MAPK Activation Research Articles

Impaired Glycosylation of Gastric Mucins Drives Gastric Tumorigenesis and Serves as a Novel Therapeutic Target

BackgroundGastric cancer is often accompanied by a loss of MUC6, but its pathogenic role in gastric carcinogenesis remains unclear. MethodMuc6 knockout (Muc6-/-) mice and Muc6-dsRED mice were newly generated. Tff1Cre, Golph3-/-, R26-Golgi-mCherry, Hes1flox/flox, Cosmcflox/flox, A4gnt-/- mice were also used. Histology, DNAs and RNAs, proteins, and sugar chains were analyzed by whole exon DNA sequence, RNA sequence, immunohistochemistry, lectin-binding assays, and LC-MS analysis. Gastric organoids and cell lines were used for in vitro assays and xenograft experiments. ResultDeletion of Muc6 in mice spontaneously causes pan-gastritis and invasive gastric cancers. Muc6-deficient tumor growth was dependent on MAPK activation, mediated by Golgi stress-induced upregulation of GOLPH3. Glycomic profiling revealed aberrant expression of mannose-rich N-linked glycans in gastric tumors, detected with Banana lectin in association with lack of MUC6 expression. We identified a precursor of clusterin as a binding partner of mannose glycans. MAPK activation, Golgi stress responses, aberrant mannose expression are found in a separate Cosmc- and A4gnt-deficient mouse models which lack normal O-glycosylation. Banana lectin-drug conjugates proved an effective treatment for mannose-rich murine and human gastric cancer. ConclusionWe propose that Golgi stress responses and aberrant glycans are important drivers of, and promising new therapeutic targets for gastric cancer.

Abstract LB453: Distinct mechanism of CXCR7 activation in EGFR-mutated NSCLC by chemokines

Abstract Erlotinib and gefitinib, EGFR TKIs, have markedly improved outcomes for NSCLC patients with EGFR mutations. However, resistance eventually develops, with the T790M mutation evident in over 50% of resistant tumors. Other resistance pathways include MET amplification, SCLC transformation, and EMT. Osimertinib, a third-generation EGFR TKI, targets the T790M mutation and is approved as a first-line treatment, reducing the incidence of T790M-related resistance. Nonetheless, non-T790M resistance mechanisms such as mesenchymal transformation are on the rise. The molecular targets or exact mechanisms of EGFR TKI resistance with mesenchymal phenotypes remain elusive. We have discovered that ERK reactivation, commonly found in EGFR TKI-resistant cells with a mesenchymal phenotype, is due to activation of an atypical GPCR, CXC chemokine receptor type 7 (CXCR7). CXCR7 is overexpressed in a cell line, an EGFR TKI-resistant tumor model, and in samples from patients that progressed on EGFR TKIs. Currently, there are no effective CXCR7 inhibitors to evaluate in NSCLC; the mechanisms and ligands for CXCR7 are not fully understood. To evaluate ligand-dependent activation of CXCR7, we generated HEK293 cells and EGFR-mutant NSCLC cells ectopically-expressing CXCR7 and stimulated the cells with CXCL12, a well-documented ligand for CXCR7. Exposures of HEK293 cells with CXCR7 to CXCL12 resulted in the internalization of CXCR7 followed by the activation of the MAPK pathway within 30 minutes of EGFR TKI treatment whereas MAPK activation in EGFR mutant NSCLC cells took 8 hours. MIF activation was also delayed in NSCLC compared to the HEK293 model, requiring the presence of an EGFR TKI. We discovered that CXCR7 co-immunoprecipitated with mutant EGFR in NSCLC cells while CXCR7 did not co-immunoprecipitate when EGFR was inhibited. Furthermore, we discovered additional chemokines including GDF15 that activate the CXCR7-MAPK axis and promote cell migration, a key characteristic of the mesenchymal phenotype in EGFR mutant cells. Taken together, we elucidated a unique mechanism of ligand-induced activation of CXCR7 and downstream MAPK pathway by canonical and putative ligands. This complex mechanism of CXCR7 activation in EGFR mutant NSCLC suggests that preventing the receptor-ligand binding may not be feasible in the context of overcoming EGFR TKI resistance. Citation Format: Laura C. Gunder, Ines Pulido, Jeffrey H. Becker, Malek G. Massad, Takeshi Shimamura. Distinct mechanism of CXCR7 activation in EGFR-mutated NSCLC by chemokines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB453.

Activating SRC/MAPK signaling via 5-HT1A receptor contributes to the effect of vilazodone on improving thrombocytopenia.

Thrombocytopenia caused by long-term radiotherapy and chemotherapy exists in cancer treatment. Previous research demonstrates that 5-Hydroxtrayptamine (5-HT) and its receptors induce the formation of megakaryocytes (MKs) and platelets. However, the relationships between 5-HT1A receptor (5-HTR1A) and MKs is unclear so far. We screened and investigated the mechanism of vilazodone as a 5-HTR1A partial agonist in promoting MK differentiation and evaluated its therapeutic effect in thrombocytopenia. We employed a drug screening model based on machine learning (ML) to screen the megakaryocytopoiesis activity of Vilazodone (VLZ). The effects of VLZ on megakaryocytopoiesis were verified in HEL and Meg-01 cells. Tg (itga2b: eGFP) zebrafish was performed to analyze the alterations in thrombopoiesis. Moreover, we established a thrombocytopenia mice model to investigate how VLZ administration accelerates platelet recovery and function. We carried out network pharmacology, Western blot, and immunofluorescence to demonstrate the potential targets and pathway of VLZ. VLZ has been predicted to have a potential biological action. Meanwhile, VLZ administration promotes MK differentiation and thrombopoiesis in cells and zebrafish models. Progressive experiments showed that VLZ has a potential therapeutic effect on radiation-induced thrombocytopenia in vivo. The network pharmacology and associated mechanism study indicated that SRC and MAPK signaling are both involved in the processes of megakaryopoiesis facilitated by VLZ. Furthermore, the expression of 5-HTR1A during megakaryocyte differentiation is closely related to the activation of SRC and MAPK. Our findings demonstrated that the expression of 5-HTR1A on MK, VLZ could bind to the 5-HTR1A receptor and further regulate the SRC/MAPK signaling pathway to facilitate megakaryocyte differentiation and platelet production, which provides new insights into the alternative therapeutic options for thrombocytopenia.

