mediated activation of the MAPK pathway, thus inhibiting ASFV replication. This study provides a theoretical basis for research on ASF pathogenesis and for antiviral drug development.

Phase I/II Study of Combined BCL-xL and MEK Inhibition with Navitoclax and Trametinib in KRAS or NRAS Mutant Advanced Solid Tumors.

MEK inhibitors (MEKi) lack monotherapy efficacy in most RAS-mutant cancers. BCL-xL is an anti-apoptotic protein identified by a synthetic lethal shRNA screen as a key suppressor of apoptotic response to MEKi. We conducted a dose escalation study (NCT02079740) of the BCL-xL inhibitor navitoclax and MEKi trametinib in patients with RAS-mutant tumors with expansion cohorts for: pancreatic, gynecologic (GYN), non-small cell lung cancer (NSCLC), and other cancers harboring KRAS/NRAS mutations. Paired pretreatment and day 15 tumor biopsies and serial cell-free (cf)DNA were analyzed. A total of 91 patients initiated treatment, with 38 in dose escalation. Fifty-eight percent had ≥3 prior therapies. A total of 15 patients (17%) had colorectal cancer, 19 (11%) pancreatic, 15 (17%) NSCLC, and 32 (35%) GYN cancers. The recommended phase II dose (RP2D) was established as trametinib 2 mg daily days 1 to 14 and navitoclax 250 mg daily days 1 to 28 of each cycle. Most common adverse events included diarrhea, thrombocytopenia, increased AST/ALT, and acneiform rash. At RP2D, 8 of 49 (16%) evaluable patients achieved partial response (PR). Disease-specific differences in efficacy were noted. In patients with GYN at the RP2D, 7 of 21 (33%) achieved a PR and median duration of response 8.2 months. No PRs occurred in patients with colorectal cancer, NSCLC, or pancreatic cancer. MAPK pathway inhibition was observed in on-treatment tumor biopsies. Reductions in KRAS/NRAS mutation levels in cfDNA correlated with clinical benefit. Navitoclax in combination with trametinib was tolerable. Durable clinical responses were observed in patients with RAS-mutant GYN cancers, warranting further evaluation in this population.

The effects of restraint stress on ceramide metabolism disorders in the rat liver: the role of CerS6 in hepatocyte injury

BackgroundStress is implicated in various pathological conditions leading to liver injury. Existing evidence suggests that excessive stress can induce mitochondrial damage in hepatocytes, yet the underlying mechanism remains unclear. Ceramide synthase 6 (CerS6)-derived C16:0 ceramide is recognised as a lipotoxic substance capable of causing mitochondrial damage. However, the role of CerS6 in stress has received insufficient attention. This study aimed to explore the involvement of CerS6 in stress-induced hepatic damage and its associated mechanisms.MethodsThe rat restraint stress model and a corticosterone (CORT)-induced hepatocyte stress model were employed for in vivo and in vitro experimental analyses, respectively. Changes in mitochondrial damage and ceramide metabolism in hepatocytes induced by stress were evaluated. The impact of CORT on mitochondrial damage and ceramide metabolism in hepatocytes was assessed following CerS6 knockdown. Mitochondria were isolated using a commercial kit, and ceramides in liver tissue and hepatocytes were detected by LC–MS/MS.ResultsIn comparison to the control group, rats subjected to one week of restraint exhibited elevated serum CORT levels. The liver displayed significant signs of mitochondrial damage, accompanied by increased CerS6 and mitochondrial C16:0 ceramide, along with activation of the AMPK/p38 MAPK pathway. In vitro studies demonstrated that CORT treatment of hepatocytes resulted in mitochondrial damage, concomitant with elevated CerS6 and mitochondrial C16:0 ceramide. Furthermore, CORT induced sequential phosphorylation of AMPK and p38 MAPK proteins, and inhibition of the p38 MAPK pathway using SB203580 mitigated the CORT-induced elevation in CerS6 protein. Knocking down CerS6 in hepatocytes inhibited both the increase in C16:0 ceramide and the release of mitochondrial cytochrome c induced by CORT.ConclusionsCerS6-associated C16:0 ceramide plays a mediating role in stress-induced mitochondrial damage in hepatocytes. The molecular mechanism is linked to CORT-induced activation of the AMPK/p38 MAPK pathway, leading to upregulated CerS6.

