Circadian rhythms of macrophages are altered by the acidic pH of the tumor microenvironment

Macrophages are prime therapeutic targets due to their pro-tumorigenic and immunosuppressive functions in tumors, but varying efficacy of therapeutic approaches targeting macrophages highlights our incomplete understanding of how the tumor microenvironment (TME) can influence regulation of macrophages. The circadian clock is a key internal regulator of macrophage function, but how circadian rhythms of macrophages may be influenced by the tumor microenvironment remains unknown. We found that conditions associated with the TME such as polarizing stimuli, acidic pH, and elevated lactate concentrations can each alter circadian rhythms in macrophages. Circadian rhythms were enhanced in pro-resolution macrophages but suppressed in pro-inflammatory macrophages, while acidic pH had divergent effects on circadian rhythms depending on macrophage phenotype. While cyclic AMP (cAMP) has been reported to play a role in macrophage response to acidic pH, our results indicate that pH-driven changes in circadian rhythms are not mediated solely by the cAMP signaling pathway. Remarkably, clock correlation distance analysis of tumor-associated macrophages (TAMs) revealed evidence of circadian disorder in TAMs. This is the first report providing evidence that circadian rhythms of macrophages are altered within the TME. Our data suggest that heterogeneity in circadian rhythms at the population level may underlie this circadian disorder. Finally, we sought to determine how circadian regulation of macrophages impacts tumorigenesis, and found that tumor growth was suppressed when macrophages had a functional circadian clock. Our work demonstrates a novel mechanism by which the tumor microenvironment can influence macrophage biology through altering circadian rhythms, and the contribution of circadian rhythms in macrophages to suppressing tumor growth.

Chewing the fat for good health: ACSM3 deficiency exacerbates metabolic syndrome

Recent work identifies mitochondrial acyl-CoA synthetase ACSM3 as a guardian of hepatic lipid processing and metabolic health in mice and patients.

MYC disrupts transcriptional and metabolic circadian oscillations in cancer and promotes enhanced biosynthesis

The molecular circadian clock, which controls rhythmic 24-hour oscillation of genes, proteins, and metabolites in healthy tissues, is disrupted across many human cancers. Deregulated expression of the MYC oncoprotein has been shown to alter expression of molecular clock genes, leading to a disruption of molecular clock oscillation across cancer types. It remains unclear what benefit cancer cells gain from suppressing clock oscillation, and how this loss of molecular clock oscillation impacts global gene expression and metabolism in cancer. We hypothesized that MYC or its paralog N-MYC (collectively termed MYC herein) suppress oscillation of gene expression and metabolism to upregulate pathways involved in biosynthesis in a static, non-oscillatory fashion. To test this, cells from distinct cancer types with inducible MYC were examined, using time-series RNA-sequencing and metabolomics, to determine the extent to which MYC activation disrupts global oscillation of genes, gene expression pathways, and metabolites. We focused our analyses on genes, pathways, and metabolites that changed in common across multiple cancer cell line models. We report here that MYC disrupted over 85% of oscillating genes, while instead promoting enhanced ribosomal and mitochondrial biogenesis and suppressed cell attachment pathways. Notably, when MYC is activated, biosynthetic programs that were formerly circadian flipped to being upregulated in an oscillation-free manner. Further, activation of MYC ablates the oscillation of nutrient transporter proteins while greatly upregulating transporter expression, cell surface localization, and intracellular amino acid pools. Finally, we report that MYC disrupts metabolite oscillations and the temporal segregation of amino acid metabolism from nucleotide metabolism. Our results demonstrate that MYC disruption of the molecular circadian clock releases metabolic and biosynthetic processes from circadian control, which may provide a distinct advantage to cancer cells.

MYC disrupts transcriptional and metabolic circadian oscillations in cancer and promotes enhanced biosynthesis

The molecular circadian clock, which controls rhythmic 24-hour oscillation of genes, proteins, and metabolites in healthy tissues, is disrupted across many human cancers. Deregulated expression of the MYC oncoprotein has been shown to alter expression of molecular clock genes, leading to a disruption of molecular clock oscillation across cancer types. It remains unclear what benefit cancer cells gain from suppressing clock oscillation, and how this loss of molecular clock oscillation impacts global gene expression and metabolism in cancer. We hypothesized that MYC or its paralog N-MYC (collectively termed MYC herein) suppress oscillation of gene expression and metabolism to upregulate pathways involved in biosynthesis in a static, non-oscillatory fashion. To test this, cells from distinct cancer types with inducible MYC were examined, using time-series RNA-sequencing and metabolomics, to determine the extent to which MYC activation disrupts global oscillation of genes, gene expression pathways, and metabolites. We focused our analyses on genes, pathways, and metabolites that changed in common across multiple cancer cell line models. We report here that MYC disrupted over 85% of oscillating genes, while instead promoting enhanced ribosomal and mitochondrial biogenesis and suppressed cell attachment pathways. Notably, when MYC is activated, biosynthetic programs that were formerly circadian flipped to being upregulated in an oscillation-free manner. Further, activation of MYC ablates the oscillation of nutrient transporter proteins while greatly upregulating transporter expression, cell surface localization, and intracellular amino acid pools. Finally, we report that MYC disrupts metabolite oscillations and the temporal segregation of amino acid metabolism from nucleotide metabolism. Our results demonstrate that MYC disruption of the molecular circadian clock releases metabolic and biosynthetic processes from circadian control, which may provide a distinct advantage to cancer cells.

Effect of Yoga and Mediational Influence of Fatigue on Walking, Physical Activity, and Quality of Life Among Cancer Survivors

BACKGROUND

Cancer-related fatigue (CRF) negatively affects survivors' walking, engagement in physical activity (PA), and quality of life (QoL). Yoga is an effective therapy for treating CRF; however, evidence from large clinical trials regarding how reducing CRF through yoga influences CRF's interference with survivors' walking, engagement in PA, and QoL is not available. We examined the effects of yoga and the mediational influence of CRF on CRF's interference with walking, PA, and QoL among cancer survivors in a multicenter phase III randomized controlled trial.

