Everolimus decreases [U-13C]glucose utilization by pyruvate carboxylase in breast cancer cells in vitro and in vivo

Reprogrammed metabolism is a hallmark of cancer, but notoriously difficult to target due to metabolic plasticity, especially in response to single metabolic interventions. Combining mTOR inhibitor everolimus and mitochondrial complex 1 inhibitor metformin results in metabolic synergy in in vitro models of triple-negative breast cancer. Here, we investigated whether the effect of this drug combination on tumor size is reflected in changes in tumor metabolism using [U-13C]glucose labeling in an MDA-MB-231 triple negative breast cancer xenograft model. The in vitro effects of everolimus and metformin treatment on oxidative phosphorylation and glycolysis reflected changes in 13C-labeling of metabolites in MDA-MB-231 cells. Treatment of MDA-MB-231 xenografts in SCID/Beige mice with everolimus resulted in slower tumor growth and reduced tumor size and tumor viability by 35%. Metformin treatment moderately inhibited tumor growth but did not enhance everolimus-induced effects. High serum levels of everolimus were reached, whereas levels of metformin were relatively low. Everolimus decreased TCA cycle metabolite labeling and inhibited pyruvate carboxylase activity. Metformin only caused a mild reduction in glycolytic metabolite labeling and did not affect pyruvate carboxylase activity or TCA cycle metabolite labeling. In conclusion, treatment with everolimus, but not metformin, decreased tumor size and viability. Furthermore, the efficacy of everolimus was reflected in reduced 13C-labeling of TCA cycle intermediates and reduced pyruvate carboxylase activity. By using in-depth analysis of drug-induced changes in glucose metabolism in combination with measurement of drug levels in tumor and plasma, effects of metabolically targeted drugs can be explained, and novel targets can be identified.

Abstract 6163: Targeting glucose metabolism through inhibition of pyruvate dehydrogenase kinase to improve response to immune-checkpoint inhibition in melanoma

Immune-checkpoint inhibitors have improved survival of patients with advanced melanoma, however, 40-50% of patients do not benefit sufficiently. Melanoma tumor lesions have high glucose uptake due to metabolic reprogramming, which supports tumor cell growth and is partially mediated through elevated expression of mitochondrial pyruvate dehydrogenase kinases (PDK1-4). Resultant decreased glucose levels and low pH in the tumor microenvironment are detrimental to antitumor immune cell function. Here, we aimed to reverse metabolic reprogramming in melanoma through PDK inhibition, thereby inhibiting tumor cell growth while maintaining or potentially enhancing antitumor immunity. We used a panel of four melanoma cell lines with genetic backgrounds similar to those most frequently found in patients, namely the BRAF-mutant A375 and S-MEL-28 cell lines, the NRAS-mutant SK-MEL-2 cell line and the BRAF/NRAS wild-type MeWo cell line. These were then treated with PDK inhibitor dichloroacetate (DCA) to determine effects on viability and metabolic phenotype. Furthermore, we investigated whether DCA synergized with treatment with the glutaminase inhibitor CB-839. Finally, we determined the effect of DCA on viability, interferon-γ (IFN-γ) secretion and antitumor activity of CD8+ T cells. MeWo cells were most sensitive to DCA, while SK-MEL-2 was the least sensitive, with IC50 values ranging from 13.3 to 27.0 mM. DCA led to an up to 6-fold increase in oxygen consumption rate:extracellular acidification rate (OCR:ECAR) ratio in all cell lines. SK-MEL-28 cells were not sensitive to CB-839, while the IC50 values in the other cell lines ranged from 7.9 nM in MeWo to 139.2 nM in SK-MEL-2 cells. DCA synergized with CB-839 in 2D and 3D culture, ranging from 2-fold sensitization compared to either drug alone in MeWo up to 5-fold sensitization in SK-MEL-2. In activated CD8+ T cells, viability was not affected by DCA treatment of up to 21 mM, whereas proliferation was only mildly inhibited. These cells also showed a 2.5-fold increase in OCR:ECAR ratio after DCA treatment. Interestingly, IFN-γ secretion by CD8+ T cells was increased 2.8-fold after DCA treatment and tumor cell killing by CD8+ T cells in a coculture with A375 cells was not impaired by DCA or CB-839 treatment. We conclude that DCA can indeed reprogram cellular metabolism in melanoma and synergizes with other metabolically targeted drugs in antitumor activity, while keeping the antitumor reactivity of CD8+ T cells intact. Supported by the Dutch Cancer Foundation (10913/2017-1).

