Fusion-fission-mitophagy cycling and metabolic reprogramming coordinate nerve growth factor (NGF)-dependent neuronal differentiation.

Neuronal differentiation is regulated by nerve growth factor (NGF) and other neurotrophins. We explored the impact of NGF on mitochondrial dynamics and metabolism through time-lapse imaging, metabolomics profiling, and computer modeling studies. We show that NGF may direct differentiation by stimulating fission, thereby causing selective mitochondrial network fragmentation and mitophagy, ultimately leading to increased mitochondrial quality and respiration. Then, we reconstructed the dynamic fusion-fission-mitophagy cycling of mitochondria in a computer model, integrating these processes into a single network mechanism. Both the computational model and the simulations are able to reproduce the proposed mechanism in terms of mitochondrial dynamics, levels of reactive oxygen species (ROS), mitophagy, and mitochondrial quality, thus providing a computational tool for the interpretation of the experimental data and for future studies aiming to detail further the action of NGF on mitochondrial processes. We also show that changes in these mitochondrial processes are intertwined with a metabolic function of NGF in differentiation: NGF directs a profound metabolic rearrangement involving glycolysis, TCA cycle, and the pentose phosphate pathway, altering the redox balance. This metabolic rewiring may ensure: (a) supply of both energy and building blocks for the anabolic processes needed for morphological reorganization, as well as (b) redox homeostasis.

'Social' versus 'asocial' cells-dynamic competition flux balance analysis.

In multicellular organisms cells compete for resources or growth factors. If any one cell type wins, the co-existence of diverse cell types disappears. Existing dynamic Flux Balance Analysis (dFBA) does not accommodate changes in cell density caused by competition. Therefore we here develop 'dynamic competition Flux Balance Analysis' (dcFBA). With total biomass synthesis as objective, lower-growth-yield cells were outcompeted even when cells synthesized mutually required nutrients. Signal transduction between cells established co-existence, which suggests that such 'socialness' is required for multicellularity. Whilst mutants with increased specific growth rate did not outgrow the other cell types, loss of social characteristics did enable a mutant to outgrow the other cells. We discuss that 'asocialness' rather than enhanced growth rates, i.e., a reduced sensitivity to regulatory factors rather than enhanced growth rates, may characterize cancer cells and organisms causing ecological blooms. Therapies reinforcing cross-regulation may therefore be more effective than those targeting replication rates.

Prognostic Value of the De Ritis Ratio for Overall Survival in Patients with Metastatic Castration-Resistant Prostate Cancer Undergoing [177Lu]Lu-PSMA-617 Radioligand Therapy.

The De Ritis ratio (=aspartate transaminase/alanine transaminase) has shown prognostic value in different cancer types. This is the first such analysis in prostate cancer patients undergoing radioligand therapy (RLT) with [177Lu]Lu-PSMA-617. This retrospective monocentric analysis included 91 patients with a median of 3 RLT cycles (range 1-6) and median cumulative activity of 17.3 GBq. Univariable Cox regression regarding overall survival (OS) included age, different types of previous treatment, metastatic patterns and different laboratory parameters before RLT. Based on multivariable Cox regression, a prognostic score was derived. Seventy-two patients (79%) died (median follow-up in survivors: 19.8 months). A higher number of previous chemotherapy lines, the presence of liver metastases, brain metastases, a higher tumor load on PSMA-PET, a higher prostate-specific antigen (PSA) level, lower red blood cell count, lower hemoglobin, higher neutrophil-lymphocyte ratio and higher De Ritis ratio were associated with shorter OS (each p < 0.05). In multivariable Cox, a higher number of chemotherapy lines (range, 0-2; p = 0.036), brain metastases (p < 0.001), higher PSA (p = 0.004) and higher De Ritis ratio before RLT (hazard ratio, 1.27 per unit increase; p = 0.023) remained significant. This prognostic score separated five groups with a significantly different median OS ranging from 4.9 to 28.1 months (log-rank test, p < 0.001). If validated independently, the De Ritis ratio could enhance multifactorial models for OS after RLT.

Transarterial Yttrium-90 Radioembolization in Intrahepatic Cholangiocarcinoma Patients: Outcome Assessment Applying a Prognostic Score.