Restoring Treg/Th17 cell balance in ulcerative colitis through HRas silencing and MAPK pathway inhibition

This study investigates HRas-dependent mechanisms in the disruption of regulatory T (Treg) cells and T helper 17 (Th17) cells balance in ulcerative colitis (UC). Comprehensive RNA sequencing and bioinformatics analyses revealed elevated HRas and MAPK pathway-related protein expression in UC samples. Using a murine UC model induced by dextran sulfate sodium (DSS), HRas silencing was found to promote Treg cell differentiation and suppress Th17 cell production, effectively restoring balance. Inactivation of the MAPK pathway played a pivotal role in this rebalancing effect. In vivo experiments further confirmed that HRas silencing mitigated colon tissue damage in DSS-induced mice, emphasizing its potential as a therapeutic strategy for UC.

4-Hydroxysesamin, a Modified Natural Compound, Attenuates Neuronal Apoptosis After Ischemic Stroke via Inhibiting MAPK Pathway.

The 4-hydroxysesamin (4-HS, a di-tetrahydrofuran lignin) is a modified sesamin that was prepared in the laboratory. This preclinical study was designed to preliminarily investigate the neuroprotective properties of 4-HS. In vitro, neuronal injury and inflammation were simulated by oxygen-glucose deprivation and lipopolysaccharide (LPS) exposure in mouse hippocampal neuronal HT22 cell line, and treated with 4-HS and/or metformin (MET, MAPK pathway activator for exploring mechanism). CCK-8, flow cytometry, and enzyme-linked immunosorbent assay were performed to evaluate cell viability, apoptosis, and inflammation. Apoptosis- and pathway-related proteins were detected by Western blotting. Middle cerebral artery occlusion (MCAO) was constructed as a stroke model and treated with 4-HS for in vivo confirmation. Histological staining was used for in vivo evaluation of 4-HS properties. The 4-HS showed similar anti-inflammatory activity to sesamin but did not affect the cell viability of HT22 cells. In vitro, 4-HS improved the cell viability, ameliorated neuronal apoptosis, along with the reversion of apoptotic proteins (Bax, cleaved-caspase 3/9, Bcl-2) expression and inflammatory cytokines (IL-6, TNF-α, IL-10) in LPS-treated HT22 cells. The 4-HS suppressed the phosphorylation of ERK, JNK, and p38 but the addition of MET reversed 4-HS-induced changes of phenotype and protein expression in LPS-treated cells. In vivo, 4-HS showed apparent improvement in cerebral infarction, brain tissue morphology, neuronal architecture, apoptosis, and inflammation of MCAO mice, and also showed inhibiting effects on the phosphorylation of ERK, JNK, and p38, confirming in vivo results. In this first pre-clinical study on 4-HS, we preliminarily demonstrated the neuroprotective properties of 4-HS both in cell and animal models, and proposed that the underlying mechanism might be associated with the MAPK pathway.

MiR-290 Family Maintains Pluripotency and Self-Renewal by Regulating MAPK Signaling Pathway in Intermediate Pluripotent Stem Cells.

Mouse embryonic stem cells (ESCs) and epiblast stem cells (EpiSCs) are derived from pre- and post-implantation embryos, representing the initial "naïve" and final "primed" states of pluripotency, respectively. In this study, novel reprogrammed pluripotent stem cells (rPSCs) were induced from mouse EpiSCs using a chemically defined medium containing mouse LIF, BMP4, CHIR99021, XAV939, and SB203580. The rPSCs exhibited domed clones and expressed key pluripotency genes, with both X chromosomes active in female cells. Furthermore, rPSCs differentiated into cells of all three germ layers in vivo through teratoma formation. Regarding epigenetic modifications, the DNA methylation of Oct4, Sox2, and Nanog promoter regions and the mRNA levels of Dnmt3a, Dnmt3b, and Dnmt1 were reduced in rPSCs compared with EpiSCs. However, the miR-290 family was significantly upregulated in rPSCs. After removing SB203580, an inhibitor of the p38 MAPK pathway, the cell colonies changed from domed to flat, with a significant decrease in the expression of pluripotency genes and the miR-290 family. Conversely, overexpression of pri-miR-290 reversed these changes. In addition, Map2k6 was identified as a direct target gene of miR-291b-3p, indicating that the miR-290 family maintains pluripotency and self-renewal in rPSCs by regulating the MAPK signaling pathway.

