FoxO3A promotes metabolic adaptation to hypoxia by antagonizing Myc function

Deubiquitinase-Targeting Chimeras (DUBTACs) as a Potential Paradigm-Shifting Drug Discovery Approach

Developing proteolysis-targeting chimeras (PROTACs) is well recognized through target protein degradation (TPD) toward promising therapeutics. While a variety of diseases are driven by aberrant ubiquitination and degradation of critical proteins with protective functions, target protein stabilization (TPS) rather than TPD is emerging as a unique therapeutic modality. Deubiquitinase-targeting chimeras (DUBTACs), a class of heterobifunctional protein stabilizers consisting of deubiquitinase (DUB) and protein-of-interest (POI) targeting ligands conjugated with a linker, can rescue such proteins from aberrant elimination. DUBTACs stabilize the levels of POIs in a DUB-dependent manner, removing ubiquitin from polyubiquitylated and degraded proteins. DUBTACs can induce a new interaction between POI and DUB by forming a POI-DUBTAC-DUB ternary complex. Herein, therapeutic benefits of TPS approaches for human diseases are introduced, and recent advances in developing DUBTACs are summarized. Relevant challenges, opportunities, and future perspectives are also discussed.

The Role of Hypoxia in Longevity

Aging is marked by a progressive decrease in physiological function and reserve capacity, which results in increased susceptibility to diseases. Understanding the mechanisms of driving aging is crucial for extending health span and promoting human longevity. Hypoxia, marked by reduced oxygen availability, has emerged as a promising area of study within aging research. This review explores recent findings on the potential of oxygen restriction to promote healthy aging and extend lifespan. While the role of hypoxia-inducible factor 1 (HIF-1) in cellular responses to hypoxia is well-established, its impact on lifespan remains complex and context-dependent. Investigations in invertebrate models suggest a role for HIF-1 in longevity, while evidence in mammalian models is limited. Hypoxia extends the lifespan independent of dietary restriction (DR), a known intervention underlying longevity. However, both hypoxia and DR converge on common downstream effectors, such as forkhead box O (FOXO) and flavin-containing monooxygenase (FMOs) to modulate the lifespan. Further work is required to elucidate the molecular mechanisms underlying hypoxia-induced longevity and optimize clinical applications. Understanding the crosstalk between HIF-1 and other longevity-associated pathways is crucial for developing interventions to enhance lifespan and healthspan. Future studies may uncover novel therapeutic strategies to promote healthy aging and longevity in human populations.

Obesity-Facilitated Colon Cancer Progression Is Mediated by Increased Diacylglycerol O-Acyltransferases 1 and 2 Levels

BACKGROUND & AIMS

The obesity epidemic is associated with increased colon cancer progression. As lipid droplets (LDs) fuel tumor growth, we aimed to determine the significance of diacyltransferases (diacylglycerol o-acyltransferases 1 and 2 [DGAT1/2]), responsible for LDs biogenesis, in obesity-mediated colonic tumorigenesis.

METHODS

Human colon cancer samples, colon cancer cells, colonospheres, and ApcMin/+ colon cancer mouse model on a high-fat diet were employed. For DGAT1/2 inhibition, enzymatic inhibitors and small interfering RNA were used. Expression, pathways, cell cycle, and growth were assessed. Bioinformatic analyses of CUT&RUN and RNA sequencing data were performed.

RESULTS

DGAT1/2 levels in human colon cancer tissue are significantly elevated with disease severity and obesity (vs normal). Their levels are increased in human colon cancer cells (vs nontransformed) and further enhanced by fatty acids prevalent in obesity; augmented DGAT2 expression is MYC-dependent. Inhibition of DGAT1/2 improves FOXO3 activity by attenuating PI3K, resulting in reduced MYC-dependent DGAT2 expression and accumulation of LDs, suggesting feedback. This inhibition attenuated growth in colon cancer cells and colonospheres via FOXO3/p27kip1 cell cycle arrest and reduced colonic tumors in ApcMin/+ mice on a high-fat diet. Transcriptomic analysis revealed that DGAT1/2 inhibition targeted metabolic and tumorigenic pathways in human colon cancer and colon cancer crypts, stratifying human colon cancer samples from normal. Further analysis revealed that this inhibition is predictive of advanced disease-free state and survival in patients with colon cancer.

CONCLUSIONS

This is a novel mechanism of DGAT1/2-dependent metabolic and tumorigenic remodeling in obesity-facilitated colon cancer, providing a platform for future development of effective treatments for patients with colon cancer.

Mechanism of PTPN18 for regulating the migration and invasion of endometrial cancer cells via the MYC/PI3K/AKT pathway

OBJECTIVE

Endometrial cancer (EC) is a prevalent gynecologic malignancy. The critical role of PTPN18 in EC has been reported, while its role in the aerobic glycolysis of EC cells remains unclear. Our current study focused on the mechanism of PTPN18 in the regulation of aerobic glycolysis in EC.

METHODS

PTPN18 expression levels in endometrial stromal cells (KC02-44D) and EC cells (KLE, HEC-1-A, HEC-1B, and HEC-50) were determined. Following transfection of sh-PTPN18 in HEC-1-A cells, the changes in cell migratory and invasive abilities were assessed by the Transwell assay, and the changes in glucose consumption, lactic acid secretion, and ATP levels were detected using kits. The expression levels of glycolysis-related proteins HIF-1α, PKM2, and LDHA and the activation of the MYC/PI3K/AKT pathway were detected by Western blot. Additionally, sh-PTPN18 and pcDNA3.1-MYC were transfected into HEC-1-A cells to further explore their roles in the changes in aerobic glycolysis, migration, and invasion ability of EC cells.

RESULTS

Expression of PTPN18 in EC cells was up-regulated (HEC-1-A>HEC-1B>HEC-50>KLE). PTPN18 knockdown suppressed EC cell migration and invasion. Additionally, PTPN18 knockdown reduced glucose consumption, lactate production, ATP levels, and glycolysis-related protein levels (HIF-1α, PKM2, LDHA). PTPN18 knockdown inhibited the activation of the MYC/PI3K/AKT pathway in EC cells. MYC overexpression partially annulled the inhibitory effects of PTPN18 knockdown on aerobic glycolysis, migration, and invasion of EC cells.

CONCLUSION

Our present study provided evidence that the knockdown of PTPN18 inhibited the aerobic glycolysis, migration, and invasion of EC cells by suppressing the MYC/PI3K/AKT pathway.

N-Acetylneuraminic acid triggers endothelial pyroptosis and promotes atherosclerosis progression via GLS2-mediated glutaminolysis pathway

Vascular endothelial injury initiates atherosclerosis (AS) progression. N-Acetylneuraminic acid (Neu5Ac) metabolic disorder was found to intensify endothelial mitochondrial damage. And GLS2-associated glutaminolysis disorder contributed to mitochondrial dysfunction. However, mechanisms underlying Neu5Ac-associated mitochondrial dysfunction as well as its association with GLS2 remains unclear. In this study, we constructed GLS2-/-ApoE-/- mice by using HBLV-GLS2 shRNA injection. And methods like immunofluorescence, western blotting, transmission electron microscopy were applied to detect profiles of endothelial injury and AS progression both in vivo and in vitro. We demonstrated that Neu5Ac accumulation increased GLS2 expression and promoted glutaminolysis disorder, which further induced endothelial mitochondrial dysfunction via a pyroptosis-dependent pathway in vivo and in vitro. Mechanically, Neu5Ac interacted with SIRT3 and led to FOXO3a deacetylation and phosphorylation, further facilitated c-Myc antagonism and ultimately increased GLS2 levels. Inhibition of GLS2 could improve mitochondrial function and mitigate pyroptosis process. In addition, blocking Neu5Ac production using neuraminidases (NEUs) inhibitor could rescue endothelial damage and alleviate AS development in ApoE-/- mice. These findings proposed that Neu5Ac induced GLS2-mediated glutaminolysis disorder and then promoted mitochondrial dysfunction in a pyroptosis-dependent pathway. Targeting GLS2 or inhibiting Neu5Ac production could prevent AS progression.

