Expression of the monocarboxylate transporter MCT1 is required for virus-specific mouse CD8+ T cell memory development

Lactate-proton symporter monocarboxylate transporter 1 (MCT1) facilitates lactic acid export from T cells. Here, we report that MCT1 is mandatory for the development of virus-specific CD8+ T cell memory. MCT1-deficient T cells were exposed to acute pneumovirus (pneumonia virus of mice, PVM) or persistent γ-herpesvirus (Murid herpesvirus 4, MuHV-4) infection. MCT1 was required for the expansion of virus-specific CD8+ T cells and the control of virus replication in the acute phase of infection. This situation prevented the subsequent development of virus-specific T cell memory, a necessary step in containing virus reactivation during γ-herpesvirus latency. Instead, persistent active infection drove virus-specific CD8+ T cells toward functional exhaustion, a phenotype typically seen in chronic viral infections. Mechanistically, MCT1 deficiency sequentially impaired lactic acid efflux from activated CD8+ T cells, caused an intracellular acidification inhibiting glycolysis, disrupted nucleotide synthesis in the upstream pentose phosphate pathway, and halted cell proliferation which, ultimately, promoted functional CD8+ T cell exhaustion instead of memory development. Taken together, our data demonstrate that MCT1 expression is mandatory for inducing T cell memory and controlling viral infection by CD8+ T cells.

Specific HIF-2α (Hypoxia-Inducible Factor-2) Inhibitor PT2385 Mitigates Placental Dysfunction In Vitro and in a Rat Model of Preeclampsia (RUPP)

BACKGROUND

Preeclampsia is one of the leading causes of maternal mortality worldwide and is strongly associated with long-term morbidity in mothers and newborns. Referred to as one of the deep placentation disorders, insufficient remodeling of the spiral arteries during the first trimester remains a major cause of placental dysfunction. Persisting pulsatile uterine blood flow causes abnormal ischemia/reoxygenation phenomenon in the placenta and stabilizes the HIF-2α (hypoxia-inducible factor-2α) in the cytotrophoblasts. HIF-2α signaling impairs trophoblast differentiation and increases sFLT-1 (soluble fms-like tyrosine kinase-1) secretion, which reduces fetal growth and causes maternal symptoms. This study aims to evaluate the benefits of using PT2385-an oral specific HIF-2α inhibitor-to treat severe placental dysfunction.

METHODS

To evaluate its therapeutic potential, PT2385 was first studied in primary human cytotrophoblasts isolated from term placenta and exposed to 2.5% O₂ to stabilize HIF-2α. Viability and luciferase assays, RNA sequencing, and immunostaining were used to analyze differentiation and angiogenic factor balance. The ability of PT2385 to mitigate maternal manifestations of preeclampsia was studied in the selective reduced uterine perfusion pressure model performed in Sprague-Dawley rats.

RESULTS

In vitro, RNA sequencing analysis and conventional techniques showed that treated cytotrophoblast displayed an enhanced differentiation into syncytiotrophoblasts and normalized angiogenic factor secretion compared with vehicle-treated cells. In the selective reduced uterine perfusion pressure model, PT2385 efficiently decreased sFLT-1 production, thus preventing the onset of hypertension and proteinuria in pregnant dams.

CONCLUSIONS

These results highlight HIF-2α as a new player in our understanding of placental dysfunction and support the use of PT2385 to treat severe preeclampsia in humans.

EPR Investigations to Study the Impact of Mito-Metformin on the Mitochondrial Function of Prostate Cancer Cells

Background: Mito-metformin10 (MM10), synthesized by attaching a triphenylphosphonium cationic moiety via a 10-carbon aliphatic side chain to metformin, is a mitochondria-targeted analog of metformin that was recently demonstrated to alter mitochondrial function and proliferation in pancreatic ductal adenocarcinoma. Here, we hypothesized that this compound may decrease the oxygen consumption rate (OCR) in prostate cancer cells, increase the level of mitochondrial ROS, alleviate tumor hypoxia, and radiosensitize tumors. Methods: OCR and mitochondrial superoxide production were assessed by EPR (9 GHz) in vitro in PC-3 and DU-145 prostate cancer cells. Reduced and oxidized glutathione were assessed before and after MM10 exposure. Tumor oxygenation was measured in vivo using 1 GHz EPR oximetry in PC-3 tumor model. Tumors were irradiated at the time of maximal reoxygenation. Results: 24-hours exposure to MM10 significantly decreased the OCR of PC-3 and DU-145 cancer cells. An increase in mitochondrial superoxide levels was observed in PC-3 but not in DU-145 cancer cells, an observation consistent with the differences observed in glutathione levels in both cancer cell lines. In vivo, the tumor oxygenation significantly increased in the PC-3 model (daily injection of 2 mg/kg MM10) 48 and 72 h after initiation of the treatment. Despite the significant effect on tumor hypoxia, MM10 combined to irradiation did not increase the tumor growth delay compared to the irradiation alone. Conclusions: MM10 altered the OCR in prostate cancer cells. The effect of MM10 on the superoxide level was dependent on the antioxidant capacity of cell line. In vivo, MM10 alleviated tumor hypoxia, yet without consequence in terms of response to irradiation.

Ketogenic diets slow melanoma growth in vivo regardless of tumor genetics and metabolic plasticity

Background

Growing evidence supports the use of low-carbohydrate/high-fat ketogenic diets as an adjunctive cancer therapy. However, it is unclear which genetic, metabolic, or immunological factors contribute to the beneficial effect of ketogenic diets. Therefore, we investigated the effect of ketogenic diets on the progression and metabolism of genetically and metabolically heterogeneous melanoma xenografts, as well as on the development of melanoma metastases in mice with a functional immune system.

Methods

Mice bearing BRAF mutant, NRAS mutant, and wild-type melanoma xenografts as well as mice bearing highly metastatic melanoma allografts were fed with a control diet or ketogenic diets, differing in their triglyceride composition, to evaluate the effect of ketogenic diets on tumor growth and metastasis. We performed an in-depth targeted metabolomics analysis in plasma and xenografts to elucidate potential antitumor mechanisms in vivo.

Results

We show that ketogenic diets effectively reduced tumor growth in immunocompromised mice bearing genetically and metabolically heterogeneous human melanoma xenografts. Furthermore, the ketogenic diets exerted a metastasis-reducing effect in the immunocompetent syngeneic melanoma mouse model. Targeted analysis of plasma and tumor metabolomes revealed that ketogenic diets induced distinct changes in amino acid metabolism. Interestingly, ketogenic diets reduced the levels of alpha-amino adipic acid, a biomarker of cancer, in circulation to levels observed in tumor-free mice. Additionally, alpha-amino adipic acid was reduced in xenografts by ketogenic diets. Moreover, the ketogenic diets increased sphingomyelin levels in plasma and the hydroxylation of sphingomyelins and acylcarnitines in tumors.

Conclusions

Ketogenic diets induced antitumor effects toward melanoma regardless of the tumors´ genetic background, its metabolic signature, and the host immune status. Moreover, ketogenic diets simultaneously affected multiple metabolic pathways to create an unfavorable environment for melanoma cell proliferation, supporting their potential as a complementary nutritional approach to melanoma therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40170-022-00288-7.

Monocarboxylate transporter 1 deficiency impacts CD8+ T lymphocytes proliferation and recruitment to adipose tissue during obesity

Lactate sits at the crossroad of metabolism, immunity, and inflammation. The expression of cellular lactate transporter MCT1 (known as Slc16a1) increases during immune cell activation to cope with the metabolic reprogramming. We investigated the impact of MCT1 deficiency on CD8+ T cell function during obesity-related inflammatory conditions. The absence of MCT1 impaired CD8+ T cell proliferation with a shift of ATP production to mitochondrial oxidative phosphorylation. In Slc16a1 f/f Tcell cre mice fed a high-fat diet, a reduction in the number of CD8+ T cells, which infiltrated epididymal visceral adipose tissue (epiWAT) or subcutaneous adipose tissue, was observed. Adipose tissue weight and adipocyte area were significantly reduced together with downregulation of adipogenic genes only in the epiWAT. Our findings highlight a distinct effect of MCT1 deficiency in CD8+ T cells in the crosstalk with adipocytes and reinforce the concept that targeting immunometabolic reprogramming in lymphocyte could impact the immune-adipose tissue axis in obesity.

