Identification of DHODH as a therapeutic target in small cell lung cancer

Discovery of piperine derivatives as inhibitors of human dihydroorotate dehydrogenase to induce ferroptosis in cancer cells

Inhibition of human dihydroorotate dehydrogenase (hDHODH) represents a promising strategy for suppressing the proliferation of cancer cells. To identify novel and potent hDHODH inhibitors, a total of 28 piperine derivatives were designed and synthesized. Their cytotoxicities against three human cancer cell lines (NCI-H226, HCT-116, and MDA-MB-231) and hDHODH inhibitory activities were also evaluated. Among them, compound H19, exhibited the strongest inhibitory activities (NCI-H226 IC50 = 0.95 µM, hDHODH IC50 = 0.21 µM). Further pharmacological investigations revealed that H19 exerted anticancer effects by inducing ferroptosis in NCI-H226 cells, with its cytotoxicity being reversed by ferroptosis inhibitors. This was supported by the intracellular growth or decline of ferroptosis markers, including lipid peroxidation, Fe2+, GSH, and 4-HNE. Overall, H19 emerges as a promising hDHODH inhibitor with potential anticancer properties warranting development.

Therapeutic targeting ERRγ suppresses metastasis via extracellular matrix remodeling in small cell lung cancer

Small-cell lung cancer (SCLC) is the most aggressive and lethal type of lung cancer, characterized by limited treatment options, early and frequent metastasis. However, the determinants of metastasis in SCLC are poorly defined. Here, we show that estrogen-related receptor gamma (ERRγ) is overexpressed in metastatic SCLC tumors, and is positively associated with SCLC progression. ERRγ functions as an essential activator of extracellular matrix (ECM) remodeling and cell adhesion, two critical steps in metastasis, by directly regulating the expression of major genes involved in these processes. Genetic and pharmacological inhibition of ERRγ markedly reduces collagen production, cell-matrix adhesion, microfilament production, and eventually blocks SCLC cell invasion and tumor metastasis. Notably, ERRγ antagonists significantly suppressed tumor growth and metastasis and restored SCLC vulnerability to chemotherapy in multiple cell-derived and patient-derived xenograft models. Taken together, these findings establish ERRγ as an attractive target for metastatic SCLC and provide a potential pharmacological strategy for treating this lethal disease.

Radiosynthesis of [18F]brequinar for in vivo PET imaging of hDHODH for potential studies of acute myeloid leukemia and cancers

Dihydroorotate dehydrogenase (DHODH), an enzyme that plays a critical role in the de novo pyrimidine biosynthesis, has been recognized as a promising target for the treatment of diseases that involve cellular proliferation, such as autoimmune diseases and cancers. Pharmacological inhibition of human DHODH (hDHODH) that offers a potential therapeutic strategy for the treatment in adult subjects with acute myeloid leukemia (AML) has recently been supported by phase I/II clinical trials for the treatment of patients with relapsed/refractory AML. To facilitate the development of optimized hDHODH inhibitors, the presence of an in vivo imaging probe that is able to demonstrate in vivo target engagement is critical and desirable. Brequinar is one of the most potent hDHODH inhibitors so far discovered. In this work, we use a copper-mediated radiofluorination (CMRF) strategy and compare the chemical design and radiosynthesis starting from either pinacole boronate p-nitrobenzyl ester (4) or tributylstannate (tin) p-nitrobenzyl ester (5), chosen for their suitability as a precursor to [18F]brequinar. We report here the design, synthesis, radiolabeling and characterization of [18F]brequinar, and a preliminary PET imaging study of DHODH in vivo. This study provides the strategies to create [18F]brequinar, the first hDHODH inhibitor PET radiotracer, which will facilitate its use as a tool (theranostics) for hDHODH drug development and for diagnosis and monitoring therapeutic efficacy in AML and cancers.

DHODH inhibition enhances the efficacy of immune checkpoint blockade by increasing cancer cell antigen presentation

Pyrimidine nucleotide biosynthesis is a druggable metabolic dependency of cancer cells, and chemotherapy agents targeting pyrimidine metabolism are the backbone of treatment for many cancers. Dihydroorotate dehydrogenase (DHODH) is an essential enzyme in the de novo pyrimidine biosynthesis pathway that can be targeted by clinically approved inhibitors. However, despite robust preclinical anticancer efficacy, DHODH inhibitors have shown limited single-agent activity in phase 1 and 2 clinical trials. Therefore, novel combination therapy strategies are necessary to realize the potential of these drugs. To search for therapeutic vulnerabilities induced by DHODH inhibition, we examined gene expression changes in cancer cells treated with the potent and selective DHODH inhibitor brequinar (BQ). This revealed that BQ treatment causes upregulation of antigen presentation pathway genes and cell surface MHC class I expression. Mechanistic studies showed that this effect is (1) strictly dependent on pyrimidine nucleotide depletion, (2) independent of canonical antigen presentation pathway transcriptional regulators, and (3) mediated by RNA polymerase II elongation control by positive transcription elongation factor B (P-TEFb). Furthermore, BQ showed impressive single-agent efficacy in the immunocompetent B16F10 melanoma model, and combination treatment with BQ and dual immune checkpoint blockade (anti-CTLA-4 plus anti-PD-1) significantly prolonged mouse survival compared to either therapy alone. Our results have important implications for the clinical development of DHODH inhibitors and provide a rationale for combination therapy with BQ and immune checkpoint blockade.

Current Progress of Ferroptosis Study in Hepatocellular Carcinoma

Ferroptosis, an emerging type of programmed cell death, is initiated by iron-dependent and excessive ROS-mediated lipid peroxidation, which eventually leads to plasma membrane rupture and cell death. Many canonical signalling pathways and biological processes are involved in ferroptosis. Furthermore, cancer cells are more susceptible to ferroptosis due to the high load of ROS and unique metabolic characteristics, including iron requirements. Recent investigations have revealed that ferroptosis plays a crucial role in the progression of tumours, especially HCC. Specifically, the induction of ferroptosis can not only inhibit the growth of hepatoma cells, thereby reversing tumorigenesis, but also improves the efficacy of immunotherapy and enhances the antitumour immune response. Therefore, triggering ferroptosis has become a new therapeutic strategy for cancer therapy. In this review, we summarize the characteristics of ferroptosis based on its underlying mechanism and role in HCC and provide possible therapeutic applications.

Teriflunomide/leflunomide synergize with chemotherapeutics by decreasing mitochondrial fragmentation via DRP1 in SCLC

Although up to 80% small cell lung cancer (SCLC) patients' response is good for first-line chemotherapy regimen, most patients develop recurrence of the disease within weeks to months. Here, we report cytostatic effect of leflunomide (Leflu) and teriflunomide (Teri) on SCLC cell proliferation through inhibition of DRP1 phosphorylation at Ser616 and decreased mitochondrial fragmentation. When administered together, Teri and carboplatin (Carbo) act synergistically to significantly inhibit cell proliferation and DRP1 phosphorylation, reduce abundance of intermediates in pyrimidine de novo pathway, and increase apoptosis and DNA damage. Combination of Leflu&Carbo has anti-tumorigenic effect in vivo. Additionally, lurbinectedin (Lur) and Teri potently and synergistically inhibited spheroid growth and depleted uridine and DRP1 phosphorylation in mouse tumors. Our results suggest combinations of Carbo and Lur with Teri or Leflu are efficacious and underscore how the relationship between DRP1/DHODH and mitochondrial plasticity serves as a potential therapeutic target to validate these treatment strategies in SCLC clinical trials.