Exploring the Relationship of rs2802292 with Diabetes and NAFLD in a Southern Italian Cohort-Nutrihep Study

Background: The minor G-allele of FOXO3 rs2802292 is associated with human longevity. The aim of this study was to test the protective effect of the variant against the association with type 2 Diabetes and NAFLD. Methods: rs2802292 was genotyped in a large population of middle-aged subjects (n = 650) from a small city in Southern Italy. All participants were interviewed to collect information about lifestyle and dietary habits; clinical characteristics were recorded, and blood samples were collected from all subjects. The association between rs2802292 and NAFLD or diabetes was tested using a logistic model and mediation analysis adjusted for covariates. Results: Overall, the results indicated a statistical association between diabetes and rs2802292, especially for the TT genotype (OR = 2.14, 1.01 to 4.53 95% C.I., p = 0.05) or in any case for those who possess the G-allele (OR = 0.45, 0.25 to 0.81 95% C.I., p = 0.008). Furthermore, we found a mediation effect of rs2802292 on diabetes (as mediator) and NAFLD. There is no direct relationship between rs2802292 and NAFLD, but the effect is direct (β = 0.10, -0.003 to 0.12 95% C.I., p = 0.04) on diabetes, but only in TT genotypes. Conclusions: The data on our cohort indicate that the longevity-associated FOXO3 variant may have protective effects against diabetes and NAFLD.

AURKA Activates FOXO3a to Form a Positive Feedback Loop in the Proliferation and Migration of Keloid Fibroblasts

Objective: Keloids are benign fibroproliferative disorders with invasive growth exceeding the wound boundary. Aurora kinase A (AURKA) is a serine/threonine kinase highly expressed in various tumors, facilitating tumor growth and invasion. Currently, the role of AURKA in keloid remains unclear. Approach: Fibroblasts were isolated from keloid and normal skin samples. AURKA was evaluated by qPCR, Western blot, and immunohistochemistry. Transcriptome sequencing and dual-luciferase reporter assays were applied to figure out targets of AURKA. Following expression alteration and MLN8237 (an AURKA kinase inhibitor, AKI) treatment, phenotypical experiments were conducted to clarify biological functions of AURKA along with its target, and to probe into the clinical potential of AURKA inhibition. Results: AURKA was upregulated in keloid tissues and fibroblasts. Forkhead box O 3a (FOXO3a) was verified as a downstream of AURKA. Further experiments demonstrated that AURKA transactivated FOXO3a by binding to FOXO3a, while FOXO3a directly transactivated AURKA. Functionally, AURKA and FOXO3a cooperated in enhancing the proliferation and migration of keloid fibroblasts via protein kinase B (AKT) phosphorylation. Although MLN8237 weakened the proliferation and migration in keloid fibroblasts, the transactivation of AURKA on FOXO3a was independent of kinase activity. Innovation: This study reveals that AURKA and FOXO3a compose a transactivation loop in enhancing the proliferative and migrative properties of keloid fibroblasts, and proposes AURKA as a promising target. Conclusion: AURKA/FOXO3a loop promotes the proliferation and migration of keloid fibroblasts via AKT signaling. Despite the anti-keloid effects of AKIs, AURKA acts as a transcription factor independently of kinase activity, deepening our understanding on AKI insensitivity.

Leukemia and mitophagy: a novel perspective for understanding oncogenesis and resistance

Mitophagy, the selective autophagic process that specifically degrades mitochondria, serves as a vital regulatory mechanism for eliminating damaged mitochondria and maintaining cellular balance. Emerging research underscores the central role of mitophagy in the initiation, advancement, and treatment of cancer. Mitophagy is widely acknowledged to govern mitochondrial homeostasis in hematopoietic stem cells (HSCs), influencing their metabolic dynamics. In this article, we integrate recent data to elucidate the regulatory mechanisms governing mitophagy and its intricate significance in the context of leukemia. An in-depth molecular elucidation of the processes governing mitophagy may serve as a basis for the development of pioneering approaches in targeted therapeutic interventions.

The hypoxia response pathway in the Antarctic fish Notothenia coriiceps is functional despite a poly Q/E insertion mutation in HIF-1α

Antarctic notothenioid fishes, inhabiting the oxygen-rich Southern Ocean, possess a polyglutamine and glutamic acid (poly Q/E) insertion mutation in the master transcriptional regulator of oxygen homeostasis, hypoxia- inducible factor-1α (HIF-1α). To determine if this mutation impairs the ability of HIF-1 to regulate gene expression in response to hypoxia, we exposed Notothenia coriiceps, with a poly Q/E insertion mutation in HIF-1α that is 9 amino acids long, to hypoxia (2.3 mg L-1 O2) or normoxia (10 mg L -1 O2) for 12 h. Heart ventricles, brain, liver, and gill tissue were harvested and changes in gene expression quantified using RNA sequencing. Levels of glycogen and lactate were also quantified to determine if anaerobic metabolism increases in response to hypoxia. Exposure to hypoxia resulted in 818 unique differentially expressed genes (DEGs) in liver tissue of N. coriiceps. Many hypoxic genes were induced, including ones involved in the MAP kinase and FoxO pathways, glycolytic metabolism, and vascular remodeling. In contrast, there were fewer than 104 unique DEGs in each of the other tissues sampled. Lactate levels significantly increased in liver in response to hypoxia, indicating that anaerobic metabolism increases in response to hypoxia in this tissue. Overall, our results indicate that the hypoxia response pathway is functional in N. coriiceps despite a poly Q/E mutation in HIF-1α, and confirm that Antarctic fishes are capable of altering gene expression in response to hypoxia.

EPAS1 expression contributes to maintenance of the primordial follicle pool in the mouse ovary

Oxygen availability can have profound effects on cell fate decisions and survival, in part by regulating expression of hypoxia-inducible factors (HIFs). In the ovary, HIF expression has been characterised in granulosa cells, however, any requirement in oocytes remains relatively undefined. Here we developed a Hif2a/Epas1 germline-specific knockout mouse line in which females were fertile, however produced 40% fewer pups than controls. No defects in follicle development were detected, and quality of MII oocytes was normal, as per assessments of viability, intracellular reactive oxygen species, and spindle parameters. However, a significant diminishment of the primordial follicle pool was evident in cKO females that was attributed to accelerated follicle loss from postnatal day 6 onwards, potentially via disruption of the autophagy pathway. These data demonstrate the importance of HIF signalling in oocytes, particularly at the primordial follicle stage, and lend to the importance of controlling oxygen tension in the development of in vitro growth and maturation approaches for assisted reproduction.

MYC Oncogene: A Druggable Target for Treating Cancers with Natural Products

Various diseases, including cancers, age-associated disorders, and acute liver failure, have been linked to the oncogene, MYC. Animal testing and clinical trials have shown that sustained tumor volume reduction can be achieved when MYC is inactivated, and different combinations of therapeutic agents including MYC inhibitors are currently being developed. In this review, we first provide a summary of the multiple biological functions of the MYC oncoprotein in cancer treatment, highlighting that the equilibrium points of the MYC/MAX, MIZ1/MYC/MAX, and MAD (MNT)/MAX complexes have further potential in cancer treatment that could be used to restrain MYC oncogene expression and its functions in tumorigenesis. We also discuss the multifunctional capacity of MYC in various cellular cancer processes, including its influences on immune response, metabolism, cell cycle, apoptosis, autophagy, pyroptosis, metastasis, angiogenesis, multidrug resistance, and intestinal flora. Moreover, we summarize the MYC therapy patent landscape and emphasize the potential of MYC as a druggable target, using herbal medicine modulators. Finally, we describe pending challenges and future perspectives in biomedical research, involving the development of therapeutic approaches to modulate MYC or its targeted genes. Patients with cancers driven by MYC signaling may benefit from therapies targeting these pathways, which could delay cancerous growth and recover antitumor immune responses.

Targeting MYC at the intersection between cancer metabolism and oncoimmunology

MYC activation is a known hallmark of cancer as it governs the gene targets involved in various facets of cancer progression. Of interest, MYC governs oncometabolism through the interactions with its partners and cofactors, as well as cancer immunity via its gene targets. Recent investigations have taken interest in characterizing these interactions through multi-Omic approaches, to better understand the vastness of the MYC network. Of the several gene targets of MYC involved in either oncometabolism or oncoimmunology, few of them overlap in function. Prominent interactions have been observed with MYC and HIF-1α, in promoting glucose and glutamine metabolism and activation of antigen presentation on regulatory T cells, and its subsequent metabolic reprogramming. This review explores existing knowledge of the role of MYC in oncometabolism and oncoimmunology. It also unravels how MYC governs transcription and influences cellular metabolism to facilitate the induction of pro- or anti-tumoral immunity. Moreover, considering the significant roles MYC holds in cancer development, the present study discusses effective direct or indirect therapeutic strategies to combat MYC-driven cancer progression.