TREM2 improves microglia function and synaptic development in autism spectrum disorders by regulating P38 MAPK signaling pathway

BackgroundAutism spectrum disorder (ASD) encompasses a diverse range of neurodevelopmental disorders, but the precise underlying pathogenesis remains elusive. This study aim to explore the potential mechanism of TREM2 in regulating microglia function in ASD.Materials and methodsThe offspring rat model of ASD was established through prenatal exposure to valproic acid (VPA), and the behavioral symptoms of the ASD model were observed. On postnatal day (PND) 7 and PND 28, the effects of prenatally exposure to VPA on synaptic development and microglia phenotype of offspring rats were observed. Primary microglia were cultured in vitro. Lentivirus and adenovirus were utilized to interfere with TREM2 and overexpress TREM2.ResultsPrenatally VPA exposure induced offspring rats to show typical ASD core symptoms, which led to abnormal expression of synapse-related proteins in the prefrontal cortex of offspring rats, changed the phenotype of microglia in offspring rats, promoted the polarization of microglia to pro-inflammatory type, and increased inflammatory response. The experimental results in vitro showed that overexpression of TREM2 could increase the expression of Gephyrin, decrease the content of CD86 protein and increase the content of CD206 protein. In addition, after the expression of TREM2 was interfered, the content of p-P38 MAPK protein increased and the content of p-ELK-1 protein decreased.ConclusionThe protective influence of TREM2 on the VPA-induced ASD model is attributed to its inhibition of the P38 MAPK pathway, this protective effect may be achieved by promoting the polarization of microglia to anti-inflammatory phenotype and improving the neuronal synaptic development.

JianPiYiShen formula prevents cisplatin-induced acute kidney injury in mice by improving necroptosis through MAPK pathway

BackgroundAcute kidney injury (AKI), characterized by necroptosis and activation of MAPK pathway, causes sudden declines in renal function. To date, efficacious treatments are lacking. JianPiYiShen Formula (JPYSF) has a protective effect on the kidneys. The aim of this study is to explore the mechanism of JPYSF in cisplatin-induced AKI.MethodsMale C57/BL6J mice were divided into control group, cisplatin group and cisplatin + JPYSF group. Before establishing the model, the cisplatin + JPYSF group was administered JPYSF (18.35 g/kg/day) by gavage for 5 consecutive days. A single intraperitoneal injection of cisplatin (20 mg/kg) was used to establish AKI model. Measurement of renal function and H&E staining were performed to assess renal damage. WB, PCR, TUNEL staining and immunohistochemistry were used to detect related indicators of mitochondrial function, oxidative stress, necroptosis, inflammation and MAPK pathway. And one-way analysis of variance was used to compare group differences.ResultsCompared with the cisplatin group, JPYSF can attenuate AKI, reflected by the decrease in Scr and BUN levels, the improvement of renal tubular injury, and the downregulation of NGAL and KIM1. Cisplatin can induce mitochondrial dysfunction and oxidative stress, triggering necroptosis. In this study, JPYSF improved mitochondrial dysfunction to enhance oxidative stress, as manifested by upregulation of OPA1, PGC-1α, SOD and CAT, and downregulation of DRP1 and MFF. Then JPYSF showed a significant protective effect in necroptosis, as embodied by reduced number of TUNEL-positive cells, decreased the gene expression of RIPK3 and MLKL, as well as downregulation the proteins expression of P-RIPK1, P-RIPK3, and P-MLKL. Moreover, necroptosis can aggravate inflammation. JPYSF ameliorated inflammation by improving inflammatory and anti-inflammatory indexes, including downregulation of TNF-α, IL-6, MCP-1 and LY6G, and upregulation of IL-10. In addition, JPYSF also inhibited MAPK pathway to improve necroptosis by decreasing the expression of P-JNK and P-ERK.ConclusionOur data showed that JPYSF prevents cisplatin-induced AKI by improving necroptosis through MAPK pathway, which is related to the improvement of mitochondrial dysfunction, oxidative stress, and inflammation.