Extremely low frequency electromagnetic stimulation reduces ischemic stroke volume by improving cerebral collateral blood flow

Extremely low frequency electromagnetic stimulation (ELF-EMS) has been considered as a neuroprotective therapy for ischemic stroke based on its capacity to induce nitric oxide (NO) signaling. Here, we examined whether ELF-EMS reduces ischemic stroke volume by stimulating cerebral collateral perfusion. Moreover, the pathway responsible for ELF-EMS-induced NO production was investigated. ELF-EMS diminished infarct growth following experimental stroke in collateral-rich C57BL/6 mice, but not in collateral-scarce BALB/c mice, suggesting that decreased lesion sizes after ELF-EMS results from improved collateral blood flow. In vitro analysis demonstrated that ELF-EMS increased endothelial NO levels by stimulating the Akt-/eNOS pathway. Furthermore, ELF-EMS augmented perfusion in the hind limb of healthy mice, which was mediated by enhanced Akt-/eNOS signaling. In healthy C57BL/6 mouse brains, ELF-EMS treatment increased cerebral blood flow in a NOS-dependent manner, whereas no improvement in cerebrovascular perfusion was observed in collateral-sparse BALB/c mice. In addition, ELF-EMS enhanced cerebral blood flow in both the contra- and ipsilateral hemispheres of C57BL/6 mice subjected to experimental ischemic stroke. In conclusion, we showed that ELF-EMS enhances (cerebro)vascular perfusion by stimulating NO production, indicating that ELF-EMS could be an attractive therapeutic strategy for acute ischemic stroke by improving cerebral collateral blood flow.

Unconventional roles of lactate along the tumor and immune landscape

The tumor ecosystem evolves with dynamic interactions between cancer and normal cells, and nutrients have emerged as new regulators of cancer hallmarks. Lactate has climbed the rankings as a multifunctional molecule orchestrating many aspects of the disease onset and progression. Here, we patchwork and discuss the main recent findings conferred during the EMBO workshop titled 'Lactate: Unconventional Roles of a Nutrient Along the Tumor Landscape.'

MitoQ Inhibits Human Breast Cancer Cell Migration, Invasion and Clonogenicity

To successfully generate distant metastases, metastatic progenitor cells must simultaneously possess mesenchymal characteristics, resist to anoïkis, migrate and invade directionally, resist to redox and shear stresses in the systemic circulation, and possess stem cell characteristics. These cells primarily originate from metabolically hostile areas of the primary tumor, where oxygen and nutrient deprivation, together with metabolic waste accumulation, exert a strong selection pressure promoting evasion. Here, we followed the hypothesis according to which metastasis as a whole implies the existence of metabolic sensors. Among others, mitochondria are singled out as a major source of superoxide that supports the metastatic phenotype. Molecularly, stressed cancer cells increase mitochondrial superoxide production, which activates the transforming growth factor-β pathway through src directly within mitochondria, ultimately activating focal adhesion kinase Pyk2. The existence of mitochondria-targeted antioxidants constitutes an opportunity to interfere with the metastatic process. Here, using aggressive triple-negative and HER2-positive human breast cancer cell lines as models, we report that MitoQ inhibits all the metastatic traits that we tested in vitro. Compared to other mitochondria-targeted antioxidants, MitoQ already successfully passed Phase I safety clinical trials, which provides an important incentive for future preclinical and clinical evaluations of this drug for the prevention of breast cancer metastasis.

MitoQ Prevents Human Breast Cancer Recurrence and Lung Metastasis in Mice

Simple Summary

Entry in the metastatic phase is often devastating for cancer patients. Metastases originate from metastatic progenitor cells that are selected in the primary tumor and which simultaneously possess several phenotypic capabilities, including migration, invasion, and clonogenicity. We previously provided in vitro evidence that these features are collectively enforced by mitochondrial superoxide in a paradigm where mitochondria act as metabolic sensors of the tumor microenvironment and produce subcytotoxic levels of superoxide to prime metastatic progenitor cells. We also showed that these metastatic traits can be collectively countered by MitoQ, a mitochondria-targeted antioxidant that selectively deactivates mitochondrial superoxide. Here, we further establish that MitoQ prevents primary tumor recurrence after surgery, tumor take and metastasis as a whole, notably in a model of human breast cancer in mice. Since MitoQ already successfully passed Phase I clinical trials, our findings support the development of this drug as a preventive treatment against breast cancer metastasis.

Abstract

In oncology, the occurrence of distant metastases often marks the transition from curative to palliative care. Such outcome is highly predictable for breast cancer patients, even if tumors are detected early, and there is no specific treatment to prevent metastasis. Previous observations indicated that cancer cell mitochondria are bioenergetic sensors of the tumor microenvironment that produce superoxide to promote evasion. Here, we tested whether mitochondria-targeted antioxidant MitoQ is capable to prevent metastasis in the MDA-MB-231 model of triple-negative human breast cancer in mice and in the MMTV-PyMT model of spontaneously metastatic mouse breast cancer. At clinically relevant doses, we report that MitoQ not only prevented metastatic take and dissemination, but also local recurrence after surgery. We further provide in vitro evidence that MitoQ does not interfere with conventional chemotherapies used to treat breast cancer patients. Since MitoQ already successfully passed Phase I safety clinical trials, our preclinical data collectively provide a strong incentive to test this drug for the prevention of cancer dissemination and relapse in clinical trials with breast cancer patients.

Olaparib Is a Mitochondrial Complex I Inhibitor That Kills Temozolomide-Resistant Human Glioblastoma Cells

Glioblastoma represents the highest grade of brain tumors. Despite maximal resection surgery associated with radiotherapy and concomitant followed by adjuvant chemotherapy with temozolomide (TMZ), patients have a very poor prognosis due to the rapid recurrence and the acquisition of resistance to TMZ. Here, initially considering that TMZ is a prodrug whose activation is pH-dependent, we explored the contribution of glioblastoma cell metabolism to TMZ resistance. Using isogenic TMZ-sensitive and TMZ-resistant human glioblastoma cells, we report that the expression of O6-methylguanine DNA methyltransferase (MGMT), which is known to repair TMZ-induced DNA methylation, does not primarily account for TMZ resistance. Rather, fitter mitochondria in TMZ-resistant glioblastoma cells are a direct cause of chemoresistance that can be targeted by inhibiting oxidative phosphorylation and/or autophagy/mitophagy. Unexpectedly, we found that PARP inhibitor olaparib, but not talazoparib, is also a mitochondrial Complex I inhibitor. Hence, we propose that the anticancer activities of olaparib in glioblastoma and other cancer types combine DNA repair inhibition and impairment of cancer cell respiration.

Clinical and in Vitro Evidence against Placenta Infection at Term by Severe Acute Respiratory Syndrome Coronavirus 2

Despite occasional reports of vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during pregnancy, the question of placental infection and its consequences for the newborn remain unanswered. Herein, we analyzed the placentas of 31 coronavirus disease 2019–positive mothers by reverse transcriptase PCR, immunohistochemistry, and in situ hybridization. Only one case of placental infection was detected, which was associated with intrauterine demise of the fetus. Differentiated primary trophoblasts were then isolated from nonpathologic human placentas at term, differentiated, and exposed to SARS-CoV-2 virions. Unlike for positive control cells Vero E6, the virus inside cytotrophoblasts and syncytiotrophoblasts or in the supernatant 4 days after infection was undetectable. As a mechanism of defense, we hypothesized that trophoblasts at term do not express angiotensin-converting enzyme 2 and transmembrane protease serine 2 (TMPRSS2), the two main host membrane receptors for SARS-CoV-2 entry. The quantification of these proteins in the placenta during pregnancy confirmed the absence of TMPRSS2 at the surface of the syncytium. Surprisingly, a transiently induced experimental expression of TMPRSS2 did not allow the entry or replication of the virus in differentiated trophoblasts. Altogether, these results underline that trophoblasts are not likely to be infected by SARS-CoV-2 at term, but raise concern about preterm infection.