Radioembolization (RE) is a viable therapy option in patients with intrahepatic cholangiocarcinoma (ICC). This study delineates a prognostic score regarding overall survival (OS) after RE using routine pre-therapeutic parameters. A retrospective analysis of 39 patients (median age, 61 [range, 32−82] years; 26 females, 13 males) with ICC and 42 RE procedures was conducted. Cox regression for OS included age, ECOG, hepatic and extrahepatic tumor burden, thrombosis of the portal vein, ascites, laboratory parameters and dose reduction due to hepatopulmonary shunt. Median OS after RE was 8.0 months. Using univariable Cox, ECOG ≥ 1 (hazard ratio [HR], 3.8), AST/ALT quotient (HR, 1.86), high GGT (HR, 1.002), high CA19-9 (HR, 1.00) and dose reduction of 40% (HR, 3.8) predicted shorter OS (each p < 0.05). High albumin predicted longer OS (HR, 0.927; p = 0.045). Multivariable Cox confirmed GGT ≥ 750 [U/L] (HR, 7.84; p < 0.001), ECOG > 1 (HR, 3.76; p = 0.021), albumin ≤ 41.1 [g/L] (HR, 3.02; p = 0.006) as a three-point pre-therapeutic prognostic score. More specifically, median OS decreased from 15.3 months (0 risk factors) to 7.6 months (1 factor) or 1.8 months (≥2 factors; p < 0.001). The proposed score may aid in improved pre-therapeutic patient identification with (un-)favorable OS after RE and facilitate the balance between potential life prolongation and overaggressive patient selection.

Cyanine Dye Coupling Mediates Self-assembly of a pH Sensitive Peptide into Novel 3D Architectures.

Synthetic multichromophore systems are of great importance in artificial light harvesting devices, organic optoelectronics, tumor imaging and therapy. Here, we introduce a promising strategy for the construction of self-assembled peptide templated dye stacks based on coupling of a de novo designed pH sensitive peptide with a cyanine dye Cy5 at its N-terminus. Microscopic techniques, in particular cryogenic TEM (cryo-TEM) and cryo-electron tomography technique (cryo-ET), reveal two types of highly ordered three-dimensional assembly structures on the micrometer scale. Unbranched compact layered rods are observed at pH 7.4 and two-dimensional membrane-like assemblies at pH 3.4, both species displaying spectral features of H-aggregates. Molecular dynamics simulations reveal that the coupling of Cy5 moieties promotes the formation of both ultrastructures, whereas the protonation states of acidic and basic amino acid side chains dictates their ultimate three-dimensional organization.

Hydrocephalus Study Design: Testing New Hypotheses in Clinical Studies and Bench-to-Bedside Research.

In this article, we aimed to describe some of the currently most challenging problems in neurosurgical management of hydrocephalus and how these can be reasons for inspiration for and development of research. We chose 4 areas of focus: 2 dedicated to improvement of current treatments (shunt implant surgery and endoscopic hydrocephalus surgery) and 2 dedicated to emerging future treatment principles (molecular mechanisms of cerebrospinal fluid secretion and hydrocephalus genetics).

Offshore field experiments with in-situ burning of oil: Emissions and burn efficiency.

In situ burning (ISB) is an oil spill response technique including ignition and burning to remove oil on the water surface. The technique rapidly and effectively removes large portions of the oil. However, the combustion process causes a large smoke plume and leaves a viscous residue in the water. During six large-scale experimental burns in the North Sea in 2018 and 2019, the smoke plume, released oil and contained residues were analysed. The objectives were to document the content of particles and gases in the smoke plume, properties of both the released oils and residues, and the effectiveness of the burns. Oseberg crude oil, Ultra Low Sulphur Fuel Oil (ULSFO), Intermediate Fuel Oil (IFO180) and Marine Gas Oil (MGO) were released into a fire-boom and ignited. Particles and gases in the smoke plume were monitored using drones with several sensors. Soot particle monitoring indicated that more than 90% of the particles produced during the burns were <1 µm. Soot fallout was mainly limited to visible smoke, and the particle concentration was highest directly under the smoke plume and declined with distance from the burn. Gas monitoring in the smoke indicated low concentrations of SO2 and NOX (<2 ppm), and the concentrations of CO2 and CO were within air quality standards. Black Carbon produced relative to the amount of oil burned was 10-18%. The burn efficiency varied and were estimated to 80-91% for Oseberg, >90% for MGO, and <60% for both ULSFO and IFO180. The present paper addresses the results of the smoke plume monitoring, properties of the ISB residues and the burn efficiency.

