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A hallmark of metastasis is the adaptation of tumor cells to new environments. Metabolic constraints imposed by the serine and glycine–limited brain environment restrict metastatic tumor growth. How brain metastases overcome these growth-prohibitive conditions is poorly understood. Here, we demonstrate that 3-phosphoglycerate dehydrogenase (PHGDH), which catalyzes the rate-limiting step of glucose-derived serine synthesis, is a major determinant of brain metastasis in multiple human cancer types and preclinical models. Enhanced serine synthesis proved important for nucleotide production and cell proliferation in highly aggressive brain metastatic cells. In vivo, genetic suppression and pharmacologic inhibition of PHGDH attenuated brain metastasis, but not extracranial tumor growth, and improved overall survival in mice. These results reveal that extracellular amino acid availability determines serine synthesis pathway dependence, and suggest that PHGDH inhibitors may be useful in the treatment of brain metastasis.Significance:Using proteomics, metabolomics, and multiple brain metastasis models, we demonstrate that the nutrient-limited environment of the brain potentiates brain metastasis susceptibility to serine synthesis inhibition. These findings underscore the importance of studying cancer metabolism in physiologically relevant contexts, and provide a rationale for using PHGDH inhibitors to treat brain metastasis.This article is highlighted in the In This Issue feature, p. 1241

A hallmark of metastasis is the adaptation of tumor cells to new environments. Metabolic constraints imposed by the serine and glycine–limited brain environment restrict metastatic tumor growth. How brain metastases overcome these growth-prohibitive conditions is poorly understood. Here, we demonstrate that 3-phosphoglycerate dehydrogenase (PHGDH), which catalyzes the rate-limiting step of glucose-derived serine synthesis, is a major determinant of brain metastasis in multiple human cancer types and preclinical models. Enhanced serine synthesis proved important for nucleotide production and cell proliferation in highly aggressive brain metastatic cells. In vivo, genetic suppression and pharmacologic inhibition of PHGDH attenuated brain metastasis, but not extracranial tumor growth, and improved overall survival in mice. These results reveal that extracellular amino acid availability determines serine synthesis pathway dependence, and suggest that PHGDH inhibitors may be useful in the treatment of brain metastasis. Significance: Using proteomics, metabolomics, and multiple brain metastasis models, we demonstrate that the nutrient-limited environment of the brain potentiates brain metastasis susceptibility to serine synthesis inhibition. These findings underscore the importance of studying cancer metabolism in physiologically relevant contexts, and provide a rationale for using PHGDH inhibitors to treat brain metastasis. This article is highlighted in the In This Issue feature, p. 1241

A hallmark of metastasis is the adaptation of tumor cells to new environments. Although it is well established that the metabolic milieu of the brain is severely deprived of nutrients, particularly the amino acids serine and its catabolite glycine, how brain metastases rewire their metabolism to survive in the nutrient-limited environment of the brain is poorly understood. Here we demonstrate that cell-intrinsic de novo serine synthesis is a major determinant of brain metastasis. Whole proteome comparison of triple-negative breast cancer (TNBC) cells that differ in their capacity to colonize the brain reveals that 3-phosphoglycerate dehydrogenase (PHGDH), which catalyzes the rate-limiting step of glucose-derived serine synthesis, is the most significantly upregulated protein in cells that efficiently metastasize to the brain. Genetic silencing or pharmacological inhibition of PHGDH attenuated brain metastasis and improved overall survival in mice, whereas expression of catalytically active PHGDH in a non-brain trophic cell line promoted brain metastasis. Collectively, these findings indicate that nutrient availability determines serine synthesis pathway dependence in brain metastasis, and suggest that PHGDH inhibitors may be useful in the treatment of patients with cancers that have spread to the brain.Statement of SignificanceOur study highlights how limited serine and glycine availability within the brain microenvironment potentiates tumor cell sensitivity to serine synthesis inhibition. This finding underscores the importance of studying cancer metabolism in physiologically-relevant contexts, and provides a rationale for using PHGDH inhibitors to treat brain metastasis.