Genome-wide CRISPR screens identify PKMYT1 as a therapeutic target in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with an overall 5-year survival rate of <12% due to the lack of effective treatments. Novel treatment strategies are urgently needed. Here, PKMYT1 is identified through genome-wide CRISPR screens as a non-mutant, genetic vulnerability of PDAC. Higher PKMYT1 expression levels indicate poor prognosis in PDAC patients. PKMYT1 ablation inhibits tumor growth and proliferation in vitro and in vivo by regulating cell cycle progression and inducing apoptosis. Moreover, pharmacological inhibition of PKMYT1 shows efficacy in multiple PDAC cell models and effectively induces tumor regression without overt toxicity in PDAC cell line-derived xenograft and in more clinically relevant patient-derived xenograft models. Mechanistically, in addition to its canonical function of phosphorylating CDK1, PKMYT1 functions as an oncogene to promote PDAC tumorigenesis by regulating PLK1 expression and phosphorylation. Finally, TP53 function and PRKDC activation are shown to modulate the sensitivity to PKMYT1 inhibition. These results define PKMYT1 dependency in PDAC and identify potential therapeutic strategies for clinical translation.

The crosstalk between oncogenic signaling and ferroptosis in cancer

Ferroptosis, a novel form of cell death regulation, was identified in 2012. It is characterized by unique features that differentiate it from other types of cell death, including necrosis, apoptosis, autophagy, and pyroptosis. Ferroptosis is defined by an abundance of iron ions and lipid peroxidation, resulting in alterations in subcellular structures, an elevation in reactive oxygen species (ROS), a reduction in glutathione (GSH) levels, and an augmentation in Fe (II) cytokines. Ferroptosis, a regulated process, is controlled by an intricate network of signaling pathways, where multiple stimuli can either enhance or hinder the process. This review primarily examines the defensive mechanisms of ferroptosis and its interaction with the tumor microenvironment. The analysis focuses on the pathways that involve AMPK, p53, NF2, mTOR, System Xc-, Wnt, Hippo, Nrf2, and cGAS-STING. The text discusses the possibilities of employing a combination therapy that targets several pathways for the treatment of cancer. It emphasizes the necessity for additional study in this field.

Unveiling the Antiviral Capabilities of Targeting Human Dihydroorotate Dehydrogenase against SARS-CoV-2

The urgent need for effective treatments against emerging viral diseases, driven by drug-resistant strains and new viral variants, remains critical. We focus on inhibiting the human dihydroorotate dehydrogenase (HsDHODH), one of the main enzymes responsible for pyrimidine nucleotide synthesis. This strategy could impede viral replication without provoking resistance. We evaluated naphthoquinone fragments, discovering potent HsDHODH inhibition with IC50 ranging from 48 to 684 nM, and promising in vitro anti-SARS-CoV-2 activity with EC50 ranging from 1.2 to 2.3 μM. These compounds exhibited low toxicity, indicating potential for further development. Additionally, we employed computational tools such as molecular docking and quantitative structure-activity relationship (QSAR) models to analyze protein-ligand interactions, revealing that these naphthoquinones exhibit a protein binding pattern similar to brequinar, a potent HsDHODH inhibitor. These findings represent a significant step forward in the search for effective antiviral treatments and have great potential to impact the development of new broad-spectrum antiviral drugs.

Small-molecule agents for cancer immunotherapy

Cancer immunotherapy, exemplified by the remarkable clinical benefits of the immune checkpoint blockade and chimeric antigen receptor T-cell therapy, is revolutionizing cancer therapy. They induce long-term tumor regression and overall survival benefit in many types of cancer. With the advances in our knowledge about the tumor immune microenvironment, remarkable progress has been made in the development of small-molecule drugs for immunotherapy. Small molecules targeting PRR-associated pathways, immune checkpoints, oncogenic signaling, metabolic pathways, cytokine/chemokine signaling, and immune-related kinases have been extensively investigated. Monotherapy of small-molecule immunotherapeutic drugs and their combinations with other antitumor modalities are under active clinical investigations to overcome immune tolerance and circumvent immune checkpoint inhibitor resistance. Here, we review the latest development of small-molecule agents for cancer immunotherapy by targeting defined pathways and highlighting their progress in recent clinical investigations.

Recent advances in nanomedicine for metabolism-targeted cancer therapy

Metabolism denotes the sum of biochemical reactions that maintain cellular function. Different from most normal differentiated cells, cancer cells adopt altered metabolic pathways to support malignant properties. Typically, almost all cancer cells need a large number of proteins, lipids, nucleotides, and energy in the form of ATP to support rapid division. Therefore, targeting tumour metabolism has been suggested as a generic and effective therapy strategy. With the rapid development of nanotechnology, nanomedicine promises to have a revolutionary impact on clinical cancer therapy due to many merits such as targeting, improved bioavailability, controllable drug release, and potentially personalized treatment compared to conventional drugs. This review comprehensively elucidates recent advances of nanomedicine in targeting important metabolites such as glucose, glutamine, lactate, cholesterol, and nucleotide for effective cancer therapy. Furthermore, the challenges and future development in this area are also discussed.

Retinoblastoma vulnerability to combined de novo and salvage pyrimidine ribonucleotide synthesis pharmacologic blockage

Retinoblastoma is an eye cancer that commonly affects young children. Despite significant advances, current treatments cause side effects even when administered locally, and patients may still have to undergo enucleation. This is particularly disheartening in cases of bilateral retinoblastoma. Hence, there is an urgent need for novel therapeutic strategies. Inhibitors of the enzyme dihydroorotate dehydrogenase (DHODH), which is involved in the de novo pyrimidine ribonucleotide synthesis pathway, have proven to be effective in preclinical trials against several cancers including pediatric cancers. Here we tested whether blocking pyrimidine ribonucleotide synthesis promotes retinoblastoma cell death. Cultured retinoblastoma cell lines were treated with small molecule inhibitors of DHODH alone or in combination with inhibitors of nucleoside uptake to also block the salvage pathway for pyrimidine ribonucleotide formation. On their own, DHODH inhibitors had a moderate killing effect. However, the combination with nucleoside uptake inhibitors greatly enhanced the effect of DHODH inhibition. In addition, we observed that pyrimidine ribonucleotide synthesis blockage can cause cell death in a p53 mutant retinoblastoma cell line derived from a patient with metastasis. Explaining these results, the analysis of a published patient cohort revealed that loss of chr16q22.2 (containing the DHODH gene) is amongst the most frequent alterations in retinoblastoma and that these tumors often show gains in chromosome regions expressing pyrimidine ribonucleotide salvage factors. Furthermore, these genome alterations associate with malignancy. These results indicate that targeting pyrimidine ribonucleotide synthesis may be an effective therapeutic strategy to consider as a treatment for retinoblastoma.

DHODH inhibition enhances the efficacy of immune checkpoint blockade by increasing cancer cell antigen presentation

Pyrimidine nucleotide biosynthesis is a druggable metabolic dependency of cancer cells, and chemotherapy agents targeting pyrimidine metabolism are the backbone of treatment for many cancers. Dihydroorotate dehydrogenase (DHODH) is an essential enzyme in the de novo pyrimidine biosynthesis pathway that can be targeted by clinically approved inhibitors. However, despite robust preclinical anticancer efficacy, DHODH inhibitors have shown limited single-agent activity in phase 1 and 2 clinical trials. Therefore, novel combination therapy strategies are necessary to realize the potential of these drugs. To search for therapeutic vulnerabilities induced by DHODH inhibition, we examined gene expression changes in cancer cells treated with the potent and selective DHODH inhibitor brequinar (BQ). This revealed that BQ treatment causes upregulation of antigen presentation pathway genes and cell surface MHC class I expression. Mechanistic studies showed that this effect is 1) strictly dependent on pyrimidine nucleotide depletion, 2) independent of canonical antigen presentation pathway transcriptional regulators, and 3) mediated by RNA polymerase II elongation control by positive transcription elongation factor B (P-TEFb). Furthermore, BQ showed impressive single-agent efficacy in the immunocompetent B16F10 melanoma model, and combination treatment with BQ and dual immune checkpoint blockade (anti-CTLA-4 plus anti-PD-1) significantly prolonged mouse survival compared to either therapy alone. Our results have important implications for the clinical development of DHODH inhibitors and provide a rationale for combination therapy with BQ and immune checkpoint blockade.