Responsiveness and minimal important change of the Oxford Shoulder Score, EQ-5D, and the Fear-Avoidance Belief Questionnaire Physical Activity subscale in patients undergoing arthroscopic subacromial decompression.

INTRODUCTION: Adequate responsiveness and knowledge of the minimal important change (MIC) is essential when using patient-reported outcome measures to assess treatment efficacy. OBJECTIVE: The objective of this study was to evaluate the responsiveness and MIC of common outcomes in patients with subacromial impingement syndrome undergoing arthroscopic subacromial decompression. METHODS: At baseline and 6 months after surgery, patients completed the Oxford Shoulder Score (OSS), EQ-5D 5-level utility index, EQ visual analogue scale, Fear-Avoidance Belief Questionnaire Physical Activity subscale (FABQ-PA), assessed pain (pain visual analogue scale), and Subjective Shoulder Value. Furthermore, at the 6-month follow-up, patients assessed the overall change with a Global Rating of Change Scale. Responsiveness was examined by analyzing the area under the receiver operating characteristics curve and correlations between the change scores. MIC was assessed using the optimal cutoff point at the receiver operating characteristics curve. RESULTS: Area under the receiver operating characteristics curve estimates were 0.96 (95% confidence interval [CI] 0.91,1.00) for OSS, 0.82 (95% CI 0.66,0.99) for EQ-5D 5-level utility index, 0.73 (95% CI 0.58,0.87) for EQ visual analogue scale, and 0.74 (95% CI 0.58,0.90) for FABQ-PA. MIC were 6.0 points for OSS, 0.024 points for EQ-5D 5-level utility index, 10.0 points for EQ visual analogue scale, and -5.0 points for FABQ-PA. CONCLUSION: Responsiveness of the OSS, EQ-5D, and FABQ-PA was sufficient to measure improvement after arthroscopic decompression surgery.

Simultaneous Integration of Gene Expression and Nutrient Availability for Studying the Metabolism of Hepatocellular Carcinoma Cell Lines.

How cancer cells utilize nutrients to support their growth and proliferation in complex nutritional systems is still an open question. However, it is certainly determined by both genetics and an environmental-specific context. The interactions between them lead to profound metabolic specialization, such as consuming glucose and glutamine and producing lactate at prodigious rates. To investigate whether and how glucose and glutamine availability impact metabolic specialization, we integrated computational modeling on the genome-scale metabolic reconstruction with an experimental study on cell lines. We used the most comprehensive human metabolic network model to date, Recon3D, to build cell line-specific models. RNA-Seq data was used to specify the activity of genes in each cell line and the uptake rates were quantitatively constrained according to nutrient availability. To integrated both constraints we applied a novel method, named Gene Expression and Nutrients Simultaneous Integration (GENSI), that translates the relative importance of gene expression and nutrient availability data into the metabolic fluxes based on an observed experimental feature(s). We applied GENSI to study hepatocellular carcinoma addiction to glucose/glutamine. We were able to identify that proliferation, and lactate production is associated with the presence of glucose but does not necessarily increase with its concentration when the latter exceeds the physiological concentration. There was no such association with glutamine. We show that the integration of gene expression and nutrient availability data into genome-wide models improves the prediction of metabolic phenotypes.

Availability, prices, and affordability of selected essential cancer medicines in a middle-income country - the case of Mexico.

BACKGROUND: More alternatives have become available for the diagnosis and treatment of cancer in low- and middle-income countries. Because of increasing demands, governments are now facing a problem of limited affordability and availability of essential cancer medicines. Yet, precise information about the access to these medicines is limited, and the methodology is not very well developed. We assessed the availability and affordability of essential cancer medicines in Mexico, and compared their prices against those in other countries of the region. METHODS: We surveyed 21 public hospitals and 19 private pharmacies in 8 states of Mexico. Data were collected on the availability and prices of 49 essential cancer medicines. Prices were compared against those in Chile, Peru, Brazil, Colombia and PAHO's Strategic Fund. RESULTS: Of the various medicines, mean availability in public and private sector outlets was 61.2 and 67.5%, respectively. In the public sector, medicines covered by the public health insurance "People's Health Insurance" were more available. Only seven (public sector) and five (private sector) out of the 49 medicines were considered affordable. Public sector procurement prices were 41% lower than in other countries of the region. CONCLUSIONS: The availability of essential cancer medicines, in the public and private sector, falls below World Health Organization's 80% target. The affordability remains suboptimal as well. A national health insurance scheme could serve as a mechanism to improve access to cancer medicines in the public sector. Comprehensive pricing policies are warranted to improve the affordability of cancer medicines in the private sector.