PATIENTS AND METHODS

Cancer survivors (n=410) with insomnia 2 to 24 months posttreatment were randomized to a 4-week yoga intervention-Yoga for Cancer Survivors (YOCAS)-or standard care. A symptom inventory was used to assess how much CRF interfered with survivors' walking, PA, and QoL. The Multidimensional Fatigue Symptom Inventory-Short Form was used to assess CRF. Two-tailed t tests and analyses of covariance were used to examine within-group and between-group differences. Path analysis was used to evaluate mediational relationships between CRF and changes in CRF's interference with walking, PA, and QoL among survivors.

RESULTS

Compared with standard care controls, YOCAS participants reported significant improvements in CRF's interference with walking, PA, and QoL at postintervention (all effect size = -0.33; all P≤.05). Improvements in CRF resulting from yoga accounted for significant proportions of the improvements in walking (44%), PA (53%), and QoL (45%; all P≤.05).

CONCLUSIONS

A significant proportion (44%-53%) of the YOCAS effect on CRF's interference with walking, PA, and QoL was due to improvements in CRF among cancer survivors. Yoga should be introduced and included as a treatment option for survivors experiencing fatigue. By reducing fatigue, survivors further improve their walking, engagement in PA, and QoL.

Do macrophages follow the beat of circadian rhythm in TIME (Tumor Immune Microenvironment)?

Advances in cancer research have made clear the critical role of the immune response in clearing tumors. This breakthrough in scientific understanding was heralded by the success of immune checkpoint blockade (ICB) therapies such as anti-programmed cell death protein 1 (PD-1)/ programmed death-ligand 1 (PD-L1) and anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), as well as the success of chimeric antigen receptor (CAR) T cells in treating liquid tumors. Thus, much effort has been made to further understand the role of the immune response in tumor progression, and how we may target it to treat cancer. Macrophages are a component of the tumor immune microenvironment (TIME) that can promote tumor growth both indirectly, by suppressing T cell responses necessary for tumor killing, as well as directly, through deposition of extracellular matrix and promotion of angiogenesis. Thus, understanding regulation of macrophages within the tumor microenvironment (TME) is key to targeting them for immunotherapy. However, circadian rhythms (24-hour cycles) are a fundamental aspect of macrophage biology that have yet to be investigated for their role in macrophage-mediated suppression of the anti-tumor immune response Circadian rhythms regulate macrophage-mediated immune responses through time-of-day-dependent regulation of macrophage function. A better understanding of the circadian biology of macrophages in the context of the TME may allow us to exploit synergy between existing and upcoming treatments and circadian regulation of immunity.

Circadian disruption enhances HSF1 signaling and tumorigenesis in Kras-driven lung cancer

Disrupted circadian rhythmicity is a prominent feature of modern society and has been designated as a probable carcinogen by the World Health Organization. However, the biological mechanisms that connect circadian disruption and cancer risk remain largely undefined. We demonstrate that exposure to chronic circadian disruption [chronic jetlag (CJL)] increases tumor burden in a mouse model of KRAS-driven lung cancer. Molecular characterization of tumors and tumor-bearing lung tissues revealed that CJL enhances the expression of heat shock factor 1 (HSF1) target genes. Consistently, exposure to CJL disrupted the highly rhythmic nuclear trafficking of HSF1 in the lung, resulting in an enhanced accumulation of HSF1 in the nucleus. HSF1 has been shown to promote tumorigenesis in other systems, and we find that pharmacological or genetic inhibition of HSF1 reduces the growth of KRAS-mutant human lung cancer cells. These findings implicate HSF1 as a molecular link between circadian disruption and enhanced tumorigenesis.

Abstract 3215: BloodCCD is a novel biomarker to detect circadian rhythm disruption in cancer survivors with insomnia

Introduction: Insomnia is a significant co-morbidity for cancer survivors, and can independently reduce lifespan, but there is currently no objective biochemical measure of insomnia. Circadian rhythms are 24 hour cycles that control physiologic processes including sleep. Disrupted circadian rhythms have been proposed as a cause of insomnia. Here, we describe the use of a novel biomarker, BloodCCD, to assess circadian rhythms from RNA-sequencing of blood samples from two independent clinical trials and one observational study. BloodCCD was adapted from Clock Correlation Distance (CCD), which assesses normal progression of the molecular circadian clock from gene expression in tissue samples. We used BloodCCD to interrogate whether 1) cancer patients and survivors with insomnia have disrupted circadian rhythms compared to healthy good sleepers, and 2) whether the degree of circadian disruption correlates with severity of insomnia in survivors.

Methods: For BloodCCD analysis, time-series RNA-sequencing of human blood from healthy subjects were used to construct a reference correlation matrix of 42 genes which oscillate with 24-hour rhythms. To assess the Aims, RNA-sequencing from patient and survivor blood samples were compared to this reference correlation matrix to generate a BloodCCD score. A higher score indicates a further distance from a healthy clock, and thus clock disruption. For the first Aim, blood RNA-sequencing from cancer patients undergoing active treatment and survivors at least 2-months post-treatment and with insomnia were compared to healthy good sleepers. For the second Aim, blood RNA-sequencing from cancer survivors with insomnia were assessed, stratified by Insomnia Severity Index (ISI) Score into mild (ISI 10-14), moderate (ISI 15-21), and severe (ISI 22-28) insomnia.

Results: Patients (n=28, 100% prostate cancer) and cancer survivors (n=497, ~72% breast cancer) had higher BloodCCD scores, indicating disrupted circadian clock, compared to healthy good sleepers (n=14), with scores of 9.98, 7.99, and 4.13, respectively. When cancer survivors were stratified by insomnia severity, those with severe insomnia (ISI 22-28) had the highest BloodCCD, 9.00, while those with moderate insomnia (ISI 15-21) had a score of 8.24 and those with mild insomnia (ISI 10-14) had the lowest score of 7.93, indicating that survivors with severe insomnia had a more disrupted circadian clock. All BloodCCD values were p < 0.001 for each value compared to reference correlation.

Conclusions: BloodCCD shows promise as a biomarker to biochemically detect disrupted circadian rhythms in cancer patients and survivors, and as a readout for insomnia severity. Future studies should investigate whether BloodCCD improves in cancer survivors receiving interventions for insomnia.