Citation Format: Jiske F. Tiersma, Bernardus Evers, Barbara M. Bakker, Steven de Jong, Mathilde Jalving. Targeting glucose metabolism through inhibition of pyruvate dehydrogenase kinase to improve response to immune-checkpoint inhibition in melanoma [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 6163.

Abstract PO-039: Combined in vivo 13C-metabolomics and proteomics approach to optimise immunotherapy response in malignant melanoma

Metabolic reprogramming is a common feature during tumourigenesis that allows tumours to adapt to nutrient-poor microenvironments, thereby maintaining cell viability and produce biomass for cell proliferation. Increased aerobic lactate fermentation, known as the "Warburg effect" is a well-studied metabolic alteration in melanoma, as well as other cancer types, that renders the tumour microenvironment hypoglycaemic and acidic. Preclinical in vitro and in vivo data show that this phenomenon has immunosuppressive effects and may as well attenuate patient response to immunotherapy. Interestingly, this metabolic alteration distinguishes a tumour and its corresponding microenvironment from healthy tissue and make their metabolic processes susceptible to drug targeting. We hypothesise that drugs normalising tumour metabolism may revert metabolic-induced immunosuppression and increase patient response to immunotherapy. In this study, we use a combined proteomics and 13C-metabolomics approach to investigate the effect of dichloroacetate (DCA) on normalizing tumour metabolism in vivo. DCA reroutes the pyruvate produced in glycolysis to be oxidized in the mitochondria, thereby reducing the flux to lactic acid and neutralising the tumour microenvironment. A seven-day, phase 2 clinical trial of DCA has been planned in 36 patients with malignant melanoma prior to immunotherapy. Pre- and post-DCA treatment biopsies will be taken after intravenous [U-13C]glucose infusion in isotopic steady-state. We present the development of GC-EI-MS(MS) methods for quantitative analysis of -13C-label incorporation in glycolytic, TCA cycle and pentose phosphate pathway intermediates. In addition we have developed targeted proteomics for the absolute quantification of glycolytic and mitochondrial metabolic enzymes using in-house designed -13C-labelled peptide standards based on QConCat technology. These methods will be applied to the respective paired biopsies. Combing the patient-specific response to immunotherapy and DCA with subsequent analysis and computational modelling will enable detailed characterisation of metabolic activity and give insight into metabolic regulation upon treatment in vivo in melanoma patients. Thus, we expect to provide an unprecedented insight into melanoma tumour metabolism and proof-of-concept that targeting metabolism improves immunotherapy response in malignant melanoma patients.

Citation Format: Bernardus Evers, Albert Gerding, Jiske Tiersma, Karen van Eunen, Justina C. Wolters, Dirk-Jan Reijngoud, Mathilde Jalving, Barbara M. Bakker. Combined in vivo 13C-metabolomics and proteomics approach to optimise immunotherapy response in malignant melanoma [abstract]. In: Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020; 2020 Oct 15-16. Philadelphia (PA): AACR; Cancer Res 2020;80(23 Suppl):Abstract nr PO-039.

C-35 Clinical Diagnosis of Behavioral Variant Frontotemporal Dementia with Underlying Primary Age-Related Tauopathy

Objective

Primary age-related tauopathy (PART) is a neuropathologic entity characterized by neurofibrillary tangles in medial temporal regions comparable to Alzheimer’s disease (AD), but with few or no amyloid plaques. A definitive clinical phenotype for PART has not been determined. Some studies report milder deficits and a longer course compared with AD. In the National Alzheimer’s Coordinating Center database, the most common clinical diagnosis of PART cases classified as dementia is AD, though primary progressive aphasia/behavioral-variant frontotemporal dementia (bvFTD) is also common. We describe 3 patients diagnosed with bvFTD later found to have PART to further describe possible PART phenotypes.