Access to cancer medication in public hospitals in a middle-income country: The view of stakeholder.

BACKGROUND: Access to cancer medicines is a core component of comprehensive cancer care; as such, it is included in Mexico's public health insurance: Seguro Popular de Salud (SPS). Learning about stakeholders' experiences on processes and barriers influencing access to essential cancer medicines within healthcare facilities allows identifying needed policies to improve access to cancer care. OBJECTIVE: The aim of this study was to obtain the insights of health professionals in public hospitals in Mexico on how SPS influences access to cancer medicines regarding medicine selection, financing, and procurement and supply systems. The purpose is to identify policy areas that need strengthening to improve access to cancer medicines. METHODS: Semi-structured interviews were conducted with 67 health professionals from 21 public hospitals accredited by SPS across Mexico. A framework analysis was used with categories of analysis derived from the World Health Organization's Access framework. RESULTS: Most stakeholders reported that the availability of listed cancer medicines was sufficient. However, cancer specialists reported that medicines coverage by SPS was restrictive covering only basic cancer care. Public hospitals followed SPS treatment protocols in selecting and prescribing cancer medicines but used different procurement procedures. When essential cancer medicines were unavailable (not listed or stocked-out), hospitals reported several strategies such as prescribing alternative therapies, resorting to direct purchases, and assisting patients in obtaining medicines elsewhere. Other reported barriers to access to treatment were: distance to health facilities, poor insurance coverage, and financial restrictions. CONCLUSIONS: Health professionals have encountered benefits and challenges from the implementation of SPS influencing access to cancer medicines and care in Mexico, pointing to areas in which action is necessary. Finding the right balance between expanding the range and cost of cancer treatments covered by insurance and making basic cancer care available to all is a challenge faced by Mexico and other middle-income countries.

Development and evaluation of a harmonized whole body physiologically based pharmacokinetic (PBPK) model for flutamide in rats and its extrapolation to humans.

By their definition, inadvertent exposure to endocrine disrupting compounds (EDCs) intervenes with the endocrine signalling system, even at low dose. On the one hand, some EDCs are used as important pharmaceutical drugs that one would not want to dismiss. On the other hand, these pharmaceutical drugs are having off-target effects and increasingly significant exposure to the general population with unwanted health implications. Flutamide, one of the top pharmaceutical products marketed all over the world for the treatment of prostate cancer, is also a pollutant. Its therapeutic action mainly depends on targeting the androgen receptors and inhibiting the androgen action that is essential for growth and survival of prostate tissue. Currently flutamide is of concern with respect to its categorization as an endocrine disruptor. In this work we have developed a physiologically based pharmacokinetic (PBPK) model of flutamide that could serve as a standard tool for its human risk assessment. First we built the model for rat (where many parameters have been measured). The rat PBPK model was extrapolated to human where the re-parameterization involved human-specific physiology, metabolic kinetics derived from in-vitro studies, and the partition coefficient same as the rat model. We have harmonized the model by integrating different sets of in-vitro, in-vivo and physiological data into a PBPK model. Then the model was used to simulate different exposure scenarios and the results were compared against the observed data. Both uncertainty and sensitivity analysis was done. Since this new whole-body PBPK model can predict flutamide concentrations not only in plasma but also in various organs, the model may have clinical applications in efficacy and safety assessment of flutamide. The model can also be used for reverse dosimetry in the context of interpreting the available biomonitoring data to estimate the degree to which the population is currently being exposed, and a tool for the pharmaceutical companies to validate the estimated Permitted Daily Exposure (PDE) for flutamide.

The Impact of Price Negotiations on Public Procurement Prices and Access to 8 Innovative Cancer Medicines in a Middle-Income Country: The Case of Mexico.