Discovery of an indolium-based, turn-on fluorescent ligand that represses the Neuroblastoma RAS expression by targeting the 5′-UTR G-quadruplex structure

The RNA G-quadruplex (RG4) at 5′-UTRs of Neuroblastoma RAS (NRAS) mRNA is considered to modulate the NRAS translation, providing new opportunities for interfering with NRAS hyperactivation. Therefore, targeting this RG4 structure by small molecules seems to be an alternative strategy for treating cancers with NRAS mutations or overexpression. In this study, we have developed a promising fluorescent ligand, which exhibited an extremely high fluorescence quantum yield as well as a relatively strong binding affinity with NRAS RG4. Then, this ligand was demonstrated to be able to illuminate the cellular RG4 structures. Furthermore, this ligand remarkably suppressed the translation level of NRAS mRNA, leading to the inhibition of downstream MAPK and AKT signaling pathways in NRAS-amplified MCF-7 cells. Increase of cell apoptosis as well as decrease of cell growth and migration were also detected in tumor cells treated with the ligand. Therefore, a novel and promising fluorescent ligand targeting NRAS RG4 was presented in this study, providing a potential strategy for the "undruggable" protein target.

Protective effect of isoquercitrin on UVB-induced injury in HaCaT cells and mice skin through anti-inflammatory, antioxidant, and regulation of MAPK and JAK2-STAT3 pathways.

Natural products are favored in the study of skin photodamage protection recently. Isoquercetin, namely 3-O-glucoside of quercetin, can be isolated from various plant species. In present research, the protective effect of isoquercitrin on UVB-induced injury in cells and mice skin were investigated. Our study reveals that 400 μM of isoquercitrin exhibits the best viability on UVB-irradiated HaCaT cells, and beneficial effects against oxidative stress UVB-induced in skin tissue by decreasing the levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and simultaneously enhancing the activity of superoxide dismutase (SOD). Additionally, isoquercitrin was identified as an anti-inflammatory agent by reducing the level of COX-2 by Western blot analysis, and inflammatory cytokines such as IL-6, IL-1β, and TNF-α by ELISA, and UVB-induced epidermal thickening evidenced by H&E staining. It also effectively prevented UVB-induced collagen fibers from degradation identified by Masson staining. Isoquercitrin significantly inhibited MAPK pathway by downregulating the levels of AP-1, MMP-1, MMP-3, phospho-p38, phospho-JNK, phospho-ERK, cleaved caspase-9, cleaved caspase-3, and JAK2-STAT3 pathway by western blot analysis. In conclusion, isoquercitrin pretreatment protected mice skin from UVB irradiation-induced injury effectively, and the underlying mechanism may involve MAPK and JAK2-STAT3 signaling pathways.

LOGGIC/FIREFLY-2: a phase 3, randomized trial of tovorafenib vs. chemotherapy in pediatric and young adult patients with newly diagnosed low-grade glioma harboring an activating RAF alteration

BackgroundPediatric low-grade glioma (pLGG) is essentially a single pathway disease, with most tumors driven by genomic alterations affecting the mitogen-activated protein kinase/ERK (MAPK) pathway, predominantly KIAA1549::BRAF fusions and BRAF V600E mutations. This makes pLGG an ideal candidate for MAPK pathway-targeted treatments. The type I BRAF inhibitor, dabrafenib, in combination with the MEK inhibitor, trametinib, has been approved by the United States Food and Drug Administration for the systemic treatment of BRAF V600E-mutated pLGG. However, this combination is not approved for the treatment of patients with tumors harboring BRAF fusions as type I RAF inhibitors are ineffective in this setting and may paradoxically enhance tumor growth. The type II RAF inhibitor, tovorafenib (formerly DAY101, TAK-580, MLN2480), has shown promising activity and good tolerability in patients with BRAF-altered pLGG in the phase 2 FIREFLY-1 study, with an objective response rate (ORR) per Response Assessment in Neuro-Oncology high-grade glioma (RANO-HGG) criteria of 67%. Tumor response was independent of histologic subtype, BRAF alteration type (fusion vs. mutation), number of prior lines of therapy, and prior MAPK-pathway inhibitor use.MethodsLOGGIC/FIREFLY-2 is a two-arm, randomized, open-label, multicenter, global, phase 3 trial to evaluate the efficacy, safety, and tolerability of tovorafenib monotherapy vs. current standard of care (SoC) chemotherapy in patients < 25 years of age with pLGG harboring an activating RAF alteration who require first-line systemic therapy. Patients are randomized 1:1 to either tovorafenib, administered once weekly at 420 mg/m2 (not to exceed 600 mg), or investigator’s choice of prespecified SoC chemotherapy regimens. The primary objective is to compare ORR between the two treatment arms, as assessed by independent review per RANO-LGG criteria. Secondary objectives include comparisons of progression-free survival, duration of response, safety, neurologic function, and clinical benefit rate.DiscussionThe promising tovorafenib activity data, CNS-penetration properties, strong scientific rationale combined with the manageable tolerability and safety profile seen in patients with pLGG led to the SIOPe-BTG-LGG working group to nominate tovorafenib for comparison with SoC chemotherapy in this first-line phase 3 trial. The efficacy, safety, and functional response data generated from the trial may define a new SoC treatment for newly diagnosed pLGG.Trial registrationClinicalTrials.gov: NCT05566795. Registered on October 4, 2022.