Activating SRC/MAPK signaling via 5-HT1A receptor contributes to the effect of vilazodone on improving thrombocytopenia

Thrombocytopenia caused by long-term radiotherapy and chemotherapy exists in cancer treatment. Previous research demonstrates that 5-Hydroxtrayptamine (5-HT) and its receptors induce the formation of megakaryocytes (MKs) and platelets. However, the relationships between 5-HT1A receptor (5-HTR1A) and MKs is unclear so far. We screened and investigated the mechanism of vilazodone as a 5-HTR1A partial agonist in promoting MK differentiation and evaluated its therapeutic effect in thrombocytopenia. We employed a drug screening model based on machine learning (ML) to screen the megakaryocytopoiesis activity of Vilazodone (VLZ). The effects of VLZ on megakaryocytopoiesis were verified in HEL and Meg-01 cells. Tg (itga2b: eGFP) zebrafish was performed to analyze the alterations in thrombopoiesis. Moreover, we established a thrombocytopenia mice model to investigate how VLZ administration accelerates platelet recovery and function. We carried out network pharmacology, Western blot, and immunofluorescence to demonstrate the potential targets and pathway of VLZ. VLZ has been predicted to have a potential biological action. Meanwhile, VLZ administration promotes MK differentiation and thrombopoiesis in cells and zebrafish models. Progressive experiments showed that VLZ has a potential therapeutic effect on radiation-induced thrombocytopenia in vivo. The network pharmacology and associated mechanism study indicated that SRC and MAPK signaling are both involved in the processes of megakaryopoiesis facilitated by VLZ. Furthermore, the expression of 5-HTR1A during megakaryocyte differentiation is closely related to the activation of SRC and MAPK. Our findings demonstrated that the expression of 5-HTR1A on MK, VLZ could bind to the 5-HTR1A receptor and further regulate the SRC/MAPK signaling pathway to facilitate megakaryocyte differentiation and platelet production, which provides new insights into the alternative therapeutic options for thrombocytopenia.

The lincRNA JUNI regulates the stress-dependent induction of c-Jun, cellular migration and survival through the modulation of the DUSP14-JNK axis

Cancer cells employ adaptive mechanisms to survive various stressors, including genotoxic drugs. Understanding the factors promoting survival is crucial for developing effective treatments. In this study, we unveil a previously unexplored long non-coding RNA, JUNI (JUN-DT, LINC01135), which is upregulated by genotoxic drugs through the activation of stress-activated MAPKs, JNK, and p38 and consequently exerts positive control over the expression of its adjacent gene product c-Jun, a well-known oncoprotein, which transduces signals to multiple transcriptional outputs. JUNI regulates cellular migration and has a crucial role in conferring cellular resistance to chemotherapeutic drugs or UV radiation. Depletion of JUNI markedly increases the sensitivity of cultured cells and spheroids to chemotherapeutic agents. We identified 57 proteins interacting with JUNI. The activity of one of them the MAPK phosphatase and inhibitor, DUSP14, is counteracted by JUNI, thereby, facilitating efficient JNK phosphorylation and c-Jun induction when cells are exposed to UV radiation. The antagonistic interplay with DUSP14 contributes not only to c-Jun induction but also augments the survival of UV-exposed cells. In summary, we introduce JUNI as a novel stress-inducible regulator of c-Jun, positioning it as a potential target for enhancing the sensitivity of cancer cells to chemotherapy.

Retraction Note to: A New Ni(II)-Containing Coordination Complex Based on Carboxylate and Multinitrogen Co-Ligands: Crystal Structure and Protective Effect on Type 2 Diabetes by Down-Regulating PKC and MAPK Activation

Retraction Note to: A New Ni(II)-Containing Coordination Complex Based on Carboxylate and Multinitrogen Co-Ligands: Crystal Structure and Protective Effect on Type 2 Diabetes by Down-Regulating PKC and MAPK Activation

Pulmonary BRAF-driven Langerhans cell histiocytosis following selpercatinib use in metastatic medullary thyroid cancer.