BACKGROUND: To mitigate the effect of high prices, in 2008 Mexico established a commission that negotiates single procurement prices for patented medicines in the public sector. OBJECTIVES: We assessed the possible effect of price negotiations on the prices of new essential cancer medicines in Mexico between 2010 and 2016 and on access to these new cancer medicines. METHODS: We retrieved the public procurement prices and volume of 8 selected innovative cancer medicines in Mexico in addition to their maximum retail prices in the private sector. We calculated the median, interquartile (25%-75%) range, and maximum and minimum public procurement prices to analyze price changes and trends. We assessed changes between the maximum retail prices and the public procurement prices and changes in the volume procured from 2010 to 2016. RESULTS: Between 2010 and 2016, the prices of selected patented cancer medicines in the public sector decreased by 40% to 85%, expressed in US dollars. When expressed in Mexican pesos, public prices for 5 medicines reduced and others remained stable, whereas prices increased in the private sector over the same period. Procurement prices were not uniform between and within public institutions. The volumes of selected cancer medicines supplied in the public sector increased over the years, suggesting better access. CONCLUSION: Although direct causality is difficult to prove, the establishment of the negotiating commission seems to have led to reduced prices and possibly better access in the public sector. Medicine procurement by public hospitals should be monitored to ensure that negotiated prices benefit all institutions.

The importance of insulin donations for children in 43 low- and middle-income countries.

Diabetes mellitus is rapidly becoming one of the major diseases affecting people's health globally. Over half of 100 million diabetes patients who need insulin to survive, especially in low- and middle-income countries (LMIC), are not able to get this medicine and die prematurely. Since 2000, insulin-producing companies have started support programmes with a component of insulin donations to children and youth with type 1 diabetes in 43 LMIC. Based on their experiences we conclude, contrary to common belief, that the diagnosis, treatment, and prevention of fatal complications in children with type 1 diabetes in LMIC are very possible in practice, with large improvements in survival, mean body weight, mean glucose levels, and frequency of complications. Medicine donations can never offer a sustainable solution and we now propose a ten-step transition process towards a fully sustainable national diabetes care and prevention programme for children and youth with diabetes type 1.

Complex Stability and an Irrevertible Transition Reverted by Peptide and Fibroblasts in a Dynamic Model of Innate Immunity.

We here apply a control analysis and various types of stability analysis to an in silico model of innate immunity that addresses the management of inflammation by a therapeutic peptide. Motivation is the observation, both in silico and in experiments, that this therapy is not robust. Our modeling results demonstrate how (1) the biological phenomena of acute and chronic modes of inflammation may reflect an inherently complex bistability with an irrevertible flip between the two modes, (2) the chronic mode of the model has stable, sometimes unique, steady states, while its acute-mode steady states are stable but not unique, (3) as witnessed by TNF levels, acute inflammation is controlled by multiple processes, whereas its chronic-mode inflammation is only controlled by TNF synthesis and washout, (4) only when the antigen load is close to the acute mode's flipping point, many processes impact very strongly on cells and cytokines, (5) there is no antigen exposure level below which reduction of the antigen load alone initiates a flip back to the acute mode, and (6) adding healthy fibroblasts makes the transition from acute to chronic inflammation revertible, although (7) there is a window of antigen load where such a therapy cannot be effective. This suggests that triple therapies may be essential to overcome chronic inflammation. These may comprise (1) anti-immunoglobulin light chain peptides, (2) a temporarily reduced antigen load, and (3a) fibroblast repopulation or (3b) stem cell strategies.

Access to innovative cancer medicines in a middle-income country - the case of Mexico.

BACKGROUND: Cancer has become the third cause of death in Mexico. Treatment for cancer is often complex and lengthy. New and better medicines enter the market at high prices, which may limit access. Like most Latin American countries, Mexico has an essential cancer medicines list that includes innovative medicines. Their accessibility and use in the public sector remains unknown. Therefore, we describe the use, as a proxy of access, of innovative and essential cancer medicines in the public sector in Mexico, by insurance institution, and by five regions between 2010 to 2016. METHODS: We used drug utilization research methods to assess the use of eight patented cancer medicines. Through the national transparency platform, we obtained data on the quantities of these medicines used in all public health facilities and social health insurance institutions and recalculated those figures into defined daily dose (DDD) per 1000 population per year. RESULTS: Overall, the use of all medicines increased over the years, especially for trastuzumab, rituximab and imatinib. The use of innovative medicines was higher per population covered in social health insurance institutions than in governmental facilities. Throughout the study period, the Central region (including Mexico City) has used more medicines per population than the other regions. CONCLUSIONS: The use and access of some essential innovative cancer medicines has increased over the years, but remains unequal across insurance schemes and regions. Particularly, the Ministry of Health Insurance scheme and Northern and Western regions in the country would benefit from additional efforts to increase access to essential cancer medicines.

Predictable Irreversible Switching Between Acute and Chronic Inflammation.

