bims-mascan 2020-05-03 papers

bims-mascan

Biomed News

on Mass spectrometry in cancer research

Issue of 2020–05–03
sixteen papers selected by
Giovanny Rodríguez Blanco, The Beatson Institute for Cancer Research

Quantitative analysis of amino acid metabolism in liver cancer links glutamate excretion to nucleotide synthesis.
De novo lipogenesis alters the phospholipidome of esophageal adenocarcinoma.
LipidCreator workbench to probe the lipidomic landscape.
A comparative pharmaco-metabolomic study of glutaminase inhibitors in glioma stem-like cells confirms biological effectiveness but reveals differences in target-specificity.
The Urinary Metabolome of Healthy Newborns.
Identification of Metabolic Alterations in Breast Cancer Using Mass Spectrometry-Based Metabolomic Analysis.
Distinguishing NASH Histological Severity Using a Multiplatform Metabolomics Approach.
Proteomics promises a new era of precision cancer medicine.
Selective alanine transporter utilization creates a targetable metabolic niche in pancreatic cancer.
The protein kinase MAP3K19 phosphorylates MAP2Ks and thereby activates ERK and JNK kinases and increases viability of KRAS-mutant lung cancer cells.
Redox Homeostasis and Metabolism in Cancer: A Complex Mechanism and Potential Targeted Therapeutics.
27-plex Tandem Mass Tag Mass Spectrometry for Profiling Brain Proteome in Alzheimer's Disease.
Metabolomics Analysis of Mesenchymal Stem Cells.
ProteoViz: a tool for the analysis and interactive visualization of phosphoproteomics data.
A simple method for sphingolipid analysis of tissues embedded in optimal cutting temperature compound.
Evaluation of LC-MS and LC×LC-MS in analysis of zebrafish embryo samples for comprehensive lipid profiling.

Proc Natl Acad Sci U S A. 2020 Apr 27. pii: 201919250. [Epub ahead of print]

Quantitative analysis of amino acid metabolism in liver cancer links glutamate excretion to nucleotide synthesis.

Avlant Nilsson, Jurgen R Haanstra, Martin Engqvist, Albert Gerding, Barbara M Bakker, Ursula Klingmüller, Bas Teusink, Jens Nielsen.

  Many cancer cells consume glutamine at high rates; counterintuitively, they simultaneously excrete glutamate, the first intermediate in glutamine metabolism. Glutamine consumption has been linked to replenishment of tricarboxylic acid cycle (TCA) intermediates and synthesis of adenosine triphosphate (ATP), but the reason for glutamate excretion is unclear. Here, we dynamically profile the uptake and excretion fluxes of a liver cancer cell line (HepG2) and use genome-scale metabolic modeling for in-depth analysis. We find that up to 30% of the glutamine is metabolized in the cytosol, primarily for nucleotide synthesis, producing cytosolic glutamate. We hypothesize that excreting glutamate helps the cell to increase the nucleotide synthesis rate to sustain growth. Indeed, we show experimentally that partial inhibition of glutamate excretion reduces cell growth. Our integrative approach thus links glutamine addiction to glutamate excretion in cancer and points toward potential drug targets.

Keywords:  flux-balance analysis; genome-scale modeling; metabolic engineering; systems biology

DOI:  https://doi.org/10.1073/pnas.1919250117
Cancer Res. 2020 Apr 28. pii: canres.4035.2019. [Epub ahead of print]

De novo lipogenesis alters the phospholipidome of esophageal adenocarcinoma.

Nima Abbassi-Ghadi, Stefan S Antonowicz, James S McKenzie, Sacheen Kumar, Juzheng Huang, Emrys A Jones, Nicole Strittmatter, Gemma Petts, Hiromi Kudo, Stephen Court, Jonathan M Hoare, Kirill Veselkov, Robert Goldin, Zoltán Takáts, George B Hanna.

