Metabolic Rewiring toward Oxidative Phosphorylation Disrupts Intrinsic Resistance to Ferroptosis of the Colon Adenocarcinoma Cells

Glutathione peroxidase 4 (GPX4) has been reported as one of the major targets for ferroptosis induction, due to its pivotal role in lipid hydroperoxide removal. However, recent studies pointed toward alternative antioxidant systems in this context, such as the Coenzyme Q-FSP1 pathway. To investigate how effective these alternative pathways are in different cellular contexts, we used human colon adenocarcinoma (CRC) cells, highly resistant to GPX4 inhibition. Data obtained in the study showed that simultaneous pharmacological inhibition of GPX4 and FSP1 strongly compromised the survival of the CRC cells, which was prevented by the ferroptosis inhibitor, ferrostatin-1. Nonetheless, this could not be phenocopied by genetic deletion of FSP1, suggesting the development of resistance to ferroptosis in FSP1-KO CRC cells. Considering that CRC cells are highly glycolytic, we used CRC Warburg-incompetent cells, to investigate the role metabolism plays in this phenomenon. Indeed, the sensitivity to inhibition of both anti-ferroptotic axes (GPx4 and FSP1) was fully revealed in these cells, showing typical features of ferroptosis. Collectively, data indicate that two independent anti-ferroptotic pathways (GPX4-GSH and CoQ10-FSP1) operate within the overall physiological context of cancer cells and in some instances, their inhibition should be coupled with other metabolic modulators, such as inhibitors of glycolysis/Warburg effect.

Pancreatic Ductal Adenocarcinoma: The Dawn of the Era of Nuclear Medicine?

Pancreatic ductal adenocarcinoma (PDAC), accounting for 90-95% of all pancreatic tumors, is a highly devastating disease associated with poor prognosis. The lack of accurate diagnostic tests and failure of conventional therapies contribute to this pejorative issue. Over the last decade, the advent of theranostics in nuclear medicine has opened great opportunities for the diagnosis and treatment of several solid tumors. Several radiotracers dedicated to PDAC imaging or internal vectorized radiotherapy have been developed and some of them are currently under clinical consideration. The functional information provided by Positron Emission Tomography (PET) or Single Photon Emission Computed Tomography (SPECT) could indeed provide an additive diagnostic value and thus help in the selection of patients for targeted therapies. Moreover, the therapeutic potential of β-- and α-emitter-radiolabeled agents could also overcome the resistance to conventional therapies. This review summarizes the current knowledge concerning the recent developments in the nuclear medicine field for the management of PDAC patients.

Whole-transcriptome Analysis of Fully Viable Energy Efficient Glycolytic-null Cancer Cells Established by Double Genetic Knockout of Lactate Dehydrogenase A/B or Glucose-6-Phosphate Isomerase

BACKGROUND/AIM

Nearly all mammalian tumors of diverse tissues are believed to be dependent on fermentative glycolysis, marked by elevated production of lactic acid and expression of glycolytic enzymes, most notably lactic acid dehydrogenase (LDH). Therefore, there has been significant interest in developing chemotherapy drugs that selectively target various isoforms of the LDH enzyme. However, considerable questions remain as to the consequences of biological ablation of LDH or upstream targeting of the glycolytic pathway.

MATERIALS AND METHODS

In this study, we explore the biochemical and whole transcriptomic effects of CRISPR-Cas9 gene knockout (KO) of lactate dehydrogenases A and B [LDHA/B double KO (DKO)] and glucose-6-phosphate isomerase (GPI KO) in the human colon cancer cell line LS174T, using Affymetrix 2.1 ST arrays.

RESULTS

The metabolic biochemical profiles corroborate that relative to wild type (WT), LDHA/B DKO produced no lactic acid, (GPI KO) produced minimal lactic acid and both KOs displayed higher mitochondrial respiration, and minimal use of glucose with no loss of cell viability. These findings show a high biochemical energy efficiency as measured by ATP in glycolysis-null cells. Next, transcriptomic analysis conducted on 48,226 mRNA transcripts reflect 273 differentially expressed genes (DEGS) in the GPI KO clone set, 193 DEGS in the LDHA/B DKO clone set with 47 DEGs common to both KO clones. Glycolytic-null cells reflect up-regulation in gene transcripts typically associated with nutrient deprivation / fasting and possible use of fats for energy: thioredoxin interacting protein (TXNIP), mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), PPARγ coactivator 1α (PGC-1α), and acetyl-CoA acyltransferase 2 (ACAA2). Other changes in non-ergometric transcripts in both KOs show losses in "stemness", WNT signaling pathway, chemo/radiation resistance, retinoic acid synthesis, drug detoxification, androgen/estrogen activation, and extracellular matrix reprogramming genes.