RET mutations are implicated in 60% of medullary thyroid cancer (MTC) cases. The RET-selective tyrosine kinase inhibitor selpercatinib is associated with unprecedented efficacy compared to previous multi-kinase treatments. Langerhans cell histiocytosis (LCH) is a clonal histiocytic neoplasm usually driven by somatic BRAF mutations, resulting in dysregulated MAPK signalling. We describe a 22-year-old woman with metastatic MTC to regional lymph nodes, lung and liver. Tumour tissue harboured a somatic pathogenic RET variant p.(M918T) and selpercatinib was commenced. She experienced sustained clinical, biochemical and radiological responses. Two years later, she developed rapidly progressive apical lung nodules, prompting biopsy. Histopathology demonstrated LCH with a rare BRAF variant p.(V600_K601>D). The lung nodules improved with inhaled corticosteroids. We hypothesize that selective pressure from RET blockade may have activated a downstream somatic BRAF mutation, resulting in pulmonary LCH. We recommend continued vigilance for neoplasms driven by dysregulated downstream MAPK signalling in patients undergoing selective RET inhibition. Patients with RET-altered MTC can experience rapid disease improvement and sustained disease stability with selective RET blockade (selpercatinib). LCH is a clonal neoplasm driven by MAPK activation, for which the most common mechanism is BRAF mutation. Both MTC and pulmonary LCH are driven by dysregulated MAPK signalling pathway activation. We hypothesise that the RET-specific inhibitor selpercatinib may have caused the activation of dormant LCH secondary to selective pressure and clonal proliferation.

Homocysteine-induced sustained GluN2A NMDA receptor stimulation leads to mitochondrial ROS generation and neurotoxicity

Homocysteine, a sulfur-containing amino acid derived from methionine metabolism, is a known agonist of N-methyl-D-aspartate receptor (NMDAR) and is involved in neurotoxicity. Our previous findings showed that neuronal exposure to elevated homocysteine levels leads to sustained low-level increase in intracellular Ca2+, which is dependent on GluN2A subunit-containing NMDAR (GluN2A-NMDAR) stimulation. These studies further showed a role of ERK MAPK in homocysteine-GluN2A-NMDAR-mediated neuronal death. However, the intracellular mechanisms associated with such sustained GluN2A-NMDAR stimulation and subsequent Ca2+ influx have remained unexplored. Using live-cell imaging with Fluo3-AM and biochemical approaches, we show that homocysteine-GluN2A NMDAR-induced initial Ca2+ influx triggers sequential phosphorylation and subsequent activation of the proline rich tyrosine kinase 2 (Pyk2) and Src family kinases, which inturn phosphorylates GluN2A-Tyr1325 residue of GluN2A-NMDARs to maintain channel activity. The continuity of this cycle of events leads to sustained Ca2+ influx through GluN2A-NMDAR. Our findings also show that lack of activation of the regulatory tyrosine phosphatase STEP, which can limit Pyk2 and Src family kinase activity further contributes to the maintenance of this cycle. Additional studies using live-cell imaging of neurons expressing a redox-sensitive GFP targeted to the mitochondrial matrix show that treatment with homocysteine leads to a progressive increase in mitochondrial reactive oxygen species generation, which is dependent on GluN2A-NMDAR-mediated sustained ERK MAPK activation. This later findingdemonstrates a novel role of GluN2A-NMDAR in homocysteine-induced mitochondrial ROS generation and highlights the role of ERK MAPK as the intermediary signaling pathway between GluN2A-NMDAR stimulation and mitochondrial reactive oxygen species generation.

African swine fever virus A137R protein inhibits NF-κB activation via suppression of MyD88 signaling in PK15 and 3D4/21 cells in vitro

African swine fever (ASF) is an infectious disease with high mortality caused by African swine fever virus (ASFV), which poses a great threat to the global swine industry. ASFV has evolved multiple strategies to evade host antiviral innate immunity by perturbing inflammatory responses and interferon production. However, the molecular mechanisms underlying manipulation of inflammatory responses by ASFV proteins are not fully understood. Here, we report that A137R protein of ASFV is a key suppressor of host inflammatory responses. Ectopic expression of ASFV A137R in HEK293T cells significantly inhibited the activation of IL-8 and NF-κB promoters triggered by Sendai virus (SeV), influenza A virus (IAV), or vesicular stomatitis virus (VSV). Accordingly, forced A137R expression caused a significant decrease in the production of several inflammatory cytokines such as IL-8, IL-6 and TNF-α in the cells infected with SeV or IAV. Similar results were obtained from experiments using A137R overexpressing PK15 and 3D4/21 cells infected with SeV or VSV. Furthermore, we observed that A137R impaired the activation of MAPK and NF-κB signaling pathways, as enhanced expression of A137R significantly decreased the phosphorylation of JNK, p38 and p65 respectively upon viral infection (SeV or IAV) and IL-1β treatment. Mechanistically, we found that A137R interacted with MyD88, and dampened MyD88-mediated activation of MAPK and NF-κB signaling. Together, these findings uncover a critical role of A137R in restraining host inflammatory responses, and improve our understanding of complicated mechanisms whereby ASFV evades innate immunity.

Geraniin Alleviates Inflammation in Caco-2 Cells and Dextran Sulfate Sodium-Induced Colitis Mice by Targeting IL-1β.

IL-1β is an important cytokine implicated in the progression of inflammatory bowel disease (IBD) and intestinal barrier dysfunction. The polyphenolic compound, geraniin, possesses bioactive properties, such as antitumor, antioxidant, anti-inflammatory, antihypertensive, and antiviral activities; however, its IL-1β-targeted anticolitis activity remains unclear. Here, we evaluated the inhibitory effect of geraniin in IL-1β-stimulated Caco-2 cells and a dextran sulfate sodium (DSS)-induced colitis mouse model. Geraniin blocked the interaction between IL-1β and IL-1R by directly binding to IL-1β and inhibited the IL-1β activity. It suppressed IL-1β-induced intestinal tight junction damage in human Caco-2 cells by inhibiting IL-1β-mediated MAPK, NF-kB, and MLC activation. Moreover, geraniin administration effectively reduced colitis symptoms and attenuated intestinal barrier injury in mice by suppressing elevated intestinal permeability and restoring tight junction protein expression through the inhibition of MAPK, NF-kB, and MLC activation. Thus, geraniin exhibits anti-IL-1β activity and anticolitis effect by hindering the IL-1β and IL-1R interaction and may be a promising therapeutic anti-IL-1β agent for IBD treatment.