The incidence of esophageal adenocarcinoma is rising, survival remains poor, and new tools to improve early diagnosis and precise treatment are needed. Cancer phospholipidomes quantified with mass spectrometry imaging can support objective diagnosis in minutes using a routine frozen tissue section. However, whether mass spectrometry imaging can objectively identify primary esophageal adenocarcinoma is currently unknown and represents a significant challenge, as this microenvironment is complex with phenotypically similar tissue-types. Here we used desorption electrospray ionisation mass spectrometry imaging (DESI-MSI) and bespoke chemometrics to assess the phospholipidomes of esophageal adenocarcinoma and relevant control tissues. Multivariable models derived from phospholipid profiles of 117 patients were highly discriminant for esophageal adenocarcinoma both in discovery (area-under-curve = 0.97) and validation cohorts (AUC = 1). Among many other changes, esophageal adenocarcinoma samples were markedly enriched for polyunsaturated phosphatidylglycerols with longer acyl chains, with stepwise enrichment in pre-malignant tissues. Expression of fatty acid and glycerophospholipid synthesis genes was significantly upregulated, and characteristics of fatty acid acyls matched glycerophospholipid acyls. Mechanistically, silencing the carbon switch ACLY in esophageal adenocarcinoma cells shortened GPL chains, linking de novo lipogenesis to the phospholipidome. Thus, DESI-MSI can objectively identify invasive esophageal adenocarcinoma from a number of pre-malignant tissues and unveils mechanisms of phospholipidomic reprogramming. These results call for accelerated diagnosis studies using DESI-MSI in the upper gastrointestinal endoscopy suite as well as functional studies to determine how polyunsaturated phosphatidylglycerols contribute to esophageal carcinogenesis.

DOI: https://doi.org/10.1158/0008-5472.CAN-19-4035
Nat Commun. 2020 Apr 28. 11(1): 2057

LipidCreator workbench to probe the lipidomic landscape.

Bing Peng, Dominik Kopczynski, Brian S Pratt, Christer S Ejsing, Bo Burla, Martin Hermansson, Peter Imre Benke, Sock Hwee Tan, Mark Y Chan, Federico Torta, Dominik Schwudke, Sven W Meckelmann, Cristina Coman, Oliver J Schmitz, Brendan MacLean, Mailin-Christin Manke, Oliver Borst, Markus R Wenk, Nils Hoffmann, Robert Ahrends.

Mass spectrometry (MS)-based targeted lipidomics enables the robust quantification of selected lipids under various biological conditions but comprehensive software tools to support such analyses are lacking. Here we present LipidCreator, a software that fully supports targeted lipidomics assay development. LipidCreator offers a comprehensive framework to compute MS/MS fragment masses for over 60 lipid classes. LipidCreator provides all functionalities needed to define fragments, manage stable isotope labeling, optimize collision energy and generate in silico spectral libraries. We validate LipidCreator assays computationally and analytically and prove that it is capable to generate large targeted experiments to analyze blood and to dissect lipid-signaling pathways such as in human platelets.

DOI: https://doi.org/10.1038/s41467-020-15960-z
Cell Death Discov. 2020 ;6 20

A comparative pharmaco-metabolomic study of glutaminase inhibitors in glioma stem-like cells confirms biological effectiveness but reveals differences in target-specificity.

Katharina Koch, Rudolf Hartmann, Julia Tsiampali, Constanze Uhlmann, Ann-Christin Nickel, Xiaoling He, Marcel A Kamp, Michael Sabel, Roger A Barker, Hans-Jakob Steiger, Daniel Hänggi, Dieter Willbold, Jaroslaw Maciaczyk, Ulf D Kahlert.