Mitochondrial Transfer in Cancer: A Comprehensive Review

Depending on their tissue of origin, genetic and epigenetic marks and microenvironmental influences, cancer cells cover a broad range of metabolic activities that fluctuate over time and space. At the core of most metabolic pathways, mitochondria are essential organelles that participate in energy and biomass production, act as metabolic sensors, control cancer cell death, and initiate signaling pathways related to cancer cell migration, invasion, metastasis and resistance to treatments. While some mitochondrial modifications provide aggressive advantages to cancer cells, others are detrimental. This comprehensive review summarizes the current knowledge about mitochondrial transfers that can occur between cancer and nonmalignant cells. Among different mechanisms comprising gap junctions and cell-cell fusion, tunneling nanotubes are increasingly recognized as a main intercellular platform for unidirectional and bidirectional mitochondrial exchanges. Understanding their structure and functionality is an important task expected to generate new anticancer approaches aimed at interfering with gains of functions (e.g., cancer cell proliferation, migration, invasion, metastasis and chemoresistance) or damaged mitochondria elimination associated with mitochondrial transfer.

Discovery of a novel lactate dehydrogenase tetramerization domain using epitope mapping and peptides

Despite being initially regarded as a metabolic waste product, lactate is now considered to serve as a primary fuel for the tricarboxylic acid cycle in cancer cells. At the core of lactate metabolism, lactate dehydrogenases (LDHs) catalyze the interconversion of lactate to pyruvate and as such represent promising targets in cancer therapy. However, direct inhibition of the LDH active site is challenging from physicochemical and selectivity standpoints. However, LDHs are obligate tetramers. Thus, targeting the LDH tetrameric interface has emerged as an appealing strategy. In this work, we examine a dimeric construct of truncated human LDH to search for new druggable sites. We report the identification and characterization of a new cluster of interactions in the LDH tetrameric interface. Using nanoscale differential scanning fluorimetry, chemical denaturation, and mass photometry, we identified several residues (E62, D65, L71, and F72) essential for LDH tetrameric stability. Moreover, we report a family of peptide ligands based on this cluster of interactions. We next demonstrated these ligands to destabilize tetrameric LDHs through binding to this new tetrameric interface using nanoscale differential scanning fluorimetry, NMR water–ligand observed via gradient spectroscopy, and microscale thermophoresis. Altogether, this work provides new insights on the LDH tetrameric interface as well as valuable pharmacological tools for the development of LDH tetramer disruptors.

Abstract PS17-55: Reactive oxygen species scavengers in triple negative breast cancer

Reactive oxygen species (ROS) are well known to play important roles in cancer. In particular, ROS of mitochondrial origin (mtROS) promote DNA mutations and cell death when produced at high levels, but rather stimulate autophagy and metastatic spread when produced at subcytotoxic levels [1]. Multiple metabolic pathways and oncogenic regulators linked to ROS have been studied in cancer cells, including MAPK/ERK, PI3K/AKT, PTEN, PKD, BREF2, HIF-1, NF-κB and p53 [2]. Abnormalities in these pathways can contribute to tumor development.By producing mtROS, mitochondria control and could even trigger metastatic spread, meaning that the use of specific mitochondria-targeted superoxide inhibitors/scavengers, such as mitoquinol mesylate (MitoQ), could reduce and/or prevent metastatic dissemination. This has been studied and reported with the use of MitoTempo, which prevents metastasis of naturally metastatic MDA-MB-231 human breast cancer cells implanted in mice [1]. Here, we show that MitoQ impairs MDA-MB-231 and SkBr3 human breast cancer cell migration and invasion in vitro, and MDA-MB-231 metastasis to the lungs in mice in vivo. In metastatic take assays, tail vein-injected MDA-MB-231 cells pretreated with MitoQ formed significantly less metastases after 4 weeks compared to vehicle. In spontaneous metastatic assays, mice bearing orthotopic MDA-MB-231 tumors were treated with ± 20 mg/kg MitoQ (per os) for 6 weeks. Primary tumors were surgically removed to allow metastatic outgrowth. In this model, MitoQ decreased primary tumor recurrence as well as the number of lung micro-metastases. Additionally, RNAseq studies in two human breast cancer cell lines identified that MitoQ significantly modulated a common set of metabolic genes in vitro and in vivo. They can be used as biomarkers of response. These results, together with a successful Phase I clinical trial and the fact that MitoQ does not interfere with the cytotoxic effects of chemotherapy, confirm that MitoQ is a potential candidate to be clinically tested in triple negative breast cancer patients.

References:

1.Porporato PE et al. A mitochondrial switch promotes tumor metastasis. Cell Rep. 2014;8(3):754-66.2.Payen VL, et al. Pro- and antitumor effects of mitochondrial reactive oxygen species. Cancer Metastasis Rev. 2019;38(1-2):189-203.

Citation Format: Francois P Duhoux, Tânia Capelôa, Pierre Sonveaux, Francoise Derouane. Reactive oxygen species scavengers in triple negative breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-55.

In Vitro and In Vivo Characterization of MCT1 Inhibitor AZD3965 Confirms Preclinical Safety Compatible with Breast Cancer Treatment

Simple Summary

The vast majority of tumors originate in tissues that use different substrates and oxygen to produce energy. However, tumors are disorganized structurally and functionally, which creates areas where oxygen and nutrients are poorly available. To survive and proliferate, cancer cells adapt by switching their metabolism to lactic fermentation. Their fate is further optimized by intercellular cooperation, but this creates a weakness that can be exploited therapeutically. Indeed, AZD3965 is a new drug currently tested in clinical trials that inhibits a cooperation based on lactate swapping for glucose between fermenting and respiring cells. It inhibits lactate transporter monocarboxylate transporter 1. Here, using malignant and nonmalignant cells representative of the breast tissue and several behavioral tests in mice, we establish that AZD3965 is safe for therapeutic use against cancer. The only side effect that we detected was a short-term memory retention defect that transiently perturbed the orientation of mice in space.

Abstract

To survive and proliferate in solid tumors, cancer cells adapt and evolve rapidly in microenvironments where oxygen and substrate bioavailability fluctuates over time and space. This creates metabolic heterogeneity. Cancer cells can further cooperate metabolically, for example by swapping glycolytic end-product lactate for blood-borne glucose. This type of cooperation can be targeted therapeutically, since transmembrane lactate exchanges are facilitated by lactate-proton symporters of the monocarboxylate (MCT) family. Among new drugs, AZD3965 is a first-in-class selective MCT1 inhibitor currently tested in Phase I/II clinical trials for patients with different types of cancers. Because MCT1 can function bidirectionally, we tested here whether and how malignant and nonmalignant cells adapt their metabolism and MCT repertoire when AZD3965 inhibits either lactate import or export. Using breast-associated malignant and nonmalignant cell lines as models, we report that AZD3965 is not directly cytotoxic. In the presence of glucose and glutamine, oxidative cells can survive when lactate uptake is blocked, and proliferating cells compensate MCT1 inhibition by overexpressing MCT4, a specialized facilitator of lactate export. Phenotypic characterization of mice focusing on metabolism, muscle and brain physiology found partial and transient memory retention defect as sole consequence of MCT1 inhibition by AZD3965. We therefore conclude that AZD3965 is compatible with anticancer therapy.

Adaptations of the human placenta to hypoxia: opportunities for interventions in fetal growth restriction

BACKGROUND

The placenta is the functional interface between the mother and the fetus during pregnancy, and a critical determinant of fetal growth and life-long health. In the first trimester, it develops under a low-oxygen environment, which is essential for the conceptus who has little defense against reactive oxygen species produced during oxidative metabolism. However, failure of invasive trophoblasts to sufficiently remodel uterine arteries toward dilated vessels by the end of the first trimester can lead to reduced/intermittent blood flow, persistent hypoxia and oxidative stress in the placenta with consequences for fetal growth. Fetal growth restriction (FGR) is observed in ∼10% of pregnancies and is frequently seen in association with other pregnancy complications, such as preeclampsia (PE). FGR is one of the main challenges for obstetricians and pediatricians, as smaller fetuses have greater perinatal risks of morbidity and mortality and postnatal risks of neurodevelopmental and cardio-metabolic disorders.

OBJECTIVE AND RATIONALE

The aim of this review was to examine the importance of placental responses to changing oxygen environments during abnormal pregnancy in terms of cellular, molecular and functional changes in order to highlight new therapeutic pathways, and to pinpoint approaches aimed at enhancing oxygen supply and/or mitigating oxidative stress in the placenta as a mean of optimizing fetal growth.