Funding: UG1CA189961-07S1 (NCI BIQSFP Program), UG1CA189961 (URCC NCORP), T32CA102618 (URCC T32 program), K07CA221931

Citation Format: Brian J. Altman, Javier Bautista, Eva Culakova, Kristina M. Morris, Rachel E. DeRollo, Elliot Outland, Amber Kleckner, Ian R. Kleckner, Nikesha J. Gilmore, Benjamin T. Esparaz, Charles S. Kuzma, Amy C. Vander Woude, Po-Ju Lin, Jacob J. Hughey, Karen M. Mustian. BloodCCD is a novel biomarker to detect circadian rhythm disruption in cancer survivors with insomnia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3215.

Time-restricted Eating to Address Cancer-related Fatigue among Cancer Survivors: A Single-arm Pilot Study

Purpose

Cancer-related fatigue is a prevalent, debilitating condition that can persist for months or years after treatment. In a single-arm clinical trial, the feasibility and safety of a time-restricted eating (TRE) intervention were evaluated among cancer survivors, and initial estimates of within-person change in cancer-related fatigue were obtained.

Methods

Participants were 4-60 months post-cancer treatment, were experiencing fatigue (≥ 3 on a scale 0-10), and were not following TRE. TRE entailed limiting all food and beverages to a self-selected 10-h window for 14 days. Participants reported their eating window in a daily diary and completed the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F), Brief Fatigue Inventory (BFI), and symptom inventory pre- and post-intervention. This study was pre-registered at clinicaltrials.gov in January 2020 (NCT04243512).

Results

Participants (n=39) were 61.5 ± 12.4 years old and 1.8 ± 1.3 years post-treatment; 89.7% had had breast cancer. The intervention was feasible in that 36/39 (92.3%) of participants completed all questionnaires and daily diaries. It was also safe with no severe adverse events or rapid weight loss (average loss of 1.1 ± 2.3 pounds, p=0.008). Most adhered to TRE; 86.1% ate within a 10-h window at least 80% of the days, and the average eating window was 9.33 ± 1.05 h. Fatigue scores improved 5.3 ± 8.1 points on the FACIT-F fatigue subscale (p<0.001, effect size [ES]=0.55), 30.6 ± 35.9 points for the FACIT-F total score (p<0.001, ES=0.50), and -1.0 ± 1.7 points on the BFI (p<0.001, ES=-0.58).

Conclusion

A 10-h TRE intervention was feasible and safe among survivors, and fatigue improved with a moderate effect size after two weeks.

Limitations

This was a single-arm study, so it is possible that expectation effects were present for fatigue outcomes, independent of effects of TRE per se. However, this feasibility trial supports evaluation of TRE in randomized controlled trials to address persistent cancer-related fatigue.

Circadian control of macrophages in the tumor microenvironment

Introduction

All leukocytes tested to date have functional circadian clocks, and nearly every arm of the immune response is subject to circadian regulation. Circadian clocks instruct the time-of-day-dependent, rhythmic expression of genes in a tissue- and cell-specific manner. In macrophages (mΦs), the circadian clock regulates several factors that are critical to executing effective immune responses. Tumor-associated mΦs are major contributors to immune suppression in the tumor microenvironment (TME). Evidence suggests that metabolically stressful factors in the TME such as acidic pH and nutrient limitation promote mΦ-mediated immune suppression, and recent data point to dysregulation of the circadian clock downstream of metabolic stress.

Methods

We study the effect of TME-associated metabolic stress on the circadian clock of mΦs in vitro by culturing bone marrow-derived mΦs in conditions mimicking acidic pH and nutrient limitations that have been observed in the TME. To study the impact of mΦ-intrinsic circadian rhythms on tumorigenesis in vivo, we use mice genetically engineered to have a myeloid cell-specific disruption of the circadian clock via deletion of the key clock protein BMAL1.

Results

Oscillation of core clock proteins is altered in mΦs subjected to TME-associated metabolic stress. Additionally, we observe increased tumor growth in mice co-injected with mΦs whose circadian clocks were disrupted compared to mice co-injected with mΦs whose circadian clocks were functional.

Conclusion

Our data suggests that stressful conditions associated with the TME can alter the mΦ circadian clock, and that a functional circadian clock in mΦs can suppress tumor growth in a syngeneic murine tumor model of pancreatic cancer.

This research has been supported by the following fellowships and grants: 2021-Current: Wilmot Predoctoral Cancer Research Fellowship, Wilmot Cancer Institute, University of Rochester Medical Center, Rochester, NY 2020-2021: NIH T32 Training Grant in Cellular, Biochemical & Molecular Sciences, University of Rochester Medical Center, Rochester, NY

Neonatal Hyperoxia Activates Activating Transcription Factor 4 to Stimulate Folate Metabolism and Alveolar Epithelial Type 2 Cell Proliferation

Oxygen supplementation in preterm infants disrupts alveolar epithelial type 2 (AT2) cell proliferation through poorly understood mechanisms. Here, newborn mice are used to understand how hyperoxia stimulates an early aberrant wave of AT2 cell proliferation that occurs between Postnatal Days (PNDs) 0 and 4. RNA-sequencing analysis of AT2 cells isolated from PND4 mice revealed hyperoxia stimulates expression of mitochondrial-specific methylenetetrahydrofolate dehydrogenase 2 and other genes involved in mitochondrial one-carbon coupled folate metabolism and serine synthesis. The same genes are induced when AT2 cells normally proliferate on PND7 and when they proliferate in response to the mitogen fibroblast growth factor 7. However, hyperoxia selectively stimulated their expression via the stress-responsive activating transcription factor 4 (ATF4). Administration of the mitochondrial superoxide scavenger mitoTEMPO during hyperoxia suppressed ATF4 and thus early AT2 cell proliferation, but it had no effect on normative AT2 cell proliferation seen on PND7. Because ATF4 and methylenetetrahydrofolate dehydrogenase are detected in hyperplastic AT2 cells of preterm infant humans and baboons with bronchopulmonary dysplasia, dampening mitochondrial oxidative stress and ATF4 activation may provide new opportunities for controlling excess AT2 cell proliferation in neonatal lung disease.