  Cancer cells upregulate anabolic processes to maintain high rates of cellular turnover. Limiting the supply of macromolecular precursors by targeting enzymes involved in biosynthesis is a promising strategy in cancer therapy. Several tumors excessively metabolize glutamine to generate precursors for nonessential amino acids, nucleotides, and lipids, in a process called glutaminolysis. Here we show that pharmacological inhibition of glutaminase (GLS) eradicates glioblastoma stem-like cells (GSCs), a small cell subpopulation in glioblastoma (GBM) responsible for therapy resistance and tumor recurrence. Treatment with small molecule inhibitors compound 968 and CB839 effectively diminished cell growth and in vitro clonogenicity of GSC neurosphere cultures. However, our pharmaco-metabolic studies revealed that only CB839 inhibited GLS enzymatic activity thereby limiting the influx of glutamine derivates into the TCA cycle. Nevertheless, the effects of both inhibitors were highly GLS specific, since treatment sensitivity markedly correlated with GLS protein expression. Strikingly, we found GLS overexpressed in in vitro GSC models as compared with neural stem cells (NSC). Moreover, our study demonstrates the usefulness of in vitro pharmaco-metabolomics to score target specificity of compounds thereby refining drug development and risk assessment.

Keywords:  CNS cancer; Cancer metabolism; Cancer stem cells; Predictive markers; Translational research

DOI:  https://doi.org/10.1038/s41420-020-0258-3
Metabolites. 2020 Apr 23. pii: E165. [Epub ahead of print]10(4):

The Urinary Metabolome of Healthy Newborns.

Yamilé López-Hernández, Juan José Oropeza-Valdez, Jorge O Blanco-Sandate, Ana Sofia Herrera-Van Oostdam, Jiamin Zheng, An Chi Guo, Victoria Lima-Rogel, Rahmatollah Rajabzadeh, Mariana Salgado-Bustamante, Jesus Adrian-Lopez, C G Castillo, Emilia Robles Arguelles, Joel Monárrez-Espino, Rupasri Mandal, David S Wishart.

  The knowledge of normal metabolite values for neonates is key to establishing robust cut-off values to diagnose diseases, to predict the occurrence of new diseases, to monitor a neonate's metabolism, or to assess their general health status. For full term-newborns, many reference biochemical values are available for blood, serum, plasma and cerebrospinal fluid. However, there is a surprising lack of information about normal urine concentration values for a large number of important metabolites in neonates. In the present work, we used targeted tandem mass spectrometry (MS/MS)-based metabolomic assays to identify and quantify 136 metabolites of biomedical interest in the urine from 48 healthy, full-term term neonates, collected in the first 24 h of life. In addition to this experimental study, we performed a literature review (covering the past eight years and over 500 papers) to update the references values in the Human Metabolome Database/Urine Metabolome Database (HMDB/UMDB). Notably, 86 of the experimentally measured urinary metabolites are being reported in neonates/infants for the first time and another 20 metabolites are being reported in human urine for the first time ever. Sex differences were found for 15 metabolites. The literature review allowed us to identify another 78 urinary metabolites with concentration data. As a result, reference concentration values and ranges for 378 neonatal urinary metabolites are now publicly accessible via the HMDB.

Keywords:  inborn errors of metabolism; metabolites; newborn; reference values; tandem mass spectrometry

DOI:  https://doi.org/10.3390/metabo10040165
Metabolites. 2020 Apr 24. pii: E170. [Epub ahead of print]10(4):

Identification of Metabolic Alterations in Breast Cancer Using Mass Spectrometry-Based Metabolomic Analysis.

Sili Fan, Muhammad Shahid, Peng Jin, Arash Asher, Jayoung Kim.

  Breast cancer (BC) is a major global health issue and remains the second leading cause of cancer-related death in women, contributing to approximately 41,760 deaths annually. BC is caused by a combination of genetic and environmental factors. Although various molecular diagnostic tools have been developed to improve diagnosis of BC in the clinical setting, better detection tools for earlier diagnosis can improve survival rates. Given that altered metabolism is a characteristic feature of BC, we aimed to understand the comparative metabolic differences between BC and healthy controls. Metabolomics, the study of metabolism, can provide incredible insight and create useful tools for identifying potential BC biomarkers. In this study, we applied two analytical mass spectrometry (MS) platforms, including hydrophilic interaction chromatography (HILIC) and gas chromatography (GC), to generate BC-associated metabolic profiles using breast tissue from BC patients. These metabolites were further analyzed to identify differentially expressed metabolites in BC and their associated metabolic networks. Additionally, Chemical Similarity Enrichment Analysis (ChemRICH), MetaMapp, and Metabolite Set Enrichment Analysis (MSEA) identified significantly enriched clusters and networks in BC tissues. Since metabolomic signatures hold significant promise in the clinical setting, more effort should be placed on validating potential BC biomarkers based on identifying altered metabolomes.