SEARCH METHODS

An extensive online search of peer-reviewed articles using PubMed was performed with combinations of search terms including pregnancy, placenta, trophoblast, oxygen, hypoxia, high altitude, FGR and PE (last updated in May 2020).

OUTCOMES

Trophoblast differentiation and placental establishment are governed by oxygen availability/hypoxia in early pregnancy. The placental response to late gestational hypoxia includes changes in syncytialization, mitochondrial functions, endoplasmic reticulum stress, hormone production, nutrient handling and angiogenic factor secretion. The nature of these changes depends on the extent of hypoxia, with some responses appearing adaptive and others appearing detrimental to the placental support of fetal growth. Emerging approaches that aim to increase placental oxygen supply and/or reduce the impacts of excessive oxidative stress are promising for their potential to prevent/treat FGR.

WIDER IMPLICATIONS

There are many risks and challenges of intervening during pregnancy that must be considered. The establishment of human trophoblast stem cell lines and organoids will allow further mechanistic studies of the effects of hypoxia and may lead to advanced screening of drugs for use in pregnancies complicated by placental insufficiency/hypoxia. Since no treatments are currently available, a better understanding of placental adaptations to hypoxia would help to develop therapies or repurpose drugs to optimize placental function and fetal growth, with life-long benefits to human health.

Evidence of metabolic activity during low-temperature ovarian tissue preservation in different media

PURPOSE

Although ovarian tissue transportation has been validated for up to 24 h, there is no standard protocol to date. We aimed to elucidate how existing media currently used for ovarian tissue transportation affect ovarian tissue metabolism and cell viability.

METHODS

Cow ovarian fragments were immersed in 0.9% NaCl solution, IVF medium, Leibovitz 15 medium (L-15), or PBS for 1, 4, or 24 h at 4 °C. Media were analyzed for pH, lactate dehydrogenase (LDH) activity, and glucose, pyruvate, and lactate concentrations, while apoptosis was assessed by TUNEL assays in fixed fragments. Viability rates were assessed by flow cytometry (FACS).

RESULTS

There were lower pH levels in NaCl at all time points compared with other media. LDH activity increased with time and was lowest in NaCl at 1 and 4 h. There was no significant difference in glucose levels, but a significant pyruvate decrease in L-15 and a significant lactate increase in all media. TUNEL showed apoptosis rates ranging from 0 to 5%. FACS showed a mean of 4% necrotic cells and 15-19% apoptotic cells after 1 h of incubation, but less than 1% necrotic cells and 2-6% apoptotic cells after 24 h in all media.

CONCLUSION

Our results indicate marked metabolic activity in ovarian tissue at 4 °C and suggest that cells use internal sources of energy, which may influence transplantation outcomes. This highlights the importance of better understanding whole tissue dynamics to develop a standard protocol for ovarian tissue transportation. Graphical abstract.

Hypoxia-inducible factor 2 alpha impairs human cytotrophoblast syncytialization: New insights into placental dysfunction and fetal growth restriction

Insufficient remodeling of uterine arteries causes pregnancy-related diseases, including fetal growth restriction and preeclampsia. In these situations, reduced maternal blood flow in the placenta is thought to be responsible for the persistence of a low oxygen environment throughout pregnancy. We hypothesized that chronic activation of transcription factors hypoxia-inducible factors (HIFs) actively participates in placental underdevelopment, which impairs fetal growth. The computer-assisted analysis in pathological placentas revealed an increased number of HIF-2α-positive nuclei in the syncytium compared to normal human placentas, while HIF-1α stabilization was unchanged. Specific involvement of HIF-2α was confirmed in primary human cytotrophoblasts rendered deficient for HIF1A or HIF2A. Silencing HIF2A increased the expression of main syncytialization markers as well as differentiation and syncytium formation. It also improved placental growth factor bioavailability. None of these changes was seen when silencing HIF1A. Conversely, the experimental induction of HIF-2α expression repressed forskolin-induced differentiation in BeWo choriocarcinoma cells. Our mechanistic insights evidence that transcription factor HIF-2α impairs placental function, thus suggesting its participation in fetal growth restriction and preeclampsia when placentas become chronically hypoxic. Furthermore, it suggests the possibility to develop novel molecular targeting therapies for placental dysfunction.

An EPR Study Using Cyclic Hydroxylamines To Assess The Level of Mitochondrial ROS in Superinvasive Cancer Cells

It has been proposed that a mitochondrial switch involving a high mitochondrial superoxide production is associated with cancer metastasis. We here report an EPR analysis of ROS production using cyclic hydroxylamines in superinvasive SiHa-F3 compared with less invasive SiHa wild-type human cervix cancer cells. Using the CMH probe, no significant difference was observed in the overall level of ROS between SiHa and SiHa-F3 cells. However, using mitochondria-targeted cyclic hydroxylamine probe mitoTEMPO-H, we detected a significantly higher mitochondrial ROS content in SiHa-F3 compared with the wild-type SiHa cells. To investigate the nature of mitochondrial ROS, we overexpressed superoxide dismutase 2, a SOD isoform exclusively localized in mitochondria, in SiHa-F3 superinvasive cells. A significantly lower signal was detected in SiHa-F3 cells overexpressing SOD2 compared with SiHa-F3. Despite some limitations discussed in the paper, our EPR results suggest that mitochondrial ROS (at least partly superoxide) are produced to a larger extent in superinvasive cancer cells compared with less invasive wild-type cancer cells.

The Risk of Arterial Thrombosis in Patients With Chronic Myeloid Leukemia Treated With Second and Third Generation BCR-ABL Tyrosine Kinase Inhibitors May Be Explained by Their Impact on Endothelial Cells: An In-Vitro Study

BCR-ABL tyrosine kinase inhibitors (TKIs) revolutionized the treatment of chronic myeloid leukemia, inducing deep molecular responses, largely improving patient survival and rendering treatment-free remission possible. However, three of the five BCR-ABL TKIs, dasatinib, nilotinib, and ponatinib, increase the risk of developing arterial thrombosis. Prior investigations reported that nilotinib and ponatinib affect the endothelium, but the mechanisms by which they exert their toxic effects are still unclear. The impact of dasatinib and bosutinib on endothelial cells has been poorly investigated. Here, we aimed to provide an in vitro homogenous evaluation of the effects of BCR-ABL TKIs on the endothelium, with a special focus on the type of cell death to elucidate the mechanisms responsible for the potential cytotoxic effects of BCR-ABL TKIs nilotinib and ponatinib on endothelial cells. We tested the five BCR-ABL TKIs at three concentrations on human umbilical venous endothelial cells (HUVECs). This study highlights the endothelial toxicity of ponatinib and provides insights about the mechanisms by which it affects endothelial cell viability. Ponatinib induced apoptosis and necrosis of HUVECs after 72 h. Dasatinib affected endothelial cells in vitro by inhibiting their proliferation and decreased wound closure as soon as 24 h of treatment and even at infra-therapeutic dose (0.005 µM). Comparatively, imatinib, nilotinib, and bosutinib had little impact on endothelial cells at therapeutic concentrations. They did not induce apoptosis nor necrosis, even after 72 h of treatment but they inhibited HUVEC proliferation. Overall, this study reports various effects of BCR-ABL TKIs on endothelial cells and suggests that ponatinib and dasatinib induce arterial thrombosis through endothelial dysfunction.

Mitochondria Participate in Chemoresistance to Cisplatin in Human Ovarian Cancer Cells

Ovarian cancer is an aggressive disease that affects about 300,000 patients worldwide, with a yearly death count of about 185,000. Following surgery, treatment involves adjuvant or neoadjuvant administration of taxane with platinum compounds cisplatin or carboplatin, which alkylate DNA through the same chemical intermediates. However, although platinum-based therapy can cure patients in a number of cases, a majority of them discontinues treatment owing to side effects and to the emergence of resistance. In this study, we focused on resistance to cisplatin and investigated whether metabolic changes could be involved. As models, we used matched pairs of cisplatin-sensitive (SKOV-3 and COV-362) and cisplatin-resistant (SKOV-3-R and COV-362-R) human ovarian carcinoma cells that were selected in vitro following exposure to increasing doses of the chemotherapy. Metabolic comparison revealed that resistant cells undergo a shift toward a more oxidative metabolism. The shift goes along with a reorganization of the mitochondrial network, with a generally increased mitochondrial compartment. More functional mitochondria in cisplatin-resistant compared with cisplatin-sensitive cells were associated to enzymatic changes affecting either the electron transport chain (SKOV-3/SKOV-3-R model) or mitochondrial coupling (COV-362/COV-362-R model). Our findings further indicate that the preservation of functional mitochondria in these cells could be due to an increased mitochondrial turnover rate, suggesting mitophagy inhibition as a potential strategy to tackle cisplatin-resistant human ovarian cancer progression. IMPLICATIONS: Besides classical mechanisms related to drug efflux and target modification, we report that preserving functional mitochondria is a strategy used by human ovarian cancer cells to resist to cisplatin chemotherapy.