MYC Ran Up the Clock: The Complex Interplay between MYC and the Molecular Circadian Clock in Cancer

The MYC oncoprotein and its family members N-MYC and L-MYC are known to drive a wide variety of human cancers. Emerging evidence suggests that MYC has a bi-directional relationship with the molecular clock in cancer. The molecular clock is responsible for circadian (~24 h) rhythms in most eukaryotic cells and organisms, as a mechanism to adapt to light/dark cycles. Disruption of human circadian rhythms, such as through shift work, may serve as a risk factor for cancer, but connections with oncogenic drivers such as MYC were previously not well understood. In this review, we examine recent evidence that MYC in cancer cells can disrupt the molecular clock; and conversely, that molecular clock disruption in cancer can deregulate and elevate MYC. Since MYC and the molecular clock control many of the same processes, we then consider competition between MYC and the molecular clock in several select aspects of tumor biology, including chromatin state, global transcriptional profile, metabolic rewiring, and immune infiltrate in the tumor. Finally, we discuss how the molecular clock can be monitored or diagnosed in human tumors, and how MYC inhibition could potentially restore molecular clock function. Further study of the relationship between the molecular clock and MYC in cancer may reveal previously unsuspected vulnerabilities which could lead to new treatment strategies.

The MYC Oncogene Cooperates with Sterol-Regulated Element-Binding Protein to Regulate Lipogenesis Essential for Neoplastic Growth

Lipid metabolism is frequently perturbed in cancers, but the underlying mechanism is unclear. We present comprehensive evidence that oncogene MYC, in collaboration with transcription factor sterol-regulated element-binding protein (SREBP1), regulates lipogenesis to promote tumorigenesis. We used human and mouse tumor-derived cell lines, tumor xenografts, and four conditional transgenic mouse models of MYC-induced tumors to show that MYC regulates lipogenesis genes, enzymes, and metabolites. We found that MYC induces SREBP1, and they collaborate to activate fatty acid (FA) synthesis and drive FA chain elongation from glucose and glutamine. Further, by employing desorption electrospray ionization mass spectrometry imaging (DESI-MSI), we observed in vivo lipidomic changes upon MYC induction across different cancers, for example, a global increase in glycerophosphoglycerols. After inhibition of FA synthesis, tumorigenesis was blocked, and tumors regressed in both xenograft and primary transgenic mouse models, revealing the vulnerability of MYC-induced tumors to the inhibition of lipogenesis.

Myc-mediated transcriptional regulation of the mitochondrial chaperone TRAP1 controls primary and metastatic tumor growth

The role of mitochondria in cancer continues to be debated, and whether exploitation of mitochondrial functions is a general hallmark of malignancy or a tumor- or context-specific response is still unknown. Using a variety of cancer cell lines and several technical approaches, including siRNA-mediated gene silencing, ChIP assays, global metabolomics and focused metabolite analyses, bioenergetics, and cell viability assays, we show that two oncogenic Myc proteins, c-Myc and N-Myc, transcriptionally control the expression of the mitochondrial chaperone TNFR-associated protein-1 (TRAP1) in cancer. In turn, this Myc-mediated regulation preserved the folding and function of mitochondrial oxidative phosphorylation (OXPHOS) complex II and IV subunits, dampened reactive oxygen species production, and enabled oxidative bioenergetics in tumor cells. Of note, we found that genetic or pharmacological targeting of this pathway shuts off tumor cell motility and invasion, kills Myc-expressing cells in a TRAP1-dependent manner, and suppresses primary and metastatic tumor growth in vivo We conclude that exploitation of mitochondrial functions is a general trait of tumorigenesis and that this reliance of cancer cells on mitochondrial OXPHOS pathways could offer an actionable therapeutic target in the clinic.

A PERK-miR-211 axis suppresses circadian regulators and protein synthesis to promote cancer cell survival

The unfolded protein response (UPR) is a stress-activated signalling pathway that regulates cell proliferation, metabolism and survival. The circadian clock coordinates metabolism and signal transduction with light/dark cycles. We explore how UPR signalling interfaces with the circadian clock. UPR activation induces a 10 h phase shift in circadian oscillations through induction of miR-211, a PERK-inducible microRNA that transiently suppresses both Bmal1 and Clock, core circadian regulators. Molecular investigation reveals that miR-211 directly regulates Bmal1 and Clock via distinct mechanisms. Suppression of Bmal1 and Clock has the anticipated impact on expression of select circadian genes, but we also find that repression of Bmal1 is essential for UPR-dependent inhibition of protein synthesis and cell adaptation to stresses that disrupt endoplasmic reticulum homeostasis. Our data demonstrate that c-Myc-dependent activation of the UPR inhibits Bmal1 in Burkitt's lymphoma, thereby suppressing both circadian oscillation and ongoing protein synthesis to facilitate tumour progression.

From Krebs to clinic: glutamine metabolism to cancer therapy

The resurgence of research into cancer metabolism has recently broadened interests beyond glucose and the Warburg effect to other nutrients, including glutamine. Because oncogenic alterations of metabolism render cancer cells addicted to nutrients, pathways involved in glycolysis or glutaminolysis could be exploited for therapeutic purposes. In this Review, we provide an updated overview of glutamine metabolism and its involvement in tumorigenesis in vitro and in vivo, and explore the recent potential applications of basic science discoveries in the clinical setting.

Cancer Clocks Out for Lunch: Disruption of Circadian Rhythm and Metabolic Oscillation in Cancer

Circadian rhythms are 24-h oscillations present in most eukaryotes and many prokaryotes that synchronize activity to the day-night cycle. They are an essential feature of organismal and cell physiology that coordinate many of the metabolic, biosynthetic, and signal transduction pathways studied in biology. The molecular mechanism of circadian rhythm is controlled both by signal transduction and gene transcription as well as by metabolic feedback. The role of circadian rhythm in cancer cell development and survival is still not well understood, but as will be discussed in this Review, accumulated research suggests that circadian rhythm may be altered or disrupted in many human cancers downstream of common oncogenic alterations. Thus, a complete understanding of the genetic and metabolic alterations in cancer must take potential circadian rhythm perturbations into account, as this disruption itself will influence how gene expression and metabolism are altered in the cancer cell compared to its non-transformed neighbor. It will be important to better understand these circadian changes in both normal and cancer cell physiology to potentially design treatment modalities to exploit this insight.

