Elevated Methionine Flux Drives Pyroptosis Evasion in Persister Cancer Cells

Methionine metabolite spermidine inhibits tumor pyroptosis by enhancing MYO6-mediated endocytosis

The connection between amino acid metabolism and pyroptosis remains elusive. Herein, we screen the effect of individual amino acid on pyroptosis and identify that methionine inhibits GSDME-mediated pyroptosis. Mechanistic analyses unveil that MYO6, a unique actin-based motor protein, bridges the GSDME N-terminus (GSDME-NT) and the endocytic adaptor AP2, mediating endolysosomal degradation of GSDME-NT. This degradation is increased by the methionine-derived metabolite spermidine noncanonically by direct binding to MYO6, which enhances MYO6 selectivity for GSDME-NT. Moreover, combination targeted therapies using dietary or pharmacological inhibition in methionine-to-spermidine metabolism in the tumor promotes pyroptosis and anti-tumor immunity, leading to a stronger tumor-suppressive effect in in vivo models. Clinically, higher levels of tumor spermidine and expression of methionine-to-spermidine metabolism-related gene signature predict poorer survival. Conclusively, our research identifies an unrecognized mechanism of pyroptotic resistance mediated by methionine-spermidine metabolic axis, providing a fresh angle for cancer treatment.

Tumor-Intrinsic SIRPA Drives Pyroptosis Evasion in Head and Neck Cancer

Pyroptosis, a gasdermin-mediated immunogenic cell death, has been shown to elicit adaptive antitumor immune responses, thereby augmenting the response to cancer immunotherapy when pyroptosis is therapeutically activated. However, despite increased gasdermin E (GSDME) expression, significant pyroptosis remains elusive in certain tumor types, and the underlying regulatory mechanisms are poorly understood. In this study, we observed high signal regulatory protein α1 (SIRPA) expression in head and neck squamous cell carcinoma (HNSCC) cells, a target in cancer immunotherapy. Intriguingly, SIRPA inhibition markedly augmented pyroptosis activity in tumor tissues and modulated tumor growth in a HNSCC mouse model. Subsequent investigations revealed that SIRPA knockout upregulated GSDME expression and potentiated cisplatin-induced pyroptosis in cancer cells. Integrative transcriptomics and metabolomics analysis suggested that the SIRPA knockout profoundly altered protein ubiquitination and augmented argininosuccinic acid levels in cancer cells. Specifically, we demonstrated that ubiquitin-specific peptidase 18 (USP18), a deubiquitinating enzyme, targets GSDME for deubiquitination and that USP18 knockdown suppressed cisplatin-induced pyroptosis. Notably, we found that succinylation of GSDME, which is mediated by succinyl-CoA, promotes GSDME cleavage without affecting caspase-3 activation. Further experiments indicated that SIRPA expression in tumor cells can decrease the antitumor efficacy of chemotherapy and immunotherapy in HNSCC mouse models. In summary, our findings reveal a novel mechanism of pyroptosis evasion in HNSCC, whereby tumor-intrinsic SIRPA enhances GSDME ubiquitylation and inhibits its succinylation. These insights suggest that inhibiting SIRPA expression may improve the efficacy of immunotherapy for HNSCC by inducing pyroptosis.

Multifaceted roles of cGAS-STING pathway in the lung cancer: from mechanisms to translation

Lung cancer (LC) remains one of the most prevalent and lethal malignancies globally, with a 5-year survival rate for advanced cases persistently below 10%. Despite the significant advancements in immunotherapy, a substantial proportion of patients with advanced LC fail to respond effectively to these treatments, highlighting an urgent need for novel immunotherapeutic targets. The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway has gained prominence as a potential target for improving LC immunotherapy due to its pivotal role in enhancing anti-tumor immune responses, augmenting tumor antigen presentation, and promoting T cell infiltration. However, emerging evidence also suggests that the cGAS-STING pathway may have pro-tumorigenic effects in the context of LC. This review aims to provide a comprehensive analysis of the cGAS-STING pathway, including its biological composition, activation mechanisms, and physiological functions, as well as its dual roles in LC and the current and emerging LC treatment strategies that target the pathway. By addressing these aspects, we intend to highlight the potential of the cGAS-STING pathway as a novel immunotherapeutic target, while also considering the challenges and future directions for its clinical application.