Mitochondria in cancer

The rediscovery and reinterpretation of the Warburg effect in the year 2000 occulted for almost a decade the key functions exerted by mitochondria in cancer cells. Until recent times, the scientific community indeed focused on constitutive glycolysis as a hallmark of cancer cells, which it is not, largely ignoring the contribution of mitochondria to the malignancy of oxidative and glycolytic cancer cells, being Warburgian or merely adapted to hypoxia. In this review, we highlight that mitochondria are not only powerhouses in some cancer cells, but also dynamic regulators of life, death, proliferation, motion and stemness in other types of cancer cells. Similar to the cells that host them, mitochondria are capable to adapt to tumoral conditions, and probably to evolve to ‘oncogenic mitochondria' capable of transferring malignant capacities to recipient cells. In the wider quest of metabolic modulators of cancer, treatments have already been identified targeting mitochondria in cancer cells, but the field is still in infancy.

Interrogating the Lactate Dehydrogenase Tetramerization Site Using (Stapled) Peptides

Lactate dehydrogenases (LDHs) are tetrameric enzymes of major significance in cancer metabolism as well as promising targets for cancer therapy. However, their wide and polar catalytic sites make them a challenging target for orthosteric inhibition. In this work, we conceived to target LDH tetramerization sites with the ambition of disrupting their oligomeric state. To do so, we designed a protein model of a dimeric LDH-H. We exploited this model through WaterLOGSY nuclear magnetic resonance and microscale thermophoresis for the identification and characterization of a set of α-helical peptides and stapled derivatives that specifically targeted the LDH tetramerization sites. This strategy resulted in the design of a macrocyclic peptide that competes with the LDH tetramerization domain, thus disrupting and destabilizing LDH tetramers. These peptides and macrocycles, along with the dimeric model of LDH-H, constitute promising pharmacological tools for the de novo design and identification of LDH tetramerization disruptors. Overall, our study demonstrates that disrupting LDH oligomerization state by targeting their tetramerization sites is achievable and paves the way toward LDH inhibition through this novel molecular mechanism.

Rosiglitazone Protects Endothelial Cells From Irradiation-Induced Mitochondrial Dysfunction

Background and Purpose

Up to 50–60% of all cancer patients receive radiotherapy as part of their treatment strategy. However, the mechanisms accounting for increased vascular risks after irradiation are not completely understood. Mitochondrial dysfunction has been identified as a potential cause of radiation-induced atherosclerosis.

Materials and Methods

Assays for apoptosis, cellular metabolism, mitochondrial DNA content, functionality and morphology were used to compare the response of endothelial cells to a single 2 Gy dose of X-rays under basal conditions or after pharmacological treatments that either reduced (EtBr) or increased (rosiglitazone) mitochondrial content.

Results

Exposure to ionizing radiation caused a persistent reduction in mitochondrial content of endothelial cells. Pharmacological reduction of mitochondrial DNA content rendered endothelial cells more vulnerable to radiation-induced apoptosis, whereas rosiglitazone treatment increased oxidative metabolism and redox state and decreased the levels of apoptosis after irradiation.

Conclusion

Pre-existing mitochondrial damage sensitizes endothelial cells to ionizing radiation-induced mitochondrial dysfunction. Rosiglitazone protects endothelial cells from the detrimental effects of radiation exposure on mitochondrial metabolism and oxidative stress. Thus, our findings indicate that rosiglitazone may have potential value as prophylactic for radiation-induced atherosclerosis.

Fitter Mitochondria Are Associated With Radioresistance in Human Head and Neck SQD9 Cancer Cells

The clinical management of head and neck squamous cell carcinoma (HNSCC) commonly involves chemoradiotherapy, but recurrences often occur that are associated with radioresistance. Using human SQD9 laryngeal squamous cell carcinoma cancer cells as a model, we aimed to identify metabolic changes associated with acquired radioresistance. In a top-down approach, matched radiosensitive and radioresistant SQD9 cells were generated and metabolically compared, focusing on glycolysis, oxidative phosphorylation (OXPHOS) and ROS production. The cell cycle, clonogenicity, tumor growth in mice and DNA damage-repair were assessed. Mitochondrial DNA (mtDNA) was sequenced. In a bottom-up approach, matched glycolytic and oxidative SQD9 cells were generated using FACS-sorting, and tested for their radiosensitivity/radioresistance. We found that acquired radioresistance is associated with a shift from a glycolytic to a more oxidative metabolism in SQD9 cells. The opposite was also true, as the most oxidative fraction isolated from SQD9 wild-type cells was also more radioresistant than the most glycolytic fraction. However, neither reduced hexokinase expression nor OXPHOS were directly responsible for the radioresistant phenotype. Radiosensitive and radioresistant cells had similar proliferation rates and were equally efficient for ATP production. They were equally sensitive to redox stress and had similar DNA damage repair, but radioresistant cells had an increased number of mitochondria and a higher mtDNA content. Thus, an oxidative switch is associated with but is not responsible for acquired radioresistance in human SQD9 cells. In radioresistant cells, more abundant and fitter mitochondria could help to preserve mitochondrial functions upon irradiation.

Pro- and antitumor effects of mitochondrial reactive oxygen species

In cancer, mitochondrial functions are commonly altered. Directly involved in metabolic reprogramming, mitochondrial plasticity confers to cancer cells a high degree of adaptability to a wide range of stresses and to the harsh tumor microenvironment. Lack of nutrients or oxygen caused by altered perfusion, metabolic needs of proliferating cells, co-option of the microenvironment, control of the immune system, cell migration and metastasis, and evasion of exogenous stress (e.g., chemotherapy) are all, at least in part, influenced by mitochondria. Mitochondria are undoubtedly one of the key contributors to cancer development and progression. Understanding their protumoral (dys)functions may pave the way to therapeutic strategies capable of turning them into innocent entities. Here, we will focus on the production and detoxification of mitochondrial reactive oxygen species (mtROS), on their impact on tumorigenesis (genetic, prosurvival, and microenvironmental effects and their involvement in autophagy), and on tumor metastasis. We will also summarize the latest therapeutic approaches involving mtROS.

Annual Meeting of the International Society of Cancer Metabolism (ISCaM): Metabolic Adaptations and Targets in Cancer

The metabolism of cancer cells differs from that of their normal counterparts in a spectrum of attributes, including imbalances in diverse metabolic arms and pathways, metabolic plasticity and extent of adaptive responses, levels, and activities of metabolic enzymes and their upstream regulators and abnormal fluxes of metabolic intermediates and products. These attributes endow cancer cells with the ability to survive stressors of the tumor microenvironment and enable them to landscape and exploit the host terrain, thereby facilitating cancer progression and therapy resistance. Understanding the molecular and physiological principles of cancer metabolism is one of the key prerequisites for the development of better anticancer treatments. Therefore, various aspects of cancer metabolism were addressed at the 5th annual meeting of the International Society of Cancer Metabolism (ISCaM) in Bratislava, Slovakia, on October 17–20, 2018. The meeting presentations and discussions were traditionally focused on mechanistic, translational, and clinical characteristics of metabolism and pH control in cancer, at the level of molecular pathways, cells, tissues, and organisms. In order to reflect major healthcare challenges of the current era, ISCaM has extended its scope to metabolic disorders contributing to cancer, as well as to opportunities for their prevention, intervention, and therapeutic targeting.