A Patent Review of Human Dihydroorotate Dehydrogenase (hDHODH) Inhibitors as Anticancer Agents and their Other Therapeutic Applications (1999-2022)

Highly proliferating cells, such as cancer cells, are in high demand of pyrimidine nucleotides for their proliferation, accomplished by de novo pyrimidine biosynthesis. The human dihydroorotate dehydrogenase (hDHODH) enzyme plays a vital role in the rate-limiting step of de novo pyrimidine biosynthesis. As a recognised therapeutic target, hDHODH plays a significant role in cancer and other illness. In the past two decades, small molecules as inhibitors hDHODH enzyme have drawn much attention as anticancer agents, and their role in rheumatoid arthritis (RA), and multiple sclerosis (MS). In this patent review, we have compiled patented hDHODH inhibitors published between 1999 and 2022 and discussed the development of hDHODH inhibitors as anticancer agents. Therapeutic potential of small molecules as hDHODH inhibitors for the treatment of various diseases, such as cancer, is very well recognised. Human DHODH inhibitors can rapidly cause intracellular uridine monophosphate (UMP) depletion to produce starvation of pyrimidine bases. Normal cells can better endure a brief period of starvation without the side effects of conventional cytotoxic medication and resume synthesis of nucleic acid and other cellular functions after inhibition of de novo pathway using an alternative salvage pathway. Highly proliferative cells such as cancer cells do not endure starvation because they are in high demand of nucleotides for cell differentiation, which is fulfilled by de novo pyrimidine biosynthesis. In addition, hDHODH inhibitors produce their desired activity at lower doses rather than a cytotoxic dose of other anticancer agents. Thus, inhibition of de novo pyrimidine biosynthesis will create new prospects for the development of novel targeted anticancer agents, which ongoing preclinical and clinical experiments define. Our work brings together a comprehensive patent review of the role of hDHODH in cancer, as well as various patents related to the hDHODH inhibitors and their anticancer and other therapeutic potential. This compiled work on patented DHODH inhibitors will guide researchers in pursuing the most promising drug discovery strategies against the hDHODH enzyme as anticancer agents.

Actionable Driver Events in Small Cell Lung Cancer

Small cell lung cancer (SCLC) stands out as the most aggressive form of lung cancer, characterized by an extremely high proliferation rate and a very poor prognosis, with a 5-year survival rate that falls below 7%. Approximately two-thirds of patients receive their diagnosis when the disease has already reached a metastatic or extensive stage, leaving chemotherapy as the remaining first-line treatment option. Other than the recent advances in immunotherapy, which have shown moderate results, SCLC patients cannot yet benefit from any approved targeted therapy, meaning that this cancer remains treated as a uniform entity, disregarding intra- or inter-tumoral heterogeneity. Continuous efforts and technological improvements have enabled the identification of new potential targets that could be used to implement novel therapeutic strategies. In this review, we provide an overview of the most recent approaches for SCLC treatment, providing an extensive compilation of the targeted therapies that are currently under clinical evaluation and inhibitor molecules with promising results in vitro and in vivo.

Applications of CRISPR screening to lung cancer treatment

Lung cancer is an extremely aggressive and highly prevalent disease worldwide, and it is one of the leading causes of cancer death. Deciphering intrinsic genetic mechanism, finding new targets, and overcoming drug resistance are the key to lung cancer treatment. High-throughput CRISPR screening has been extensively used to obtain the genes related to cancers including lung cancer. This review describes CRISPR/Cas9 or CRISPR/dCas9-based technologies for high-throughput screening. We summarize the applications of CRISPR screening technology in exploring the mechanism of lung cancer development in vivo or in vitro, overcoming drug resistance, improving the effect of immunotherapy, and discovering new therapeutic targets. This review highlights the potential of CRISPR screening in combination with tumor barcoding and high-throughput sequencing (Tuba-seq) to precisely quantify the impact of alterations in many tumor suppressor genes on lung cancer.

Ferroptosis: an important player in the inflammatory response in diabetic nephropathy

Diabetic nephropathy (DN) is a chronic inflammatory disease that affects millions of diabetic patients worldwide. The key to treating of DN is early diagnosis and prevention. Once the patient enters the clinical proteinuria stage, renal damage is difficult to reverse. Therefore, developing early treatment methods is critical. DN pathogenesis results from various factors, among which the immune response and inflammation play major roles. Ferroptosis is a newly discovered type of programmed cell death characterized by iron-dependent lipid peroxidation and excessive ROS production. Recent studies have demonstrated that inflammation activation is closely related to the occurrence and development of ferroptosis. Moreover, hyperglycemia induces iron overload, lipid peroxidation, oxidative stress, inflammation, and renal fibrosis, all of which are related to DN pathogenesis, indicating that ferroptosis plays a key role in the development of DN. Therefore, this review focuses on the regulatory mechanisms of ferroptosis, and the mutual regulatory processes involved in the occurrence and development of DN and inflammation. By discussing and analyzing the relationship between ferroptosis and inflammation in the occurrence and development of DN, we can deepen our understanding of DN pathogenesis and develop new therapeutics targeting ferroptosis or inflammation-related regulatory mechanisms for patients with DN.

Blockade of de novo pyrimidine biosynthesis triggers autophagic degradation of oncoprotein FLT3-ITD in acute myeloid leukemia

The internal tandem duplication of the FMS-like tyrosine kinase 3 (FLT3-ITD) is one of the most frequent genetic alterations in acute myeloid leukemia (AML). Limited and transient clinical benefit of FLT3 kinase inhibitors (FLT3i) emphasizes the need for alternative therapeutic options for this subset of myeloid malignancies. Herein, we showed that FLT3-ITD mutant (FLT3-ITD+) AML cells were susceptible toward inhibitors of DHODH, a rate-limiting enzyme of de novo pyrimidine biosynthesis. Genetic and pharmacological blockade of DHODH triggered downregulation of FLT3-ITD protein, subsequently suppressed activation of downstream ERK and STAT5, and promoted cell death of FLT3-ITD+ AML cells. Mechanistically, DHODH blockade triggered autophagy-mediated FLT3-ITD degradation via inactivating mTOR, a potent autophagy repressor. Notably, blockade of DHODH synergized with an FDA-approved FLT3i quizartinib in significantly impairing the growth of FLT3-ITD+ AML cells and improving tumor-bearing mice survival. We further demonstrated that DHODH blockade exhibited profound anti-proliferation effect on quizartinib-resistant cells in vitro and in vivo. In summary, this study demonstrates that the induction of degradation of FLT3-ITD protein by DHODH blockade may offer a promising therapeutic strategy for AML patients harboring FLT3-ITD mutation.

Mismatch repair deficiency is not sufficient to elicit tumor immunogenicity

DNA mismatch repair deficiency (MMRd) is associated with a high tumor mutational burden (TMB) and sensitivity to immune checkpoint blockade (ICB) therapy. Nevertheless, most MMRd tumors do not durably respond to ICB and critical questions remain about immunosurveillance and TMB in these tumors. In the present study, we developed autochthonous mouse models of MMRd lung and colon cancer. Surprisingly, these models did not display increased T cell infiltration or ICB response, which we showed to be the result of substantial intratumor heterogeneity of mutations. Furthermore, we found that immunosurveillance shapes the clonal architecture but not the overall burden of neoantigens, and T cell responses against subclonal neoantigens are blunted. Finally, we showed that clonal, but not subclonal, neoantigen burden predicts ICB response in clinical trials of MMRd gastric and colorectal cancer. These results provide important context for understanding immune evasion in cancers with a high TMB and have major implications for therapies aimed at increasing TMB.