A phase 1 study of triple-targeted therapy with BRAF, MEK, and AKT inhibitors for patients with BRAF-mutated cancers.

Aberrant PI3K/AKT signaling in BRAF-mutant cancers contributes to resistance to BRAF inhibitors. The authors examined dual MAPK and PI3K pathway inhibition in patients who had BRAF-mutated solid tumors (ClinicalTrials.gov identifier NCT01902173). Patients with BRAF V600E/V600K-mutant solid tumors received oral dabrafenib at 150mg twice daily with dose escalation of oral uprosertib starting at 50mg daily, or, in the triplet cohorts, with dose escalation of both oral trametinib starting at 1.5mg daily and oral uprosertib starting at 25mg daily. Dose-limiting toxicities (DLTs) were assessed within the first 56days of treatment. Radiographic responses were assessed at 8-week intervals. Twenty-seven patients (22 evaluable) were enrolled in parallel doublet and triplet cohorts. No DLTs were observed in the doublet cohorts (N=7). One patient had a DLT at the maximum administered dose of triplet therapy (dabrafenib 150mg twice daily and trametinib 2mg daily plus uprosertib 75mg daily). Three patients in the doublet cohorts had partial responses (including one who had BRAF inhibitor-resistant melanoma). Two patients in the triplet cohorts had a partial response, and one patient had an unconfirmed partial response. Pharmacokinetic data suggested reduced dabrafenib and dabrafenib metabolite exposure in patients who were also exposed to both trametinib and uprosertib, but not in whose who were exposed to uprosertib without trametinib. Concomitant inhibition of both the MAPK and PI3K-AKT pathways for the treatment of BRAF-mutated cancers was well tolerated, leading to objective responses, but higher level drug-drug interactions affected exposure to dabrafenib and its metabolites.

A phase 1 trial of combined MEK, STAT3 and PD-1 inhibition in metastatic pancreatic ductal adenocarcinoma (PDAC).

TPS713 Background: PDAC is characterized by its innate and acquired resistance to both MAPK pathway inhibition and immune checkpoint (e.g. PD-1/PD-L1) inhibition (ICI) via multiple mechanisms. In preclinical models of PDAC, combined MEK and STAT3 inhibition (MEKi+STAT3i) uncovers stromal plasticity by attenuating cancer-associated fibroblasts (CAF) with IL-6/CXCL1-secretory phenotypes while enriching for Ly6a/CD34-expressing CAF phenotypes with mesenchymal stem cell-like features. This remodeling of CAF heterogeneity is associated with a striking attenuation in and reprogramming of tumor-associated macrophages (TAMs) as well as enhanced trafficking of CD8 T cells, which exhibit a distinct effector and anti-apoptotic transcriptional program. The addition of MEKi+STAT3i to PD-1 blockade overcomes ICI resistance by significantly enhancing the recruitment, degranulating capacity, and functional cytotoxicity of CD8+ T-cells, thereby augmenting antitumor responses and dramatically improving survival in these models. Furthermore, a patient with refractory PDAC treated off-label with this combination achieved a meaningful response. Based on this strong rationale, a phase 1 trial was initiated to test the combination of MEKi+STAT3 and PD1 inhibition in patients with metastatic PDAC. Methods: NCT05440942 is an open-label, prospective, single-institution phase 1 trial testing the safety, preliminary efficacy, and biomarkers of response to the combination of trametinib (MEKi), ruxolitinib (JAK2/STAT3 inhibitor) and retifanlimab (PD-1 inhibitor) in patients with metastatic PDAC. Patients with metastatic PDAC who have had disease progression on at least one line of prior therapy, with good organ function, preserved performance status, and without major intercurrent illness are eligible. Patients must have an accessible lesion for biopsy and must be willing to undergo this research biopsy at baseline and on treatment. Part 1 of the study is a dose-escalation phase with 3 dose levels and a target dose of trametinib 2mg orally daily, ruxolitinib 15mg orally twice daily, and retifanlimab 500mg intravenously every 28 days. The dose escalation is being done using the novel Bayesian keyboard design and 9-15 patients will be treated to get to the potential maximum tolerated dose (MTD). Dose level 1 has been completed without any dose-limiting toxicities seen. Part 2 is an expansion phase which will accrue an additional 20 patients. All patients in part 1 and 2 will have core-needle biopsies pre-treatment and after 4 weeks. Serial blood samples will be collected at baseline and on treatment. Biopsies are being analyzed by multiparameter immune profiling using mass cytometry and bulk RNA sequencing; blood is being analyzed for circulating tumor DNA and immune profiling. These results will be correlated with clinical response to therapy to determine biomarkers of response and resistance. Clinical trial information: NCT05440942 .