Prolonged inhibition and incomplete recovery of mitochondrial function in oxazolidinone-treated megakaryoblastic cell lines

Thrombocytopenia is commonly seen in patients receiving linezolid for >14 days. Linezolid is a reversible inhibitor of mitochondrial function in various cell types. This study investigated the inhibitory effects of linezolid and tedizolid, and their potential recovery on (i) CYTox I expression (subunit I of cytochrome c-oxidase; encoded by the mitochondrial genome), (ii) cytochrome c-oxidase activity and (iii) mitochondrial respiration (Seahorse bioanalysis) in two megakaryocytic cell lines [UT-7 WT (human acute megakaryoblastic leukaemia cells) and UT-7 MPL (transduced to express the thrombopoietin receptor)]. Cells were exposed to linezolid (0.5-25 mg/L) or tedizolid (0.1-5 mg/L) for up to 5 days and recovery followed after drug removal. Both oxazolidinones caused concentration- and time-dependent inhibition of CYTox I expression, cytochrome c-oxidase activity and mitochondrial spare capacity. On electron microscopy, mitochondria appeared dilated with a loss of cristae. Globally, tedizolid exerted stronger effects than linezolid. While CYTox I expression recovered completely after 6 days of drug washout, only partial (linezolid) or no (tedizolid) recovery of cytochrome c-oxidase activity, and no rescue of mitochondrial spare capacity (after 3 days) was observed. Thus, and in contrast to previous studies using a variety of cell lines unrelated to megakaryocytic lineages, the inhibitory effects exerted by oxazolidinones on the mitochondrial function of megakaryoblastic cells appear to be particularly protracted. Given the dynamics of platelet production and destruction, these results may explain why oxazolidinone-induced thrombocytopenia is one of the most common side effects in patients exposed to these antibiotics.

Monocarboxylate transporters in cancer

Background

Tumors are highly plastic metabolic entities composed of cancer and host cells that can adopt different metabolic phenotypes. For energy production, cancer cells may use 4 main fuels that are shuttled in 5 different metabolic pathways. Glucose fuels glycolysis that can be coupled to the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) in oxidative cancer cells or to lactic fermentation in proliferating and in hypoxic cancer cells. Lipids fuel lipolysis, glutamine fuels glutaminolysis, and lactate fuels the oxidative pathway of lactate, all of which are coupled to the TCA cycle and OXPHOS for energy production. This review focuses on the latter metabolic pathway.

Scope of review

Lactate, which is prominently produced by glycolytic cells in tumors, was only recently recognized as a major fuel for oxidative cancer cells and as a signaling agent. Its exchanges across membranes are gated by monocarboxylate transporters MCT1-4. This review summarizes the current knowledge about MCT structure, regulation and functions in cancer, with a specific focus on lactate metabolism, lactate-induced angiogenesis and MCT-dependent cancer metastasis. It also describes lactate signaling via cell surface lactate receptor GPR81.

Major conclusions

Lactate and MCTs, especially MCT1 and MCT4, are important contributors to tumor aggressiveness. Analyses of MCT-deficient (MCT^+/- and MCT^−/-) animals and (MCT-mutated) humans indicate that they are druggable, with MCT1 inhibitors being in advanced development phase and MCT4 inhibitors still in the discovery phase. Imaging lactate fluxes non-invasively using a lactate tracer for positron emission tomography would further help to identify responders to the treatments.

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In cancer, hypoxia and cell proliferation are associated to lactic acid production.

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Lactate exchanges are at the core of tumor metabolism.

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Transmembrane lactate trafficking depends on monocarboxylate transporters (MCTs).

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MCTs are implicated in tumor development and aggressiveness.

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Targeting MCTs is a therapeutic option for cancer treatment.

Selective pro-apoptotic and antimigratory effects of polyphenol complex catechin:lysine 1:2 in breast, pancreatic and colorectal cancer cell lines

Cancer is a major cause of death in both developed and developing countries. Polyphenols, abundantly found in plants, possess many anticarcinogenic properties, including inhibition of cancer cell proliferation, tumor growth, angiogenesis, metastasis and inflammation, as well as pro-apoptotic effects. Our study aimed to investigate the effects of a complex of (+)-catechin with 2 lysines (Cat:Lys) on cancer and non-cancer cells. For this, the in vitro effects of Cat:Lys on the viability, growth, proliferation, apoptosis, nutrient uptake and migration of breast, pancreatic and colorectal cancer and non-cancer cell lines was evaluated. We found that Cat:Lys exerted antiproliferative and cytotoxic effects in all breast, pancreatic and colorectal cell lines tested, but with a much less marked amplitude in non-cancer cell lines. It nevertheless interfered with nutrient (³H-deoxy-D-glucose and ³H-lactate) uptake and with lactate production in both cancer and non-cancer cell lines. Cat:Lys was found to possess selective antimigratory effects in breast, pancreatic and colorectal cancer cell lines compared to non-cancer cell lines. Cat:Lys also exerted pro-apoptotic effects in all the cancer cell lines that we tested, but not in non-cancer breast and pancreatic cell lines. The antimigratory, but not the pro-apoptotic, effects of Cat:Lys were found to be mediated by JAK2/STAT3 and Wnt pathway inhibition. In conclusion, Cat:Lys is a strong candidate for the development of new, effective anticancer agents against cancer.

Abstract 793: The prometastatic effects of subcytotoxic doses of doxorubicin are countered by agents inactivating mitochondrial reactive oxygen species

Mitochondrial reactive oxygen species (mtROS) possess both tumor-promoting and tumor-suppressive activities according to their net concentration resulting for production levels and antioxidant detoxification. mtROS promote cancer cell fitness at low doses (mitohormesis), are cytotoxic at high doses and promote cancer migration, invasion and metastasis at intermediate doses. These intracellular doses vary from a model to another. Yet, we recently identified that mitochondria-targeted ROS scavengers mitoTEMPO and mitoQ prevent cancer metastasis in several in vivo models (Porporato et al. Cell Reports 2014;8:754-66). Interestingly, several anticancer drugs, among which doxorubicin, are well known to trigger mtROS production in cancer cells, but whether this response participates in cell killing or in resistance is still debated. We therefore tested whether combining mitochondria-targeted antioxidants with doxorubicin could help controlling cancer cell proliferation in vitro and tumor growth in mice. Using breast cancer cells lines MCF7 and 4T1 as models, we first found that subcytotoxic doses of doxorubicin increased cell respiration and, thereby, mitochondrial superoxide production. Downstream, mtROS activated the TGFβ pathway and induced cancer cell migration, invasion, epithelial-mesenchymal transition (EMT) and metastatic take in lungs. MitoTEMPO and mitoQ almost totally blocked these phenotypical changes. Together, our data provide a strong rationale for combining doxorubicin chemotherapy with drugs lowering mtROS production in breast cancer.

Citation Format: Paolo E. Porporato, Pierre Sonveaux. The prometastatic effects of subcytotoxic doses of doxorubicin are countered by agents inactivating mitochondrial reactive oxygen species [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 793.

Metabolic and non-metabolic pathways that control cancer resistance to anthracyclines

Anthracyclines Doxorubicin, Epirubicin, Daunorubicin and Idarubicin are used to treat a variety of tumor types in the clinics, either alone or, most often, in combination therapies. While their cardiotoxicity is well known, the emergence of chemoresistance is also a major issue accounting for treatment discontinuation. Resistance to anthracyclines is associated to the acquisition of multidrug resistance conferred by overexpression of permeability glycoprotein-1 or other efflux pumps, by altered DNA repair, changes in topoisomerase II activity, cancer stemness and metabolic adaptations. This review further details the metabolic aspects of resistance to anthracyclines, emphasizing the contributions of glycolysis, the pentose phosphate pathway and nucleotide biosynthesis, glutathione, lipid metabolism and autophagy to the chemoresistant phenotype.

Cancer-associated fibroblasts promote prostate cancer malignancy via metabolic rewiring and mitochondrial transfer

Cancer-associated fibroblasts (CAFs) are the major cellular stromal component of many solid tumors. In prostate cancer (PCa), CAFs establish a metabolic symbiosis with PCa cells, contributing to cancer aggressiveness through lactate shuttle. In this study, we report that lactate uptake alters the NAD⁺/NADH ratio in the cancer cells, which culminates with SIRT1-dependent PGC-1α activation and subsequent enhancement of mitochondrial mass and activity. The high exploitation of mitochondria results in tricarboxylic acid cycle deregulation, accumulation of oncometabolites and in the altered expression of mitochondrial complexes, responsible for superoxide generation. Additionally, cancer cells hijack CAF-derived functional mitochondria through the formation of cellular bridges, a phenomenon that we observed in both in vitro and in vivo PCa models. Our work reveals a crucial function of tumor mitochondria as the energy sensors and transducers of CAF-dependent metabolic reprogramming and underscores the reliance of PCa cells on CAF catabolic activity and mitochondria trading.