The brain environment is low in amino acids, including serine and glycine, both of which are important for tumor growth as they are precursors of proteins and nucleotide bases. How tumor cells overcome these conditions to proliferate and survive in the brain is incompletely understood. Here, we show that 3-phosphoglycerate dehydrogenase (PHGDH), which catalyzes the first and rate-limiting step of glucose-derived serine synthesis, enables brain metastasis in multiple human types and in preclinical models. Genetic suppression and small molecule inhibition of PHGDH attenuated brain metastasis, but not extra cranial tumors, and improved the overall survival of mice bearing brain metastasis. These results demonstrate that the tumor nutrient microenvironment determines tumor cell sensitivity to loss of serine synthesis pathway activity and raise the possibility that serine synthesis inhibitors may be useful in the treatment of brain metastases.

The metabolic milieu of the brain is severely deprived of nutrients, including the amino acids serine and its catabolite glycine. The metabolic rewiring required for tumor cells to survive in the nutrient-limited environment of the brain and the metabolic vulnerabilities this confers are poorly understood. Here we demonstrate that cell-intrinsic de novo serine synthesis is a major determinant of triple-negative breast cancer (TNBC) brain metastasis. Whole proteome comparison of TNBC cells that differ in their capacity to colonize the brain reveals that 3-phosphoglycerate dehydrogenase (PHGDH), which catalyzes the rate-limiting step of glucose-derived serine synthesis, is the most significantly upregulated protein in cells that efficiently metastasize to the brain. Expression of catalytically active PHGDH in a non-brain trophic cell line promoted brain metastasis. Furthermore, genetic silencing or pharmacological inhibition of PHGDH attenuated brain metastasis burden in mice. These findings indicate that nutrient availability determines serine synthesis pathway dependence in brain metastasis, and suggest that PHGDH inhibitors may be useful in the treatment of patients with cancers that have spread to the brain. Citation Format: Bryan Ngo, Eugenie Kim, Sophia Doll, Sophia Bustraan, Alba Luengo, Shawn M. Davidson, Ahmed Ali, Gino Ferraro, Diane Kang, Jing Ni, Roger Liang, Ariana Plasger, Edward R. Kastenhuber, Roozbeh Eskandari, Sarah Bacha, Roshan Sriram, Benjamin D. Stein, Samuel F. Bakhoum, Edouard Mullarky, Matija Snuderl, Nello Mainolfi, Vipin Suri, Adam Friedman, Mark Manfredi, David M. Sabatini, Drew Jones, Min Yu, Jean J. Zhao, Rakesh K. Jain, Matthew G. Vander Heiden, Matthias Mann, Lewis C. Cantley, Michael E. Pacold. Nutrient scarcity confers breast cancer brain metastasis sensitivity to serine synthesis pathway inhibition [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5712.

Microalgal bioassays are currently used worldwide to help assess the impacts of contaminants on aquatic ecosystems. Algae are particularly important to such assessments because they represent the basic trophic level of the aquatic food web and contribute to ecosystem biodiversity. Toxicological impacts to these species may have follow-on effects (e.g., depletion of food source) on higher trophic levels and subsequent biodiversity consequences. ExxonMobil Research Qatar in collaboration with Qatar University Environmental Sciences Center and the Ministry of Environment are currently conducting researchto understand the impact of several water borne contaminantsto species of microalgae found in the Qatari marine environment.The two algal species used in this study included Synechococcus sp. which is a unicellular cyanobacterium that is very widespread in the marine environment and are preferentially found in the upper well–lit surface waters. The other species, Chaetoceros sp. is a centric diatom and is abundantly found in Qatari seawaters. Chaetoceros is a highly diverse diatom genus and has been described as the most dominant phytoplankton group in the ocean, in general. They play an important role in various marine ecosystem as a preferred food source for zooplankton and invertebrate larvae.Two microalgal species were isolated from the Qatari coastal watersand cultured in the laboratory. The cultures were maintained at 22 ± 1.0°C, under a 14 h:10 h/light:dark cycle provided by cool white fluorescence light (7000 ± 10% lux), in nutrient-enriched synthetic seawater (F/2 medium) at pH 8.0 ± 0.5 and salinity 40 g/L. The effect of abiotic factors such as salinity and temperature on the growth of both species was also investigated during culture development. Salinity effects were studied in therange of 25 to 45%. The results show that both species are euryhaline - that is, able to grow at all tested salinities – with best growth achieved at 30 and 40%. Both species were subsequently tested for tolerance to temperature ranging between 16 to 38°C,at both 30 and 40% salinities. These temperature experiments show that the highest growth rate was observed in cultures at 30°C and salinity 30%. Similar results were obtained at 30°C and salinity 40%. The lowest growth rates were observed at the lowest temperatures, while a decreased rate was also observed at the highest temperature.Acute (24 hr) and chronic (72 hr) toxicity tests were carried out on both microalgae species, with copper chloride which is widely used as a reference toxicant. Tests were performed using copper chloride at concentrations ranging between 0.05 and 0.75 mg/l. The test endpoints included: cell division rate inhibition, light-scattering properties of algal species, chlorophyll a fluorescence and esterase activity. Results for Synechococcus sp. and Cheatoceros sp. show a dose-dependent response to contaminant exposure. Consequently, it is apparent that both species may be considered as model test species for use in toxicity assessment and serve as akey component in a battery of toxicity tests with other native Qatari marine organisms. In particular, the toleranceof these microalgae species to fluctuations in salinity and temperature make them an ideal species to further explore the impact of potential effects of toxicants in Qatari waters.