Comprehensive metabolomic analysis identifies key biomarkers and modulators of immunotherapy response in NSCLC patients

Although immune checkpoint inhibitors (ICIs) have revolutionized immuno-oncology with effective clinical responses, only 30 to 40 % of patients respond to ICIs, highlighting the need for reliable biomarkers to predict and enhance therapeutic outcomes. This study investigated how amino acid, glycolysis, and bile acid metabolism affect ICI efficacy in non-small cell lung cancer (NSCLC) patients. Through targeted metabolomic profiling and machine learning analysis, we identified amino acid metabolism as a key factor, with histidine (His) linked to favorable outcomes and homocysteine (HCys), phenylalanine (Phe), and sarcosine (Sar) linked to poor outcomes. Importantly, the His/HCys+Phe+Sar ratio emerges as a robust biomarker. Furthermore, we emphasize the role of glycolysis-related metabolites, particularly lactate. Elevated lactate levels post-immunotherapy treatment correlate with poorer outcomes, underscoring lactate as a potential indicator of treatment efficacy. Moreover, specific bile acids, glycochenodeoxycholic acid (GCDCA) and taurolithocholic acid (TLCA), are associated with better survival and therapeutic response. Particularly, TLCA enhances T cell activation and anti-tumor immunity, suggesting its utility as a predictive biomarker and therapeutic agent. We also suggest a connection between gut microbiota and TLCA levels, with the Eubacterium genus modulating this relationship. Therefore, modulating specific metabolic pathways-particularly amino acid, glycolysis, and bile acid metabolism-could predict and enhance the efficacy of ICI therapy in NSCLC patients, with potential implications for personalized treatment strategies in immuno-oncology. ONE SENTENCE SUMMARY: Our study identifies metabolic biomarkers and pathways that could predict and enhance the outcomes of immune checkpoint inhibitor therapy in NSCLC patients.

Mechanisms of Response and Tolerance to Active RAS Inhibition in KRAS-Mutant Non-Small Cell Lung Cancer

Resistance to inactive state-selective RASG12C inhibitors frequently entails accumulation of RASGTP, rendering effective inhibition of active RAS potentially desirable. Here, we evaluated the antitumor activity of the RAS(ON) multiselective tricomplex inhibitor RMC-7977 and dissected mechanisms of response and tolerance in KRASG12C-mutant non-small cell lung cancer (NSCLC). Broad-spectrum reversible RASGTP inhibition with or without concurrent covalent targeting of active RASG12C yielded superior and differentiated antitumor activity across diverse comutational KRASG12C-mutant NSCLC mouse models of primary or acquired RASG12C(ON) or RASG12C(OFF) inhibitor resistance. Interrogation of time-resolved single-cell transcriptional responses established an in vivo atlas of multimodal acute and chronic RAS pathway inhibition in the NSCLC ecosystem and uncovered a regenerative mucinous transcriptional program that supports long-term tumor cell persistence. In patients with advanced KRASG12C-mutant NSCLC, the presence of mucinous histologic features portended poor response to sotorasib or adagrasib. Our results have potential implications for personalized medicine and the development of rational RAS inhibitor-anchored therapeutic strategies. Significance: Our work reveals robust and durable antitumor activity of the preclinical RAS(ON) multiselective inhibitor RMC-7977 against difficult-to-treat subsets of KRASG12C-mutant NSCLC with primary or acquired RASG12C inhibitor resistance and identifies a conserved mucinous transcriptional state that supports RAS inhibitor tolerance. See related commentary by Marasco and Misale, p. 2018.