Targeting pan-essential pathways in cancer with cytotoxic chemotherapy: challenges and opportunities

Cytotoxic chemotherapy remains a key modality in cancer treatment. These therapies, successfully used for decades, continue to transform the lives of cancer patients daily. With the high attrition rate of current oncology drug development, combined with the knowledge that most new therapies do not displace standard-of-care treatments and that many healthcare systems cannot afford these new therapies; cytotoxic chemotherapies will remain an important component of cancer therapy for many years to come. The clinical value of these therapies is often under-appreciated within the pre-clinical cancer research community, where this diverse class of agents are often grouped together as non-specific cellular poisons killing tumor cells based solely upon proliferation rate; however, this is inaccurate. This review article seeks to reaffirm the importance of focusing research efforts upon improving our basic understanding of how these drugs work, discussing their ability to target pan-essential pathways in cancer cells, the relationship of this to the chemotherapeutic window, and highlighting basic science approaches that can be employed towards refining their use.

The Role of Cellular Defense Systems of Ferroptosis in Parkinson's Disease and Alzheimer's Disease

Parkinson's disease (PD) and Alzheimer's disease (AD) are the most common rapidly developing neurodegenerative diseases that lead to serious health and socio-economic consequences. Ferroptosis is a non-apoptotic form of cell death; there is growing evidence to support the notion that ferroptosis is involved in a variety of pathophysiological contexts, and there is increasing interest in the role of ferroptosis in PD and AD. Simultaneously, cells may have evolved four defense systems to counteract the toxic effects of ferroptosis occasioned by lipid peroxidation. This review, which focuses on the analysis of ferroptosis in the PD and AD context, outlines four cellular defense systems against ferroptosis and how each of them is involved in PD and AD.

Neuroendocrine lineage commitment of small cell lung cancers can be leveraged into p53-independent non-cytotoxic therapy

Small cell lung cancers (SCLCs) rapidly resist cytotoxic chemotherapy and immune checkpoint inhibitor (ICI) treatments. New, non-cross-resistant therapies are thus needed. SCLC cells are committed into neuroendocrine lineage then maturation arrested. Implicating DNA methyltransferase 1 (DNMT1) in the maturation arrests, we find (1) the repression mark methylated CpG, written by DNMT1, is retained at suppressed neuroendocrine-lineage genes, even as other repression marks are erased; (2) DNMT1 is recurrently amplified, whereas Ten-Eleven-Translocation 2 (TET2), which functionally opposes DNMT1, is deleted; (3) DNMT1 is recruited into neuroendocrine-lineage master transcription factor (ASCL1, NEUROD1) hubs in SCLC cells; and (4) DNMT1 knockdown activated ASCL1-target genes and released SCLC cell-cycling exits by terminal lineage maturation, which are cycling exits that do not require the p53/apoptosis pathway used by cytotoxic chemotherapy. Inhibiting DNMT1/corepressors with clinical compounds accordingly extended survival of mice with chemorefractory and ICI-refractory, p53-null, disseminated SCLC. Lineage commitment of SCLC cells can hence be leveraged into non-cytotoxic therapy able to treat chemo/ICI-refractory SCLC.

Modulation of host glutamine anabolism enhances the sensitivity of small cell lung cancer to chemotherapy

Small cell lung cancer (SCLC) is one of the deadliest human cancers, with a 5-year survival rate of ∼7%. Here, we performed a targeted proteomics analysis of human SCLC samples and thereby identified hypoxanthine phosphoribosyltransferase 1 (HPRT1) in the salvage purine synthesis pathway as a factor that contributes to SCLC malignancy by promoting cell survival in a glutamine-starved environment. Inhibition of HPRT1 by 6-mercaptopurine (6-MP) in combination with methotrexate (MTX), which blocks the de novo purine synthesis pathway, attenuated the growth of SCLC in mouse xenograft models. Moreover, modulation of host glutamine anabolism with the glutamine synthetase inhibitor methionine sulfoximine (MSO) in combination with 6-MP and MTX treatment resulted in marked tumor suppression and prolongation of host survival. Our results thus suggest that modulation of host glutamine anabolism combined with simultaneous inhibition of the de novo and salvage purine synthesis pathways may be of therapeutic benefit for SCLC.

Orchestrating smart therapeutics to achieve optimal treatment in small cell lung cancer: recent progress and future directions

Small cell lung cancer (SCLC) is a recalcitrant malignancy with elusive mechanism of pathogenesis and dismal prognosis. Over the past decades, platinum-based chemotherapy has been the backbone treatment for SCLC. However, subsequent chemoresistance after initial effectiveness urges researchers to explore novel therapeutic targets of SCLC. Recent years have witnessed significant improvements in targeted therapy in SCLC. New molecular candidates such as Ataxia telangiectasia and RAD3-related protein (ATR), WEE1, checkpoint kinase 1 (CHK1) and poly-ADP-ribose polymerase (PARP) have shown promising therapeutic utility in SCLC. While immune checkpoint inhibitor (ICI) has emerged as an indispensable treatment modality for SCLC, approaches to boost efficacy and reduce toxicity as well as selection of reliable biomarkers for ICI in SCLC have remained elusive and warrants our further investigation. Given the increasing importance of precision medicine in SCLC, optimal subtyping of SCLC using multi-omics have gradually applied into clinical practice, which may identify more drug targets and better tailor treatment strategies to each individual patient. The present review summarizes recent progress and future directions in SCLC. In addition to the emerging new therapeutics, we also focus on the establishment of predictive model for early detection of SCLC. More importantly, we also propose a multi-dimensional model in the prognosis of SCLC to ultimately attain the goal of accurate treatment of SCLC.

Identification of Potent hDHODH Inhibitors for Lung Cancer via Virtual Screening of a Rationally Designed Small Combinatorial Library

Cancer is characterized by altered cellular metabolism, and metabolic enzymes are considered as a promising target for anticancer therapy. Pyrimidine metabolism dysregulation is associated with various types of cancer, particularly lung cancer, which is one of the leading causes of cancer-related mortality worldwide. Recent studies have shown that small-cell lung cancer cells are particularly reliant on the pyrimidine biosynthesis pathway and are sensitive to its disruption. DHODH, the rate-limiting enzyme of the de novo pyrimidine production pathway, is essential in the production of RNA and DNA and is overexpressed in malignancies such as AML, skin cancer, breast cancer, and lung cancer, thereby highlighting DHODH as a viable target for developing drugs to combat lung cancer. Herein, rational drug design and computational techniques were used to discover novel DHODH inhibitors. A small combinatorial library was generated, and the top hits were synthesized and tested for anticancer activity against three lung cancer cell lines. Among the tested compounds, compound 5c possessed a stronger cytotoxicity (TC₅₀ of 11 μM) compared to the standard FDA-approved drug (Regorafenib, TC₅₀ of 13 μM) on the A549 cell line. Furthermore, compound 5c demonstrated potent inhibitory activity against hDHODH at a nanomolar level of 421 nM. DFT, molecular docking, molecular dynamic simulations, and free energy calculations were also carried out to understand the inhibitory mechanisms of the synthesized scaffolds. These in silico studies identified key mechanisms and structural features that will be crucial for future studies.

Assessment of a novel variation in DHODH gene causing Miller syndrome: The first report in Chinese population

BACKGROUND

Miller syndrome is a rare type of postaxial acrofacial dysostosis caused by biallelic mutations in the DHODH gene, which is characterized mainly by craniofacial malformations of micrognathia, orofacial clefts, cup-shaped ears, and malar hypoplasia, combined with postaxial limb deformities like the absence of fifth digits.

METHODS

In this study, a prenatal case with multiple orofacial-limb abnormities was enrolled, and a thorough clinical and imaging examination was performed. Subsequently, genetic detection with karyotyping, chromosomal microarray analysis (CMA) and whole-exome sequencing (WES) was carried out. In vitro splicing analysis was also conducted to clarify the impact of one novel variant.

RESULTS

The affected fetus displayed typical manifestations of Miller syndrome, and WES identified a diagnostic compound heterozygous variation in DHODH, consisting of two variants: exon(1-3)del and c.819 + 5G > A. We conducted a further in vitro validation with minigene system, and the result indicated that the c.819 + 5G > A variant would lead to an exon skipping in mRNA splicing.