Normobaric hypoxia shows enhanced FOXO1 signaling in obese mouse gastrocnemius muscle linked to metabolism and muscle structure and neuromuscular innervation

Skeletal muscle relies on mitochondria for sustainable ATP production, which may be impacted by reduced oxygen availability (hypoxia). Compared with long-term hypoxia, the mechanistic in vivo response to acute hypoxia remains elusive. Therefore, we aimed to provide an integrated description of the Musculus gastrocnemius response to acute hypoxia. Fasted male C57BL/6JOlaHsd mice, fed a 40en% fat diet for six weeks, were exposed to 12% O2 normobaric hypoxia or normoxia (20.9% O2) for six hours (n = 12 per group). Whole-body energy metabolism and the transcriptome response of the M. gastrocnemius were analyzed and confirmed by acylcarnitine determination and Q-PCR. At the whole-body level, six hours of hypoxia reduced energy expenditure, increased blood glucose and tended to decreased the respiratory exchange ratio (RER). Whole-genome transcriptome analysis revealed upregulation of forkhead box-O (FOXO) signalling, including an increased expression of tribbles pseudokinase 3 (Trib3). Trib3 positively correlated with blood glucose levels. Upregulated carnitine palmitoyltransferase 1A negatively correlated with the RER, but the significantly increased in tissue C14-1, C16-0 and C18-1 acylcarnitines supported that β-oxidation was not regulated. The hypoxia-induced FOXO activation could also be connected to altered gene expression related to fiber-type switching, extracellular matrix remodeling, muscle differentiation and neuromuscular junction denervation. Our results suggest that a six-hour exposure of obese mice to 12% O2 normobaric hypoxia impacts M. gastrocnemius via FOXO1, initiating alterations that may contribute to muscle remodeling of which denervation is novel and warrants further investigation. The findings support an early role of hypoxia in tissue alterations in hypoxia-associated conditions such as aging and obesity.

Genome-Wide Identification of lncRNA and mRNA for Diagnosing Type 2 Diabetes in Saudi Arabia

Purpose

According to the World Health Organization, Saudi Arabia ranks seventh worldwide in the number of patients with diabetes mellitus. To our knowledge, no research has addressed the potential of noncoding RNA as a diagnostic and/or management biomarker for patients with type 2 diabetes mellitus (T2DM) living in high-altitude areas. This study aimed to identify molecular biomarkers influencing patients with T2DM living in high-altitude areas by analyzing lncRNA and mRNA.

Patients and Methods

RNA sequencing and bioinformatics analyses were used to identify significantly expressed lncRNAs and mRNAs in T2DM and healthy control groups. Coding potential was analyzed using coding-noncoding indices, the coding potential calculator, and PFAM, and the lncRNA function was predicted using Pearson's correlation. Differentially expressed transcripts between the groups were identified, and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed to identify the biological functions of both lncRNAs and mRNAs.

Results

We assembled 1766 lncRNAs in the T2DM group, of which 582 were novel. This study identified three lncRNA target genes (KLF2, CREBBP, and REL) and seven mRNAs (PIK3CD, PIK3R5, IL6R, TYK2, ZAP70, LAMTOR4, and SSH2) significantly enriched in important pathways, playing a role in the progression of T2DM.

Conclusion

To the best of our knowledge, this comprehensive study is the first to explore the applicability of certain lncRNAs as diagnostic or management biomarkers for T2DM in females in Taif City, Saudi Arabia through the genome-wide identification of lncRNA and mRNA profiling using RNA seq and bioinformatics analysis. Our findings could help in the early diagnosis of T2DM and in designing effective therapeutic targets.

High Prevalence of Non-Responders Based on Quadriceps Force after Pulmonary Rehabilitation in COPD

Pulmonary rehabilitation (PR) in patients with COPD improves quality of life, dyspnea, and exercise tolerance. However, 30 to 50% of patients are "non-responders" (NRs) according to considered variables. Surprisingly, peripheral muscle force is never taken into account to attest the efficacy of PR, despite its major importance. Thus, we aimed to estimate the prevalence of force in NRs, their characteristics, and predictors of non-response. In total, 62 COPD patients were included in this retrospective study (May 2019 to December 2020). They underwent inpatient PR, and their quadriceps isometric maximal force (Q_MVC) was assessed. The PR program followed international guidelines. Patients with a Q_MVC increase <7.5 N·m were classified as an NR. COPD patients showed a mean improvement in Q_MVC after PR (10.08 ± 12.97 N·m; p < 0.001). However, 50% of patients were NRs. NRs had lower pre-PR values for body mass, height, body mass index, PaO₂, and Q_MVC. Non-response can be predicted by low Q_MVC, high PaCO₂, and gender (when male). This model has a sensitivity of 74% and specificity of 81%. The study highlights the considerable number of NRs and potential risk factors for non-response. To systematize the effects, it may be interesting to implement blood gas correction and/or optimize the programs to enhance peripheral and central effects.

The "Superoncogene" Myc at the Crossroad between Metabolism and Gene Expression in Glioblastoma Multiforme

The concept of the Myc (c-myc, n-myc, l-myc) oncogene as a canonical, DNA-bound transcription factor has consistently changed over the past few years. Indeed, Myc controls gene expression programs at multiple levels: directly binding chromatin and recruiting transcriptional coregulators; modulating the activity of RNA polymerases (RNAPs); and drawing chromatin topology. Therefore, it is evident that Myc deregulation in cancer is a dramatic event. Glioblastoma multiforme (GBM) is the most lethal, still incurable, brain cancer in adults, and it is characterized in most cases by Myc deregulation. Metabolic rewiring typically occurs in cancer cells, and GBM undergoes profound metabolic changes to supply increased energy demand. In nontransformed cells, Myc tightly controls metabolic pathways to maintain cellular homeostasis. Consistently, in Myc-overexpressing cancer cells, including GBM cells, these highly controlled metabolic routes are affected by enhanced Myc activity and show substantial alterations. On the other hand, deregulated cancer metabolism impacts Myc expression and function, placing Myc at the intersection between metabolic pathway activation and gene expression. In this review paper, we summarize the available information on GBM metabolism with a specific focus on the control of the Myc oncogene that, in turn, rules the activation of metabolic signals, ensuring GBM growth.

FOXO3a-dependent up-regulation of HSP90 alleviates cisplatin-induced apoptosis by activating FUNDC1-mediated mitophagy in hypoxic osteosarcoma cells

Hypoxia-induced decrease in cisplatin (CDDP) sensitivity in human osteosarcoma (OS) is a significant obstacle to effective chemotherapy. Recently, mitophagy has been shown to be associated with CDDP sensitivity. However, whether it regulates hypoxia-induced decreases in CDDP sensitivity in OS and the underlying mechanisms remain unknown. In this study, we found that hypoxia activated mitophagy and suppressed mitophagy with specific inhibitors, mitochondrial division inhibitor-1 (Mdivi-1) or lysosome inhibitor chloroquine (CQ), which inhibited CDDP-induced apoptosis in hypoxic U-2OS and MG-63 cells. In addition, hypoxia upregulated the phosphorylation level of FUN14 domain-containing protein 1 (FUNDC1), whereas the activation of mitophagy and decreased CDDP sensitivity were inhibited by transfection with FUNDC1 small interfering RNA (siRNA). Hypoxia treatment also led to the up-regulation of heat shock protein 90 (HSP90), whereas HSP90 siRNA inhibited FUNDC1-mediated activation of mitophagy and decreased CDDP sensitivity. Furthermore, activation of Unc-51 like autophagy activating kinase 1 (Ulk1) was found in U-2OS and MG-63 cells after induction of hypoxia. Overexpression of Ulk1 prevented the inhibitory effect of HSP90 siRNA on the activation of FUNDC1 and mitophagy and decreased CDDP sensitivity in hypoxic U-2OS and MG-63 cells. Finally, hypoxia induced the activation of forkhead box transcription factor 3a (FOXO3a), whereas FOXO3a siRNA inhibited hypoxia-induced HSP90 up-regulation, Ulk1 activation, and FUNDC1-mediated activation of mitophagy, and decreased CDDP sensitivity in U-2OS and MG-63 cells. Using a chromatin immunoprecipitation (ChIP) assay, we confirmed that FOXO3a binds to the HSP90 promoter region. In conclusion, our findings suggest that hypoxia alleviates CDDP-induced apoptosis by activating mitophagy through the FOXO3a/HSP90/Ulk1/FUNDC1 signaling pathway in OS cells.