MYC Disrupts the Circadian Clock and Metabolism in Cancer Cells

The MYC oncogene encodes MYC, a transcription factor that binds the genome through sites termed E-boxes (5'-CACGTG-3'), which are identical to the binding sites of the heterodimeric CLOCK-BMAL1 master circadian transcription factor. Hence, we hypothesized that ectopic MYC expression perturbs the clock by deregulating E-box-driven components of the circadian network in cancer cells. We report here that deregulated expression of MYC or N-MYC disrupts the molecular clock in vitro by directly inducing REV-ERBα to dampen expression and oscillation of BMAL1, and this could be rescued by knockdown of REV-ERB. REV-ERBα expression predicts poor clinical outcome for N-MYC-driven human neuroblastomas that have diminished BMAL1 expression, and re-expression of ectopic BMAL1 in neuroblastoma cell lines suppresses their clonogenicity. Further, ectopic MYC profoundly alters oscillation of glucose metabolism and perturbs glutaminolysis. Our results demonstrate an unsuspected link between oncogenic transformation and circadian and metabolic dysrhythmia, which we surmise to be advantageous for cancer.

MYC, Metabolism, and Cancer

The MYC oncogene encodes a transcription factor, MYC, whose broad effects make its precise oncogenic role enigmatically elusive. The evidence to date suggests that MYC triggers selective gene expression amplification to promote cell growth and proliferation. Through its targets, MYC coordinates nutrient acquisition to produce ATP and key cellular building blocks that increase cell mass and trigger DNA replication and cell division. In cancer, genetic and epigenetic derangements silence checkpoints and unleash MYC's cell growth- and proliferation-promoting metabolic activities. Unbridled growth in response to deregulated MYC expression creates dependence on MYC-driven metabolic pathways, such that reliance on specific metabolic enzymes provides novel targets for cancer therapy.

SIGNIFICANCE

MYC's expression and activity are tightly regulated in normal cells by multiple mechanisms, including a dependence upon growth factor stimulation and replete nutrient status. In cancer, genetic deregulation of MYC expression and loss of checkpoint components, such as TP53, permit MYC to drive malignant transformation. However, because of the reliance of MYC-driven cancers on specific metabolic pathways, synthetic lethal interactions between MYC overexpression and specific enzyme inhibitors provide novel cancer therapeutic opportunities.

MYC and metabolism on the path to cancer

The MYC proto-oncogene is frequently deregulated in human cancers, activating genetic programs that orchestrate biological processes to promote growth and proliferation. Altered metabolism characterized by heightened nutrients uptake, enhanced glycolysis and glutaminolysis and elevated fatty acid and nucleotide synthesis is the hallmark of MYC-driven cancer. Recent evidence strongly suggests that Myc-dependent metabolic reprogramming is critical for tumorigenesis, which could be attenuated by targeting specific metabolic pathways using small drug-like molecules. Understanding the complexity of MYC-mediated metabolic re-wiring in cancers as well as how MYC cooperates with other metabolic drivers such as mammalian target of rapamycin (mTOR) will provide translational opportunities for cancer therapy.

Abstract 4708: Mammalian glutamine metabolism controls circadian rhythm through regulation of reactive oxygen species

Circadian rhythms are twenty-four hour physiologic cycles present in all eukaryotes that control a variety of organismal processes, including metabolism, but the role of metabolism in control of circadian rhythms is still not well understood. Peripheral clocks such as those present in the liver control metabolic pathways such as glucose metabolism and respiration as well as amino acid metabolism. It has been recently demonstrated that the availability of the metabolite NAD (nicotinamide adenine dinucleotide) can feed back to control circadian rhythm. There is much interest in targeting glutamine metabolism in cancer, but it is still not fully understood how inhibition of glutamine metabolism affects normal cell physiology, including circadian rhythm. Here we show using the commonly-used circadian model U2OS osteosarcoma cells and other cell lines that glutamine withdrawal blocked proper circadian oscillation of gene expression. Glutamine withdrawal led to distinct and dramatic changes in circadian gene expression in several cell lines with highly different tissue origins, which could be rescued by addition of the cell permeable TCA-intermediate α-ketoglutarate. However, cells withdrawn from glutamine did not show signs of metabolic stress or impairment of the mTOR pathway. While alterations to histone modifications possibly stemming from impairment of αKG-dependent enzymes were observed, these did not explain the observed alterations in circadian rhythm. Rather, RNA-seq analysis of genetic changes after glutamine withdrawal and α-ketoglutarate rescue revealed strong induction of several genetic pathways associated with reactive-oxygen species (ROS) induction, particularly those resulting from chemotherapy or photodynamic therapy of cancer. Further supporting the importance of ROS in regulation of circadian rhythm, addition of cell permeable antioxidants rescued the disruption of circadian oscillation in the absence of glutamine. Finally, inhibiting expression of the key ROS-defense catalase phenocopied circadian rhythm disruption observed after glutamine withdrawal. Together, these data suggest that glutamine availability and metabolism are critical to support circadian rhythm and gene expression through modulation of intracellular ROS, and furthermore that cancer treatments that lead to induction of ROS could affect normal cellular circadian rhythm.

We thank the following funding: NIH F32CA180370, NIH F32CA174148, NIH R01CA051497, LLS 610614

Citation Format: Brian J. Altman, Zachary E, Stine, Annie L. Hsieh, Ralph J. Deberardinis, Chi V. Dang. Mammalian glutamine metabolism controls circadian rhythm through regulation of reactive oxygen species. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4708. doi:10.1158/1538-7445.AM2015-4708

Targeted inhibition of tumor-specific glutaminase diminishes cell-autonomous tumorigenesis