CONCLUSIONS

These findings provided with the first exonic deletion and first splice site variant in DHODH, which expanded the mutation spectrum of Miller syndrome and offered reliable evidence for genetic counseling to the affected family.

Nucleotide metabolism: a pan-cancer metabolic dependency

Metabolic alterations are a key hallmark of cancer cells, and the augmented synthesis and use of nucleotide triphosphates is a critical and universal metabolic dependency of cancer cells across different cancer types and genetic backgrounds. Many of the aggressive behaviours of cancer cells, including uncontrolled proliferation, chemotherapy resistance, immune evasion and metastasis, rely heavily on augmented nucleotide metabolism. Furthermore, most of the known oncogenic drivers upregulate nucleotide biosynthetic capacity, suggesting that this phenotype is a prerequisite for cancer initiation and progression. Despite the wealth of data demonstrating the efficacy of nucleotide synthesis inhibitors in preclinical cancer models and the well-established clinical use of these drugs in certain cancer settings, the full potential of these agents remains unrealized. In this Review, we discuss recent studies that have generated mechanistic insights into the diverse biological roles of hyperactive cancer cell nucleotide metabolism. We explore opportunities for combination therapies that are highlighted by these recent advances and detail key questions that remain to be answered, with the goal of informing urgently warranted future studies.

Nucleolar stress: From development to cancer

The nucleolus is a large nuclear membraneless organelle responsible for ribosome biogenesis. Ribosomes are cytoplasmic macromolecular complexes comprising RNA and proteins that link amino acids together to form new proteins. The biogenesis of ribosomes is an intricate multistep process that involves the transcription of ribosomal DNA (rDNA), the processing of ribosomal RNA (rRNA), and the assembly of rRNA with ribosomal proteins to form active ribosomes. Nearly all steps necessary for ribosome production and maturation occur in the nucleolus. Nucleolar shape, size, and number are directly linked to ribosome biogenesis. Errors in the steps of ribosomal biogenesis are sensed by the nucleolus causing global alterations in nucleolar function and morphology. This phenomenon, known as nucleolar stress, can lead to molecular changes such as stabilization of p53, which in turn activates cell cycle arrest or apoptosis. In this review, we discuss recent work on the association of nucleolar stress with degenerative diseases and developmental defects. In addition, we highlight the importance of de novo nucleotide biosynthesis for the enhanced nucleolar activity of cancer cells and discuss targeting nucleotide biosynthesis as a strategy to activate nucleolar stress to specifically target cancer cells.

Identifying CDC7 as a synergistic target of chemotherapy in resistant small-cell lung cancer via CRISPR/Cas9 screening

There is currently a lack of efficacious treatments for patients with chemo-resistant small-cell lung cancer (SCLC), leading to poor prognoses. We examined a chemo-resistant SCLC cell line using genome-wide CRISPR/Cas9 screening and identified serine/threonine kinase cell division cycle 7 (CDC7) as a potential synergistic target. Silencing CDC7 in chemo-resistant SCLC cells decreased the IC₅₀ and improved the efficacy of chemotherapy. Based on the highest single agent model, the CDC7 inhibitor XL413 had a synergistic effect with both cisplatin and etoposide in chemo-resistant SCLC cells, but had no such effect in chemo-sensitive SCLC cells; the combination of XL413 and chemotherapy significantly inhibited cell growth. Western blot and flow cytometry showed that the combined treatments increased apoptosis, whereas XL413 alone had little effect on apoptosis. An analysis of cell cycle and cyclin protein levels indicated that the combination of XL413 and chemotherapy-induced G1/S phase arrest and DNA damage in chemo-resistant SCLC cells. Xenografted tumor and histoculture drug response assays using patient-derived xenografts showed that XL413 improved the efficacy of chemotherapy in vivo and with SCLC tissues. These results suggest that XL413 exerts a synergistic effect with chemotherapy on chemo-resistant SCLC.

A multiplexed in vivo approach to identify driver genes in small cell lung cancer

Small cell lung cancer (SCLC) is a lethal form of lung cancer. Here, we develop a quantitative multiplexed approach on the basis of lentiviral barcoding with somatic CRISPR-Cas9-mediated genome editing to functionally investigate candidate regulators of tumor initiation and growth in genetically engineered mouse models of SCLC. We found that naphthalene pre-treatment enhances lentiviral vector-mediated SCLC initiation, enabling high multiplicity of tumor clones for analysis through high-throughput sequencing methods. Candidate drivers of SCLC identified from a meta-analysis across multiple human SCLC genomic datasets were tested using this approach, which defines both positive and detrimental impacts of inactivating 40 genes across candidate pathways on SCLC development. This analysis and subsequent validation in human SCLC cells establish TSC1 in the PI3K-AKT-mTOR pathway as a robust tumor suppressor in SCLC. This approach should illuminate drivers of SCLC, facilitate the development of precision therapies for defined SCLC genotypes, and identify therapeutic targets.

Adaptive risk-aware sharable and individual subspace learning for cancer survival analysis with multi-modality data

Biomedical multi-modality data (also named multi-omics data) refer to data that span different types and derive from multiple sources in clinical practices (e.g. gene sequences, proteomics and histopathological images), which can provide comprehensive perspectives for cancers and generally improve the performance of survival models. However, the performance improvement of multi-modality survival models may be hindered by two key issues as follows: (1) how to learn and fuse modality-sharable and modality-individual representations from multi-modality data; (2) how to explore the potential risk-aware characteristics in each risk subgroup, which is beneficial to risk stratification and prognosis evaluation. Additionally, learning-based survival models generally refer to numerous hyper-parameters, which requires time-consuming parameter setting and might result in a suboptimal solution. In this paper, we propose an adaptive risk-aware sharable and individual subspace learning method for cancer survival analysis. The proposed method jointly learns sharable and individual subspaces from multi-modality data, whereas two auxiliary terms (i.e. intra-modality complementarity and inter-modality incoherence) are developed to preserve the complementary and distinctive properties of each modality. Moreover, it equips with a grouping co-expression constraint for obtaining risk-aware representation and preserving local consistency. Furthermore, an adaptive-weighted strategy is employed to efficiently estimate crucial parameters during the training stage. Experimental results on three public datasets demonstrate the superiority of our proposed model.

DHODH Inhibition Exerts Synergistic Therapeutic Effect with Cisplatin to Induce Ferroptosis in Cervical Cancer through Regulating mTOR Pathway

Ferroptosis exhibits a potent antitumor effect and dihydroorotate dehydrogenase (DHODH) has recently been identified as a novel ferroptosis defender. However, the role of DHODH inhibition in cervical cancer cells is unclear, particularly in synergy with cisplatin via ferroptosis. Herein, shRNA and brequinar were used to knock down DHODH and directly inhibit DHODH, respectively. Immunohistochemistry and Western blotting assays were performed to measure the expression of proteins. CCK-8 and colony formation assays were employed to assess the cell viability and proliferation. Ferroptosis was monitored through flow cytometry, the malondialdehyde assay kit and JC-1 staining analyses. The nude mouse xenograft model was generated to examine the effect of combination of DHODH inhibition and cisplatin on tumor growth in vivo. The expression of DHODH was increased in cervical cancer tissues. DHODH inhibition inhibited the proliferation and promoted the ferroptosis in cervical cancer cells. A combination of DHODH inhibition and cisplatin synergistically induced both in vitro and in vivo ferroptosis and downregulated the ferroptosis defender mTOR pathway. Therefore, the combination of DHODH inhibition and cisplatin exhibits synergistic effects on ferroptosis induction via inhibiting the mTOR pathway could provide a promising way for cervical cancer therapy.

MicroRNA-1 attenuates the growth and metastasis of small cell lung cancer through CXCR4/FOXM1/RRM2 axis

BACKGROUND

Small cell lung cancer (SCLC) is an aggressive lung cancer subtype that is associated with high recurrence and poor prognosis. Due to lack of potential drug targets, SCLC patients have few therapeutic options. MicroRNAs (miRNAs) provide an interesting repertoire of therapeutic molecules; however, the identification of miRNAs regulating SCLC growth and metastasis and their precise regulatory mechanisms are not well understood.