CONCLUSION

These findings demonstrate that: 1) The "Warburg effect" is dispensable, 2) loss of the LDHAB gene is not only inconsequential to viability but fosters greater mitochondrial energy, and 3) drugs that target LDHA/B are likely to be ineffective without a plausible combination second drug target.

From Malignant Progression to Therapeutic Targeting: Current Insights of Mesothelin in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC), accounting for 90% of all pancreatic tumors, is a highly devastating disease with poor prognosis and rising incidence. The lack of available specific diagnostics tests and the limited treatment opportunities contribute to this pejorative issue. Over the last 10 years, a growing interest pointing towards mesothelin (MSLN) as a promising PDAC-associated antigen has emerged. The limited expression of MSLN in normal tissues (peritoneum, pleura and pericardium) and its overexpression in 80 to 90% of PDAC make it an attractive candidate for therapeutic management of PDAC patients. Moreover, its role in malignant progression related to its involvement in tumor cell proliferation and resistance to chemotherapy has highlighted the relevance of its targeting. Hence, several clinical trials are investigating anti-MSLN efficacy in PDAC. In this review, we provide a general overview of the different roles sustained by MSLN during PDAC progression. Finally, we also summarize the different MSLN-targeted therapies that are currently tested in the clinic.

Warburg and Beyond: The Power of Mitochondrial Metabolism to Collaborate or Replace Fermentative Glycolysis in Cancer

A defining hallmark of tumor phenotypes is uncontrolled cell proliferation, while fermentative glycolysis has long been considered as one of the major metabolic pathways that allows energy production and provides intermediates for the anabolic growth of cancer cells. Although such a vision has been crucial for the development of clinical imaging modalities, it has become now evident that in contrast to prior beliefs, mitochondria play a key role in tumorigenesis. Recent findings demonstrated that a full genetic disruption of the Warburg effect of aggressive cancers does not suppress but instead reduces tumor growth. Tumor growth then relies exclusively on functional mitochondria. Besides having fundamental bioenergetic functions, mitochondrial metabolism indeed provides appropriate building blocks for tumor anabolism, controls redox balance, and coordinates cell death. Hence, mitochondria represent promising targets for the development of novel anti-cancer agents. Here, after revisiting the long-standing Warburg effect from a historic and dynamic perspective, we review the role of mitochondria in cancer with particular attention to the cancer cell-intrinsic/extrinsic mechanisms through which mitochondria influence all steps of tumorigenesis, and briefly discuss the therapeutic potential of targeting mitochondrial metabolism for cancer therapy.

Oxaloacetate Protects Rat Liver From Experimental Warm Ischemia/Reperfusion Injury by Improving Cellular Energy Metabolism

Liver ischemia/reperfusion injury (IRI) is an important cause of liver damage especially early after liver transplantation, following liver resection, and in other clinical situations. Using rat experimental models, we identified oxaloacetate (OAA) as a key metabolite able to protect hepatocytes from hypoxia and IRI. In vitro screening of metabolic intermediates beneficial for hepatocyte survival under hypoxia was performed by measures of cell death and injury. In vivo, the effect of OAA was evaluated using the left portal vein ligation (LPVL) model of liver ischemia and a model of warm IRI. Liver injury was evaluated in vivo by serum transaminase levels, liver histology, and liver weight (edema). Levels and activity of caspase 3 were also measured. In vitro, the addition of OAA to hepatocytes kept in a hypoxic environment significantly improved cell viability (P < 0.01), decreased cell injury (P < 0.01), and improved energy metabolism (P < 0.01). Administration of OAA significantly reduced the extent of liver injury in the LPVL model with lower levels of alanine aminotransferase (ALT; P < 0.01), aspartate aminotransferase (AST; P < 0.01), and reduced liver necrosis (P < 0.05). When tested in a warm IRI model, OAA significantly decreased ALT (P < 0.001) and AST levels (P < 0.001), prevented liver edema (P < 0.001), significantly decreased caspase 3 expression (P < 0.01), as well as histological signs of cellular vesiculation and vacuolation (P < 0.05). This was associated with higher adenosine triphosphate (P < 0.05) and energy charge levels (P < 0.01). In conclusion, OAA can significantly improve survival of ischemic hepatocytes. The hepatoprotective effect of OAA was associated with increased levels of liver bioenergetics both in vitro and in vivo. These results suggest that it is possible to support mitochondrial activity despite the presence of ischemia and that OAA can effectively reduce ischemia-induced injury in the liver.