Keywords:  biomarkers; breast cancer; mass spectrometry; metabolomics

DOI:  https://doi.org/10.3390/metabo10040170
Metabolites. 2020 Apr 24. pii: E168. [Epub ahead of print]10(4):

Distinguishing NASH Histological Severity Using a Multiplatform Metabolomics Approach.

George N Ioannou, G A Nagana Gowda, Danijel Djukovic, Daniel Raftery.

  Nonalcoholic fatty liver disease (NAFLD) is categorized based on histological severity into nonalcoholic fatty liver (NAFL) or nonalcoholic steatohepatitis (NASH). We used a multiplatform metabolomics approach to identify metabolite markers and metabolic pathways that distinguish NAFL from early NASH and advanced NASH. We analyzed fasting serum samples from 57 prospectively-recruited patients with histologically-proven NAFLD, including 12 with NAFL, 31 with early NASH and 14 with advanced NASH. Metabolite profiling was performed using a combination of liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy analyzed with multivariate statistical and pathway analysis tools. We targeted 237 metabolites of which 158 were quantified. Multivariate analysis uncovered metabolite profile clusters for patients with NAFL, early NASH, and advanced NASH. Also, multiple individual metabolites were associated with histological severity, most notably spermidine which was more than 2-fold lower in advanced fibrosis vs. early fibrosis, in advanced NASH vs. NAFL and in advanced NASH vs. early NASH, suggesting that spermidine exercises a protective effect against development of fibrosing NASH. Furthermore, the results also showed metabolic pathway perturbations between early-NASH and advanced-NASH. In conclusion, using a combination of two reliable analytical platforms (LC-MS and NMR spectroscopy) we identified individual metabolites, metabolite clusters and metabolic pathways that were significantly different between NAFL, early-NASH, and advanced-NASH. These differences provide mechanistic insights as well as potentially important metabolic biomarker candidates that may noninvasively distinguish patients with NAFL, early-NASH, and advanced-NASH. The associations of spermidine levels with less advanced histology merit further assessment of the potential protective effects of spermidine in NAFLD.

Keywords:  liquid chromatography-mass spectrometry; metabolic pathway; nonalcoholic fatty liver; nonalcoholic steatohepatitis; nuclear magnetic resonance spectroscopy

DOI:  https://doi.org/10.3390/metabo10040168
Signal Transduct Target Ther. 2019 May 03. 4(1): 13

Proteomics promises a new era of precision cancer medicine.

Chong Wu, Limin Zheng.

DOI: https://doi.org/10.1038/s41392-019-0046-9
Cancer Discov. 2020 Apr 27. pii: CD-19-0959. [Epub ahead of print]

Selective alanine transporter utilization creates a targetable metabolic niche in pancreatic cancer.

Seth J Parker, Caroline R Amendola, Kate E R Hollinshead, Qijia Yu, Keisuke Yamamoto, Joel Encarnacion-Rosado, Rebecca E Rose, Madeleine M LaRue, Albert S W Sohn, Doug E Biancur, Joao A Paulo, Steven P Gygi, Drew R Jones, Huamin Wang, Mark R Philips, Dafna Bar-Sagi, Joseph D Mancias, Alec C Kimmelman.

Pancreatic ductal adenocarcinoma (PDAC) evolves a complex microenvironment comprised of multiple cell types, including pancreatic stellate cells (PSCs). Previous studies have demonstrated that stromal supply of alanine, lipids, and nucleotides supports the metabolism, growth, and therapeutic resistance of PDAC. Here we demonstrate that alanine crosstalk between PSCs and PDAC is orchestrated by the utilization of specific transporters. PSCs utilize SLC1A4 and other transporter(s) to rapidly exchange and maintain environmental alanine concentrations. Moreover, PDAC cells upregulate SLC38A2 to supply their increased alanine demand. Cells lacking SLC38A2 fail to concentrate intracellular alanine and undergo a profound metabolic crisis resulting in markedly impaired tumor growth. Our results demonstrate that stromal-cancer metabolic niches can form through differential transporter expression, creating unique therapeutic opportunities to target metabolic demands of cancer.