Metabolism in Hematopoiesis and Its Malignancy

Hematopoietic stem cells (HSCs) are multipotent stem cells that can self-renew and generate all blood cells of different lineages. The system is under tight control in order to maintain a precise equilibrium of the HSC pool and the effective production of mature blood cells to support various biological activities. Cell metabolism can regulate different molecular activities, such as epigenetic modification and cell cycle regulation, and subsequently affects the function and maintenance of HSC. Upon malignant transformation, oncogenic drivers in malignant hematopoietic cells can remodel the metabolic pathways for supporting the oncogenic growth. The dysregulation of metabolism results in oncogene addiction, implying the development of malignancy-specific metabolism-targeted therapy. In this chapter, we will discuss the significance of different metabolic pathways in hematopoiesis, specifically, the distinctive metabolic dependency in hematopoietic malignancies and potential metabolic therapy.

FOXOs: masters of the equilibrium

Forkhead box O (FOXO) transcription factors (TFs) are a subclass of the larger family of forkhead TFs. Mammalians express four members FOXO1, FOXO3, FOXO4, and FOXO6. The interest in FOXO function stems mostly from their observed role in determining lifespan, where in model organisms, increased FOXO activity results in extended lifespan. FOXOs act as downstream of several signaling pathway and are extensively regulated through post-translational modifications. The transcriptional program activated by FOXOs in various cell types, organisms, and under various conditions has been described and has shed some light on what the critical transcriptional targets are in mediating FOXO function. At the cellular level, these studies have revealed a role for FOXOs in cell metabolism, cellular redox, cell proliferation, DNA repair, autophagy, and many more. The general picture that emerges hereof is that FOXOs act to preserve equilibrium, and they are important for cellular homeostasis. Here, we will first briefly summarize the general knowledge of FOXO regulation and possible functions. We will use genomic stability to illustrate how FOXOs ensure homeostasis. Genomic stability is critical for maintaining genetic integrity, and therefore preventing disease. However, genomic mutations need to occur during lifetime to enable evolution, yet their accumulation is believed to be causative to aging. Therefore, the role of FOXO in genomic stability may underlie its role in lifespan and aging. Finally, we will come up with questions on some of the unknowns in FOXO function, the answer(s) to which we believe will further our understanding of FOXO function and ultimately may help to understand lifespan and its consequences.

Comparative genomics reveals putative evidence for high-elevation adaptation in the American pika (Ochotona princeps)

High-elevation environments have lower atmospheric oxygen content, reduced temperatures, and higher levels of UV radiation than found at lower elevations. As such, species living at high elevations must overcome these challenges to survive, grow, and reproduce. American pikas (Ochotona princeps) are alpine lagomorphs that are habitat specialists typically found at elevations >2,000 m. Previous research has shown putative evidence for high-elevation adaptation; however, investigations to date have been limited to a fraction of the genome. Here, we took a comparative genomics approach to identify putative regions under selection using a chromosomal reference genome assembly for the American pika relative to 8 other mammalian species targeted based on phylogenetic relatedness and (dis)similarity in ecology. We first identified orthologous gene groups across species and then extracted groups containing only American pika genes as well as unclustered pika genes to inform functional enrichment analyses; among these, we found 141 enriched terms with many related to hypoxia, metabolism, mitochondrial function/development, and DNA repair. We identified 15 significantly expanded gene families within the American pika across all orthologous gene groups that displayed functionally enriched terms associated with hypoxia adaptation. We further detected 196 positively selected genes, 41 of which have been associated with putative adaptation to hypoxia, cold tolerance, and response to UV following a literature review. In particular, OXNAD1, NRDC, and those genes critical in DNA repair represent important targets for future research to examine their functional implications in the American pika, especially as they may relate to adaptation to rapidly changing environments.

The Role of Hypoxia-Inducible Factor in the Mechanisms of Aging

Aging is accompanied by a reduction in the oxygen delivery to all organs and tissues and decrease in the oxygen partial pressure in them, resulting in the development of hypoxia. The lack of oxygen activates cell signaling pathway mediated by the hypoxia-inducible transcription factor (HIF), which exists in three isoforms - HIF-1, HIF-2, and HIF-3. HIF regulates expression of several thousand genes and is a potential target for the development of new drugs for the treatment of many diseases, including those associated with age. Human organism and organisms of laboratory animals differ in their tolerance to hypoxia and expression of HIF and HIF-dependent genes, which may contribute to the development of inflammatory, tumor, and cardiovascular diseases. Currently, the data on changes in the HIF expression with age are contradictory, which is mostly due to the fact that such studies are conducted in different age groups, cell types, and model organisms, as well as under different hypoxic conditions and mainly in vitro. Furthermore, the observed discrepancies can be due to the individual tolerance of the studied organisms to hypoxia, which is typically not taken into account. Therefore, the purpose of this review was to analyze the published data on the connection between the mechanisms of aging, basal tolerance to hypoxia, and changes in the level of HIF expression with age. Here, we summarized the data on the age-related changes in the hypoxia tolerance, HIF expression and the role of HIF in aging, which is associated with its involvement in the molecular pathways mediated by insulin and IGF-1 (IIS), sirtuins (SIRTs), and mTOR. HIF-1 interacts with many components of the IIS pathway, in particular with FOXO, the activation of which reduces production of reactive oxygen species (ROS) and increases hypoxia tolerance. Under hypoxic conditions, FOXO is activated via both HIF-dependent and HIF-independent pathways, which contributes to a decrease in the ROS levels. The activity of HIF-1 is regulated by all members of the sirtuin family, except SIRT5, while the mechanisms of SIRT interaction with HIF-2 and HIF-3 are poorly understood. The connection between HIF and mTOR and its inhibitor, AMPK, has been identified, but its exact mechanism has yet to be studied. Understanding the role of HIF and hypoxia in aging and pathogenesis of age-associated diseases is essential for the development of new approaches to the personalized therapy of these diseases, and requires further research.

Deciphering the molecular mechanism underlying the effects of epimedium on osteoporosis through system bioinformatic approach

Epimedium has gained widespread clinical application in Traditional Chinese Medicine, with the functions of promoting bone reproduction, regulating cell cycle and inhibiting osteoclastic activity. However, its precise cellular pharmacological therapeutic mechanism on osteoporosis (OP) remains elusive. This study aims to elucidate the molecular mechanism of epimedium in the treatment of OP based on system bioinformatic approach. Predicted targets of epimedium were collected from TCMSP, BATMAN-TCM and ETCM databases. Differentially expressed mRNAs of OP patients were obtained from Gene Expression Omnibus database by performing Limma package of R software. Epimedium-OP common targets were obtained by Venn diagram package for further analysis. The protein-protein interaction network was constructed using Cytoscape software. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were carried out by using clusterProfiler package. Molecular docking analysis was conducted by AutoDock 4.2 software to validate the binding affinity between epimedium and top 3 proteins based on the result of protein-protein interaction. A total of 241 unique identified epimedium targets were screened from databases, of which 62 overlapped with the targets of OP and were considered potential therapeutic targets. The results of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that these targets were positive regulation of cell cycle, cellular response to oxidative stress and positive regulation of cell cycle process as well as cellular senescence, FoxO, PI3K-Akt, and NF-kappa B signaling pathways. Molecular docking showed that epimedium have a good binding activity with key targets. Our study demonstrated the multitarget and multi-pathway characteristics of epimedium on OP, which elucidates the potential mechanisms of epimedium against OP and provides theoretical basis for further drug development.

