ARNT deficiency represses pyruvate dehydrogenase kinase 1 to trigger ROS production and melanoma metastasis

Inhibition of programmed cell death by melanoma cell subpopulations reveals mechanisms of melanoma metastasis and potential therapeutic targets

Melanoma is an aggressive type of skin cancer that arises from melanocytes, the cells responsible for producing skin pigment. In contrast to non-melanoma skin cancers like basal cell carcinoma and squamous cell carcinoma, melanoma is more invasive. Melanoma was distinguished by its rapid progression, high metastatic potential, and significant resistance to conventional therapies. Although it accounted for a small proportion of skin cancer cases, melanoma accounts for the majority of deaths caused by skin cancer due to its ability to invade deep tissues, adapt to diverse microenvironments, and evade immune responses. These unique features highlighted the challenges of treating melanoma and underscored the importance of advanced tools, such as single-cell sequencing, to unravel its biology and develop personalized therapeutic strategies. Thus, we conducted a single-cell analysis of the cellular composition within melanoma tumor tissues and further subdivided melanoma cells into subpopulations. Through analyzing metabolic pathways, stemness genes, and transcription factors (TFs) among cells in different phases (G1, G2/M, and S) as well as between primary and metastatic foci cells, we investigated the specific mechanisms underlying melanoma metastasis. We also revisited the cellular stemness and temporal trajectories of melanoma cell subpopulations, identifying the core subpopulation as C0 SOD3 + Melanoma cells. Our findings revealed a close relationship between the pivotal C0 SOD3 + Melanoma cells subpopulation and oxidative pathways in metastatic tumor tissues. Additionally, we analyzed prognostically relevant differentially expressed genes (DEGs) within the C0 SOD3 + Melanoma cells subpopulation and built a predictive model associated with melanoma outcomes. We selected the gene IGF1 with the highest coefficient (coef) value for further analysis, and experimentally validated its essential function in the proliferation and invasive metastasis of melanoma. In immune infiltration analysis, we discovered the critical roles played by M1/M2 macrophages in melanoma progression and immune evasion. Furthermore, the development and progression of malignant melanoma were closely associated with various forms of programmed cell death (PCD), including apoptosis, autophagic cell death, ferroptosis, and pyroptosis. Melanoma cells often resisted cell death mechanisms, maintaining their growth by inhibiting apoptosis and evading autophagic cell death. Meanwhile, the induction of ferroptosis and pyroptosis was thought to trigger immune responses that helped suppress melanoma dissemination. A deeper understanding of the relationship between melanoma and PCD pathways provided a critical foundation for developing novel targeted therapies, with the potential to enhance melanoma treatment efficacy. These findings contributed to the development of novel prognostic models for melanoma and shed light on research directions concerning melanoma metastasis mechanisms and therapeutic targets.

CRISPR-StAR enables high-resolution genetic screening in complex in vivo models

Pooled genetic screening with CRISPR-Cas9 has enabled genome-wide, high-resolution mapping of genes to phenotypes, but assessing the effect of a given genetic perturbation requires evaluation of each single guide RNA (sgRNA) in hundreds of cells to counter stochastic genetic drift and obtain robust results. However, resolution is limited in complex, heterogeneous models, such as organoids or tumors transplanted into mice, because achieving sufficient representation requires impractical scaling. This is due to bottleneck effects and biological heterogeneity of cell populations. Here we introduce CRISPR-StAR, a screening method that uses internal controls generated by activating sgRNAs in only half the progeny of each cell subsequent to re-expansion of the cell clone. Our method overcomes both intrinsic and extrinsic heterogeneity as well as genetic drift in bottlenecks by generating clonal, single-cell-derived intrinsic controls. We use CRISPR-StAR to identify in-vivo-specific genetic dependencies in a genome-wide screen in mouse melanoma. Benchmarking against conventional screening demonstrates the improved data quality provided by this technology.