DOI: https://doi.org/10.1158/2159-8290.CD-19-0959
J Biol Chem. 2020 Apr 30. pii: jbc.RA119.012365. [Epub ahead of print]

The protein kinase MAP3K19 phosphorylates MAP2Ks and thereby activates ERK and JNK kinases and increases viability of KRAS-mutant lung cancer cells.

Van T Hoang, Katherine Nyswaner, Pedro Torres-Ayuso, John Brognard.

  Identifying additional mitogen-activated protein kinase (MAPK) pathway regulators is invaluable in aiding our understanding of the complex signaling networks that regulate cellular processes, including cell proliferation and survival. Here, using in vitro kinase assays and by expressing wild-type (WT) or kinase-dead (KD) MAPK kinase kinase 19 (MAP3K19) in the HEK293T cell line and assessing activation of the extracellular signal-regulated kinase (ERK) and JUN N-terminal kinase (JNK) signaling pathways, we defined MAP3K19 as a novel regulator of MAPK signaling. We also observed that overexpression of WT MAP3K19 activates both the ERK and JNK pathways in a panel of cancer cell lines. Furthermore, MAP3K19 sustained ERK pathway activation in the presence of inhibitors targeting the RAF proto-oncogene Ser/Thr protein kinase (RAF) and MAPK/ERK kinase (MEK), indicating that MAP3K19 activates ERK via a RAF-independent mechanism. Findings from in vitro and in cell kinase assays demonstrate that MAP3K19 is a kinase that directly phosphorylates both MEK and MAPK kinase 7 (MKK7). Results from an shRNA screen indicated that MAP3K19 is essential for maintaining survival in KRAS-mutant cancers; therefore, we depleted or inhibited MAP3K19 in KRAS-mutant cancer cell lines and observed that this reduces viability and decreases ERK and JNK pathway activation. In summary, our results reveal that MAP3K19 directly activates the ERK and JNK cascades and highlight a role for this kinase in maintaining survival of KRAS-mutant lung cancer cells.

Keywords:  GTPase Kras (KRAS); YSK4; c-Jun N-terminal kinase (JNK); cell proliferation; extracellular-signal-regulated kinase (ERK); kinase signaling; kinome; lung cancer; mitogen-activated protein kinase kinase kinase 19 (MAP3K19); oncogene; protein kinase

DOI:  https://doi.org/10.1074/jbc.RA119.012365
Int J Mol Sci. 2020 Apr 28. pii: E3100. [Epub ahead of print]21(9):

Redox Homeostasis and Metabolism in Cancer: A Complex Mechanism and Potential Targeted Therapeutics.

Alia Ghoneum, Ammar Yasser Abdulfattah, Bailey Olivia Warren, Junjun Shu, Neveen Said.

  Reactive Oxygen Species or "ROS" encompass several molecules derived from oxygen that can oxidize other molecules and subsequently transition rapidly between species. The key roles of ROS in biological processes are cell signaling, biosynthetic processes, and host defense. In cancer cells, increased ROS production and oxidative stress are instigated by carcinogens, oncogenic mutations, and importantly, metabolic reprograming of the rapidly proliferating cancer cells. Increased ROS production activates myriad downstream survival pathways that further cancer progression and metastasis. In this review, we highlight the relation between ROS, the metabolic programing of cancer, and stromal and immune cells with emphasis on and the transcription machinery involved in redox homeostasis, metabolic programing and malignant phenotype. We also shed light on the therapeutic targeting of metabolic pathways generating ROS as we investigate: Orlistat, Biguandes, AICAR, 2 Deoxyglucose, CPI-613, and Etomoxir.