Anti-inflammatory effects and related mechanisms in vitro and in vivo of Hedychium coccineum rhizome essential oil

Ethnopharmacological relevanceHedychium coccineum rhizome is an anti-inflammatory ethnomedicine used to remedy inflammation-related swelling and bronchial asthma. Aim of the studyThe study aimed to analyze the phytochemical constituents of H. coccineum rhizome essential oil (EO) and evaluate its in vitro and in vivo anti-inflammatory effects and underlying mechanisms. Materials and methodsPhytochemical constituents of H. coccineum rhizome EO were analyzed using GC-FID/MS. In RAW264.7 macrophages induced by LPS, blockade of PGE2, NO, IL-1β, IL-6, and TNF-α secretion by H. coccineum rhizome EO was measured, and then Western blot, qRT-PCR, and immunofluorescent staining were used to evaluate its underlying mechanisms. Moreover, we used the xylene-induced ear edema model for testing anti-inflammatory potential in vivo and examined auricular swelling as well as tissue and serum contents of IL-1β, IL-6, and TNF-α. ResultsEO's main components were E-nerolidol (40.5%), borneol acetate (24.8%), spathulenol (4.5%), linalool (3.8%), elemol (3.5%), and borneol (3.4%). In RAW264.7 cells stimulated by LPS, EO downregulated the expression of pro-inflammatory enzyme (iNOS and COX-2) genes and proteins, thereby suppressing pro-inflammatory mediators (NO and PGE2) secretion. Simultaneously, it reduced TNF-α, IL-1β, and IL-6 release by downregulating their mRNA expression. Besides, H. coccineum EO attenuated LPS-stimulated activation of NF-κB (by reducing IκBα phosphorylation and degradation to inhibit NF-κB nuclear translocation) and MAPK (by downregulating JNK, p38, and ERK phosphorylation). In xylene-induced mouse ear edema, EO relieved auricular swelling and lowered serum and tissue levels of TNF-α, IL-1β, and IL-6. ConclusionsH. coccineum EO had powerful in vivo and in vitro anti-inflammatory effects by inhibiting MAPK and NF-κB activation. Hence, H. coccineum EO should have great potential for application in the pharmaceutical field as a novel anti-inflammatory agent.

MAPK-dependent control of mitotic progression in S. pombe

BackgroundMitogen-activated protein kinases (MAPKs) preserve cell homeostasis by transducing physicochemical fluctuations of the environment into multiple adaptive responses. These responses involve transcriptional rewiring and the regulation of cell cycle transitions, among others. However, how stress conditions impinge mitotic progression is largely unknown. The mitotic checkpoint is a surveillance mechanism that inhibits mitotic exit in situations of defective chromosome capture, thus preventing the generation of aneuploidies. In this study, we investigate the role of MAPK Pmk1 in the regulation of mitotic exit upon stress.ResultsWe show that Schizosaccharomyces pombe cells lacking Pmk1, the MAP kinase effector of the cell integrity pathway (CIP), are hypersensitive to microtubule damage and defective in maintaining a metaphase arrest. Epistasis analysis suggests that Pmk1 is involved in maintaining spindle assembly checkpoint (SAC) signaling, and its deletion is additive to the lack of core SAC components such as Mad2 and Mad3. Strikingly, pmk1Δ cells show up to twofold increased levels of the anaphase-promoting complex (APC/C) activator Cdc20Slp1 during unperturbed growth. We demonstrate that Pmk1 physically interacts with Cdc20Slp1 N-terminus through a canonical MAPK docking site. Most important, the Cdc20Slp1 pool is rapidly degraded in stressed cells undergoing mitosis through a mechanism that requires MAPK activity, Mad3, and the proteasome, thus resulting in a delayed mitotic exit.ConclusionsOur data reveal a novel function of MAPK in preventing mitotic exit and activation of cytokinesis in response to stress. The regulation of Cdc20Slp1 turnover by MAPK Pmk1 provides a key mechanism by which the timing of mitotic exit can be adjusted relative to environmental conditions.

Abstract 4709: The RASMULTI(ON) inhibitor RMC-7977 blocks downstream MAPK and PI3K pathway activation in KRASG12X_mutant cancers