TF-DUBTACs Stabilize Tumor Suppressor Transcription Factors

Targeted protein degradation approaches have been widely used for degrading oncogenic proteins, providing a potentially promising therapeutic strategy for cancer treatment. However, approaches to targeting tumor suppressor proteins are very limited, and only a few agonists have been developed to date. Here, we report the development of a platform termed TF-DUBTAC, which links a DNA oligonucleotide to a covalent ligand of the deubiquitinase OTUB1 via a click reaction, to selectively stabilize tumor suppressor transcription factors. We developed three series of TF-DUBTACs, namely, FOXO-DUBTAC, p53-DUBTAC, and IRF-DUBTAC, which stabilize FOXO3A, p53, and IRF3 in cells, respectively, in an OTUB1-dependent manner. These results suggest that TF-DUBTAC is a generalizable platform to achieve selective stabilization of tumor suppressor transcription factors as a therapeutic means to suppress tumorigenesis.

Metabolic Adaptation-Mediated Cancer Survival and Progression in Oxidative Stress

Undue elevation of ROS levels commonly occurs during cancer evolution as a result of various antitumor therapeutics and/or endogenous immune response. Overwhelming ROS levels induced cancer cell death through the dysregulation of ROS-sensitive glycolytic enzymes, leading to the catastrophic depression of glycolysis and oxidative phosphorylation (OXPHOS), which are critical for cancer survival and progression. However, cancer cells also adapt to such catastrophic oxidative and metabolic stresses by metabolic reprograming, resulting in cancer residuality, progression, and relapse. This adaptation is highly dependent on NADPH and GSH syntheses for ROS scavenging and the upregulation of lipolysis and glutaminolysis, which fuel tricarboxylic acid cycle-coupled OXPHOS and biosynthesis. The underlying mechanism remains poorly understood, thus presenting a promising field with opportunities to manipulate metabolic adaptations for cancer prevention and therapy. In this review, we provide a summary of the mechanisms of metabolic regulation in the adaptation of cancer cells to oxidative stress and the current understanding of its regulatory role in cancer survival and progression.

Regulation of mitochondrial function by forkhead transcription factors

Mitochondria play a central role in several important cellular processes such as energy production, apoptosis, fatty acid catabolism, calcium regulation, and cellular stress response. Multiple nuclear transcription factors have been reported for their role in the regulation of mitochondrial gene expression. More recently, the role of the forkhead family of transcription factors in various mitochondrial pathways has been reported. Among them, FOXO1, FOXO3a, FOXG1, and FOXM1 have been reported to localize to the mitochondria, of which the first two have been observed to bind to the mitochondrial D-loop. This suggests an important role for forkhead transcription factors in the direct regulation of the mitochondrial genome and function. Forkheads such as FOXO3a, FOXO1, and FOXM1 are involved in the cellular response to oxidative stress, hypoxia, and nutrient limitation. Several members of the forkhead family of transcription factors are also involved in the regulation of nuclear-encoded genes associated with the mitochondrial pathway of apoptosis, respiration, mitochondrial dynamics, and homeostasis.

Mitochondrial Creatine Kinase Attenuates Pathologic Remodeling in Heart Failure

BACKGROUND

Abnormalities in cardiac energy metabolism occur in heart failure (HF) and contribute to contractile dysfunction, but their role, if any, in HF-related pathologic remodeling is much less established. CK (creatine kinase), the primary muscle energy reserve reaction which rapidly provides ATP at the myofibrils and regenerates mitochondrial ADP, is down-regulated in experimental and human HF. We tested the hypotheses that pathologic remodeling in human HF is related to impaired cardiac CK energy metabolism and that rescuing CK attenuates maladaptive hypertrophy in experimental HF.

METHODS

First, in 27 HF patients and 14 healthy subjects, we measured cardiac energetics and left ventricular remodeling using noninvasive magnetic resonance 31P spectroscopy and magnetic resonance imaging, respectively. Second, we tested the impact of metabolic rescue with cardiac-specific overexpression of either Ckmyofib (myofibrillar CK) or Ckmito (mitochondrial CK) on HF-related maladaptive hypertrophy in mice.

RESULTS

In people, pathologic left ventricular hypertrophy and dilatation correlate closely with reduced myocardial ATP levels and rates of ATP synthesis through CK. In mice, transverse aortic constriction-induced left ventricular hypertrophy and dilatation are attenuated by overexpression of CKmito, but not by overexpression of CKmyofib. CKmito overexpression also attenuates hypertrophy after chronic isoproterenol stimulation. CKmito lowers mitochondrial reactive oxygen species, tissue reactive oxygen species levels, and upregulates antioxidants and their promoters. When the CK capacity of CKmito-overexpressing mice is limited by creatine substrate depletion, the protection against pathologic remodeling is lost, suggesting the ADP regenerating capacity of the CKmito reaction rather than CK protein per se is critical in limiting adverse HF remodeling.

CONCLUSIONS

In the failing human heart, pathologic hypertrophy and adverse remodeling are closely related to deficits in ATP levels and in the CK energy reserve reaction. CKmito, sitting at the intersection of cardiac energetics and redox balance, plays a crucial role in attenuating pathologic remodeling in HF. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT00181259.

Luteolin can ameliorate renal interstitial fibrosis-induced renal anaemia through the SIRT1/FOXO3 pathway

Luteolin is a natural flavonoid exhibiting multiple pharmacological activities.

MYC: a multipurpose oncogene with prognostic and therapeutic implications in blood malignancies

MYC oncogene is a transcription factor with a wide array of functions affecting cellular activities such as cell cycle, apoptosis, DNA damage response, and hematopoiesis. Due to the multi-functionality of MYC, its expression is regulated at multiple levels. Deregulation of this oncogene can give rise to a variety of cancers. In this review, MYC regulation and the mechanisms by which MYC adjusts cellular functions and its implication in hematologic malignancies are summarized. Further, we also discuss potential inhibitors of MYC that could be beneficial for treating hematologic malignancies.

SIRT1/PGC-1α/PPAR-γ Correlate With Hypoxia-Induced Chemoresistance in Non-Small Cell Lung Cancer

Resistance is the major cause of treatment failure and disease progression in non-small cell lung cancer (NSCLC). There is evidence that hypoxia is a key microenvironmental stress associated with resistance to cisplatin, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), and immunotherapy in solid NSCLCs. Numerous studies have contributed to delineating the mechanisms underlying drug resistance in NSCLC; nevertheless, the mechanisms involved in the resistance associated with hypoxia-induced molecular metabolic adaptations in the microenvironment of NSCLC remain unclear. Studies have highlighted the importance of posttranslational regulation of molecular mediators in the control of mitochondrial function in response to hypoxia-induced metabolic adaptations. Hypoxia can upregulate the expression of sirtuin 1 (SIRT1) in a hypoxia-inducible factor (HIF)-dependent manner. SIRT1 is a stress-dependent metabolic sensor that can deacetylate some key transcriptional factors in both metabolism dependent and independent metabolic pathways such as HIF-1α, peroxisome proliferator-activated receptor gamma (PPAR-γ), and PPAR-gamma coactivator 1-alpha (PGC-1α) to affect mitochondrial function and biogenesis, which has a role in hypoxia-induced chemoresistance in NSCLC. Moreover, SIRT1 and HIF-1α can regulate both innate and adaptive immune responses through metabolism-dependent and -independent ways. The objective of this review is to delineate a possible SIRT1/PGC-1α/PPAR-γ signaling-related molecular metabolic mechanism underlying hypoxia-induced chemotherapy resistance in the NSCLC microenvironment. Targeting hypoxia-related metabolic adaptation may be an attractive therapeutic strategy for overcoming chemoresistance in NSCLC.

HIF-1-induced mitochondrial ribosome protein L52: a mechanism for breast cancer cellular adaptation and metastatic initiation in response to hypoxia

Background: Hypoxia is a hallmark of the physical microenvironment of solid tumors. As a key factor that regulates tumor development and progression, hypoxia can reprogram the expression of multiple genes, whose biological function and molecular mechanism in cancer remain largely unclear. The mitochondrial ribosome protein family consists of nuclear-encoded mitochondrial proteins that are responsible for protein synthesis in the mitochondria.