The promotion of cell proliferation and invasion in cutaneous squamous cell carcinomas after ARNT downregulation is associated with CXCL3

The aryl hydrocarbon receptor nuclear translocator (ARNT) is a transcription factor associated with adaptive responses to cellular stress. Its role in cutaneous squamous cell carcinoma (cSCC) remains poorly understood. The aim of this study was to investigate the role of ARNT in cSCC. Immunohistochemistry revealed downregulation of ARNT in cSCC, precancerous lesions (actinic keratosis), and cells. Knockdown of ARNT in A431 and SCL-1 cells significantly enhanced cell growth and metastasis. Microarray analysis and Ingenuity Pathway Analysis confirmed that loss of ARNT in A431 cells was highly correlated with cell growth and movement and upregulated CXCL3 expression. Cellular and xenograft experiments further confirmed that ARNT regulates cSCC proliferation and invasiveness in a CXCL3-dependent manner. ARNT may regulate CXCL3 expression through ROS-STAT3 pathway. In conclusion, this study demonstrates that ARNT plays a critical role in the development of cSCC and significantly affects the proliferation and metastatic ability of cSCC cells. It has the potential to serve as an ideal treatment target for cSCC.

Melatonin ameliorates multiorgan injuries induced by severe acute pancreatitis in mice by regulating the Nrf2 signaling pathway

Severe acute pancreatitis (SAP) is a complicated inflammatory reaction that impacts the pancreas, often resulting in damage to numerous organs. This disorder encompasses a range of processes such as inflammation, oxidative stress, and pancreatitis. The hormone melatonin (MT) is primarily secreted by the pineal gland and plays a crucial role in mitigating inflammation, countering the harmful effects of free radicals, and regulating oxidative stress. The aim of this research was to investigate the potential protective impact and the underlying mechanism of melatonin in mice afflicted with SAP. The biochemical and histological assessments unequivocally demonstrated that melatonin effectively inhibited necrosis, infiltration, edema and cell death in pancreatic tissues, thereby suppressing acute pancreatitis. Notably, melatonin also alleviated the consequent harm to distant organs, notably the lungs, liver, and kidneys. Furthermore, both preventive and therapeutic administration of melatonin prompted nuclear factor E2-related factor 2 (Nrf2) activation followed by Nrf2 target gene expression. Nrf2 initiates the activation of antioxidant genes, thereby providing defense against oxidative stress. Conversely, Nrf2 reduction may contribute to impaired antioxidant protection in SAP. The beneficial impact of Nrf2 on antioxidants was absent in Nrf2-knockout mice, leading to the accumulation of LDH and exacerbation of cell death. This deterioration in both pancreatitis and injuries in distant organs intensified significantly. The results indicate that melatonin has an enhanced ability to protect against multiorgan damage caused by SAP, which is accomplished through the increase in Nrf2 expression. Additionally, Nrf2 initiates the activation of antioxidant genes that offer defense against cell death.

Discovery and Mechanistic Elucidation of NQO1-Bioactivatable Small Molecules That Overcome Resistance to Degraders

Degraders hold the promise to efficiently inactivate previously intractable disease-relevant targets. Unlike traditional inhibitors, degraders act substoichiometrically and rely on the hijacked proteolysis machinery, which can also act as an entry point for resistance. To fully harness the potential of targeted protein degradation, it is crucial to comprehend resistance mechanisms and formulate effective strategies to overcome them. We conducted a chemical screening to identify synthetic lethal vulnerabilities of cancer cells that exhibit widespread resistance to degraders. Comparative profiling followed by tailored optimization delivered the small molecule RBS-10, which shows preferential cytotoxicity against cells pan-resistant to degraders. Multiomics deconvolution of the mechanism of action revealed that RBS-10 acts as a prodrug bioactivated by the oxidoreductase enzyme NQO1, which is highly overexpressed in our resistance models. Collectively, our work informs on NQO1 as an actionable vulnerability to overcome resistance to degraders and as a biomarker to selectively exploit bioactivatable prodrugs in cancer.

Heterogeneity in the Metastatic Microenvironment: JunB-Expressing Microglia Cells as Potential Drivers of Melanoma Brain Metastasis Progression