Abstract Oncogenic RAS binds to multiple effector proteins to activate downstream signaling pathways, including the MAPK and PI3K axes. While RAS-mediated MAPK activation has a well-validated role in driving cancer progression, the contribution of PI3K activation has been more difficult to assess. Understanding the degree to which different KRAS-mutant genotypes stimulate PI3K activity may inform biomarker and combination strategies for RAS inhibitors currently undergoing clinical evaluation.RMC-7977 is a RASMULTI(ON) inhibitor that targets GTP-bound RAS(ON) and blocks effector protein binding. RMC-7977 exhibits similar potency for wild-type and oncogenic mutant RAS and is a powerful preclinical tool, representative of the investigational RASMULTI(ON) inhibitor RMC-6236, for comparing how RAS-mutant genotypes differ with respect to signal activation. MAPK signaling proceeds through a protein phosphorylation cascade that is readily detectable using standard cell biology methods, but PI3K is a lipid kinase whose activity is not amenable to protein characterization techniques. An assay of phosphatidylinositol (3,4,5)-trisphosphate (PIP3) was developed to directly measure the activity of PI3K in the context of RAS inhibition.In isogenic LIM1215 cell lines expressing different KRASG12X mutants (KRASG12D, KRASG12V, KRASG12C and KRASG12R), RAS inhibition by RMC-7977 completely suppressed PI3K activity in cells with wild-type KRAS and KRASG12D, had a moderate inhibitory effect in KRASG12C and KRASG12V, and had no effect in KRASG12R. To confirm that this inhibition is dependent on a direct interaction between RAS(ON) and PI3K, CRISPR engineering was used to introduce mutations in PIK3CA to perturb the RAS-binding domain. In cells with disrupted RAS-PI3K interactions, the basal levels of PIP3 are significantly reduced and no longer change in response to treatment with RMC-7977.Based on the isogenic cell line results, KRASG12D and KRASG12R-mutant pancreatic cancer cell lines were profiled for their response to RAS inhibition. RMC-7977 decreased the levels of MAPK signaling in both KRASG12D and KRASG12R genotypes, but PI3K activity was only inhibited in KRASG12D lines. MEK inhibitors only inhibited MAPK signaling and had no effect on PI3K activity in either genotype. The simultaneous inhibition of MAPK and PI3K signaling by RMC-7977 led to deeper suppression of cyclin D levels and a more pronounced G1 cell cycle arrest as compared with MAPK inhibitors.We demonstrate that the coupling between RAS activation and PI3K signaling varies between oncogenic mutants, with KRASG12D showing the greatest degree of PI3K stimulation. In KRASG12D-mutant pancreatic cancer cell lines, a RASMULTI(ON) inhibitor suppresses both PI3K and MAPK signaling. These preclinical results may be used to inform potential, rational, mechanism-based combination treatment strategies for RAS(ON) inhibitors. Citation Format: Priyanka S. Bapat, Kyle Seamon, Andrea Gould, David Wildes. The RASMULTI(ON) inhibitor RMC-7977 blocks downstream MAPK and PI3K pathway activation in KRASG12X_mutant cancers [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 4709.

Abstract 5064: Wild type KRAS amplification as de novo oncogenic driver in non-small cell lung cancer

Abstract Introduction: Oncogenic KRAS mutations define subsets of non-small cell lung cancer (NSCLC) with unique clinicopathologic and genomic features, and the recent development of direct KRAS inhibitors has changed the treatment landscape of these patients (pts). However, whether KRAS amplification is oncogenic and defines unique subset of potentially targetable NSCLCs is currently unknown. Methods: Clinicopathologic and genomic data were abstracted from multiple independent cohorts of NSCLCs which underwent tumor genomic profiling at the Dana-Farber Cancer Institute (Cohort 1), AACR-GENIE v.13, TCGA, and other 212 studies (Cohort 2). Whole transcriptome sequencing and quantitative proteomics data from the The Cancer Genome Atlas (TCGA) and the Cancer Cell Lines Encyclopedia (CCLE) were used to correlate KRAS amplification with KRAS RNA levels and protein expression. KRAS doxycycline-inducible models were generated to determine in vitro and in vivo oncogenicity of wild-type KRAS overexpression. Results: Among 15,341 pts with NSCLC identified, KRAS amplification was identified in 355 (2.4%) cases. Compared to KRAS not amplified cases, pts with KRAS amplified NSCLC were more likely to be males (52.4% vs 45.6%, p=0.01), have a history of smoking (82.1% vs 64.2%, p<0.01), and higher median pack-years (35 vs 23.5, p<0.01). KRAS amplification was also associated with higher median aneuploidy levels (as fraction of genome altered) (30.4% vs 14.3%, p<0.01), tumor mutational burden (p<0.01), and increased median PD-L1 expression (20% vs 5%, p=0.01). KRAS amplified cases were enriched with KRAS, POLE2, SLC34A2 and PALB2 mutations, while EGFR mutations were mutually exclusive (Q<0.1). Among NSCLC samples with transcriptomic and proteomic profiling from the TCGA and CCLE cohorts, KRAS amplification was associated with significantly increased KRAS mRNA (p<0.01) and protein expression (p<0.01), compared to KRAS diploid samples. Among pts with clinical outcomes data available (N=9,335), median overall survival (OS) from the date of diagnosis was significantly shorter in pts with KRAS amplified vs KRAS diploid genotype in both KRAS mutant (HR: 0.71, P=0.02) and KRAS WT (HR: 0.74, P=0.02) NSCLCs. In KRAS doxycycline-inducible models (BEAS-2B cells) we demonstrated increased cell proliferation and MAPK activation upon doxycycline-induced KRAS expression. In vivo, sustained expression of KRAS in animals constantly fed with doxycycline-diet triggered tumor formation and development of metastasis, indicating that WT KRAS overexpression is oncogenic. Conclusion: KRAS amplification defines a novel subset of NSCLCs characterized by distinct clinicopathologic and genomic features, and worse survival. Developing novel therapeutic strategies to target KRAS amplification may improve outcomes in pts with NSCLC. Citation Format: Biagio Ricciuti, Sandra V. Michelina, Joao Alessi, Xinan Wang, Federica Pecci, Alessandro Di Federico, Malini Gandhi, Giuseppe Lamberti, Enrico Patrucco, Lynette Sholl, Andrew Aguirre, Chiara Ambrogio, Mark Magdi Awad. Wild type KRAS amplification as de novo oncogenic driver in non-small cell lung cancer [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 5064.