Keywords:  HIF-1α; Nrf2; PGC-1α; ROS; metabolic targeting; metabolism; oxidative stress; redox systems

DOI:  https://doi.org/10.3390/ijms21093100
Anal Chem. 2020 Apr 28.

27-plex Tandem Mass Tag Mass Spectrometry for Profiling Brain Proteome in Alzheimer's Disease.

Zhen Wang, Kaiwen Yu, Haiyan Tan, Zhiping Wu, Ji-Hoon Cho, Xian Han, Huan Sun, Thomas G Beach, Junmin Peng.

Multiplexed isobaric labeling methods, such as Tandem Mass Tags (TMT), remarkably improve the throughput of quantitative mass spectrometry. Here we present a 27-plex TMT method coupled with two-dimensional liquid chromatography (LC/LC) for extensive peptide fractionation and high-resolution tandem mass spectrometry (MS/MS) for peptide quantification, and then apply the method to profile complex human brain proteome of Alzheimer's disease (AD). The 27-plex method combines multiplexed capacities of the 11-plex and the 16-plex TMT, as the peptides labeled by the two TMT sets display different mass and hydrophobicity, which can be well separated in LC-MS/MS. We first systematically optimized the protocol for the newly developed 16-plex TMT, including labeling reaction, desalting, and MS conditions, and then directly compared the 11-plex and 16-plex methods by analyzing the same human AD samples. Both methods yielded similar proteome coverage, analyzing > 100,000 peptides in > 10,000 human proteins. Furthermore, the 11-plex and 16-plex samples were mixed for a 27-plex assay, resulting in more than 8,000 protein measurements within the same MS time. The 27-plex results are highly consistent with those of the individual 11-plex and 16-plex TMT analyses. We also used these proteomics datasets to compare AD brain with the non-dementia controls, discovering major AD-related proteins and revealing numerous novel protein alterations enriched in the pathways of amyloidosis, immunity, mitochondrial and synaptic functions. Overall, our data strongly demonstrate that this new 27-plex strategy is highly feasible for routine large-scale proteomic analysis.

DOI: https://doi.org/10.1021/acs.analchem.0c00655
Int J Mol Cell Med. 2019 ;8(Suppl1): 30-40

Metabolomics Analysis of Mesenchymal Stem Cells.

Parisa Goodarzi, Sepideh Alavi-Moghadam, Moloud Payab, Bagher Larijani, Fakher Rahim, Kambiz Gilany, Nikoo Bana, Akram Tayanloo-Beik, Najmeh Foroughi Heravani, Mahdieh Hadavandkhani, Babak Arjmand.

  Various mesenchymal stem cells as easily accessible and multipotent cells can share different essential signaling pathways related to their stemness ability. Understanding the mechanism of stemness ability can be useful for controlling the stem cells for regenerative medicine targets. In this context, OMICs studies can analyze the mechanism of different stem cell properties or stemness ability via a broad range of current high-throughput techniques. This field is fundamentally directed toward the analysis of whole genome (genomics), mRNAs (transcriptomics), proteins (proteomics) and metabolites (metabolomics) in biological samples. According to several studies, metabolomics is more effective than other OMICs ّfor various system biology concerns. Metabolomics can elucidate the biological mechanisms of various mesenchymal stem cell function by measuring their metabolites such as their secretome components. Analyzing the metabolic alteration of mesenchymal stem cells can be useful to promote their regenerative medicine application.

Keywords:  Mesenchymal stem cells; metabolic pathways; metabolomics; systems biology

DOI:  https://doi.org/10.22088/IJMCM.BUMS.8.2.30
Mol Omics. 2020 Apr 29.

ProteoViz: a tool for the analysis and interactive visualization of phosphoproteomics data.

Aaron J Storey, Kevin S Naceanceno, Renny S Lan, Charity L Washam, Lisa M Orr, Samuel G Mackintosh, Alan J Tackett, Rick D Edmondson, Zhengyu Wang, Hong-Yu Li, Brendan Frett, Samantha Kendrick, Stephanie D Byrum.