Pyroptosis and chemical classification of pyroptotic agents

Pyroptosis, as a lytic-inflammatory type of programmed cell death, has garnered considerable attention due to its role in cancer chemotherapy and many inflammatory diseases. This review will discuss the biochemical classification of pyroptotic inducers according to their chemical structure, pyroptotic mechanism, and cancer type of these targets. A structure-activity relationship study on pyroptotic inducers is revealed based on the surveyed pyroptotic inducer chemotherapeutics. The shared features in the chemical structures of current pyroptotic inducer agents were displayed, including an essential cyclic head, a vital linker, and a hydrophilic tail that is significant for π-π interactions and hydrogen bonding. The presented structural features will open the way to design new hybridized classes or scaffolds as potent pyroptotic inducers in the future, which may represent a solution to the apoptotic-resistance dilemma along with synergistic chemotherapeutic advantage.

Epigenetic reprogramming in gastrointestinal cancer: biology and translational perspectives

Gastrointestinal tumors, the second leading cause of human mortality, are characterized by their association with inflammation. Currently, progress in the early diagnosis and effective treatment of gastrointestinal tumors is limited. Recent whole-genome analyses have underscored their profound heterogeneity and extensive genetic and epigenetic reprogramming. Epigenetic reprogramming pertains to dynamic and hereditable alterations in epigenetic patterns, devoid of concurrent modifications in the underlying DNA sequence. Common epigenetic modifications encompass DNA methylation, histone modifications, noncoding RNA, RNA modifications, and chromatin remodeling. These modifications possess the potential to invoke or suppress a multitude of genes associated with cancer, thereby governing the establishment of chromatin configurations characterized by diverse levels of accessibility. This intricate interplay assumes a pivotal and indispensable role in governing the commencement and advancement of gastrointestinal cancer. This article focuses on the impact of epigenetic reprogramming in the initiation and progression of gastric cancer, esophageal cancer, and colorectal cancer, as well as other uncommon gastrointestinal tumors. We elucidate the epigenetic landscape of gastrointestinal tumors, encompassing DNA methylation, histone modifications, chromatin remodeling, and their interrelationships. Besides, this review summarizes the potential diagnostic, therapeutic, and prognostic targets in epigenetic reprogramming, with the aim of assisting clinical treatment strategies.

Research progress on the effect of pyroptosis on the occurrence, development, invasion and metastasis of colorectal cancer

Pyroptosis is a type of programmed cell death mediated by gasdermines (GSDMs). The N-terminal domain of GSDMs forms pores in the plasma membrane, causing cell membrane rupture and the release of cell contents, leading to an inflammatory response and mediating pyrodeath. Pyroptosis plays an important role in inflammatory diseases and malignant tumors. With the further study of pyroptosis, an increasing number of studies have shown that the pyroptosis pathway can regulate the tumor microenvironment and antitumor immunity of colorectal cancer and is closely related to the occurrence, development, treatment and prognosis of colorectal cancer. This review aimed to explore the molecular mechanism of pyroptosis and the role of pyroptosis in the occurrence, development, treatment and prognosis of colorectal cancer (CRC) and to provide ideas for the clinical diagnosis and treatment of CRC.

Immunohistochemical Expression of Caspase1 and Epidermal Growth Factor Receptor in Invasive Breast Carcinoma and Their Biological and Prognostic Associations

BACKGROUND

Despite advances in breast carcinoma therapies, drug resistance mechanisms as anti-apoptosis and anti-pyroptosis limit the application of these therapies. This work assesses the immunohistochemical (IHC) expression of Caspase1 and EGFR in breast carcinoma and analyzes their clinicopathological associations as prognostic markers and potential therapeutic targets. Caspase1/EGFR expression patterns are utilized to specify breast carcinoma patients who may benefit from these therapies.

METHODS

After reviewing the hematoxylin and eosin-stained slides and the routine breast carcinoma IHC stains (estrogen receptors, progesterone receptors, HER2/NEU, Ki-67) by two pathologists and preparation of tissue microarray blocks, anti-Caspase-1 and EGFR IHC staining was performed using Horseradish Peroxidase (HRP) technique. Intensity and percentage-based scoring was applied dividing the 153 included breast carcinomas into Caspase1-negative and positive expression groups; and EGFR low and overexpression groups. Groups were statistically analyzed in relation to age, tumor size, histological and molecular subtype, grade, nodal status, metastasis/recurrence, TNM stage and Ki-67 proliferation index. Kaplan-Meier's analysis was used to compare disease-free survival (DFS) and overall survival (OS). Combined patterns based on Caspase1 and EGFR expression status were created to stratify patients into prognostic groups.