Glutaminase (GLS), which converts glutamine to glutamate, plays a key role in cancer cell metabolism, growth, and proliferation. GLS is being explored as a cancer therapeutic target, but whether GLS inhibitors affect cancer cell-autonomous growth or the host microenvironment or have off-target effects is unknown. Here, we report that loss of one copy of Gls blunted tumor progression in an immune-competent MYC-mediated mouse model of hepatocellular carcinoma. Compared with results in untreated animals with MYC-induced hepatocellular carcinoma, administration of the GLS-specific inhibitor bis-2-(5-phenylacetamido-1,3,4-thiadiazol-2-yl)ethyl sulfide (BPTES) prolonged survival without any apparent toxicities. BPTES also inhibited growth of a MYC-dependent human B cell lymphoma cell line (P493) by blocking DNA replication, leading to cell death and fragmentation. In mice harboring P493 tumor xenografts, BPTES treatment inhibited tumor cell growth; however, P493 xenografts expressing a BPTES-resistant GLS mutant (GLS-K325A) or overexpressing GLS were not affected by BPTES treatment. Moreover, a customized Vivo-Morpholino that targets human GLS mRNA markedly inhibited P493 xenograft growth without affecting mouse Gls expression. Conversely, a Vivo-Morpholino directed at mouse Gls had no antitumor activity in vivo. Collectively, our studies demonstrate that GLS is required for tumorigenesis and support small molecule and genetic inhibition of GLS as potential approaches for targeting the tumor cell-autonomous dependence on GLS for cancer therapy.

Abstract 1419: Oncogenic Myc disrupts NAMPT circadian oscillation in mouse hepatocellular carcinoma cell line

MYC, which is overexpressed in a variety of human cancers, drives aerobic glycolysis, also called the Warburg effect. The Warburg effect results in regeneration of NAD+ from increased conversion of pyruvate to lactate, such that decreased lactate dehydrogenase A (LDHA) activity results in NAD+ depletion and can result in cell death. Nicotinamide phosphoribosyltransferase (NAMPT), a rate-limiting enzyme that is involved in the NAD+ salvage pathway, was reported to be directly upregulated by Myc. Increased NAD+ synthesis thus helps to replenish NAD+ along with LDHA. In this regard, we have previously reported the synergy of inhibiting LDHA and NAMPT in causing lymphoma xenograft regression. Targeting NAMPT by its inhibitor FK866 has been tested in clinical trials. However, the toxicity of FK866 in normal cells is not negligible, with thrombocytopenia being reported. Toxicity, however, could be diminished if therapy is administered at specific times of the day (termed chronotherapy) when normal cells are least dependent on NAMPT, whose levels oscillate every 24 hours. We have previously found that Myc upregulates Rev-erbα, which inhibits and disrupts oscillation of the circadian rhythm gene ARNTL (protein name Bmal1) in the osteosarcoma cell line U2OS. However, although NAMPT was shown oscillating in normal mouse liver and other tissues, how the oscillation of NAMPT is affected in cancer especially under Myc overexpression is still poorly understood.

Here we show Myc induces Nampt mRNA and protein in mouse hepatocellular carcinoma (mHCC) cell line that has been engineered tetracycline inducible Myc transgene expression vector. Inhibition of NAMPT by FK866 induces perturbation of circadian gene expression in mHCC cells, including Rev-erbα, Per1 and Cry1. The alteration of circadian gene expression can be rescued by nicotinamide, suggesting that the circadian clock is affected by NAD+/NADH ratio. Interestingly, Nampt mRNA oscillates in mHCC cell lines in the absence of Myc and the oscillation was lost when Myc is induced, suggesting a therapeutic opportunity could exist in the window between circadian regulation of the ebb-and-flow of normal cell NAMPT level and the sustained, non-circadian cancer cell NAMPT level. Our observation that Myc disrupts the oscillation its target gene NAMPT provides a conceptual framework for metabolic chronotherapy that could potentially lead to better cancer treatment strategies that reduce side effects.

We thank the following founding sources: NIH R01CA57341, LLS 6106-14.

Citation Format: Annie L. Hsieh, Brian J. Altman, Anand Venkataraman, David I. Bellovin, Dean W. Felsher, John B. Hogenesch, Chi V. Dang. Oncogenic Myc disrupts NAMPT circadian oscillation in mouse hepatocellular carcinoma cell line. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1419. doi:10.1158/1538-7445.AM2014-1419

Abstract 2953: Rev-erbα modulates Myc-driven cancer cell growth and altered metabolism

Circadian rhythms are regulated by feedback loops comprising a network of factors that regulate Clock-associated genes. Chronotherapy seeks to take advantage of altered circadian rhythms in some cancers to better time administration of treatments to increase efficacy and reduce toxicity. While many cancers have perturbed expression of core circadian rhythm genes, the molecular basis underlying these perturbations and their functional implications in oncogenesis are still poorly understood, and so it is impossible to predict which cancers have altered circadian rhythms and would best benefit from chronotherapy. We have observed in cancer cell models of osteosarcoma, hepatocellular carcinoma, and neuroblastoma that the c-Myc and N-Myc oncogenic transcription factors disrupt oscillation of the circadian clock by specifically upregulating the circadian rhythm gene and nuclear hormone receptor NR1D1 (Rev-erbα). Interestingly, while Rev-erbα has not been previously recognized as an oncogene, data from The Cancer Genome Atlas revealed that it is amplified in many forms of human cancer, and we also observed that Rev-erbα was upregulated in primary human neuroblastoma and associated with poor prognosis. Therefore, we hypothesized that Rev-erbα is a novel oncogene downstream of Myc and is important for cancer cell growth.

Here we show that Rev-erbα is specifically essential for the growth of Myc-driven hepatocellular carcinoma cells, as the related protein Rev-erbβ did not strongly influence growth. While knockdown of Rev-erbα expression by siRNA slowed growth, it did not cause cell death or canonical cell cycle arrest. Rev-erbα modulates circadian rhythm by downregulating the central circadian regulatory protein Bmal1, but this pathway did not play a central role in Rev-erbα control of cell growth. Additionally, while Rev-erbα has a well-described role in heme metabolism and subsequent support of mitochondria respiration, this pathway was not directly altered in Myc-driven liver cancer cells. Rather, knockdown of Rev-erbα was associated with decreased glycolytic activity characterized by a decrease in intracellular lactate and extracellular lactate production as well as an increase in certain glycolytic intermediates. In addition to these glycolytic changes, the maximum respiratory capacity of cells lacking Rev-erbα increased, as measured by oxygen consumption. These data suggest a novel role for Rev-erbα in promoting the growth of cancer cells through modulation of glucose metabolism and a shift towards increased respiration, and imply that cancers with upregulated Myc and Rev-erbα may be good candidates for chronotherapy.