Abstract C077: Elucidation and exploitation of critical nutrient scavenging regulation in ERK MAPK inhibited pancreatic cancer

Abstract Alteration of essential metabolic pathways is a major mechanism by which oncogenic KRAS promotes tumor development and growth in pancreatic ductal adenocarcinoma (PDAC). KRAS-driven PDAC is dependent on nutrient scavenging pathways, including macropinocytosis and autophagy to fuel the high metabolic demand of rapid proliferation. Thus, these metabolic processes are attractive targets for the development of treatments for PDAC. KRAS loss results in downregulation of macropinocytosis in PDAC. Additionally, our lab demonstrated that KRAS loss or inhibition of ERK MAPK signaling decreased glucose consumption and glycolysis but increased autophagy, thereby enhancing dependency on autophagy for survival and growth. Accordingly, dual ERK MAPK and autophagy inhibition (via chloroquine) synergistically enhanced anti-tumor efficacy in PDAC. Early clinical data has demonstrated that resistance to this treatment arises over time through unknown mechanisms. Our preliminary data indicates that following ERK MAPK inhibition both autophagy induction and macropinocytosis downregulation is transient—with autophagic and macropinocytic activity returning to/surpassing basal levels after prolonged treatment. The underlying mechanistic and signaling crosstalk between autophagy and macropinocytosis remains poorly understood. We hypothesize that there is compensatory regulation between autophagy and macropinocytosis signaling following ERK MAPK inhibition. We propose that prolonged activation of autophagy upregulates macropinocytosis over time, consequently abrogating dependency on autophagy and therefore reducing sensitivity to autophagy inhibition. We demonstrate an inverse temporal relationship between autophagic flux and macropinocytosis following genetic loss of KRAS or pharmacological inhibition of the KRAS-ERK MAPK pathway. Furthermore, we show that chloroquine, which is commonly thought of as a lysosomotropic drug, does not prevent degradation of proteins engulfed via macropinocytosis. Together our data suggest that upregulation of macropinocytosis may mediate resistance to the combination of ERK MAPK inhibition and chloroquine. Additionally, we present the unexpected observation that prolonged pharmacological inhibition of the ERK MAPK pathway results in the upregulation of macropinocytosis. Furthermore, we demonstrate that this upregulation of macropinocytosis is accompanied by increased albumin uptake and sensitivity to albumin-bound paclitaxel (nab-paclitaxel). Given the dependence of PDAC on macropinocytic uptake for tumorigenic growth, as well as the potential to exploit macropinocytosis for drug-delivery, it is imperative to understand how ERK MAPK inhibitors regulate macropinocytosis. A better understanding of the regulation underlying these essential metabolic pathways will better inform future ERK MAPK inhibitor combinations. Citation Format: Ryan Robb, Kirsten L. Bryant. Elucidation and exploitation of critical nutrient scavenging regulation in ERK MAPK inhibited pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C077.