Methods: A high-throughput RNA sequencing assay was carried out to identify differentially expressed mRNAs between breast cancer tissues and adjacent normal tissues as well as breast tumors with metastasis and those without metastasis. Our clinical samples and TCGA database were analyzed to observe the clinical value of mitochondrial ribosome protein L52 (MRPL52) in human breast cancer. Potent hypoxia response elements in the promoter region of MRPL52 were identified and validated by chromatin immunoprecipitation and luciferase reporter assays. Functional experiments were performed using breast cancer cell lines with MRPL52 ectopic expression and knockdown cultured in a 20% or 1% O₂ environment.

Results: MRPL52 expression was upregulated in human breast cancer and was significantly associated with aggressive clinicopathological characteristics and a higher metastatic risk of breast cancer patients. We found that the overexpression of MRPL52 in breast cancer is induced by hypoxia-inducible factor-1 in response to hypoxic exposure. The role of MRPL52 in suppressing apoptosis and promoting migration and invasion of hypoxic breast cancer cells was demonstrated by our experimental evidence. Mechanistically, MRPL52 promoted PTEN-induced putative kinase 1 /Parkin-dependent mitophagy to remove oxidatively damaged mitochondria and prevent uncontrolled reactive oxygen species (ROS) generation, thus repressing activation of the mitochondrial apoptotic cascade. Additionally, MRPL52 augmented epithelial-mesenchymal transition, migration and invasion of hypoxic breast cancer cells by activating the ROS-Notch1-Snail signaling pathway. Benefited from this bidirectional regulatory mechanism, MRPL52 is responsible for maintaining ROS levels in a window that can induce tumorigenic signal transduction without causing cytotoxicity in hypoxic breast cancer cells.

Conclusions: This work elucidates the molecular mechanism by which MRPL52 mediates hypoxia-induced apoptotic resistance and metastatic initiation of breast cancer, and provides new insights into the interplay between cancer and the tumor microenvironment.

To breathe or not to breathe: Understanding how oxygen sensing contributes to age-related phenotypes

Aging is characterized by a progressive loss of tissue integrity and functionality due to disrupted homeostasis. Molecular oxygen is pivotal to maintain tissue functions, and aerobic species have evolved a sophisticated sensing system to ensure proper oxygen supply and demand. It is not surprising that aberrations in oxygen and oxygen-associated pathways subvert health and promote different aspects of aging. In this review, we discuss emerging findings on how oxygen-sensing mechanisms regulate different cellular and molecular processes during normal physiology, and how dysregulation of oxygen availability lead to disease and aging. We describe various clinical manifestations associated with deregulation of oxygen balance, and how oxygen-modulating therapies and natural oxygen oscillations influence longevity. We conclude by discussing how a better understanding of oxygen-related mechanisms that orchestrate aging processes may lead to the development of new therapeutic strategies to extend healthy aging.

FOXO3A-induced LINC00926 suppresses breast tumor growth and metastasis through inhibition of PGK1-mediated Warburg effect

Phosphoglycerate kinase 1 (PGK1), a critical component of the glycolytic pathway, relates to the development of various cancers. However, the mechanisms of PGK1 inhibition and physiological significance of PGK1 inhibitors in cancer cells are unclear. Long non-coding RNAs (lncRNAs) play a vital role in tumor growth and progression. Here, we identify a lncRNA LINC00926 that negatively regulates PGK1 expression and predicts good clinical outcome of breast cancer. LINC00926 downregulates PGK1 expression through the enhancement of PGK1 ubiquitination mediated by E3 ligase STUB1. Moreover, hypoxia inhibits LINC00926 expression and activates PGK1 expression largely through FOXO3A. FOXO3A/LINC00926/PGK1 axis regulates breast cancer glycolysis, tumor growth, and lung metastasis both in vitro and in vivo. In breast cancer patients, LINC00926 expression is negatively correlated with PGK1 and positively correlated with FOXO3A expression. Our work established FOXO3A/LINC00926/PGK1 as a critical axis to regulate breast cancer growth and progression. Targeting PGK1 or supplement of LINC00926 or FOXO3A could be potential therapeutic strategies in breast cancer.

Differentiation of Hodgkin lymphoma cells by reactive oxygen species and regulation by heme oxygenase-1 through HIF-1α

We previously indicated that Hodgkin lymphoma (HL) cells contain a small side population (SP) that differentiate into a large major population (MP) with giant Hodgkin and Reed‐Sternberg (H and RS)‐like cells. However, its molecular mechanisms are not fully understood. In this study, we found that intracellular reactive oxygen species (ROS) are low in the SP compared to the MP. Hydrogen peroxide induces large H‐ and RS‐like cells in HL cell lines, but induces cell death in unrelated lymphoid cell lines. Microarray analyses revealed the enrichment of upregulated genes under hypoxic conditions in the SP compared to the MP, and we verified that the SP cells are hypoxic. Hypoxia inducible factor (HIF)‐1α was preferentially expressed in the SP. CoCl₂, a HIF‐1α stabilizer, blunted the effect of hydrogen peroxide. Heme oxygenase‐1 (HO‐1), a scavenger of ROS, was triggered by HIF‐1α. The effect of hydrogen peroxide was inhibited by HO‐1 induction, whereas it was promoted by HO‐1 knockdown. HO‐1 inhibition by zinc protoporphyrin promoted the differentiation and increased ROS. These results stress the unique roles of ROS in the differentiation of HL cells. Immature HL cells are inhibited from differentiation by a reduction of ROS through the induction of HO‐1 via HIF‐1α. The breakdown of this might cause the accumulation of intracellular ROS, resulting in the promotion of HL cell differentiation.

Tumor Suppressors Having Oncogenic Functions: The Double Agents

Cancer progression involves multiple genetic and epigenetic events, which involve gain-of-functions of oncogenes and loss-of-functions of tumor suppressor genes. Classical tumor suppressor genes are recessive in nature, anti-proliferative, and frequently found inactivated or mutated in cancers. However, extensive research over the last few years have elucidated that certain tumor suppressor genes do not conform to these standard definitions and might act as “double agents”, playing contrasting roles in vivo in cells, where either due to haploinsufficiency, epigenetic hypermethylation, or due to involvement with multiple genetic and oncogenic events, they play an enhanced proliferative role and facilitate the pathogenesis of cancer. This review discusses and highlights some of these exceptions; the genetic events, cellular contexts, and mechanisms by which four important tumor suppressors—pRb, PTEN, FOXO, and PML display their oncogenic potentials and pro-survival traits in cancer.

Hypoxia induces sorafenib resistance mediated by autophagy via activating FOXO3a in hepatocellular carcinoma

Sorafenib, a multikinase inhibitor, is considered as the only approved drug to cure the advanced hepatocellular carcinoma (HCC); however, the acquired chemoresistance caused by intratumoral hypoxia through sorafenib long term therapy induces sorafenib inefficacy. We demonstrated here that hypoxia significantly attenuated sensitivity of HCC cells to sorafenib treatment and reduced its proliferation. Autophagy was observed in sorafenib-treated HCC cells in hypoxia, and inhibition of autophagy by 3-MA eliminated hypoxia-induced sorafenib resistance. Further study revealed hypoxia-activated FOXO3a, an important cellular stress transcriptional factor, via inducing its dephosphorylation and nuclear location; and FOXO3a-dependent transcriptive activation of beclin-1 was responsible for hypoxia-induced autophagy in HCC cells. Knockout of FOXO3a inhibited the autophagy induced by sorafenib itself in normoxia and significantly enhanced the cytotoxicity of sorafenib in HCC cells; and it also inhibited the hypoxia-induced autophagy and achieved the same effect in sorafenib sensitivity-enhancement in HCC cells as it in normoxia. Finally, knockout of intratumoral FOXO3a significantly enhanced curative efficacy of sorafenib via inhibition of autophagy in xenograft tumors in nude mice. Collectively, our study suggests that FOXO3a plays a key role in regulating hypoxia-induced autophagy in sorafenib-treated HCC, and FOXO3-targeted therapy may serve as a promising approach to improve clinical prognosis of patients suffering from HCC.