Comparison of different methods for measuring the superoxide radical by EPR spectroscopy in buffer, cell lysates and cells

As superoxide anion is of keen interest in biomedical research, it is highly desirable to have a technique allowing its detection sensitively and specifically in biological media. If electron paramagnetic resonance (EPR) techniques and probes have been individually described in the literature, there is actually no comparison of these techniques in the same conditions that may help guiding researchers for selecting the most appropriate approach. The aim of the present study was to compare different EPR strategies in terms of sensitivity and specificity to detect superoxide (vs. hydroxyl radical). Three main classes of EPR probes were used, including paramagnetic superoxide scavengers (such as nitroxides TEMPOL and mitoTEMPO as well as trityl CT-03), a spin trap (DIPPMPO), and diamagnetic superoxide scavengers (such as cyclic hydroxylamines CMH and mitoTEMPO-H). We analysed the reactivity of the different probes in the presence of a constant production of superoxide or hydroxyl radical in buffers and in cell lysates. We also assessed the performances of the different probes to detect superoxide produced by RAW264.7 macrophages stimulated by phorbol 12-myristate 13-acetate. In our conditions and models, we found that nitroxides were not specific for superoxide. CT-03 was specific, but the sensitivity of detection was low. Comparatively, we found that nitrone DIPPMPO and cyclic hydroxylamine CMH were good candidates to sensitively and specifically detect superoxide in complex biological media, CMH offering the best sensitivity.

Annual Meeting of the International Society of Cancer Metabolism (ISCaM): Cancer Metabolism

Tumors are metabolic entities wherein cancer cells adapt their metabolism to their oncogenic agenda and microenvironmental influences. Metabolically different cancer cell subpopulations collaborate to optimize nutrient delivery with respect to immediate bioenergetic and biosynthetic needs. They can also metabolically exploit host cells. These metabolic networks are directly linked with cancer progression, treatment, resistance, and relapse. Conversely, metabolic alterations in cancer are exploited for anticancer therapy, imaging, and stratification for personalized treatments. These topics were addressed at the 4th annual meeting of the International Society of Cancer Metabolism (ISCaM) in Bertinoro, Italy, on 19-21 October 2017.

Acute iodine deficiency induces a transient VEGF-dependent microvascular response in mammary glands involving HIF-1, ROS, and mTOR

Iodine deficiency (ID), which affects almost two billion people worldwide, is associated with breast pathologies such as fibrosis in human and induces breast atypia in animal models. Because ID induces vascular activation in the thyroid, another iodide-uptaking organ, and as breast is also sensitive to ID, we aimed to characterize ID-induced effects on the breast microvasculature in vivo and in two different breast cell lines in vitro. Virgin and lactating NMRI mice received an iodide-deficient diet and a Na⁺/I^- symporter inhibitor for 1 to 20 days. Some virgin mice were treated with vascular endothelial growth factor A (VEGF) or VEGF receptor inhibitors. In vitro, ID was induced in MCF7 and MCF12A cells by replacing the iodide-containing medium by an iodide-deficient medium. In vivo, VEGF expression was increased following ID in mammary tissues. Consequently, ID induced a transient increase in mammary gland blood flow, measured after anesthesia, in virgin and lactating mice, which was repressed by VEGF or VEGF receptor inhibitors. In MCF7 cells, ID induced a transient increase in reactive oxygen species, followed by an increase in hypoxia-inducible factor-1α (HIF-1α) protein and VEGF mRNA expression. Antioxidant N-acetylcysteine and mammalian target of rapamycin (mTOR) inhibitor blocked ID-induced HIF-1α protein increase and VEGF transcription. However, mTOR activity was not inhibited by N-acetylcysteine. Similar responses were observed in MCF12A cells. These data indicate that ID activates the canonical VEGF pathway and mTOR in breast tissues, which provides new insights to better understand the correlation between ID, vascular activation, and breast pathologies.

Long-term antigen exposure irreversibly modifies metabolic requirements for T cell function

Energy metabolism is essential for T cell function. However, how persistent antigenic stimulation affects T cell metabolism is unknown. Here, we report that long-term in vivo antigenic exposure induced a specific deficit in numerous metabolic enzymes. Accordingly, T cells exhibited low basal glycolytic flux and limited respiratory capacity. Strikingly, blockade of inhibitory receptor PD-1 stimulated the production of IFNγ in chronic T cells, but failed to shift their metabolism towards aerobic glycolysis, as observed in effector T cells. Instead, chronic T cells appeared to rely on oxidative phosphorylation (OXPHOS) and fatty acid oxidation (FAO) to produce ATP for IFNγ synthesis. Check-point blockade, however, increased mitochondrial production of superoxide and reduced viability and effector function. Thus, in the absence of a glycolytic switch, PD-1-mediated inhibition appears essential for limiting oxidative metabolism linked to effector function in chronic T cells, thereby promoting survival and functional fitness.

Radiosynthesis and validation of (±)-[18F]-3-fluoro-2-hydroxypropionate ([18F]-FLac) as a PET tracer of lactate to monitor MCT1-dependent lactate uptake in tumors

Cancers develop metabolic strategies to cope with their microenvironment often characterized by hypoxia, limited nutrient bioavailability and exposure to anticancer treatments. Among these strategies, the metabolic symbiosis based on the exchange of lactate between hypoxic/glycolytic cancer cells that convert glucose to lactate and oxidative cancer cells that preferentially use lactate as an oxidative fuel optimizes the bioavailability of glucose to hypoxic cancer cells. This metabolic cooperation has been described in various human cancers and can provide resistance to anti-angiogenic therapies. It depends on the expression and activity of monocarboxylate transporters (MCTs) at the cell membrane. MCT4 is the main facilitator of lactate export by glycolytic cancer cells, and MCT1 is adapted for lactate uptake by oxidative cancer cells. While MCT1 inhibitor AZD3965 is currently tested in phase I clinical trials and other inhibitors of lactate metabolism have been developed for anticancer therapy, predicting and monitoring a response to the inhibition of lactate uptake is still an unmet clinical need. Here, we report the synthesis, evaluation and in vivo validation of (±)-[18F]-3-fluoro-2-hydroxypropionate ([18F]-FLac) as a tracer of lactate for positron emission tomography. [18F]-FLac offers the possibility to monitor MCT1-dependent lactate uptake and inhibition in tumors in vivo.

(+)-Catechin in a 1:2 Complex with Lysine Inhibits Cancer Cell Migration and Metastatic Take in Mice

Metastasis is of dismal prognosis for cancer patients, but recent evidence in mouse models of cancer shows that metastasis prevention is a reachable clinical objective. These experiments indicate that altered mitochondrial activities are associated with the metastatic phenotype. Mitochondrial transfer from metastatic to non-metastatic cells can indeed transfer the metastatic phenotype, and metastatic progenitor cells differ from other cancer cells by a higher sublethal production of mitochondrial reactive oxygen species (ROS). Moreover, mitochondria-targeted antioxidants can prevent metastatic dissemination in mouse models of cancer. Comparatively, general antioxidants have unpredictable effects on cancer metastasis, most probably because they affect several cell types, several subcellular ROS production sites and, often, several endogenous oxidant species. Thus, targeting antioxidants to mitochondria could improve their antimetastatic activities, as previously exemplified with mitochondria-targeted mitoTEMPO and mitoQ that can prevent metastatic dissemination in cancer-bearing mice. Our objective in this study was to identify whether catechins, which are known to be potent antioxidants, can inhibit cancer cell migration in vitro and metastatic take in vivo. Comparative analysis of the response to epigallocatechin-3-gallate, (+)-catechin and (+)-catechin:lysine complexes revealed that, whereas all compounds had similar general antioxidant properties, (+)-catechin:lysine 1:2, but not epigallocatechin-3-gallate, can prevent metastatic take of melanoma cells to the lungs of mice. (+)-Catechin:lysine 1:2 possesses two net positive charges provided by lysines at physiological pH, which could provide high affinity for the negatively charged mitochondrial matrix. While this study reveals that (+)-catechin:lysine 1:2 has interesting antimetastatic effects, future experiments are needed to formally demonstrate the stability of the complex, its effective tropism for mitochondria and whether or not its activity can be globally attributed to its antioxidant activity at this precise subcellular location.