BackgroundChlorine is extensively used as a powerful oxidizing agent in the countries surrounding the Arabian Gulf for water treatments and biofouling control. The usage has been increasing significantly as demand for water grows considerably both in industry and domestic use. This is due to the fact that it is a well-tested technology, has had a history of long-term worldwide industrial use and is of acceptable cost. Sodium hypochlorite (NaOCl, commonly termed chlorine) is a common form of chlorine that is used and in all cases it is produced on site by means of an electro-chlorination plant (ECP). In seawater, chlorine produces a mixture of hypochlorous acid (HOCl) and hypochlorite ion (OCl − ). These rapidly react with the bromide ion to form a mixture of hypobromous acid (HOBr) and hypobromite ion (OBr − ). The acute oxidants formed by chlorination are therefore short lived and are not persistent in seawater, but can be quite toxic. Further complicating the environmental concern of chlorination is the production of numerous, and more persistent, compounds formed by complex reactions between chlorine/bromine and the organic constituents of seawater, collectively described as chlorination by-products (CBPs). Many CBPs are persistent and may be toxic to marine organisms subjected to long-term exposures. The Gulf waters support a range of coastal and marine habitats including mangrove swamps, seagrass beds and coral reefs. However, marine organisms in the Arabian Gulf are living close to their tolerance limits due to the extreme environmental stressors of temperature and salinity. Anthropogenic stressors such as chlorine may further exacerbate these natural stressors.ObjectivesIn order to evaluate the risks of chlorine exposure to Arabian Gulf marine organisms, the aims of this study were to 1) develop protocols for acute and chronic toxicity tests involving native species at different trophic levels, 2) correlate sensitivity to other marine organisms used as indicator species in risk assessments, 3) draw conclusion from the results and explore ways that this could be used for informing environmental management activities.MethodologyMaterials and methodsStock solution of calcium hypochlorite was prepared in filtered artificial seawater (0.45 μm filter paper) daily in dark bottles. Concentration of chlorine in the experimental chambers were verified daily by the N,N-diethyl-p-phenlenediamine (DPD) colorimetric method. Different concentrations of chlorine were either administered as a continuous flow through or via daily renewal.Exposure to test speciesSpecies were collected from different location around the coastal areas of Qatar. They were then cultured in the laboratory using conditions of the Arabian Gulf. Species used in the tests include phytoplankton (Synechococcus sp.), zooplankton (Uterpina acutifrons), pearl oysters (Pinctada radiata), sea urchins (Diadema setosum) and killifish embryos (Aphanius dispar).ResultsSensitivity varied across the trophic levels for each species and was found to be in line with other test organisms that are used in established toxicity procedures. All five species used were found to be useful for certain types of toxicity testing. For example, Pinctada radiata and Diadema setosum were excellent in testing for successful fertilization and early development stages, while local Aphanius dispar embryos were useful for following sub-lethal effects such as malformation and hatchability. Embryos of oysters and urchins were found to be the most sensitive to chlorine (Fig. 1.). Effect of chlorine was only observed near or after hatching has occurred. Continuous exposure showed more effective than the semi-renewal method.Discussion and conclusionWhile chlorine continues to be used heavily globally, available toxicology data are either very limited or out dated especially those based on the Arabian Gulf. The purpose of this study was to increase the knowledge of chlorine chemistry and toxicity especially the sensitivity towards the Arabian Gulf species. Results obtained reveal that the sensitivities of all five species used in this study are in line with species used internationally in similar tests. LC50s were determined for all species and are currently being used in modelling tools to determine the fate and environmental risks of chlorine. Chlorine being a powerful oxidizing agent asserted its effect immediately after contact. It loses its potency within the first hour in seawater and this may contribute to the low effect shown in this study compared those in fresh water. Given the short-lived nature of chlorine as an oxidant in seawater, our attention has also been focused on the sub-lethal effects that may be attributed from the by-products. Work is ongoing in this area. Expanding tests with species used in this study to evaluate their sensitivity towards chlorine by-products will further increase our understanding of their chemistry and environmental risk in the Arabian Gulf and will provide a science-based tools for making management decisions.