Molecular Crosstalk Between MYC and HIF in Cancer

The transcription factor c-MYC (MYC thereafter) is a global regulator of gene expression. It is overexpressed or deregulated in human cancers of diverse origins and plays a key role in the development of cancers. Hypoxia-inducible factors (HIFs), a central regulator for cells to adapt to low cellular oxygen levels, is also often overexpressed and activated in many human cancers. HIF mediates the primary transcriptional response of a wide range of genes in response to hypoxia. Earlier studies focused on the inhibition of MYC by HIF during hypoxia, when MYC is expressed at physiological level, to help cells survive under low oxygen conditions. Emerging evidence suggests that MYC and HIF also cooperate to promote cancer cell growth and progression. This review will summarize the current understanding of the complex molecular interplay between MYC and HIF.

The role of FOXOs and autophagy in cancer and metastasis-Implications in therapeutic development

Autophagy is a highly conserved intracellular degradation process that plays a crucial role in cell survival and stress reactions as well as in cancer development and metastasis. Autophagy process involves several steps including sequestration, fusion of autophagosomes with lysosomes and degradation. Forkhead box O (FOXO) transcription factors regulate the expression of genes involved in cellular metabolic activity and signaling pathways of cancer growth and metastasis. Recent evidence suggests that FOXO proteins are also involved in autophagy regulation. The relationship among FOXOs, autophagy, and cancer has been drawing attention of many who work in the field. This study summarizes the role of FOXO proteins and autophagy in cancer growth and metastasis and analyzes their potential roles in cancer disease management.

18F-FDG PET is Superior to WHO Grading as a Prognostic Tool in Neuroendocrine Neoplasms and Useful in Guiding PRRT: A Prospective 10-Year Follow-up Study

Accurate grading of patients with neuroendocrine neoplasms (NENs) is essential for risk stratification and optimal choice of therapy. Currently, grading is based on histologically assessed degree of tumor proliferation. The aim of the present study was to assess the long-term prognostic value of ¹⁸F-FDG PET imaging for risk stratification of NENs and compare it with tumor grading (World Health Organization 2010 classification). Methods: We conducted a prospective cohort study evaluating the prognostic value of ¹⁸F-FDG PET imaging and compared it with histologic grading. Enrolled were 166 patients of all grades and with histologically confirmed NENs of gastroenteropancreatic origin. The primary endpoint was overall survival (OS). Progression-free survival (PFS) was a secondary endpoint. In addition, OS in relation to peptide receptor radionuclide therapy (PRRT) was analyzed as an exploratory endpoint. The median follow-up time was 9.8 y. Results: Analysis of the whole cohort revealed that a positive ¹⁸F-FDG PET scan was associated with a shorter OS than a negative ¹⁸F-FDG PET scan (hazard ratio: 3.8; 95% CI: 2.4-5.9; P < 0.001). In G1 and G2 patients (n = 140), a positive ¹⁸F-FDG PET scan was the only identifier of high risk for death (hazard ratio: 3.6; 95% CI, 2.2-5.9; P < 0.001). In multivariate analysis, ¹⁸F-FDG PET, G3 tumor, ≥2 liver metastases, and ≥2 prior therapies were independent prognostic factors for OS, and ¹⁸F-FDG PET, G3 tumor, and ≥3 liver metastases were independent prognostic factors for PFS. For patients receiving PRRT, ¹⁸F-FDG-negative cases had a significantly longer survival than ¹⁸F-FDG-positive cases, whereas no difference was identified for tumor grading. ¹⁸F-FDG-positive patients receiving PRRT had a significantly longer median survival than patients not receiving PRRT (4.4 vs. 1.4 y, P = 0.001), whereas no difference was seen for ¹⁸F-FDG-negative patients. Conclusion: ¹⁸F-FDG PET is useful for risk stratification of all NEN grades and is superior to histologic grading. ¹⁸F-FDG PET could differentiate G1 and G2 tumors into low- and high-risk groups. In the selection of therapy and for risk stratification of NEN patients, ¹⁸F-FDG PET status should be considered.

Cancer Metabolism: Phenotype, Signaling and Therapeutic Targets

Aberrant metabolism is a major hallmark of cancer. Abnormal cancer metabolism, such as aerobic glycolysis and increased anabolic pathways, has important roles in tumorigenesis, metastasis, drug resistance, and cancer stem cells. Well-known oncogenic signaling pathways, such as phosphoinositide 3-kinase (PI3K)/AKT, Myc, and Hippo pathway, mediate metabolic gene expression and increase metabolic enzyme activities. Vice versa, deregulated metabolic pathways contribute to defects in cellular signal transduction pathways, which in turn provide energy, building blocks, and redox potentials for unrestrained cancer cell proliferation. Studies and clinical trials are being performed that focus on the inhibition of metabolic enzymes by small molecules or dietary interventions (e.g., fasting, calorie restriction, and intermittent fasting). Similar to genetic heterogeneity, the metabolic phenotypes of cancers are highly heterogeneous. This heterogeneity results from diverse cues in the tumor microenvironment and genetic mutations. Hence, overcoming metabolic plasticity is an important goal of modern cancer therapeutics. This review highlights recent findings on the metabolic phenotypes of cancer and elucidates the interactions between signal transduction pathways and metabolic pathways. We also provide novel rationales for designing the next-generation cancer metabolism drugs.

Mitochondrial DNA Mutation, Diseases, and Nutrient-Regulated Mitophagy

A wide spectrum of human diseases, including cancer, neurodegenerative diseases, and metabolic disorders, have been shown to be associated with mitochondrial dysfunction through multiple molecular mechanisms. Mitochondria are particularly susceptible to nutrient deficiencies, and nutritional intervention is an essential way to maintain mitochondrial homeostasis. Recent advances in genetic manipulation and next-generation sequencing reveal the crucial roles of mitochondrial DNA (mtDNA) in various pathophysiological conditions. Mitophagy, a term coined to describe autophagy that targets dysfunctional mitochondria, has emerged as an important cellular process to maintain mitochondrial homeostasis and has been shown to be regulated by various nutrients and nutritional stresses. Given the high prevalence of mtDNA mutations in humans and their impact on mitochondrial function, it is important to investigate the mechanisms that regulate mtDNA mutation. Here, we discuss mitochondrial genetics and mtDNA mutations and their implications for human diseases. We also examine the role of mitophagy as a therapeutic target, highlighting how nutrients may eliminate mtDNA mutations through mitophagy.

Molecular regulation and function of FoxO3 in chronic kidney disease

PURPOSE OF REVIEW

FOXOs are transcription factors that regulate downstream target genes to counteract to cell stress. Here we review the function and regulation of FOXO transcription factors, the mechanism of FOXO3 activation in the kidney, and the role of FOXO3 in delaying the development of chronic kidney disease (CKD).

RECENT FINDINGS

Progressive renal hypoxia from vascular dropout and metabolic perturbation is a pathogenic factor for the initiation and development of CKD. Hypoxia and low levels of α-ketoglutarate generated from the TCA cycle inhibit prolyl hydroxylase domain (PHD)-mediated prolyl hydroxylation of FoxO3, thus reducing FoxO3 protein degradation via the ubiquitin proteasomal pathway, similar to HIF stabilization under hypoxic conditions. FoxO3 accumulation and nuclear translocation activate two key cellular defense mechanisms, autophagy and antioxidative response in renal tubular cells, to reduce cell injury and promote cell survival. FoxO3 directly activates the expression of Atg proteins, which replenishes core components of the autophagic machinery to allow sustained autophagy in the chronically hypoxic kidney. FoxO3 protects mitochondria by stimulating the expression of superoxide dismutase 2 (SOD2), as tubular deletion of FoxO3 in mice results in reduced SOD2 levels and profound mitochondrial damage.

SUMMARY

Knowledge gained from animal studies may help understand the function of stress responsive transcription factors that could be targeted to prevent or treat CKD.

Tolerance to Hypoxia Is Promoted by FOXO Regulation of the Innate Immunity Transcription Factor NF-κB/Relish in Drosophila

Exposure of tissues and organs to low oxygen (hypoxia) occurs in both physiological and pathological conditions in animals. Under these conditions, organisms have to adapt their physiology to ensure proper functioning and survival. Here, we define a role for the transcription factor Forkhead Box-O (FOXO) as a mediator of hypoxia tolerance in Drosophila We find that upon hypoxia exposure, FOXO transcriptional activity is rapidly induced in both larvae and adults. Moreover, we see that foxo mutant animals show misregulated glucose metabolism in low oxygen and subsequently exhibit reduced hypoxia survival. We identify the innate immune transcription factor, NF-κB/Relish, as a key FOXO target in the control of hypoxia tolerance. We find that expression of Relish and its target genes is increased in a FOXO-dependent manner in hypoxia, and that relish mutant animals show reduced survival in hypoxia. Together, these data indicate that FOXO is a hypoxia-inducible factor that mediates tolerance to low oxygen by inducing immune-like responses.