We thank the following funding sources: NIH R01CA57341, LLS 6106-14.

Citation Format: Brian J. Altman, Annie Hsieh, Arvin M. Gouw, Zachary E. Stine, Anand Venkataraman, David I. Bellovin, Sharon J. Diskin, Wenyun Lu, Sisi Zhang, Dean W. Felsher, John M. Maris, Mitchell A. Lazar, Joshua D. Rabinowitz, John B. Hogenesch, Chi V. Dang. Rev-erbα modulates Myc-driven cancer cell growth and altered metabolism. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2953. doi:10.1158/1538-7445.AM2014-2953

Abstract 4616: Oncogenic c- and N-Myc disrupt circadian rhythm

Circadian rhythms are regulated by feedback loops comprising a network of factors that regulate Clock-associated genes. Chronotherapy seeks to take advantage of altered circadian rhythms in some cancers to better time administration of treatments to increase efficacy and reduce toxicity. Taking advantage of cancers that have substantially different circadian rhythms, or are ‘out of phase’, with normal tissues, could open a wide therapeutic window to make them vulnerable to chemotherapy or targeted drugs at different times than normal tissue. However, there is currently no basis to identify which cancers have disrupted circadian rhythms and would be amenable to chronotherapy. c- and N-Myc are oncogenic transcription factors translocated or amplified in many cancers. While the role of Myc in circadian rhythm is currently unknown, it may affect circadian rhythm by binding to the same E-box promoter regions used by the central regulators of circadian rhythm, Clock/Bmal1. Additionally, Myc increases NAD+ levels through upregulation of NAMPT, and NAD+ is a crucial cofactor in the activity of the circadian regulator Sirt1. Thus, we hypothesized that Myc may disrupt circadian rhythm through two mechanisms: inappropriate engagement of E-box promoters and also upregulation of NAMPT leading to dysregulated Sirt1 activity.

Here we show in neuroblastoma, osteosarcoma, and hepatocellular carcinoma cells that overexpressed Myc specifically upregulated the negative circadian regulator Rev-erbα, which in turn decreased expression of Bmal1. Inhibition of NAMPT downstream of Myc upregulation also led to major perturbations in circadian gene expression, suggesting a role for NAD modulation downstream of Myc in disruption of circadian rhythm. Importantly, My-expressing cells showed dramatically disrupted circadian oscillations, which could be partially rescued by inhibiting expression of Rev-erbα. Together, these data suggest that Myc-driven cancers have altered circadian oscillation due to upregulation of Rev-erbα and NAMPT, and that cancers driven by Myc may thus be good candidates for chronotherapy.

We thank the following funding sources: NIH R01CA051497, R01CA57341, LLS 636311

Citation Format: Brian J. Altman, Annie Hsieh, Arvin Gouw, Anand Venkataraman, Bo Li, David Bellovin, M. Celeste Simon, Dean Felsher, John Hogenesch, Chi V. Dang. Oncogenic c- and N-Myc disrupt circadian rhythm. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4616. doi:10.1158/1538-7445.AM2013-4616

Metabolic stress in autophagy and cell death pathways

Growth factors and oncogenic kinases play important roles in stimulating cell growth during development and transformation. These processes have significant energetic and synthetic requirements and it is apparent that a central function of growth signals is to promote glucose metabolism to support these demands. Because metabolic pathways represent a fundamental aspect of cell proliferation and survival, there is considerable interest in targeting metabolism as a means to eliminate cancer. A challenge, however, is that molecular links between metabolic stress and cell death are poorly understood. Here we review current literature on how cells cope with metabolic stress and how autophagy, apoptosis, and necrosis are tightly linked to cell metabolism. Ultimately, understanding of the interplay between nutrients, autophagy, and cell death will be a key component in development of new treatment strategies to exploit the altered metabolism of cancer cells.

Normal and cancer cell metabolism: lymphocytes and lymphoma

Recent studies of normal and neoplastic lymphocytes have revealed overlapping metabolic rewiring in activated T cells and Myc-transformed lymphocytes. Myc expression is attenuated in normal lymphocytes that return to the basal state, but Notch-activated or Myc-transformed lymphocytes persistently express Myc, which activates genes involved in glucose and glutamine metabolism. Although this difference could provide a therapeutic window for the treatment of cancers, the overlapping metabolic profiles suggest a potential for immunosuppression by metabolic inhibitors.

Akt requires glucose metabolism to suppress puma expression and prevent apoptosis of leukemic T cells

The PI3K/Akt pathway is activated in stimulated cells and in many cancers to promote glucose metabolism and prevent cell death. Although inhibition of Akt-mediated cell survival may provide a means to eliminate cancer cells, this survival pathway remains incompletely understood. In particular, unlike anti-apoptotic Bcl-2 family proteins that prevent apoptosis independent of glucose, Akt requires glucose metabolism to inhibit cell death. This glucose dependence may occur in part through metabolic regulation of pro-apoptotic Bcl-2 family proteins. Here, we show that activated Akt relies on glycolysis to inhibit induction of Puma, which was uniquely sensitive to metabolic status among pro-apoptotic Bcl-2 family members and was rapidly up-regulated in glucose-deficient conditions. Importantly, preventing Puma expression was critical for Akt-mediated cell survival, as Puma deficiency protected cells from glucose deprivation and Akt could not readily block Puma-mediated apoptosis. In contrast, the pro-apoptotic Bcl-2 family protein Bim was induced normally even when constitutively active Akt was expressed, yet Akt could provide protection from Bim cytotoxicity. Up-regulation of Puma appeared mediated by decreased availability of mitochondrial metabolites rather than glycolysis itself, as alternative mitochondrial fuels could suppress Puma induction and apoptosis upon glucose deprivation. Metabolic regulation of Puma was mediated through combined p53-dependent transcriptional induction and control of Puma protein stability, with Puma degraded in nutrient-replete conditions and long lived in nutrient deficiency. Together, these data identify a key role for Bcl-2 family proteins in Akt-mediated cell survival that may be critical in normal immunity and in cancer through Akt-dependent stimulation of glycolysis to suppress Puma expression.