METHODS

To identify novel miRNAs regulating SCLC, we performed miRNA-sequencing from donor/patient serum samples and analyzed the bulk RNA-sequencing data from the tumors of SCLC patients. Further, we developed a nanotechnology-based, highly sensitive method to detect microRNA-1 (miR-1, identified miRNA) in patient serum samples and SCLC cell lines. To assess the therapeutic potential of miR-1, we developed various in vitro models, including miR-1 sponge (miR-1Zip) and DOX-On-miR-1 (Tet-ON) inducible stable overexpression systems. Mouse models derived from intracardiac injection of SCLC cells (miR-1Zip and DOX-On-miR-1) were established to delineate the role of miR-1 in SCLC metastasis. In situ hybridization and immunohistochemistry were used to analyze the expression of miR-1 and target proteins (mouse and human tumor specimens), respectively. Dual-luciferase assay was used to validate the target of miR-1, and chromatin immunoprecipitation assay was used to investigate the protein-gene interactions.

RESULTS

A consistent downregulation of miR-1 was observed in tumor tissues and serum samples of SCLC patients compared to their matched normal controls, and these results were recapitulated in SCLC cell lines. Gain of function studies of miR-1 in SCLC cell lines showed decreased cell growth and oncogenic signaling, whereas loss of function studies of miR-1 rescued this effect. Intracardiac injection of gain of function of miR-1 SCLC cell lines in the mouse models showed a decrease in distant organ metastasis, whereas loss of function of miR-1 potentiated growth and metastasis. Mechanistic studies revealed that CXCR4 is a direct target of miR-1 in SCLC. Using unbiased transcriptomic analysis, we identified CXCR4/FOXM1/RRM2 as a unique axis that regulates SCLC growth and metastasis. Our results further showed that FOXM1 directly binds to the RRM2 promoter and regulates its activity in SCLC.

CONCLUSIONS

Our findings revealed that miR-1 is a critical regulator for decreasing SCLC growth and metastasis. It targets the CXCR4/FOXM1/RRM2 axis and has a high potential for the development of novel SCLC therapies. MicroRNA-1 (miR-1) downregulation in the tumor tissues and serum samples of SCLC patients is an important hallmark of tumor growth and metastasis. The introduction of miR-1 in SCLC cell lines decreases cell growth and metastasis. Mechanistically, miR-1 directly targets CXCR4, which further prevents FOXM1 binding to the RRM2 promoter and decreases SCLC growth and metastasis.

Footprints: Stamping hallmarks of lung cancer with patient-derived models, from molecular mechanisms to clinical translation

The conventional two-dimensional (2D) tumor cell lines in Petri dishes have played an important role in revealing the molecular biological mechanism of lung cancer. However, they cannot adequately recapitulate the complex biological systems and clinical outcomes of lung cancer. The three-dimensional (3D) cell culture enables the possible 3D cell interactions and the complex 3D systems with co-culture of different cells mimicking the tumor microenvironments (TME). In this regard, patient-derived models, mainly patient-derived tumor xenograft (PDX) and patient-derived organoids discussed hereby, are with higher biological fidelity of lung cancer, and regarded as more faithful preclinical models. The significant Hallmarks of Cancer is believed to be the most comprehensive coverage of current research on tumor biological characteristics. Therefore, this review aims to present and discuss the application of different patient-derived lung cancer models from molecular mechanisms to clinical translation with regards to the dimensions of different hallmarks, and to look to the prospects of these patient-derived lung cancer models.

Drug repurposing of ilepcimide that ameliorates experimental autoimmune encephalomyelitis via restricting inflammatory response and oxidative stress

Multiple sclerosis (MS) is an inflammatory and demyelinating disease of the central nervous system (CNS) that remains incurable. Herein, we demonstrated that ilepcimide (Antiepilepsirine), an antiepileptic drug used for decades, protects mice from experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. Our studies found that ilepcimide treatment effectively ameliorates demyelination, blood-brain barrier leakage and infiltration of CD4⁺ and CD8⁺ T cells in EAE mice. On the one hand, ilepcimide can inhibit dihydroorotate dehydrogenase (DHODH), an important therapeutic target for MS. Computer molecular docking, thermal shift and fluorescence quenching assay demonstrated the directly interaction between ilepcimide and DHODH. Accordingly, ilepcimide observably repressed T cell proliferation in mixed lymphocyte reaction (MLR) assay and concanavalin A (Con-A) model in a DHODH-dependent manner. On the other hand, ilepcimide exhibited neuroprotective effect possibly through activating NRF2 antioxidant pathway in mouse neural crest-derived Neuro2a cells. Collectively, our findings have revealed the therapeutic potential of ilepcimide in EAE mouse model via restricting inflammatory response and oxidative stress, offering a potential opportunity for repurposing existing drug ilepcimide for MS therapy.

The role of biomarkers in stage III non-small cell lung cancer

INTRODUCTION

Stage III non-small cell lung cancer (NSCLC) is a composite of the regional spread of lung cancer with different levels of potential lymph node involvement and tumor size that often deem the stage at time of diagnosis to be unresectable and suitable for chemoradiation plus consolidation immunotherapy with durvalumab for 12 months. Chemoradiation plus durvalumab consolidation yielded a landmark 49.2% 5-year overall survival in unresectable NSCLC.

AREAS COVERED

Sub-optimal results lead us to focus on the mechanisms of resistance responsible for intractability in a significant proportion of cases that fail with chemoradiation and immunotherapy. In stage III NSCLC it is opportune to explore the accumulated evidence on ferroptosis resistance that can lead to cancer progression and metastasis. Strong data shows that three anti-ferroptosis pathways are principally involved in resistance to chemotherapy, radiation, and immunotherapy.

EXPERT OPINION

Because a large part of stage III NSCLCs is resistant to chemoradiation and durvalumab consolidation, a ferroptosis-based therapeutic approach, combined with standard-of-care therapy, can lead to improved clinical outcomes in patients diagnosed with stage III and possibly stage IV NSCLCs.

ENT1 blockade by CNX-774 overcomes resistance to DHODH inhibition in pancreatic cancer

Inhibitors of dihydroorotate dehydrogenase (DHODH), a key enzyme for de novo synthesis of pyrimidine nucleotides, have failed in clinical trials for various cancers despite robust efficacy in preclinical animal models. To probe for druggable mediators of DHODH inhibitor resistance, we performed a combination screen with a small molecule library against pancreatic cancer cell lines that are highly resistant to the DHODH inhibitor brequinar (BQ). The screen revealed that CNX-774, a preclinical Bruton tyrosine kinase (BTK) inhibitor, sensitizes resistant cell lines to BQ. Mechanistic studies showed that this effect is independent of BTK and instead results from inhibition of equilibrative nucleoside transporter 1 (ENT1) by CNX-774. We show that ENT1 mediates BQ resistance by taking up extracellular uridine, which is salvaged to generate pyrimidine nucleotides in a DHODH-independent manner. In BQ-resistant cell lines, BQ monotherapy slowed proliferation and caused modest pyrimidine nucleotide depletion, whereas combination treatment with BQ and CNX-774 led to profound cell viability loss and pyrimidine starvation. We also identify N-acetylneuraminic acid accumulation as a potential marker of the therapeutic efficacy of DHODH inhibitors. In an aggressive, immunocompetent pancreatic cancer mouse model, combined targeting of DHODH and ENT1 dramatically suppressed tumor growth and prolonged mouse survival. Overall, our study defines CNX-774 as a previously uncharacterized ENT1 inhibitor and provides strong proof of concept support for dual targeting of DHODH and ENT1 in pancreatic cancer.