Method

Charts of 3 autopsy-proven PART cases clinically diagnosed as bvFTD by consensus conference were reviewed. All patients (A, B, C) were male and presented with behavioral changes. Only B was APOE4+. Neuroimaging was mostly unremarkable (ventriculomegaly in patient C).

Results

All subjects presented with anosognosia, fatigue, and behavioral changes, 1 (A) with pronounced apathy and 2 (B, C) with disinhibition, impulsivity, and mood swings. Onset was early 70’s for A & C, and 50’s for B. Patients B & C had gradual onset/course (~20 years) with initial subtle executive (EF) dysfunction and intact memory. Patient A had a 6-year course and initial deficits in EF and memory.

Conclusion

This review underscores the varied presentation and clinical course of PART, including presence of early behavioral changes. Slower progression as previously reported was seen in 2 of 3 patients. Future research is warranted to better characterize the entire spectrum of clinical presentations in subjects with PART neuropathology.

Prognostic aspects, survival rate, and predisposing risk factors in patients with Fournier's gangrene and necrotizing soft tissue infections: evaluation of clinical outcome of 55 patients

OBJECTIVE

To determine predisposing or prognostic factors and mortality rates of patients with Fournier's gangrene compared to other necrotizing soft tissue infections (NSTI).

MATERIAL AND METHODS

Data of 55 intensive care patients (1981-2010) with NSTI were evaluated. Data were collected prospectively.

RESULTS

43.4% of the patients were in septic condition and 27.3% were hemodynamically unstable. Half of the patients showed predisposing factors (52.7%). The lower extremity (63.2%), abdomen (30.9%), and perineum (14.5%) were most affected. Polymicrobial infections were frequent (65.5%, mean 2.8, range: 1-4). The mortality rate was 16.4% (n = 9). An increase was shown for diabetes mellitus (20%), cardiac insufficiency (22.3%), septic condition at presentation (33.3%), abdominal affection (47.1%), and hemodynamic instability (46.7%). Comparing survivors and nonsurvivors, statistical significance was seen with age (p < 0.001), septic condition at admission (p < 0.001), hemodynamic instability (p < 0.001), low blood pressure (p < 0.001), and abdominal affection (p < 0.001). In laboratory findings, an increase of creatine kinase (p < 0.001) and lactate (p < 0.001) and a decrease of antithrombin III (p < 0.007) and the Quick value (p < 0.01) proved to be significant.

CONCLUSION

Patients with Fournier's gangrene do not differ in all aspects from those with other NSTI. Successful treatment consists of immediate surgical debridement, broad-spectrum antibiotic treatment, and critical care management. Supportive hyperbaric oxygen therapy should be considered.

Mouse models of BRCA1 and BRCA2 deficiency: past lessons, current understanding and future prospects

Germline mutations in BRCA1 and BRCA2 are responsible for a large proportion of hereditary breast and ovarian cancers. Soon after the identification of both genes in the mid-1990s, investigators set out to develop mouse models for the associated disease. Whereas conventional Brca1 and Brca2 mouse mutants did not reveal a strong phenotype in a heterozygous setting, most homozygous mutations caused embryonic lethality. Consequently, development of mouse models for BRCA-associated tumorigenesis required the generation of tissue-specific conditional knockout animals. In this review, we give an overview of the conventional and the conditional mouse models of BRCA1 and BRCA2 deficiency generated over the last decade, as well as the contribution of these models to our understanding of the biological and molecular functions of BRCA1 and BRCA2. The most advanced mouse models for BRCA1- and BRCA2-associated tumorigenesis mimic human disease to the extent that they can be used in studies addressing clinically relevant questions. These models will help to resolve yet unanswered questions and to translate our increasing knowledge of BRCA1 and BRCA2 biology into clinical practice.