Abstract 1923: Cytoplasmic localization of KRAS in Her2-amplified colorectal cancer induces an altered dependency of the oncogenic signaling pathway from RAS/MAPK to PI3K/AKT

Abstract Nowadays, KRAS-G12C specific inhibitor has been used for the treatment of patients with KRAS mutated non-small cell lung cancer, but not for colorectal cancer (CRC) patients. Recent clinical trials have shown that the efficacy of a single KRAS inhibitor treatment was limited for CRC due to multiple primary/adaptive resistance mechanisms. In the CRC, clinical trial with dual inhibition of KRAS-G12C and EGFR has demonstrated that combination therapy had improved partial response rate, suggesting that primary resistance to KRAS inhibitor is mainly caused by EGFR-mediated adaptation. Meanwhile, more than half of the primary resistance mechanisms are still unknown. To understand the intrinsic resistance mechanisms to KRAS inhibitors in CRC, KRAS G12C- or G12D-positive CRC patient-derived cells (PDCs) were established from surgically resected tumor specimens. Analysis of cell proliferation under KRAS inhibitor treatment or KRAS knockdown revealed these PDCs were not solely dependent on KRAS mediated growth signaling. To clarify the compensatory activated pathways in KRAS inhibitor, inhibitor library screening and sequencing analysis were performed among 8 KRAS-mutated PDCs. As a result, PDCs were categorized into EGFR inhibitor with KRAS inhibitor sensitive group and PI3K pathway activating group harboring PIK3CA mutation or/and ERBB2 amplification with KRAS mutation. To explore the novel intrinsic resistance mechanisms, we deeply analyzed one of the PDC named JC261, harboring PIK3CA, ERBB2, and KRAS alterations. We observed that PI3K pathway was highly activated in JC261 cells, and cell proliferation was mainly dependent on PI3K/AKT/mTOR pathway regardless the existence of KRAS-G12C mutation. To examine whether Her2 amplification contributes to the PI3K pathway dependency, we established Her2 knockout JC261 cells. Notably, Her2 knockout suppressed Her2-Her3-PI3K signaling and restored KRAS-MAPK dependency. To analyze the mechanism of how KRAS-MAPK pathway was activated in Her2 knockout cells, we focused on KRAS localization, since the MAPK activation is known to initiate from plasma membrane localization of KRAS after appropriate modifications. Remarkably, immunofluorescence staining of KRAS revealed that KRAS was aberrantly localized in the cytoplasm in JC261, while KRAS localization was changed to the plasm membrane in Her2 knockout JC261 cells. In addition, the cytoplasmic KRAS localization was also observed in Her2-amplified, KRAS-WT PDC (JC69). These results suggest that Her2 amplification may induce aberrant KRAS localization, resulting in low dependence on the KRAS-MAPK pathway. Thus, KRAS localization may regulate the balance between MAPK and PI3K signaling intensity. Citation Format: Kohei Maruyama, Satoshi Nagayama, Ryohei Katayama. Cytoplasmic localization of KRAS in Her2-amplified colorectal cancer induces an altered dependency of the oncogenic signaling pathway from RAS/MAPK to PI3K/AKT [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 1923.

Abstract 3163: (Phospho)proteomic analysis reveals vulnerabilities in refractory metastatic colorectal cancer

Abstract Proteomic networks are crucial for cellular homeostasis maintenance and, indeed, their aberrant regulation is implicated in cancer development and progression. Understanding alterations underlying these pathways, provides a way to design therapeutic interventions in human cancer. Improvements in mass spectrometry analysis have unlocked our potential to unveil cancer vulnerabilities. Here, we performed (phospho)proteomic analysis and ex-vivo drug testing on a cohort of refractory metastatic colorectal cancer (mCRC) tissues and matched patients-Derived Organoids (PDO) to identify new putative druggable biomarkers. The comparison between the proteome and phosphoproteome of 10 mCRCs tissues with their matched PDOs normalized to a pool of 6 colon mucosa tissues highlighted a strong overall correlation (R= 0.57 and R=0.6, respectively) suggesting a good level of similarity. Applying GSEA on our proteomic dataset, we identified up-regulation in MYC, cell cycle and MTORC1 signaling pathways in mCRC tissues and PDO, while kinase enrichment analysis highlighted an increase in Casein Kinase II (CKII) activity, an important cell cycle regulator. Our ex-vivo experiments showed that silmitasertib-mediated CKII inhibition reduced the cell viability in our PDO models, but with an overall modest effect. Analysis revealed that, even though not statistically significant, high Wnt signaling score correlated with an higher resistance to silmitasertib treatment (R=0.61; p=0.08). Previous works highlighted that MAPK activity is increased after silmitasertib treatment and responsible for resistance mechanisms to CKII inhibition. Strikingly, the combined trametinib-mediated MEK blockade and CKII blockade resulted in a synergistic interaction leading to enhanced antitumor activity, especially in PDO harboring high Wnt (R=0.74; p=0.022) and cell cycle (R=0.69; p=0.04) pathway activity. Moreover, the combined treatment strongly reduced S6 activity and RAPTOR expression, overcoming the significant effect exerted by the single agents. Surprisingly, none of them altered baseline MAPK activity, suggesting that silmitasertib and trametinib synergize their activity via inactivating the MTORC1-S6 axis in an ERK-independent manner. We are currently integrating genomic and transcriptomic data to better characterize the observed drug synergy. Taken together, our findings propose the silmitasertib and trametinib combination as a new therapeutic opportunity for refractory mCRC patients and strengthen the use of PDO as a suitable model for drug screening. Citation Format: Mattia Marinucci, Gina Faye Boot, Lara Zaidi, Cinzia Esposito, Mairene Coto Llerena, Savas Soysal, Otto Kolmar, Charlotte K Y Ng, Salvatore Piscuoglio. (Phospho)proteomic analysis reveals vulnerabilities in refractory metastatic colorectal cancer [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 3163.