RESULTS

Caspase1 was positive in 54.2% of breast carcinomas and its positivity was significantly associated with smaller tumor size, absence of metastasis/recurrence, luminal A and B molecular subtypes and longer OS (p<0.05). EGFR overexpression was detected in 32.7% of carcinomas and was significantly associated with larger tumor size, TNBLBC and a shorter OS (p<0.05). Caspase1-negative/EGFR-overexpression pattern comprised 14.4% of carcinomas and had the worst prognostic associations including larger tumor size, metastasis/recurrence, TNBLBC subtype and shortest OS (p=0.002, 0.002, 0.004 and ≤0.001 respectively).  Conclusions: Combined Caspase1/EGFR IHC expression may provide a tool for selection of patients who benefit from combined EGFR-inhibitors with miR-155-5p down-regulators or photodynamic therapy via induction of apoptosis/pyroptosis in EGFR-overexpression carcinomas through enhanced Caspase1 signaling.

Targeting methionine metabolism in cancer: opportunities and challenges

Reprogramming of methionine metabolism is a conserved hallmark of tumorigenesis. Recent studies have revealed mechanisms regulating methionine metabolism within the tumor microenvironment (TME) that drive both cancer development and antitumor immunity evasion. In this review article we summarize advancements in our understanding of tumor regulation of methionine metabolism and therapies in development that target tumor methionine metabolism. We also delineate the challenges of methionine blockade therapies in cancer and discuss emerging strategies to address them.

Glutamine inhibition combined with CD47 blockade enhances radiotherapy-induced ferroptosis in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a formidable cancer type that poses significant treatment challenges, including radiotherapy (RT) resistance. The metabolic characteristics of tumors present substantial obstacles to cancer therapy, and the relationship between RT and tumor metabolism in HNSCC remains elusive. Ferroptosis is a type of iron-dependent regulated cell death, representing an emerging disease-modulatory mechanism. Here, we report that after RT, glutamine levels rise in HNSCC, and the glutamine transporter protein SLC1A5 is upregulated. Notably, blocking glutamine significantly enhances the therapeutic efficacy of RT in HNSCC. Furthermore, inhibition of glutamine combined with RT triggers immunogenic tumor ferroptosis, a form of nonapoptotic regulated cell death. Mechanistically, RT increases interferon regulatory factor (IRF) 1 expression by activating the interferon signaling pathway, and glutamine blockade augments this efficacy. IRF1 drives transferrin receptor expression, elevating intracellular Fe2+ concentration, disrupting iron homeostasis, and inducing cancer cell ferroptosis. Importantly, the combination treatment-induced ferroptosis is dependent on IRF1 expression. Additionally, blocking glutamine combined with RT boosts CD47 expression and hinders macrophage phagocytosis, attenuating the treatment effect. Dual-blocking glutamine and CD47 promote tumor remission and enhance RT-induced ferroptosis, thereby ameliorating the tumor microenvironment. Our work provides valuable insights into the metabolic and immunological mechanisms underlying RT-induced ferroptosis, highlighting a promising strategy to augment RT efficacy in HNSCC.

Metabolic challengers selecting tumor-persistent cells

Resistance to anticancer therapy still represents one of the main obstacles to cancer treatment. Numerous components of the tumor microenvironment (TME) contribute significantly to the acquisition of drug resistance. Microenvironmental pressures arising during cancer evolution foster tumor heterogeneity (TH) and facilitate the emergence of drug-resistant clones. In particular, metabolic pressures arising in the TME may favor epigenetic adaptations supporting the acquisition of persistence features in tumor cells. Tumor-persistent cells (TPCs) are characterized by high phenotypic and metabolic plasticity, representing a noticeable advantage in chemo- and radio-resistance. Understanding the crosslink between the evolution of metabolic pressures in the TME, epigenetics, and TPC evolution is significant for developing novel therapeutic strategies specifically targeting TPC vulnerabilities to overcome drug resistance.