Fam65b Phosphorylation Relieves Tonic RhoA Inhibition During T Cell Migration

We previously identified Fam65b as an atypical inhibitor of the small G protein RhoA. Using a conditional model of a Fam65b-deficient mouse, we first show that Fam65b restricts spontaneous RhoA activation in resting T lymphocytes and regulates intranodal T cell migration in vivo. We next aimed at understanding, at the molecular level, how the brake that Fam65b exerts on RhoA can be relieved upon signaling to allow RhoA activation. Here, we show that chemokine stimulation phosphorylates Fam65b in T lymphocytes. This post-translational modification decreases the affinity of Fam65b for RhoA and favors Fam65b shuttling from the plasma membrane to the cytosol. Functionally, we show that the degree of Fam65b phosphorylation controls some cytoskeletal alterations downstream active RhoA such as actin polymerization, as well as T cell migration in vitro. Altogether, our results show that Fam65b expression and phosphorylation can finely tune the amount of active RhoA in order to favor optimal T lymphocyte motility.

Metabolic reprogramming enables hepatocarcinoma cells to efficiently adapt and survive to a nutrient-restricted microenvironment

Hepatocellular carcinoma (HCC) is a metabolically heterogeneous cancer and the use of glucose by HCC cells could impact their tumorigenicity. Dt81Hepa1-6 cells display enhanced tumorigenicity compared to parental Hepa1-6 cells. This increased tumorigenicity could be explained by a metabolic adaptation to more restrictive microenvironments. When cultured at high glucose concentrations, Dt81Hepa1-6 displayed an increased ability to uptake glucose (P<0.001), increased expression of 9 glycolytic genes, greater GTP and ATP (P<0.001), increased expression of 7 fatty acid synthesis-related genes (P<0.01) and higher levels of Acetyl-CoA, Citrate and Malonyl-CoA (P<0.05). Under glucose-restricted conditions, Dt81Hepa1-6 used their stored fatty acids with increased expression of fatty acid oxidation-related genes (P<0.01), decreased triglyceride content (P<0.05) and higher levels of GTP and ATP (P<0.01) leading to improved proliferation (P<0.05). Inhibition of lactate dehydrogenase and aerobic glycolysis with sodium oxamate led to decreased expression of glycolytic genes, reduced lactate, GTP and ATP levels (P<0.01), increased cell doubling time (P<0.001) and reduced fatty acid synthesis. When combined with cisplatin, this inhibition led to lower cell viability and proliferation (P<0.05). This metabolic-induced tumorigenicity was also reflected in human Huh7 cells by a higher glucose uptake and proliferative capacity compared to HepG2 cells (P<0.05). In HCC patients, increased tumoral expression of Glut-1, Hexokinase II and Lactate dehydrogenase correlated with poor survival (P = 2.47E^-5, P = 0.016 and P = 6.58E^-5). In conclusion, HCC tumorigenicity can stem from a metabolic plasticity allowing them to thrive in a broader range of glucose concentrations. In HCC, combining glycolytic inhibitors with conventional chemotherapy could lead to improved treatment efficacy.

Novel Immunotherapies for Autoimmune Hepatitis

Autoimmune hepatitis (AIH) is a multifactorial autoimmune disease of unknown pathogenesis, characterized by a loss of immunological tolerance against liver autoantigens resulting in the progressive destruction of the hepatic parenchyma. Current treatments are based on non-specific immunosuppressive drugs. Although tremendous progress has been made using specific biological agents in other inflammatory diseases, progress has been slow to come for AIH patients. While current treatments are successful in the majority of patients, treatment discontinuation is difficult to achieve, and relapses are frequent. Lifelong immunosuppression is not without risks, especially in the pediatric population; 4% of patient with type 1 AIH will eventually develop hepatocellular carcinoma with a 2.9% probability after 10 years of treatment. Therefore, future treatments should aim to restore tolerance to hepatic autoantigens and induce long-term remission. Promising new immunotherapies have been tested in experimental models of AIH including T and B cell depletion and regulatory CD4+ T cells infusion. Clinical studies on limited numbers of patients have also shown encouraging results using B-cell-depleting (rituximab) and anti-TNF-α (infliximab) antibodies. A better understanding of key molecular targets in AIH combined with effective site-specific immunotherapies could lead to long-term remission without blanket immunosuppression and with minimal deleterious side effects.