Reciprocal signaling between melanoma brain metastatic (MBM) cells and microglia reprograms the phenotype of both interaction partners, including upregulation of the transcription factor JunB in microglia. Here, we aimed to elucidate the impact of microglial JunB upregulation on MBM progression. For molecular profiling, we employed RNA-seq and reverse-phase protein array (RPPA). To test microglial JunB functions, we generated microglia variants stably overexpressing JunB (JunBhi) or with downregulated levels of JunB (JunBlo). Melanoma-derived factors, namely leukemia inhibitory factor (LIF), controlled JunB upregulation through Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) signaling. The expression levels of JunB in melanoma-associated microglia were heterogeneous. Flow cytometry analysis revealed the existence of basal-level JunB-expressing microglia alongside microglia highly expressing JunB. Proteomic profiling revealed a differential protein expression in JunBhi and JunBlo cells, namely the expression of microglia activation markers Iba-1 and CD150, and the immunosuppressive molecules SOCS3 and PD-L1. Functionally, JunBhi microglia displayed decreased migratory capacity and phagocytic activity. JunBlo microglia reduced melanoma proliferation and migration, while JunBhi microglia preserved the ability of melanoma cells to proliferate in three-dimensional co-cultures, that was abrogated by targeting leukemia inhibitory factor receptor (LIFR) in control microglia-melanoma spheroids. Altogether, these data highlight a melanoma-mediated heterogenous effect on microglial JunB expression, dictating the nature of their functional involvement in MBM progression. Targeting microglia highly expressing JunB may potentially be utilized for MBM theranostics.

Targeting Endothelial HIF2α/ARNT Expression for Ischemic Heart Disease Therapy

Ischemic heart disease (IHD) is a major cause of mortality and morbidity worldwide, with novel therapeutic strategies urgently needed. Endothelial dysfunction is a hallmark of IHD, contributing to its development and progression. Hypoxia-inducible factors (HIFs) are transcription factors activated in response to low oxygen levels, playing crucial roles in various pathophysiological processes related to cardiovascular diseases. Among the HIF isoforms, HIF2α is predominantly expressed in cardiac vascular endothelial cells and has a key role in cardiovascular diseases. HIFβ, also known as ARNT, is the obligate binding partner of HIFα subunits and is necessary for HIFα's transcriptional activity. ARNT itself plays an essential role in the development of the cardiovascular system, regulating angiogenesis, limiting inflammatory cytokine production, and protecting against cardiomyopathy. This review provides an overview of the current understanding of HIF2α and ARNT signaling in endothelial cell function and dysfunction and their involvement in IHD pathogenesis. We highlight their roles in inflammation and maintaining the integrity of the endothelial barrier, as well as their potential as therapeutic targets for IHD.

Integrated high-throughput analysis identifies super enhancers in metastatic castration-resistant prostate cancer

Background: Metastatic castration-resistant prostate cancer (mCRPC) is a highly aggressive stage of prostate cancer, and non-mutational epigenetic reprogramming plays a critical role in its progression. Super enhancers (SE), epigenetic elements, are involved in multiple tumor-promoting signaling pathways. However, the SE-mediated mechanism in mCRPC remains unclear. Methods: SE-associated genes and transcription factors were identified from a cell line (C4-2B) of mCRPC by the CUT&Tag assay. Differentially expressed genes (DEGs) between mCRPC and primary prostate cancer (PCa) samples in the GSE35988 dataset were identified. What's more, a recurrence risk prediction model was constructed based on the overlapping genes (termed SE-associated DEGs). To confirm the key SE-associated DEGs, BET inhibitor JQ1 was applied to cells to block SE-mediated transcription. Finally, single-cell analysis was performed to visualize cell subpopulations expressing the key SE-associated DEGs. Results: Nine human TFs, 867 SE-associated genes and 5417 DEGs were identified. 142 overlapping SE-associated DEGs showed excellent performance in recurrence prediction. Time-dependent receiver operating characteristic (ROC) curve analysis showed strong predictive power at 1 year (0.80), 3 years (0.85), and 5 years (0.88). The efficacy of his performance has also been validated in external datasets. In addition, FKBP5 activity was significantly inhibited by JQ1. Conclusion: We present a landscape of SE and their associated genes in mCPRC, and discuss the potential clinical implications of these findings in terms of their translation to the clinic.

Chrysin induces autophagy through the inactivation of the ROS‑mediated Akt/mTOR signaling pathway in endometrial cancer