EEBR induces Caspase-1-dependent pyroptosis through the NF-κB/NLRP3 signalling cascade in non-small cell lung cancer

Lung cancer is a leading cause of cancer-related deaths worldwide. Recent studies have identified pyroptosis, a type of programmed cell death, as a critical process in the development and progression of lung cancer. In this study, we investigated the effect of EEBR, a new compound synthesized by our team, on pyroptosis in non-small cell lung cancer cells (NSCLC) and the underlying molecular mechanisms. Our results demonstrated that EEBR significantly reduced the proliferation and metastasis of NSCLC cells in vitro. Moreover, EEBR-induced pyroptosis in NSCLC cells, as evidenced by cell membrane rupture, the release of cytokines such as interleukin-18 and interleukin-1 beta and the promotion of Gasdermin D cleavage in a Caspase-1-dependent manner. Furthermore, EEBR promoted the nuclear translocation of NF-κB and upregulated the protein level of NLRP3. Subsequent studies revealed that EEBR-induced pyroptosis was suppressed by the inhibition of NF-κB. Finally, EEBR effectively suppressed the growth of lung cancer xenograft tumours by promoting NSCLC pyroptosis in animal models. Taken together, our findings suggest that EEBR induces Caspase-1-dependent pyroptosis through the NF-κB/NLRP3 signalling cascade in NSCLC, highlighting its potential as a candidate drug for NSCLC treatment.

Salmonella-mediated methionine deprivation drives immune activation and enhances immune checkpoint blockade therapy in melanoma

BACKGROUND

Although immune checkpoint inhibitor (ICI)-based therapy is advantageous for patients with advanced melanoma, resistance and relapse are frequent. Thus, it is crucial to identify effective drug combinations and develop new therapies for the treatment of melanoma. SGN1, a genetically modified Salmonella typhimurium species that causes the targeted deprivation of methionine in tumor tissues, is currently under investigation in clinical trials. However, the inhibitory effect of SGN1 on melanoma and the benefits of SGN1 in combination with ICIs remain largely unexplored. Therefore, this study aims to investigate the antitumor potential of SGN1, and its ability to enhance the efficacy of antibody-based programmed cell death-ligand 1 (PD-L1) inhibitors in the treatment of murine melanoma.

METHODS

The antitumor activity of SGN1 and the effect of SGN1 on the efficacy of PD-L1 inhibitors was studied through murine melanoma models. Further, The Cancer Genome Atlas-melanoma cohort was clustered using ConsensusClusterPlus based on the methionine deprivation-related genes, and immune characterization was performed using xCell, Microenvironment Cell Populations-counter, Estimation of Stromal and Immune cells in MAlignant Tumor tissues using Expression data, and immunophenoscore (IPS) analyses. The messenger RNA data on programmed death-1 (PD-1) immunotherapy response were obtained from the Gene Expression Omnibus database. Gene Set Enrichment Analysis of methionine deprivation-up gene set was performed to determine the differences between pretreatment responders and non-responders.

RESULTS

This study showed that both, the intratumoral and the intravenous administration of SGN1 in subcutaneous B16-F10 melanomas, suppress tumor growth, which was associated with an activated CD8+T-cell response in the tumor microenvironment. Combination therapy of SGN1 with systemic anti-PD-L1 therapy resulted in better antitumor activity than the individual monotherapies, respectively, and the high therapeutic efficacy of the combination was associated with an increase in the systemic level of tumor-specific CD8+ T cells. Two clusters consisting of methionine deprivation-related genes were identified. Patients in cluster 2 had higher expression of methionine_deprivation_up genes, better clinical outcomes, and higher immune infiltration levels compared with patients in cluster 1. Western blot, IPS analysis, and immunotherapy cohort study revealed that methionine deficiency may show a better response to ICI therapy CONCLUSIONS：: This study reports Salmonella-based SGN1 as a potent anticancer agent against melanoma, and lays the groundwork for the potential synergistic effect of ICIs and SGN1 brought about by improving the immune microenvironment in melanomas.