Background Marine phytoplankton form the basis of the marine food chain and are essential for the normal functioning of ecosystems. Any disturbance to this component, due to the release and accumulation of toxic compounds can have an impact on higher trophic levels. In this study, we investigate the impact of toxicants on the microalgae isolated from Qatari seawater and cultured under controlled laboratory conditions. Objectives * Develop a toxicity test for Synechococcus sp that can be added to the suite of tests currently available for marine invertebrates and fish. * Perform chronic toxicity tests of three reference toxicants (DCA, SDS and Zn) * Evaluate the sensitivity of Synechococcus sp to three reference toxicants and compare sensitivity to other species used in toxicity tests. Methodology Chronic toxicity tests were carried out in 24-well microplate for a period of 3 days for the DCA and Zn tests and 7 days for SDS test. Algal cultures in logarithmic growth phase (cell density of about 3.105 cells mL?1) were used as inoculum. Each test consisted of at least five test concentrations and a control, in triplicate. A different range of concentrations were used to estimate the range findings for each toxicant. * Cell counting using an hemocytometer was conducted to evaluate the inhibition of microalgal growth * The average specific growth rate and the percent inhibition of growth rate were calculated, the lowest observed effect concentration (LOEC) and the no observed effect concentration (NOEC) were statistically determined. Results A growth inhibition toxicity test was successfully developed for Synechococcus sp, which was isolated from Qatari coastal waters. Prior to conducting the toxicity testing, key environmental parameters including light, temperature and nutrients were optimized to obtain acceptable algal growth rates over 72 hours. Results showed that Synechococcus sp was more sensitive to DCA than SDS and Zn. The growth of Synechococcus sp was found to be stimulated by the SDS at the beginning of the test. The growth inhibition by the SDS on Synechococcus sp was shown by day 3 of the experiment. At a longer exposure time, significant values of the percent inhibition of growth rate were reached compared to the control. Conclusion and Discussion Controlled experiments on microalgae under laboratory conditions provide an opportunity to understand the action of these toxicants in the ecosystem. The growth stimulation in the Synechococcus sp test sample seems to be related to the ability of the microalgae to use the SDS as a source of carbon. Inhibition of cell growth under the influence of high concentrations of SDS may result from the destruction of cellular structures and disruptions of metabolism. The findings in this study showed that Synechococcus sp possess a number of desirable characteristics for use in toxicity assessment. In particular, the algae's high sensitivity to environmentally relevant toxicants makes it a suitable choice for site-specific testing. Therefore, we recommend that they be considered, along with other local organisms, as part toxicity tests in the region. qscience

Background Unicellular algae, at the base of aquatic food chains, are particularly sensitive to a wide range of pollutants and are therefore important in toxicity tests for hazard assessment and aquatic environment protection. EMRQ (ExxonMobil Research Qatar) in collaboration with ESC (Environmental Studies Center, Qatar) and the Ministry of Environment, Qatar, is investigating the impact of common toxicants on the performance (growth and survival) of microalgae found in the coastal regions of Qatar. The present work was undertaken to establish the techniques for the isolation and purification of four microalgal species in order to culture them under specific laboratory conditions. Objectives * To conduct laboratory experiments to determine the most appropriate method for the isolation and purification of different microalgal species found in the coastal waters of Qatar. * To establish axenic cultures of the purified unialgae at EMRQ. * To conduct chronic toxicity tests of certain toxicants commonly found in seawaters on the microalgal species isolated and cultured. Methodology Different phytoplankton species were identified and isolated from freshly collected seawater from various sites around the coast of Qatar. * Unialgal isolates were obtained by four major techniques: streaking, spraying, serial dilution, and single-cell isolations by capillary method * Purifications of the unialgal samples to obtain axenic cultures were realized by micropipette washing technique followed by streak-plating technique and using antibiotics. Results The isolation by streak-plating showed to be the most suitable method for the small non motile microalgal species (