Presenilin 2-Dependent Maintenance of Mitochondrial Oxidative Capacity and Morphology

Mitochondrial dysfunction plays a pivotal role in the progression of Alzheimer's disease (AD), and yet the mechanisms underlying the impairment of mitochondrial function in AD remain elusive. Recent evidence suggested a role for Presenilins (PS1 or PS2) in mitochondrial function. Mutations of PSs, the catalytic subunits of the γ-secretase complex, are responsible for the majority of inherited AD cases (FAD). PSs were shown to be present in mitochondria and particularly enriched in mitochondria-associated membranes (MAM), where PS2 is involved in the calcium shuttling between mitochondria and the endoplasmic reticulum (ER). We investigated the precise contribution of PS1 and PS2 to the bioenergetics of the cell and to mitochondrial morphology in cell lines derived from wild type (PS+/+), PS1/2 double knock-out (PSdKO), PS2KO and PS1KO embryos. Our results showed a significant impairment in the respiratory capacity of PSdKO and PS2KO cells with reduction of basal oxygen consumption, oxygen utilization dedicated to ATP production and spare respiratory capacity. In line with these functional defects, we found a decrease in the expression of subunits responsible for mitochondrial oxidative phosphorylation (OXPHOS) associated with an altered morphology of the mitochondrial cristae. This OXPHOS disruption was accompanied by a reduction of the NAD⁺/NADH ratio. Still, neither ADP/ATP ratio nor mitochondrial membrane potential (ΔΨ) were affected, suggesting the existence of a compensatory mechanism for energetic balance. We observed indeed an increase in glycolytic flux in PSdKO and PS2KO cells. All these effects were truly dependent on PS2 since its stable re-expression in a PS2KO background led to a complete restoration of the parameters impaired in the absence of PS2. Our data clearly demonstrate here the crucial role of PS2 in mitochondrial function and cellular bioenergetics, pointing toward its peculiar role in the formation and integrity of the electron transport chain.

Differential Impact of Single-Dose Fe Ion and X-Ray Irradiation on Endothelial Cell Transcriptomic and Proteomic Responses

Background and Purpose: Radiotherapy is an essential tool for cancer treatment. In order to spare normal tissues and to reduce the risk of normal tissue complications, particle therapy is a method of choice. Although a large part of healthy tissues can be spared due to improved depth dose characteristics, little is known about the biological and molecular mechanisms altered after particle irradiation in healthy tissues. Elucidation of these effects is also required in the context of long term space flights, as particle radiation is the main contributor to the radiation effects observed in space. Endothelial cells (EC), forming the inner layer of all vascular structures, are especially sensitive to irradiation and, if damaged, contribute to radiation-induced cardiovascular disease. Materials and Methods: Transcriptomics, proteomics and cytokine analyses were used to compare the response of ECs irradiated or not with a single 2 Gy dose of X-rays or Fe ions measured one and 7 days post-irradiation. To support the observed inflammatory effects, monocyte adhesion on ECs was also assessed. Results: Experimental data indicate time- and radiation quality-dependent changes of the EC response to irradiation. The irradiation impact was more pronounced and longer lasting for Fe ions than for X-rays. Both radiation qualities decreased the expression of genes involved in cell-cell adhesion and enhanced the expression of proteins involved in caveolar mediated endocytosis signaling. Endothelial inflammation and adhesiveness were increased with X-rays, but decreased after Fe ion exposure. Conclusions: Fe ions induce pro-atherosclerotic processes in ECs that are different in nature and kinetics than those induced by X-rays, highlighting radiation quality-dependent differences which can be linked to the induction and progression of cardiovascular diseases (CVD). Our findings give a better understanding of the underlying processes triggered by particle irradiation in ECs, a crucial aspect for the development of protective measures for cancer patients undergoing particle therapy and for astronauts in space.

Lactate stimulates CA IX expression in normoxic cancer cells

Besides hypoxia, other factors and molecules such as lactate, succinate, and reactive oxygen species activate transcription factor hypoxia-inducible factor-1 (HIF-1) even in normoxia. One of the main target gene products of HIF-1 is carbonic anhydrase IX (CA IX). CA IX is overexpressed in many tumors and serves as prognostic factor for hypoxic, aggressive and malignant cancers. CA IX is also induced in normoxia in high cell density. In this study, we observed that lactate induces CA IX expression in normoxic cancer cells in vitro and in vivo. We further evidenced that participation of both HIF-1 and specificity protein 1 (SP1) transcription factors is crucial for lactate-driven normoxic induction of the CA9 gene. By inducing CA IX, lactate can facilitate the maintenance of cancer cell aggressive behavior in normoxia.

Ffar2 expression regulates leukaemic cell growth in vivo

Background:

Activation of free fatty acid receptor 2 (FFAR2) by microbiota-derived metabolites (e.g., propionate) reduces leukaemic cell proliferation in vitro. This study aims to test whether Ffar2 expression per se also influences leukaemia cell growth in vivo.

Methods:

Bcr-Abl-expressing BaF cells were used as a leukaemia model and the role of Ffar2 was evaluated in Balb/c mice after lentiviral shRNA transduction.

Results:

Our data formally establish that reduced leukaemic cell proliferation is associated with increased Ffar2 expression in vivo and in vitro. Going beyond association, we point out that decreasing Ffar2 expression fosters cancer cell growth in vitro and in vivo.

Conclusions:

Our data demonstrate the role of Ffar2 in the control of leukaemic cell proliferation in vivo and indicate that a modulation of Ffar2 expression through nutritional tools or pharmacological agents may constitute an attractive therapeutic approach to tackle leukaemia progression in humans.

MDA-MB-231 breast cancer cells fuel osteoclast metabolism and activity: A new rationale for the pathogenesis of osteolytic bone metastases

Recent progress in dissecting the molecular paracrine circuits of cancer and stromal cells in bone metastases (BM) are offering new options to improve current merely palliative approach. The study of tumor-stroma metabolic interplay may further ameliorate this scenario. In this context, we demonstrated that highly glycolytic MDA-MB-231 cancer cells, that form osteolytic BM in vivo, release a large amount of lactate at a significantly higher level than MCF7 cells. Thus, we speculated that lactate released from carcinoma cells is uptaken and metabolically used by osteoclasts, the key players of osteolysis associated with BM. First, we demonstrated that the release of lactate at the bone site is mediated by monocarboxylate transporter 4 (MCT4), as revealed by immunostaining and MCT4 localization at the plasma membrane of tumor cells in mouse model of BM and in human tissue sections of BM. Then, we showed that in vitro lactate is uptaken by osteoclasts to be used as a fuel for the oxidative metabolism of osteoclasts, ultimately enhancing Type I collagen resorption. The passive transport of lactate into osteoclasts was mediated by MCT1: MCT1 expression is significantly upregulated during osteoclast differentiation and Type I collagen resorption is significantly impaired when osteoclasts are treated with 7-(N-benzyl-N-methylamino)-2-oxo-2H-chromene-3-carboxylic acid, an MCT-1 inhibitor. Together, these data demonstrate that lactate released by glycolytic breast carcinoma cells in the bone microenvironment promotes the formation of osteolytic lesions, and provide the rationale for further studies on the use of MCT1 targeting as a novel therapeutic approach in advanced cancer patients with BM.

Annual Meeting of the International Society of Cancer Metabolism (ISCaM): Metabolic Networks in Cancer

Cancers are metabolic entities wherein cancer cells adapt their metabolism to their oncogenic agenda and microenvironmental influences. Metabolically different cancer cell subpopulations collaborate to optimize nutrient delivery with respect to immediate bioenergetic and biosynthetic needs. They can also metabolically exploit host cells. These metabolic networks are directly linked with cancer progression, treatment resistance and relapse. Conversely, metabolic alterations in cancer are exploited for anticancer therapy, imaging and personalized medicine. These topics were addressed at the 3rd annual meeting of the International Society of Cancer Metabolism (ISCaM) in Brussels, Belgium, on 26–29 October 2016.