The Role of Methionine Restriction in Gastric Cancer: A Summary of Mechanisms and a Discussion on Tumor Heterogeneity

Gastric cancer is ranked as the fifth most prevalent cancer globally and has long been a topic of passionate discussion among numerous individuals. However, the incidence of gastric cancer in society has not decreased, but instead has shown a gradual increase in recent years. For more than a decade, the treatment effect of gastric cancer has not been significantly improved. This is attributed to the heterogeneity of cancer, which makes popular targeted therapies ineffective. Methionine is an essential amino acid, and many studies have shown that it is involved in the development of gastric cancer. Our study aimed to review the literature on methionine and gastric cancer, describing its mechanism of action to show that tumor heterogeneity in gastric cancer does not hinder the effectiveness of methionine-restricted therapies. This research also aimed to provide insight into the inhibition of gastric cancer through metabolic reprogramming with methionine-restricted therapies, thereby demonstrating their potential as adjuvant treatments for gastric cancer.

SHP2 potentiates anti-PD-1 effectiveness through intervening cell pyroptosis resistance in triple-negative breast cancer

Triple negative breast cancer (TNBC) presents a formidable challenge due to the lack of effective treatment modalities. Immunotherapy stands as a promising therapeutic approach; however, the emergence of drug resistance mechanisms within tumor cells, particularly those targeting apoptosis and pyroptosis, has hampered its clinical efficacy. SHP2 is intricately involved in diverse physiological processes, including immune cell proliferation, infiltration, and tumor progression. Nevertheless, the precise contribution of SHP2 to tumor cell pyroptosis resistance remains inadequately understood. Herein, we demonstrate that SHP2 inhibition hampers the proliferative, migratory, and invasive capabilities of TNBC, accompanied by noticeable alterations in cellular membrane architecture. Mechanistically, we provide evidence that SHP2 depletion triggers the activation of Caspase-1 and GSDMD, resulting in GSDMD-dependent release of LDH, IL-1β, and IL-18. Furthermore, computational analyses and co-localization investigations substantiate the hypothesis that SHP2 may hinder pyroptosis through direct binding to JNK, thereby impeding JNK phosphorylation. Our cellular experiments further corroborate these findings by demonstrating that JNK inhibition rescues pyroptosis induced by SHP2 knockdown. Strikingly, in vivo experiments validate the suppressive impact of SHP2 knockdown on tumor progression via enhanced JNK phosphorylation. Additionally, SHP2 knockdown augments tumor sensitivity to anti-PD-1 therapy, thus reinforcing the pro-pyroptotic effects and inhibiting tumor growth. In summary, our findings elucidate the mechanism by which SHP2 governs TNBC pyroptosis, underscoring the potential of SHP2 inhibition to suppress cell pyroptosis resistance and its utility as an adjunctive agent for tumor immunotherapy.

Drug-tolerant persister cells in cancer: the cutting edges and future directions

Drug-tolerant persister (DTP) cell populations were originally discovered in antibiotic-resistant bacterial biofilms. Similar populations with comparable features have since been identified among cancer cells and have been linked with treatment resistance that lacks an underlying genomic alteration. Research over the past decade has improved our understanding of the biological roles of DTP cells in cancer, although clinical knowledge of the role of these cells in treatment resistance remains limited. Nonetheless, targeting this population is anticipated to provide new treatment opportunities. In this Perspective, we aim to provide a clear definition of the DTP phenotype, discuss the underlying characteristics of these cells, their biomarkers and vulnerabilities, and encourage further research on DTP cells that might improve our understanding and enable the development of more effective anticancer therapies.