Abstract 544: Reverse engineering strategy for new targets identification

Abstract The issue of drug resistance in cancer is very similar to the field of infectious disease, either existing before treatment (intrinsic) or generated during therapy (acquired), highly affected by cell endogenous factors and/or the surrounding environment. Acquired resistance can be occurred several months after targeted therapy via alternations of drug targets due to the genomic mutations of the targets, epigenetic transcriptional or translational changes, for example the C797S mutation impairs AZ9291 binding to the EGFR kinase domain. To overcome this, novel well-designed chemical compounds targeting new mutations would be urgently needed, as well as the potential new oncogenes/susceptible genes driving the resistance. Considering about the heterogeneity of primary tumor tissues, LIDE has established one functional cost-effective in vitro and in vivo screening method, named reverse engineering strategy for targets identification by using patients-derived conditional reprogramed cancer cell lines (CRs) and IO-FIVE (Immuno-Oncology drugs Five In Vivo Efficacy test). Basically, pro-siRNA library or CRISPR/sgRNA library is carried out in CRs for candidates hunting, alternatively drug-response evaluation among multiple clinical biopsies in mice cancer trials, after filtered with bioinformatic scanning from large groups of patients, and finally it is validated in vivo by CRISPR, shRNA silence or targeted compounds. In addition to these known factors (EGFR C797S, Her2/Met amplification, Ras and MAPK activation), we have discovered that epigenetic factors for DNA modification, protein translation kinases, mitochondrial/peroxisomal transporters and cell membrane lectins may contribute to AZ92921 resistance in vivo. And one previously unknown acyltransferase member has been identified as key driver gene for pan-cancer development by IO-FIVE, and patients with high expression level of this enzyme have had poor survival outcomes, accompany with uncontrolled tumor growth and immunotherapy resistance, which is becoming a promising therapeutic target. Citation Format: Bin Xie, Taimei Zhang, Le Li, Hongkui Chen, Yang Liu, Lintao Bi, Danyi Wen. Reverse engineering strategy for new targets identification [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 544.

Abstract 1997: The small GTPase ARF6 augments BRAF and PI3K expression to promote melanoma survival

Abstract RAF and MEK inhibitors greatly benefit BRAF-mutant melanoma patients, but eventually, nearly 80% of patients relapse. Reactivation of MAPK signaling and activation of PI3K/AKT signaling play a major role in the development of targeted therapy resistance. Therefore, understanding how tumor cells regulate these signaling pathways may yield new insights into drug resistance. The small GTPase ARF6, a member of the RAS superfamily, influences oncogenic signaling by controlling cytoskeletal rearrangements and through endomembrane trafficking. We previously reported that ARF6 is aberrantly activated in metastatic melanoma and that activation of ARF6 is sufficient to promote invasion and accelerate spontaneous metastasis in vivo through WNT5A/beta-catenin and PI3K/AKT signaling. In contrast to ARF6 activation, herein we show that tumor-specific deletion of Arf6 significantly limits development and progression of BRAFV600E melanoma in vivo. Mechanistically, we discovered these ARF6-dependent phenotypes may be attributed to a previously unknown role for ARF6 in augmenting BRAFV600E and PI3K protein levels. Specifically, pharmacologic or genetic activation ARF6 (ARF6-GTP) is sufficient to increase BRAFV600E and PI3K protein levels in both murine and human melanoma. As a result, ARF6-GTP is also sufficient to enhance activation of MEK, ERK and AKT. Importantly, murine tumors expressing constitutively active ARF6 (ARF6Q67L) show increased expression of anti-apoptotic proteins compared to ARF6WT tumors. Together these data suggest that ARF6 promotes tumor survival through augmentation of the BRAF/MAPK and PI3K/AKT pathways. To test this, we pharmacologically activated ARF6 during serum withdrawal or vemurafenib treatment. In both conditions, ARF6 activation is sufficient to prevent apoptosis. Surprisingly, we found that vemurafenib treatment leads to ARF6 activation, suggesting that ARF6 may be an important component of the cellular machinery that reactivates MAPK signaling after RAF inhibition. Indeed, pharmacologic activation of ARF6 maintains MAPK signaling (pERK levels) in the presence of vemurafenib and enhances pERK and pAKT-mediated suppression of apoptotic signaling. In summary, our data suggest that in addition to well-established roles in tumor cell invasion, ARF6 is a crucial mediator of survival during tumor progression and in the context of BRAF targeted therapy. More work is needed to understand how ARF6 activation increases BRAF and PI3K expression and if ARF6 activation contributes to the development of persister cells in melanoma. Citation Format: Junhua Wang, Coulson Rich, Aaron Rogers, Sheri Holmen, Roger Wolff, Allie Grossmann. The small GTPase ARF6 augments BRAF and PI3K expression to promote melanoma survival [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 1997.