Specificity of amylases and cyclodextrin-glucanotransferase in reactions with 2-deoxy-maltooligosaccharides

2-Deoxy-maltooligosaccharides of different chain length were tested as substrates for exo- and endo-amylases. Cleavage occurred with beta-amylase, yielding 2,2'-dideoxy-maltose, and with amyloglucosidase. With the alpha-amylase from Thermomonospora curvata tris-(2-deoxy)-maltotriose and the corresponding tetra- and pentasaccharides were formed. Porcine pancreatic alpha-amylase did not tolerate the deoxygenated substrate, nor were cyclization experiments with cyclodextrin-glucanotransferase (CGT) successful. In a coupling reaction with CGT, however, a series of transfer products to the acceptor 2-deoxyglucose were obtained.

Further syntheses employing phosphorylase

Maltopentaose was immobilized on silica gel and used as a recyclable primer in the reaction of glycogen phosphorylase with D-glucal. An improved method to obtain 2-deoxy-alpha-D-arabino-hexopyranosyl phosphate (4) by using this catalyst as well as the specific synthesis of low molecular weight, water-soluble 2-deoxy-maltooligosaccharides (12, 13, 14 and 15) are described. Further investigations with modified phosphorylase substrates showed that mannosyl phosphate (16) can be slowly transferred to the primer maltotetraose. alpha-1,4-Mannosyl-maltotetraose (17) and its degradation product alpha-1,4-mannosyl-maltose (18) were identified.

Unusual development of acute exertional compartment syndrome due to delayed diagnosis. A case report

Our report describes the case of a 20 year old man who developed an acute exertional anterior tibial compartment syndrome after playing soccer for five minutes. No trauma was reported. Correct diagnosis was delayed for 18 hours, because pain was misinterpreted as resulting from acute muscular tetanic spasm induced by hyperventilation. Fasciotomy was contributed. After one year, the patient complained of early fatigue. Electromyographically the reinnervation had not yet been completed. This case illustrates the necessity for careful observation of non-trauma related acute tibial anterior pain appearing even at the beginning of strenuous exercise. It is important to recognize the possibility of a very acute onset of exertional compartment syndrome that does not subside with rest. Only early diagnosis and fasciotomy can prevent severe complications of an acute exertional compartment syndrome.

Analysis of oligosaccharides containing 2-deoxy-alpha-D-arabino-hexosyl residues by the reductive-cleavage method

A mixture of oligosaccharides containing (1-->4)-linked 2-deoxy-alpha-D-arabino-hexosyl ("2-deoxyglucosyl") and (1-->4)-linked alpha-D-glucosyl residues (1) was analyzed by reduction, permethylation (perethylation), degradation to monomers, and GLC-MS. Degradation was performed either by hydrolysis with subsequent reduction, by methanolysis, or by reductive cleavage, always followed by acetylation. Reductive cleavage turned out to be the method of choice for the acid-labile 2-deoxy sugars. The main degradation product formed during acid hydrolysis of 2-deoxy-D-arabino-hexosyl residues yielded, after reduction and acetylation, (4R,S)-6-O-acetyl-2,3,5-trideoxyhexono-1,4-lactone (7). By methanolysis, in addition to the expected methyl glycosides, methyl 2,3,5-trideoxy-6-O-methyl-4-hexulosonate (12) is formed as a by-product. For determination of the distribution of chain lengths, the permethylated oligomers were separated by reversed-phase HPLC. For peak assignment, one isolated oligomer was investigated by FABMS and 1H NMR spectroscopy. The average degree of polymerization (dp) calculated from the HPLC chromatogram is in good agreement with the reductive-cleavage results.

Synthesis of 2-deoxy-alpha-D-arabino-hexopyranosyl phosphate and 2-deoxy-maltooligosaccharides with phosphorylase

A convenient one-step synthesis of 2-deoxy-alpha-D-arabino-hexopyranosyl phosphate on a millimolar scale is described by reaction of potato phosphorylase with D-glucal at equimolar phosphate concentration. Furthermore, in the presence of catalytic amounts of phosphate, a 2-deoxy-maltooligosaccharide is obtained from maltotetraose and D-glucal. The water-insoluble oligosaccharide was isolated and characterized by 1H and 13C NMR spectroscopy. An average dp of 20 was thus determined.