Effects of metabolic cancer therapy on tumor microenvironment

Targeting tumor metabolism for cancer therapy is an old strategy. In fact, historically the first effective cancer therapeutics were directed at nucleotide metabolism. The spectrum of metabolic drugs considered in cancer increases rapidly - clinical trials are in progress for agents directed at glycolysis, oxidative phosphorylation, glutaminolysis and several others. These pathways are essential for cancer cell proliferation and redox homeostasis, but are also required, to various degrees, in other cell types present in the tumor microenvironment, including immune cells, endothelial cells and fibroblasts. How metabolism-targeted treatments impact these tumor-associated cell types is not fully understood, even though their response may co-determine the overall effectivity of therapy. Indeed, the metabolic dependencies of stromal cells have been overlooked for a long time. Therefore, it is important that metabolic therapy is considered in the context of tumor microenvironment, as understanding the metabolic vulnerabilities of both cancer and stromal cells can guide new treatment concepts and help better understand treatment resistance. In this review we discuss recent findings covering the impact of metabolic interventions on cellular components of the tumor microenvironment and their implications for metabolic cancer therapy.

Cellular Genome-Scale Metabolic Modeling Identifies New Potential Drug Targets Against Hepatocellular Carcinoma

Genome-scale metabolic modeling (GEM) is one of the key approaches to unpack cancer metabolism and for discovery of new drug targets. In this study, we report the Transcriptional Regulated Flux Balance Analysis-CORE (TRFBA-), an algorithm for GEM using key growth-correlated reactions using hepatocellular carcinoma (HCC), an important global health burden, as a case study. We generated a HepG2 cell-specific GEM by integrating this cell line transcriptomic data with a generic human metabolic model to forecast potential drug targets for HCC. A total of 108 essential genes for growth were predicted by the TRFBA-CORE. These genes were enriched for metabolic pathways involved in cholesterol, sterol, and steroid biosynthesis. Furthermore, we silenced a predicted essential gene, 11-beta dehydrogenase hydroxysteroid type 2 (HSD11B2), in HepG2 cells resulting in a reduction in cell viability. To further identify novel potential drug targets in HCC, we examined the effect of nine drugs targeting the essential genes, and observed that most drugs inhibited the growth of HepG2 cells. Some of these drugs in this model performed better than Sorafenib, the first-line therapeutic against HCC. A HepG2 cell-specific GEM highlights sterol metabolism to be essential for cell growth. HSD11B2 downregulation results in lower cell growth. Most of the compounds, selected by drug repurposing approach, show a significant inhibitory effect on cell growth in a wide range of concentrations. These findings offer new molecular leads for drug discovery for hepatic cancer while also illustrating the importance of GEM and drug repurposing in cancer therapeutics innovation.

Proof-of-principle studies on a strategy to enhance nucleotide imbalance specifically in cancer cells

Highly specific and potent inhibitors of dihydroorotate dehydrogenase (DHODH), an essential enzyme of the de novo pyrimidine ribonucleotide synthesis pathway, are in clinical trials for autoimmune diseases, viral infections and cancer. However, because DHODH inhibitors (DHODHi) are immunosuppressants they may reduce the anticancer activity of the immune system. Therefore, there may be a need to improve the therapeutic index of DHODHi in cancer patients. The aim of this study was to find strategies to protect activated T cells from DHODHi and to identify cancer types hypersensitive to these inhibitors. First, we observed that like uridine supplementation, adding cytidine to the culture medium protects T cells from DHODH blockage. Next, we identified tumor types with altered expression of pyrimidine ribonucleotide synthesis enzymes. In this regard, we detected that the expression of cytidine deaminase (CDA), which converts cytidine into uridine, is low in an important proportion of cancer cell lines and consistently low in neuroblastoma samples and in cell lines from neuroblastoma and small cell lung carcinoma. This suggested that in the presence of a DHODHi, an excess of cytidine would be deleterious for low CDA expressing cancer cell lines. We show that this was the case (as could be seen almost immediately after treatment) when cells were cultured with fetal bovine serum but, was significantly less evident when cultures contained human serum. One interesting feature of CDA is that aside from acting intracellularly, it is also present in human plasma/serum. Altogether, experiments using recombinant CDA, human serum, pharmacologic inhibition of CDA and T cell/cancer cell co-cultures suggest that the therapeutic index of DHODHi could be improved by selecting patients with low-CDA expressing cancers in combination with strategies to increase cytidine or the cytidine/uridine ratio in the extracellular environment. Collectively, this proof-of-principle study warrants the discovery of agents to deplete extracellular CDA.

Evolution of small cell lung cancer tumor mutation: from molecular mechanisms to novel viewpoints

Small cell lung cancer (SCLC) is a clinically common malignant tumor originating from the lung neuroendocrine stem cells, which has a poor prognosis and accounts for approximately 15% of all lung cancer cases. However, research on its treatment has been slow, and the 5-year survival rate of patients with SCLC has been < 5% for many years. In recent years, the development and popularization of gene sequencing technology have facilitated the understanding of the gene mutation landscape and tumor evolution of SCLC, thereby leading to a more accurate prediction of the prognosis of SCLC and the development of individualized treatment. In this review, we aimed to discuss the mutation evolution of SCLC from the perspective of a tumor evolution theory and described the sequence of mutation evolution in the occurrence and development of SCLC. In addition, we summarized the existing whole-exome sequencing (WES) data of SCLC cases at our center along with relevant publications on sequencing. Thereafter, we discuss the role of different mutated pathways in the occurrence of SCLC to predict its prognosis more accurately and summarized individualized treatment strategies.

GPX4-independent ferroptosis—a new strategy in disease’s therapy

Ferroptosis is a form of programmed cell death characterized by intracellular iron accumulation and lipid peroxidation, and earlier studies identified glutathione peroxidase 4 (GPX4) as an essential regulator of this process. Ferroptosis plays an essential role in tumors, degenerative diseases, and ischemia-reperfusion injury. However, researchers have found that inhibition of GPX4 does not entirely suppress ferroptosis in certain diseases, or cells express resistance to ferroptosis agonists that inhibit GPX4. As research progresses, it has been discovered that there are multiple regulatory pathways for ferroptosis that are independent of GPX4. The study of GPX4-independent ferroptosis pathways can better target ferroptosis to prevent and treat various diseases. Here, the currently inhibited pulmonary GPX4-dependent ferroptosis pathways will be reviewed.

Identification of the effects of COVID-19 on patients with pulmonary fibrosis and lung cancer: a bioinformatics analysis and literature review

Coronavirus disease 2019 (COVID-19) poses a serious threat to human health and life. The effective prevention and treatment of COVID-19 complications have become crucial to saving patients’ lives. During the phase of mass spread of the epidemic, a large number of patients with pulmonary fibrosis and lung cancers were inevitably infected with the SARS-CoV-2 virus. Lung cancers have the highest tumor morbidity and mortality rates worldwide, and pulmonary fibrosis itself is one of the complications of COVID-19. Idiopathic lung fibrosis (IPF) and various lung cancers (primary and metastatic) become risk factors for complications of COVID-19 and significantly increase mortality in patients. Therefore, we applied bioinformatics and systems biology approaches to identify molecular biomarkers and common pathways in COVID-19, IPF, colorectal cancer (CRC) lung metastasis, SCLC and NSCLC. We identified 79 DEGs between COVID-19, IPF, CRC lung metastasis, SCLC and NSCLC. Meanwhile, based on the transcriptome features of DSigDB and common DEGs, we identified 10 drug candidates. In this study, 79 DEGs are the common core genes of the 5 diseases. The 10 drugs were found to have positive effects in treating COVID-19 and lung cancer, potentially reducing the risk of pulmonary fibrosis.