Endometrial cancer (EC) is widely known as an aggressive malignancy. Due to the limited therapeutic options and poor prognosis of patients with advanced-stage EC, there is a need to identify effective alternative treatments. Chrysin is a naturally active flavonoid (5,7-dihydroxyflavone), which has been demonstrated to exert anticancer effects and may present a novel strategy for EC treatment. However, the role of chrysin in EC remains largely unclear. The aim of the present study was to examine the anticancer effects of chrysin on EC. The results revealed that, in addition to apoptosis, chrysin increased the LC3II expression levels and markedly accelerated the autophagic flux, suggesting that chrysin induced both the autophagy and apoptosis of EC cells. Furthermore, the inhibition of autophagy by chloroquine enhanced the inhibitory effect on cell proliferation and the promotion of the chrysin-induced apoptosis of EC cells, indicating that chrysin-induced autophagy was a cytoprotective mechanism. Additionally, chrysin led to the production of intracellular reactive oxygen species (ROS). N-acetylcysteine (NAC) pretreatment significantly inhibited chrysin-induced autophagy, suggesting that ROS activated autophagy induced by chrysin in EC cells. Furthermore, the phosphorylated (p-) Akt and p-mTOR levels were significantly decreased in a concentration-dependent manner following treatment with chrysin, while NAC blocked these effects. Taken together, these findings demonstrated that chrysin-induced autophagy via the inactivation of the ROS-mediated Akt/mTOR signaling pathway in EC cells.

Endothelial Aryl Hydrocarbon Receptor Nuclear Translocator Mediates the Angiogenic Response to Peripheral Ischemia in Mice With Type 2 Diabetes Mellitus

Hypoxia-inducible factors (HIFs) are the master regulators of angiogenesis, a process that is impaired in patients with diabetes mellitus (DM). The transcription factor aryl hydrocarbon receptor nuclear translocator (ARNT, also known as HIF1β) has been implicated in the development and progression of diabetes. Angiogenesis is driven primarily by endothelial cells (ECs), but both global and EC-specific loss of ARNT-cause are associated with embryonic lethality. Thus, we conducted experiments in a line of mice carrying an inducible, EC-specific ARNT-knockout mutation (Arnt Δ EC, ERT2) to determine whether aberrations in ARNT expression might contribute to the vascular deficiencies associated with diabetes. Mice were first fed with a high-fat diet to induce diabetes. Arnt Δ EC, ERT2 mice were then adminstrated with oral tamoxifen to disrupt Arnt and peripheral angiogenesis was evaluated by using laser-Doppler perfusion imaging to monitor blood flow after hindlimb ischemia. The Arnt Δ EC, ERT2 mice had impaired blood flow recovery under both non-diabetic and diabetic conditions, but the degree of impairment was greater in diabetic animals. In addition, siRNA-mediated knockdown of ARNT activity reduced measurements of tube formation, and cell viability in human umbilical vein endothelial cells (HUVECs) cultured under high-glucose conditions. The Arnt Δ EC, ERT2 mutation also reduced measures of cell viability, while increasing the production of reactive oxygen species (ROS) in microvascular endothelial cells (MVECs) isolated from mouse skeletal muscle, and the viability of Arnt Δ EC, ERT2 MVECs under high-glucose concentrations increased when the cells were treated with an ROS inhibitor. Collectively, these observations suggest that declines in endothelial ARNT expression contribute to the suppressed angiogenic phenotype in diabetic mice, and that the cytoprotective effect of ARNT expression in ECs is at least partially mediated by declines in ROS production.

Coordinated Contribution of NADPH Oxidase- and Mitochondria-Derived Reactive Oxygen Species in Metabolic Syndrome and Its Implication in Renal Dysfunction

Metabolic syndrome (MetS), a complex of interrelated risk factors for cardiovascular disease and diabetes, is comprised of central obesity (increased waist circumference), hyperglycemia, dyslipidemia (high triglyceride blood levels, low high-density lipoprotein blood levels), and increased blood pressure. Oxidative stress, caused by the imbalance between pro-oxidant and endogenous antioxidant systems, is the primary pathological basis of MetS. The major sources of reactive oxygen species (ROS) associated with MetS are nicotinamide-adenine dinucleotide phosphate (NADPH) oxidases and mitochondria. In this review, we summarize the current knowledge regarding the generation of ROS from NADPH oxidases and mitochondria, discuss the NADPH oxidase- and mitochondria-derived ROS signaling and pathophysiological effects, and the interplay between these two major sources of ROS, which leads to chronic inflammation, adipocyte proliferation, insulin resistance, and other metabolic abnormalities. The mechanisms linking MetS and chronic kidney disease are not well known. The role of NADPH oxidases and mitochondria in renal injury in the setting of MetS, particularly the influence of the pyruvate dehydrogenase complex in oxidative stress, inflammation, and subsequent renal injury, is highlighted. Understanding the molecular mechanism(s) underlying MetS may lead to novel therapeutic approaches by targeting the pyruvate dehydrogenase complex in MetS and prevent its sequelae of chronic cardiovascular and renal diseases.