Many a disease associates with inflammation. Upon binding of antigen-antibody complexes to immunoglobulin-like receptors, mast cells release tumor necrosis factor-α and proteases, causing fibroblasts to release endogenous antigens that may be cross reactive with exogenous antigens. We made a predictive dynamic map of the corresponding extracellular network. In silico, this map cleared bacterial infections, via acute inflammation, but could also cause chronic inflammation. In the calculations, limited inflammation flipped to strong inflammation when cross-reacting antigen exceeded an "On threshold." Subsequent reduction of the antigen load to below this "On threshold" did not remove the strong inflammation phenotype unless the antigen load dropped below a much lower and subtler "Off" threshold. In between both thresholds, the network appeared caught either in a "low" or a "high" inflammatory state. This was not simply a matter of bi-stability, however, the transition to the "high" state was temporarily revertible but ultimately irreversible: removing antigen after high exposure reduced the inflammatory phenotype back to "low" levels but if then the antigen dosage was increased only a little, the high inflammation state was already re-attained. This property may explain why the high inflammation state is indeed "chronic," whereas only the naive low-inflammation state is "acute." The model demonstrates that therapies of chronic inflammation such as with anti-IgLC should require fibroblast implantation (or corresponding stem cell activation) for permanence in order to redress the irreversible transition.

Neutral metalloaminopeptidases APN and MetAP2 as newly discovered anticancer molecular targets of actinomycin D and its simple analogs.

The potent transcription inhibitor Actinomycin D is used with several cancers. Here, we report the discovery that this naturally occurring antibiotic inhibits two human neutral aminopeptidases, the cell-surface alanine aminopeptidase and intracellular methionine aminopeptidase type 2. These metallo-containing exopeptidases participate in tumor cell expansion and motility and are targets for anticancer therapies. We show that the peptide portions of Actinomycin D and Actinomycin X2 are not required for effective inhibition, but the loss of these regions changes the mechanism of interaction. Two structurally less complex Actinomycin D analogs containing the phenoxazone chromophores, Questiomycin A and Actinocin, appear to be competitive inhibitors of both aminopeptidases, with potencies similar to the non-competitive macrocyclic parent compound (Ki in the micromolar range). The mode of action for all four compounds and both enzymes was demonstrated by molecular modeling and docking in the corresponding active sites. This knowledge gives new perspectives to Actinomycin D's action on tumors and suggests new avenues and molecules for medical applications.

The protofilament architecture of a de novo designed coiled coil-based amyloidogenic peptide.

Amyloid fibrils are polymers formed by proteins under specific conditions and in many cases they are related to pathogenesis, such as Parkinson's and Alzheimer's diseases. Their hallmark is the presence of a ß-sheet structure. High resolution structural data on these systems as well as information gathered from multiple complementary analytical techniques is needed, from both a fundamental and a pharmaceutical perspective. Here, a previously reported de novo designed, pH-switchable coiled coil-based peptide that undergoes structural transitions resulting in fibril formation under physiological conditions has been exhaustively characterized by transmission electron microscopy (TEM), cryo-TEM, atomic force microscopy (AFM), wide-angle X-ray scattering (WAXS) and solid-state NMR (ssNMR). Overall, a unique 2-dimensional carpet-like assembly composed of large coexisiting ribbon-like, tubular and funnel-like structures with a clearly resolved protofilament substructure is observed. Whereas electron microscopy and scattering data point somewhat more to a hairpin model of ß-fibrils, ssNMR data obtained from samples with selectively labelled peptides are in agreement with both, hairpin structures and linear arrangements.

Rational cell culture optimization enhances experimental reproducibility in cancer cells.

Optimization of experimental conditions is critical in ensuring robust experimental reproducibility. Through detailed metabolomic analysis we found that cell culture conditions significantly impacted on glutaminase (GLS1) sensitivity resulting in variable sensitivity and irreproducibility in data. Baseline metabolite profiling highlighted that untreated cells underwent significant changes in metabolic status. Both the extracellular levels of glutamine and lactate and the intracellular levels of multiple metabolites changed drastically during the assay. We show that these changes compromise the robustness of the assay and make it difficult to reproduce. We discuss the implications of the cells' metabolic environment when studying the effects of perturbations to cell function by any type of inhibitor. We then devised 'metabolically rationalized standard' assay conditions, in which glutaminase-1 inhibition reduced glutamine metabolism differently in both cell lines assayed, and decreased the proliferation of one of them. The adoption of optimized conditions such as the ones described here should lead to an improvement in reproducibility and help eliminate false negatives as well as false positives in these assays.