Abstract 6836: Single-cell RNA sequencing of FUS::DDIT3 myxoid/round cell liposarcoma delineates mechanisms of oncogenic progression and immune escape

Abstract Myxoid/Round Cell Liposarcoma (MRCL) is an understudied soft tissue sarcoma that typically affects young adults and accounts for 30% of all liposarcomas. MRCL is characterized by oncogenic DDIT3 fusions, with FUS::DDIT3 being present in over 90% of cases. However, the cellular origins and oncogenic mechanisms of MRCL remain incompletely defined. Here we report oncogene transcription, and tumor-immune interactions in a cohort of 5 patient tumors with matched normal tissue for which we sequenced the transcriptomes of approximately 45,000 single cells using 10X Genomics, and full-length transcripts in approximately 20,000 single cells via Oxford Nanopore in 2 of these patients. Our results reveal two distinct cancer cell populations: Early Cancer Cells (ECC) and Advanced Cancer Cells (ACC). These cells appear to derive from adipose stem progenitor cells (ASPC) and fall along an ASPC→ECC→ACC pseudo-time axis. Along this axis, a distinct pattern emerges where oncogenes tend to be upregulated and tumor suppressor genes (TSG) tend to be downregulated and these appear to be mutually exclusive. Comparing ECC to ASPC we see increased expression of HIPPO and PI3K pathway oncogenes, FGFR2 and IGF1R RTKs, and downregulation of the TSG CDKN2A and CDKN1A. ACC show upregulation of hedgehog, ErbB, WNT, HIPPO, PI3K, and MAPK signaling pathways compared to ECC. Full-length transcript sequencing at the single-cell level shows a consistent expression of the FUS::DDIT3 fusion transcript in both ECC and ACC populations, confirming that these populations are cancer cells. Furthermore, MRCL displays several immune escape mechanisms, including poor immune infiltration and a marked decline of HLA Class I expression along the pseudo-time axis from ECC to ACC, suggesting a complex interplay between oncogenic signaling and immune evasion. These results suggest that MRCL likely originates from ASPC and expression of FUS:DDIT3 oncoprotein induces early HIPPO, PI3K, FGFR2, and insulin signaling pathway expression in ECC with further hedgehog, ErbB, MAPK, and WNT pathway activation in ACC. This progressive activation in oncogenic signaling is associated with immune evasion. This is the first single-cell RNA seq analysis to detect the presence of the FUS::DDIT3 fusion in ECC and ACC significantly advancing our understanding of the mechanisms of MRCL oncogenesis, immune escape, and identifies potential novel therapeutic targets. Citation Format: Rodrigo Gularte-Mérida, Evan Seffar, George Li, Young-Mi Kim, Narasimhan P. Agaram, Nicholas Socci, Francisco Sanchez-Vega, Nikolaus Schultz, Samuel Singer. Single-cell RNA sequencing of FUS::DDIT3 myxoid/round cell liposarcoma delineates mechanisms of oncogenic progression and immune escape [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 6836.

Abstract 7476: Obtusifolin attenuates LPS-induced inflammation and NLRP3 inflammasome activation by suppressing the MAPK/NF-κB signaling pathway and ROS production in BV2 cells

Abstract Neuroinflammation, along with activation of microglia and oxidative stress, plays an important role in the development and progression of neurodegenerative diseases. During the inflammation process, immune cells release inflammatory mediators such as cytokines and chemicals that may promote the formation and growth of cancer cells. Obtusifolin, an anthraquinone extracted from the seeds of Senna obtusifolin, has anti-inflammatory properties. However, the effect of obtusifolin on neuroinflammation and its regulatory mechanism have not been yet investigated. In the present study, BV2 microglial cells were used to investigate the effects of obtusifolin on LPS-induced inflammatory responses, NLRP3 inflammasome activation, and reactive oxygen species (ROS) production. The secretion of nitric oxide (NO) was analyzed by Griess reagent assay, and the cell viability was detected by the CCK-8 assay. The expressions of iNOS, COX-2, STAT3, ERK, JNK, and p38 were examined using Western blotting, and the production of IL-6 and TNF-α was measured by ELISA. To examine whether obtusifolin affected NLRP3 inflammasome activation, BV2 cells were pretreated with LPS and then stimulated with ATP or nigericin. The secretion of IL-1β was measured by ELISA, whereas the expression of NLRP3 inflammasome-related proteins was detected using Western blotting. The production of ROS was analyzed by flow cytometry. Our experimental results showed that obtusifolin suppressed the production of NO and the secretion of proinflammatory cytokines by LPS-induced BV2 cells under noncytotoxic concentrations. In addition, obtusifolin decreased the expression of iNOS, COX-2, phospho-STAT3, phospho-ERK, phosphor-JNK and phospho-p38, and also attenuated the expression of NLRP3 and ASC, cleaved caspase-1 and cleaved IL-1β by LPS- induced BV2 cells. Moreover, obtusifolin reduced the production of both intracellular and mitochondrial ROS by LPS-induced BV2 cells. Overall, these results demonstrated that obtusifolin attenuated LPS-induced inflammation by suppressing the activation of MAPK and NF-κB signaling pathways, inhibiting NLRP3 inflammasome activation, and reducing the production of ROS in microglia, suggesting that obtusifolin might have benefits in the treatment of neurodegenerative diseases. Citation Format: Hsin Yi Lin, Che-Hsin Lee, Chia-Yang Li. Obtusifolin attenuates LPS-induced inflammation and NLRP3 inflammasome activation by suppressing the MAPK/NF-κB signaling pathway and ROS production in BV2 cells [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 7476.