Pancreatic cancer acquires resistance to MAPK pathway inhibition by clonal expansion and adaptive DNA hypermethylation

BackgroundPancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with poor prognosis. It is marked by extraordinary resistance to conventional therapies including chemotherapy and radiation, as well as to essentially all targeted therapies evaluated so far. More than 90% of PDAC cases harbor an activating KRAS mutation. As the most common KRAS variants in PDAC remain undruggable so far, it seemed promising to inhibit a downstream target in the MAPK pathway such as MEK1/2, but up to now preclinical and clinical evaluation of MEK inhibitors (MEKi) failed due to inherent and acquired resistance mechanisms. To gain insights into molecular changes during the formation of resistance to oncogenic MAPK pathway inhibition, we utilized short-term passaged primary tumor cells from ten PDACs of genetically engineered mice. We followed gain and loss of resistance upon MEKi exposure and withdrawal by longitudinal integrative analysis of whole genome sequencing, whole genome bisulfite sequencing, RNA-sequencing and mass spectrometry data.ResultsWe found that resistant cell populations under increasing MEKi treatment evolved by the expansion of a single clone but were not a direct consequence of known resistance-conferring mutations. Rather, resistant cells showed adaptive DNA hypermethylation of 209 and hypomethylation of 8 genomic sites, most of which overlap with regulatory elements known to be active in murine PDAC cells. Both DNA methylation changes and MEKi resistance were transient and reversible upon drug withdrawal. Furthermore, MEKi resistance could be reversed by DNA methyltransferase inhibition with remarkable sensitivity exclusively in the resistant cells.ConclusionOverall, the concept of acquired therapy resistance as a result of the expansion of a single cell clone with epigenetic plasticity sheds light on genetic, epigenetic and phenotypic patterns during evolvement of treatment resistance in a tumor with high adaptive capabilities and provides potential for reversion through epigenetic targeting.

Abstract B089: Oncogenic signaling and responses to treatment in RAS mutant cancers are mutation-specific

Abstract The KRAS, NRAS, and HRAS genes are frequently mutated in cancer, often at hotspots altering codons 12, 13, and 61. Yet how different RAS isoforms and mutations precisely regulate oncogenic signaling is still largely unknown. For example, the role of mutant RAS in driving overactivation of ERK signaling in cancer has long been elucidated, but its involvement in the oncogenic activation of PI3K is still controversial, and different studies have reported conflicting findings regarding the requirement of RAS for physiological and oncogenic PI3K signaling. One of the reasons for this lack of understanding has been the inability to directly target RAS, which has historically been circumvented through genomic perturbation and murine models. However, these approaches are limited because it is not possible to distinguish between the direct effects of RAS on PI3K and compensatory events that occur as an adaptation to the oncogene. With the discovery of RAS inhibitors, we can now directly interrogate the biological effects of RAS isoforms and hotspot mutations in cancer cells with improved time resolution. Here, we use RM-042, a first-in-class broad-spectrum RAS·GTP inhibitor (RASMULTI(ON)), to characterize the features and therapeutic vulnerabilities of mutant RAS signaling in human cancers. Through a detailed biochemical analysis of the signaling response to RAS and MEK inhibition, we reveal that RAS-mediated oncogenic signaling is largely independent of the mutant RAS isoform, rather depending on the mutant codon. Specifically, RASQ61X is exquisitely sensitive to MAPK pathway inhibition, confers near-complete independence of upstream regulation, and is impaired in its signaling to PI3K/Akt/mTOR. Conversely, RASG12X enables oncogenic signaling to both MAPK and PI3K/Akt/mTOR by amplifying upstream input from receptor tyrosine kinases (RTKs). Simultaneous RAS and RTK inhibition selectively impairs the growth of RASG12X-mutant tumors, irrespective of RAS isoform and tumor type, and we investigate the molecular mechanisms behind this synergistic effect. Additionally, we have generated a genetically modified mouse model (GEMM) harboring liver tumors induced by RASG12D or RASQ61R. In cell lines derived from these respective models, RASG12D but not RASQ61R activates PI3K upon growth-factor stimulation. Furthermore, in this system, RASQ61R is less oncogenic than RASG12D, an effect that can be rescued by the concurrent deletion of PTEN. These findings provide mechanistic insights into how mutant RAS interacts with upstream and downstream partners to maximize oncogenic signaling. Furthermore, our results shed light on the selective pressure driving the emergence of RASQ61X mutations as a mechanism of resistance against RTK inhibition: we show that colorectal cancer cells that acquire RASQ61X mutations to overcome EGFR inhibition become more independent of upstream signaling than those that acquire RASG12X. Citation Format: Michelangelo Marasco, Dinesh Kumar, Riccardo Mezzadra, Wei Luan, Ilinca Aricescu, Rona Yaeger, Vladimir Markov, Yu Zhu, Elisa de Stanchina, Scott Lowe, Sandra Misale, Neal Rosen. Oncogenic signaling and responses to treatment in RAS mutant cancers are mutation-specific [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B089.