[Periimplant alterations under cyclosporin A drug treatment]

One titanium implant of the Brånemark system and one Al2O2 ceramic implant each were inserted in the lower jaws of 6 Beagle dogs to evaluate the alterations of the periimplant tissues under CsA therapy. During the 3-6 months of CsA substitution hyperplastic alterations were observed as soon as after the 3rd week. These anomalies were most pronounced around the titanium implants.

[In situ protection of the liver with Bretschneider HTK solution]

Liver resections are usually performed under occlusion of the hepatoduodenal ligament (Pringle manoeuvre) in order to limit operative blood loss. The maximal ischemic tolerance, although individually different, is generally accepted to be 60 min. Resections of centrally located tumors require precise preparation, sometimes combined with vascular reconstructions. In such cases a prolonged ischemic time is inevitable. A save prolongation of the ischemic tolerance could be useful for extensive liver resections. In an experimental study in pigs ischemic tolerance of the liver was studied under hypothermic protection with the HTK solution of Bretschneider during 2 and 3 h. Deterioration of liver function was compared with a warm ischemia during 2 h. Results showed significantly less serum transaminase activities and better hepatic blood flow (ICG test) after an ischemia under protection with the HTK solution compared to a warm ischemia during 2 h. A prolonged ischemia during 3 h under protection with the HTK solution was well tolerated. First clinical applications of hypothermic hepatic protection during resection were successful.

Enzymatic formation of nitrogen oxides from L-arginine in bovine brain cytosol

In dialyzed bovine brain cytosol, the enzymatic formation of nitrogen oxides was directly determined. The basal formation of nitrite and nitrate was concentration-dependently enhanced by L-arginine (EC50 about 3.10(-5) M). Both the basal and L-arginine induced formations were inhibited by NG-monomethyl-L-arginine (EC50 about 2.10(-4) M). In the presence of L-arginine, a concomitant formation of citrulline was detected. L-Arginine methyl ester also served as a substrate, but neither D-arginine, D-arginine methyl ester nor N alpha-benzoyl-L-arginine ethyl ester did so. The formation of nitrite and nitrate was time-dependent, increased linearly with the protein concentration of the cytosol and was not observed when the cytosolic proteins were heat-denaturated. Exogenous NADPH (or NADP+) concentration-dependently enhanced the formation of nitrite and nitrate, whereas NADH, NAD+, FAD, Ca2+, Mg2+ and calmodulin were ineffective. These results indicate that bovine brain contains a cytosolic enzyme which uses NADPH or NADP+ as cofactors to form nitrogen oxides from both an endogenous non-dialyzable substrate and from L-arginine.

[Use of 51-Cr2O3 and TiO2 as markers for the determination of passage rate and protein digestibility in rats]

In a tripartite experiment with five rats each the suitability of 51Cr2O3 and TiO2 as markers was tested for estimating the transit time and passage rate as well as the total protein digestibility and the proportion of endogenous nitrogen in the small intestine with very small samples. Both markers are suited for these tests because of their simple analysis, their high recovery rate (94...105% for 51Cr2O3; 98...105% for TiO2) and their quantitative excretion in faeces within 3 days. Depending on the level of crude fibre (5.1 resp. 9.4% of DM) the transit time was found to be 7...8 h for a commercial breeding feed and 5...6 h for this commercial feed +15% straw meal. After the application of a single doses, the marker excretion of 50% appeared within 10 +/- 1 h resp. 8 +/- 1 h, and after the 12th hour there were no significant differences at all. The apparent N-digestibilities estimated by the conventional or the 51Cr2O3 resp. TiO2 indicator method did not show any differences. The proportion of endogenous nitrogen at the end of the small intestine calculated on the basis of the indicator dilution method was 83 +/- 11% for 51Cr2O3 and 83 +/- 12% for TiO2.