Autophagy is essential to suppress cell stress and to allow BCR-Abl-mediated leukemogenesis

Hematopoietic cells normally require cell extrinsic signals to maintain metabolism and survival. In contrast, cancer cells can express constitutively active oncogenic kinases such as BCR-Abl that promote these processes independent of extrinsic growth factors. When cells receive insufficient growth signals or when oncogenic kinases are inhibited, glucose metabolism decreases and the self-digestive process of autophagy is elevated to degrade bulk cytoplasm and organelles. While autophagy has been proposed to provide a cell-intrinsic nutrient supply for mitochondrial oxidative metabolism and to maintain cellular homeostasis through degradation of damaged organelles or protein aggregates, its acute role in growth factor deprivation or inhibition of oncogenic kinases remains poorly understood. We therefore developed a growth factor-dependent hematopoietic cell culture model in which autophagy can be acutely disrupted through conditional Cre-mediated excision of the autophagy-essential gene Atg3. Treated cells rapidly lost their ability to perform autophagy and underwent cell cycle arrest and apoptosis. While Atg3 was essential for optimal upregulation of mitochondrial oxidative pathways in growth factor withdrawal, this metabolic contribution of autophagy did not appear critical for cell survival, as provision of exogenous pyruvate or lipids could not completely rescue Atg3-deficiency. Instead, autophagy suppressed a stress response that otherwise led to p53 phosphorylation and upregulation of p21 and the pro-apoptotic Bcl-2 family protein Puma. Importantly, BCR-Abl-expressing cells had low basal levels of autophagy but were highly dependent on this process, and rapidly underwent apoptosis upon disruption of autophagy through Atg3 deletion or treatment with chemical autophagy inhibitors. This dependence on autophagy extended in vivo, as Atg3 deletion also prevented BCR-Abl-mediated leukemogenesis in a cell transfer model. Together these data demonstrate a critical role for autophagy to mitigate cell stress, and that cells expressing the oncogenic kinase BCR-Abl appear particularly dependent on autophagy for cell survival and leukemogenesis.

Autophagy: not good OR bad, but good AND bad

Autophagy is a well-established mechanism to degrade intracellular components and provide a nutrient source to promote survival of cells in metabolic distress. Such stress can be caused by a lack of available nutrients or by insufficient rates of nutrient uptake. Indeed, growth factor deprivation leads to internalization and degradation of nutrient transporters, leaving cells with limited means to access extracellular nutrients even when plentiful.This loss of growth factor signaling and extracellular nutrients ultimately leads to apoptosis, but also activates autophagy, which may degrade intracellular components and provide fuel for mitochondrial bioenergetics. The precise metabolic role of autophagy and how it intersects with the apoptotic pathways in growth factor withdrawal, however, has been uncertain. Our recent findings ingrowth factor-deprived hematopoietic cells show that autophagy can simultaneously contribute to cell metabolism and initiate a pathway to sensitize cells to apoptotic death. This pathway may promote tissue homeostasis by ensuring that only cells with high resistance to apoptosis may utilize autophagy as a survival mechanism when growth factors are limiting and nutrient uptake decreases.

Autophagy provides nutrients but can lead to Chop-dependent induction of Bim to sensitize growth factor-deprived cells to apoptosis

Tissue homeostasis is controlled by the availability of growth factors, which sustain exogenous nutrient uptake and prevent apoptosis. Although autophagy can provide an alternate intracellular nutrient source to support essential basal metabolism of apoptosis-resistant growth factor-withdrawn cells, antiapoptotic Bcl-2 family proteins can suppress autophagy in some settings. Thus, the role of autophagy and interactions between autophagy and apoptosis in growth factor-withdrawn cells expressing Bcl-2 or Bcl-xL were unclear. Here we show autophagy was rapidly induced in hematopoietic cells upon growth factor withdrawal regardless of Bcl-2 or Bcl-xL expression and led to increased mitochondrial lipid oxidation. Deficiency in autophagy-essential gene expression, however, did not lead to metabolic catastrophe and rapid death of growth factor-deprived cells. Rather, inhibition of autophagy enhanced survival of cells with moderate Bcl-2 expression for greater than 1 wk, indicating that autophagy promoted cell death in this time frame. Cell death was not autophagic, but apoptotic, and relied on Chop-dependent induction of the proapoptotic Bcl-2 family protein Bim. Therefore, although ultimately important, autophagy-derived nutrients appear initially nonessential after growth factor withdrawal. Instead, autophagy promotes tissue homeostasis by sensitizing cells to apoptosis to ensure only the most apoptosis-resistant cells survive long-term using autophagy-derived nutrients when growth factor deprived.

Glycogen synthase kinase 3alpha and 3beta mediate a glucose-sensitive antiapoptotic signaling pathway to stabilize Mcl-1

Glucose uptake and utilization are growth factor-stimulated processes that are frequently upregulated in cancer cells and that correlate with enhanced cell survival. The mechanism of metabolic protection from apoptosis, however, has been unclear. Here we identify a novel signaling pathway initiated by glucose catabolism that inhibited apoptotic death of growth factor-deprived cells. We show that increased glucose metabolism protected cells against the proapoptotic Bcl-2 family protein Bim and attenuated degradation of the antiapoptotic Bcl-2 family protein Mcl-1. Maintenance of Mcl-1 was critical for this protection, as glucose metabolism failed to protect Mcl-1-deficient cells from apoptosis. Increased glucose metabolism stabilized Mcl-1 in both cell lines and primary lymphocytes via inhibitory phosphorylation of glycogen synthase kinase 3alpha and 3beta (GSK-3alpha/beta), which otherwise promoted Mcl-1 degradation. While a number of kinases can phosphorylate and inhibit GSK-3alpha/beta, we provide evidence that protein kinase C may be stimulated by glucose-induced alterations in diacylglycerol levels or distribution to phosphorylate GSK-3alpha/beta, maintain Mcl-1 levels, and inhibit cell death. These data provide a novel nutrient-sensitive mechanism linking glucose metabolism and Bcl-2 family proteins via GSK-3 that may promote survival of cells with high rates of glucose utilization, such as growth factor-stimulated or cancerous cells.