The FOXO's Advantages of Being a Family: Considerations on Function and Evolution

The nematode Caenorhabditis elegans possesses a unique (with various isoforms) FOXO transcription factor DAF-16, which is notorious for its role in aging and its regulation by the insulin-PI3K-AKT pathway. In humans, five genes (including a protein-coding pseudogene) encode for FOXO transcription factors that are targeted by the PI3K-AKT axis, such as in C. elegans. This common regulation and highly conserved DNA-binding domain are the pillars of this family. In this review, I will discuss the possible meaning of possessing a group of very similar proteins and how it can generate additional functionality to more complex organisms. I frame this discussion in relation to the much larger super family of Forkhead proteins to which they belong. FOXO members are very often co-expressed in the same cell type. The overlap of function and expression creates a certain redundancy that might be a safeguard against the accidental loss of FOXO function, which could otherwise lead to disease, particularly, cancer. This is one of the points that will be examined in this "family affair" report.

Environmental factors for establishment of the dormant state in oocytes

Guaranteeing the sustainability of gametogenesis is a fundamental issue for perpetuating the species. In the mammalian ovary, sustainability is accomplished by keeping a number of oocytes “stocked” in the dormant state. Despite the evident importance of this state, the mechanisms underlying the oocyte dormancy are not fully understood, although it is presumed that both intrinsic and extrinsic factors are involved. Here, we review environmental factors involved in the regulation of oocyte dormancy. Consideration of the environmental factors illustrates the nature of the ovarian compartment, in which primordial follicles reside. This should greatly improve our understanding of the mechanisms and also assist in reconstitution of the dormant state in culture. Accumulating knowledge on the dormant state of oocytes will contribute to a wide range of research in fields such as developmental biology, reproductive biology and regenerative medicine.

The PI3K-AKT network at the interface of oncogenic signalling and cancer metabolism

The altered metabolic programme of cancer cells facilitates their cell-autonomous proliferation and survival. In normal cells, signal transduction pathways control core cellular functions, including metabolism, to couple the signals from exogenous growth factors, cytokines or hormones to adaptive changes in cell physiology. The ubiquitous, growth factor-regulated phosphoinositide 3-kinase (PI3K)-AKT signalling network has diverse downstream effects on cellular metabolism, through either direct regulation of nutrient transporters and metabolic enzymes or the control of transcription factors that regulate the expression of key components of metabolic pathways. Aberrant activation of this signalling network is one of the most frequent events in human cancer and serves to disconnect the control of cell growth, survival and metabolism from exogenous growth stimuli. Here we discuss our current understanding of the molecular events controlling cellular metabolism downstream of PI3K and AKT and of how these events couple two major hallmarks of cancer: growth factor independence through oncogenic signalling and metabolic reprogramming to support cell survival and proliferation.

The Roles of FoxO Transcription Factors in Regulation of Bone Cells Function

Forkhead box class O family member proteins (FoxOs) are evolutionarily conserved transcription factors for their highly conserved DNA-binding domain. In mammalian species, all the four FoxO members, FoxO1, FoxO3, FoxO4, and FoxO6, are expressed in different organs. In bone, the first three members are extensively expressed and more studied. Bone development, remodeling, and homeostasis are all regulated by multiple cell lineages, including osteoprogenitor cells, chondrocytes, osteoblasts, osteocytes, osteoclast progenitors, osteoclasts, and the intercellular signaling among these bone cells. The disordered FoxOs function in these bone cells contribute to osteoarthritis, osteoporosis, or other bone diseases. Here, we review the current literature of FoxOs for their roles in bone cells, focusing on helping researchers to develop new therapeutic approaches and prevent or treat the related bone diseases.

Role of Sirtuins in Tumor Angiogenesis

Generally, changes in the metabolic status of cells under conditions like hypoxia and accumulation of lactate can be sensed by various sensing mechanisms, leading to modulation of a number of signal transduction pathways and transcription factors. Several of the proangiogenic cytokines like VEGF, FGF, PDGF, TGF-β, Ang-2, ILs, etc. are secreted by cancer cells, under hypoxic microenvironment. These cytokines bind to their receptors on the endothelial cells and activates a number of signaling pathways including Akt/PIP3, Src, p38/MAPK, Smad2/3, etc., which ultimately results in the proliferation and migration of endothelial cells. Transcription factors that are activated in response to the metabolic status of tumors include HIFs, NF-κb, p53, El-2, and FOXO. Many of these transcription factors has been reported to be regulated by a class of histone deacetylase called sirtuins. Sirtuins are NAD+ dependent histone deacetylases that play pivotal role in the regulation of tumor cell metabolism, proliferation, migration and angiogenesis. The major function of sirtuins include, deacetylation of histones as well as some non-histone proteins like NF-κB, FOXOs, PPAR⋎, PGC1-α, enzymes like acetyl coenzymeA and structural proteins like α tubulin. In the cell, sirtuins are generally considered as the redox sensors and their activities are dependent on the metabolic status of the cell. Understanding the intricate regulatory mechanisms adopted by sirtuins, is crucial in devising effective therapeutic strategies against angiogenesis, metastasis and tumor progression. Keeping this in mind, the present review focuses on the role of sirtuins in the process of tumor angiogenesis and the regulatory mechanisms employed by them.

FOXO3a from the Nucleus to the Mitochondria: A Round Trip in Cellular Stress Response

Cellular stress response is a universal mechanism that ensures the survival or negative selection of cells in challenging conditions. The transcription factor Forkhead box protein O3 (FOXO3a) is a core regulator of cellular homeostasis, stress response, and longevity since it can modulate a variety of stress responses upon nutrient shortage, oxidative stress, hypoxia, heat shock, and DNA damage. FOXO3a activity is regulated by post-translational modifications that drive its shuttling between different cellular compartments, thereby determining its inactivation (cytoplasm) or activation (nucleus and mitochondria). Depending on the stress stimulus and subcellular context, activated FOXO3a can induce specific sets of nuclear genes, including cell cycle inhibitors, pro-apoptotic genes, reactive oxygen species (ROS) scavengers, autophagy effectors, gluconeogenic enzymes, and others. On the other hand, upon glucose restriction, 5′-AMP-activated protein kinase (AMPK) and mitogen activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) -dependent FOXO3a mitochondrial translocation allows the transcription of oxidative phosphorylation (OXPHOS) genes, restoring cellular ATP levels, while in cancer cells, mitochondrial FOXO3a mediates survival upon genotoxic stress induced by chemotherapy. Interestingly, these target genes and their related pathways are diverse and sometimes antagonistic, suggesting that FOXO3a is an adaptable player in the dynamic homeostasis of normal and stressed cells. In this review, we describe the multiple roles of FOXO3a in cellular stress response, with a focus on both its nuclear and mitochondrial functions.

MYC Expression and Metabolic Redox Changes in Cancer Cells: A Synergy Able to Induce Chemoresistance

Chemoresistance is due to multiple factors including the induction of a metabolic adaptation of tumor cells. In fact, in these cells, stress conditions induced by therapies stimulate a metabolic reprogramming which involves the strengthening of various pathways such as glycolysis, glutaminolysis and the pentose phosphate pathway. This metabolic reprogramming is the result of a complex network of mechanisms that, through the activation of oncogenes (i.e., MYC, HIF1, and PI3K) or the downregulation of tumor suppressors (i.e., TP53), induces an increased expression of glucose and/or glutamine transporters and of glycolytic enzymes. Therefore, in order to overcome chemoresistance, it is necessary to develop combined therapies which are able to selectively and simultaneously act on the multiple molecular targets responsible for this adaptation. This review is focused on highlighting the role of MYC in modulating the epigenetic redox changes which are crucial in the acquisition of therapy resistance.