Cooperation effects of radiation and ferroptosis on tumor suppression and radiation injury

Ferroptosis is a kind of oxidative stress-dependent cell death characterized by iron accumulation and lipid peroxidation. It can work in conjunction with radiation to increase reactive oxygen species (ROS) generation and disrupt the antioxidant system, suppressing tumor progression. Radiation can induce ferroptosis by creating ROS, depleting glutathione, activating genes linked to DNA damage and increasing the expression of acyl-CoA synthetase long-chain family member 4 (ACSL4) in tumor cells. Furthermore, ferroptosis can enhance radiosensitivity by causing an iron overload, destruction of the antioxidant system, and lipid peroxidation. Radiation can also cause ferroptosis in normal cells, resulting in radiation injury. The role of ferroptosis in radiation-induced lung, intestinal, skin, and hematological injuries have been studied. In this review, we summarize the potential mechanisms linking ferroptosis, oxidative stress and radiation; analyze the function of ferroptosis in tumor suppression and radiation injury; and discuss the potential of ferroptosis regulation to improve radiotherapy efficacy and reduce adverse effects.

DHODH is an independent prognostic marker and potent therapeutic target in neuroblastoma

Despite intensive therapy, children with high-risk neuroblastoma are at risk of treatment failure. We applied a multiomic system approach to evaluate metabolic vulnerabilities in human neuroblastoma. We combined metabolomics, CRISPR screening, and transcriptomic data across more than 700 solid tumor cell lines and identified dihydroorotate dehydrogenase (DHODH), a critical enzyme in pyrimidine synthesis, as a potential treatment target. Of note, DHODH inhibition is currently under clinical investigation in patients with hematologic malignancies. In neuroblastoma, DHODH expression was identified as an independent risk factor for aggressive disease, and high DHODH levels correlated to worse overall and event-free survival. A subset of tumors with the highest DHODH expression was associated with a dismal prognosis, with a 5-year survival of less than 10%. In xenograft and transgenic neuroblastoma mouse models treated with the DHODH inhibitor brequinar, tumor growth was dramatically reduced, and survival was extended. Furthermore, brequinar treatment was shown to reduce the expression of MYC targets in 3 neuroblastoma models in vivo. A combination of brequinar and temozolomide was curative in the majority of transgenic TH-MYCN neuroblastoma mice, indicating a highly active clinical combination therapy. Overall, DHODH inhibition combined with temozolomide has therapeutic potential in neuroblastoma, and we propose this combination for clinical testing.

Nucleotide imbalance decouples cell growth from cell proliferation

Nucleotide metabolism supports RNA synthesis and DNA replication to enable cell growth and division. Nucleotide depletion can inhibit cell growth and proliferation, but how cells sense and respond to changes in the relative levels of individual nucleotides is unclear. Moreover, the nucleotide requirement for biomass production changes over the course of the cell cycle, and how cells coordinate differential nucleotide demands with cell cycle progression is not well understood. Here we find that excess levels of individual nucleotides can inhibit proliferation by disrupting the relative levels of nucleotide bases needed for DNA replication and impeding DNA replication. The resulting purine and pyrimidine imbalances are not sensed by canonical growth regulatory pathways like mTORC1, Akt and AMPK signalling cascades, causing excessive cell growth despite inhibited proliferation. Instead, cells rely on replication stress signalling to survive during, and recover from, nucleotide imbalance during S phase. We find that ATR-dependent replication stress signalling is activated during unperturbed S phases and promotes nucleotide availability to support DNA replication. Together, these data reveal that imbalanced nucleotide levels are not detected until S phase, rendering cells reliant on replication stress signalling to cope with this metabolic problem and disrupting the coordination of cell growth and division.

Cancer cells depend on environmental lipids for proliferation when electron acceptors are limited

Production of oxidized biomass, which requires regeneration of the cofactor NAD⁺, can be a proliferation bottleneck that is influenced by environmental conditions. However, a comprehensive quantitative understanding of metabolic processes that may be affected by NAD⁺ deficiency is currently missing. Here, we show that de novo lipid biosynthesis can impose a substantial NAD⁺ consumption cost in proliferating cancer cells. When electron acceptors are limited, environmental lipids become crucial for proliferation because NAD⁺ is required to generate precursors for fatty acid biosynthesis. We find that both oxidative and even net reductive pathways for lipogenic citrate synthesis are gated by reactions that depend on NAD⁺ availability. We also show that access to acetate can relieve lipid auxotrophy by bypassing the NAD⁺ consuming reactions. Gene expression analysis demonstrates that lipid biosynthesis strongly anti-correlates with expression of hypoxia markers across tumor types. Overall, our results define a requirement for oxidative metabolism to support biosynthetic reactions and provide a mechanistic explanation for cancer cell dependence on lipid uptake in electron acceptor-limited conditions, such as hypoxia.

Glycosylated Cathepsin V Serves as a Prognostic Marker in Lung Cancer

Dysregulation of cysteine cathepsin protease activity is pivotal in tumorigenic transformation. However, the role of cathepsin protease in lung cancer remains unknown. Here, we analyzed GEO database and found that lung cancer presented high expression of cathepsin V (CTSV). We then performed immunohistochemistry assay in 73 paired lung cancer tissues and normal lung tissues and confirmed that CTSV is overexpressed in lung cancer and correlates with poor prognosis. The mass spectrometry experiment showed that the N-glycosylation locus of CTSV are N221 and N292, glycosylated CTSV (band 43 kDa) was particularly expressed in lung cancer samples and correlated with lymph node metastasis. Mechanistic studies showed that only glycosylated CTSV (43-kDa band) are secreted to extracellular matrix (ECM) and promoted the metastasis of lung cancer. Importantly, the Elisa detection in serum of 12 lung cancer patients and 12 healthy donors showed that the level of CTSV in serum distinguished lung cancer patients from healthy donors. Together, our findings reveal the clinical relevance of CTSV glycosylation and CTSV drives the metastasis of lung cancer, suggesting that the glycosylated CTSV in serum is a promising biomarker for lung cancer.

Organoids as a Systems Platform for SCLC Brain Metastasis

Small Cell Lung Cancer (SCLC) is a highly aggressive, neuroendocrine tumor. Traditional reductionist approaches have proven ineffective to ameliorate the uniformly dismal outcomes for SCLC - survival at 5 years remains less than 5%. A major obstacle to improving treatment is that SCLC tumor cells disseminate early, with a strong propensity for metastasizing to the brain. Accumulating evidence indicates that, contrary to previous textbook knowledge, virtually every SCLC tumor is comprised of multiple subtypes. Important questions persist regarding the role that this intra-tumor subtype heterogeneity may play in supporting the invasive properties of SCLC. A recurrent hypothesis in the field is that subtype interactions and/or transition dynamics are major determinants of SCLC metastatic seeding and progression. Here, we review the advantages of cerebral organoids as an experimentally accessible platform for SCLC brain metastasis, amenable to genetic manipulations, drug perturbations, and assessment of subtype interactions when coupled, e.g., to temporal longitudinal monitoring by high-content imaging or high-throughput omics data generation. We then consider systems approaches that can produce mathematical and computational models useful to generalize lessons learned from ex vivo organoid cultures, and integrate them with in vivo observations. In summary, systems approaches combined with ex vivo SCLC cultures in brain organoids may effectively capture both tumor-tumor and host-tumor interactions that underlie general principles of brain metastasis.

Targeting nucleotide metabolism: a promising approach to enhance cancer immunotherapy

Targeting nucleotide metabolism can not only inhibit tumor initiation and progression but also exert serious side effects. With in-depth studies of nucleotide metabolism, our understanding of nucleotide metabolism in tumors has revealed their non-proliferative effects on immune escape, indicating the potential effectiveness of nucleotide antimetabolites for enhancing immunotherapy. A growing body of evidence now supports the concept that targeting nucleotide metabolism can increase the antitumor immune response by (1) activating host immune systems via maintaining the concentrations of several important metabolites, such as adenosine and ATP, (2) promoting immunogenicity caused by increased mutability and genomic instability by disrupting the purine and pyrimidine pool, and (3) releasing nucleoside analogs via microbes to regulate immunity. Therapeutic approaches targeting nucleotide metabolism combined with immunotherapy have achieved exciting success in preclinical animal models. Here, we review how dysregulated nucleotide metabolism can promote tumor growth and interact with the host immune system, and we provide future insights into targeting nucleotide metabolism for immunotherapeutic treatment of various malignancies.