Systematic review of comparative transcriptomic studies of cellular resistance to genotoxic stress

The development of resistance by tumor cells to various types of therapy is a significant problem that decreases the effectiveness of oncology treatments. For more than two decades, comparative transcriptomic studies of tumor cells with different sensitivities to ionizing radiation and chemotherapeutic agents have been conducted in order to identify the causes and mechanisms underlying this phenomenon. However, the results of such studies have little in common and often contradict each other. We have assumed that a systematic analysis of a large number of such studies will provide new knowledge about the mechanisms of development of therapeutic resistance in tumor cells. Our comparison of 123 differentially expressed gene (DEG) lists published in 98 papers suggests a very low degree of consistency between the study results. Grouping the data by type of genotoxic agent and tumor type did not increase the similarity. The most frequently overexpressed genes were found to be those encoding the transport protein ABCB1 and the antiviral defense protein IFITM1. We put forward a hypothesis that the role played by the overexpression of the latter in the development of resistance may be associated not only with the stimulation of proliferation, but also with the limitation of exosomal communication and, as a result, with a decrease in the bystander effect. Among down regulated DEGs, BNIP3 was observed most frequently. The expression of BNIP3, together with BNIP3L, is often suppressed in cells resistant to non-platinum genotoxic chemotherapeutic agents, whereas it is increased in cells resistant to ionizing radiation. These observations are likely to be mediated by the binary effects of these gene products on survival, and regulation of apoptosis and autophagy. The combined data also show that even such obvious mechanisms as inhibition of apoptosis and increase of proliferation are not universal but show multidirectional changes.

Biological insights in non-small cell lung cancer

Lung oncogenesis relies on intracellular cysteine to overcome oxidative stress. Several tumor types, including non-small cell lung cancer (NSCLC), upregulate the system xc- cystine/glutamate antiporter (xCT) through overexpression of the cystine transporter SLC7A11, thus sustaining intracellular cysteine levels to support glutathione synthesis. Nuclear factor erythroid 2-related factor 2 (NRF2) serves as a master regulator of oxidative stress resistance by regulating SLC7A11, whereas Kelch-like ECH-associated protein (KEAP1) acts as a cytoplasmic repressor of the oxidative responsive transcription factor NRF2. Mutations in KEAP1/NRF2 and p53 induce SLC7A11 activation in NSCLC. Extracellular cystine is crucial in supplying the intracellular cysteine levels necessary to combat oxidative stress. Disruptions in cystine availability lead to iron-dependent lipid peroxidation, thus resulting in a type of cell death called ferroptosis. Pharmacologic inhibitors of xCT (either SLC7A11 or GPX4) induce ferroptosis of NSCLC cells and other tumor types. When cystine uptake is impaired, the intracellular cysteine pool can be sustained by the transsulfuration pathway, which is catalyzed by cystathionine-B-synthase (CBS) and cystathionine g-lyase (CSE). The involvement of exogenous cysteine/cystine and the transsulfuration pathway in the cysteine pool and downstream metabolites results in compromised CD8+ T cell function and evasion of immunotherapy, diminishing immune response and potentially reducing the effectiveness of immunotherapeutic interventions. Pyroptosis is a previously unrecognized form of regulated cell death. In NSCLCs driven by EGFR, ALK, or KRAS, selective inhibitors induce pyroptotic cell death as well as apoptosis. After targeted therapy, the mitochondrial intrinsic apoptotic pathway is activated, thus leading to the cleavage and activation of caspase-3. Consequently, gasdermin E is activated, thus leading to permeabilization of the cytoplasmic membrane and cell-lytic pyroptosis (indicated by characteristic cell membrane ballooning). Breakthroughs in KRAS G12C allele-specific inhibitors and potential mechanisms of resistance are also discussed herein.

Targeted deprivation of methionine with engineered Salmonella leads to oncolysis and suppression of metastasis in broad types of animal tumor models

The strong dependency of almost all malignant tumors on methionine potentially offers a pathway for cancer treatment. We engineer an attenuated strain of Salmonella typhimurium to overexpress an L-methioninase with the aim of specifically depriving tumor tissues of methionine. The engineered microbes target solid tumors and induce a sharp regression in several very divergent animal models of human carcinomas, cause a significant decrease in tumor cell invasion, and essentially eliminate the growth and metastasis of these tumors. RNA sequencing analyses reveal that the engineered Salmonella reduce the expression of a series of genes promoting cell growth, cell migration, and invasion. These findings point to a potential treatment modality for many metastatic solid tumors, which warrants further tests in clinical trials.