Quantitative proteomics generates large datasets with increasing depth and quantitative information. With the advance of mass spectrometry and increasingly larger data sets, streamlined methodologies and tools for analysis and visualization of phosphoproteomics are needed both at the protein and modified peptide levels. To assist in addressing this need, we developed ProteoViz, which includes a set of R scripts that perform normalization and differential expression analysis of both the proteins and enriched phosphorylated peptides, and identify sequence motifs, kinases, and gene set enrichment pathways. The tool generates interactive visualization plots that allow users to interact with the phosphoproteomics results and quickly identify proteins and phosphorylated peptides of interest for their biological study. The tool also links significant phosphosites with sequence motifs and pathways that will help explain the experimental conditions and guide future experiments. Here, we present the workflow and demonstrate its functionality by analyzing a phosphoproteomic data set from two lymphoma cell lines treated with kinase inhibitors. The scripts and data are freely available at https://github.com/ByrumLab/ProteoViz and via the ProteomeXchange with identifier PXD015606.

DOI: https://doi.org/10.1039/c9mo00149b
J Lipid Res. 2020 Apr 27. pii: jlr.D120000809. [Epub ahead of print]

A simple method for sphingolipid analysis of tissues embedded in optimal cutting temperature compound.

Timothy D Rohrbach, April E Boyd, Pamela J Grizzard, Sarah Spiegel, Jeremy Allegood, Santiago Lima.

  Mass spectrometry (MS) assisted lipidomic tissue analysis is a valuable tool to assess sphingolipid metabolism dysfunction in disease. These analyses can reveal potential pharmacological targets or direct mechanistic studies to better understand the molecular underpinnings and influence of sphingolipid metabolism alterations on disease etiology. But procuring sufficient human tissues for adequately powered studies can be challenging. Therefore, biorepositories, which hold large collections of cryopreserved human tissues, are an ideal retrospective source of specimens. However, this resource has been vastly underutilized by lipid biologists, as the components of optimal cutting temperature compound (OCT) used in cryopreservation are incompatible with MS analyses. Here, we report results indicating that OCT also interferes with protein quantification assays, and that the presence of OCT impacts the quantification of extracted sphingolipids by LC-ESI-MS/MS. We developed and validated a simple and inexpensive method that removes OCT from OCT-embedded tissues. Our results indicate that removal of OCT from cryopreserved tissues does not significantly affect the accuracy of sphingolipid measurements with LC-ESI-MS/MS. We used the validated method to analyze sphingolipid alterations in tumors compared with normal adjacent uninvolved lung tissues from individuals with lung cancer, and to determine the long-term stability of sphingolipids in OCT-cryopreserved normal lung tissues. We show that lung cancer tumors have significantly altered sphingolipid profiles and that sphingolipids are stable for up to 16 years in OCT-cryopreserved normal lung tissues. This validated sphingolipidomic OCT-removal protocol should be a valuable addition to the lipid biologist's toolbox.

Keywords:  Cancer; Ceramides; Lipidomics; Mass spectrometry; OCT; Sphingolipids; biorepository; lung adenocarcinoma; lung squamous cell carcinoma; non-small cell lung cancer

DOI:  https://doi.org/10.1194/jlr.D120000809
Anal Bioanal Chem. 2020 Apr 29.

Evaluation of LC-MS and LC×LC-MS in analysis of zebrafish embryo samples for comprehensive lipid profiling.

Mengmeng Xu, Jessica Legradi, Pim Leonards.

  In this study, both conventional one-dimensional liquid chromatography (1DLC) and comprehensive two-dimensional liquid chromatography (2DLC) coupled to a high-resolution time-of-flight mass spectrometer (HR-TOF MS) were used for full-scale lipid characterization of lipid extracts from zebrafish embryos. We investigated the influence on annotated lipids and different separation mechanisms (HILIC, C18, and PFP), and their different orders arranged in the first and the second dimensions. As a result, the number of lipid species annotated by conventional one-dimensional LC-MS was between 212 and 448. In contrast, the number of individual lipids species annotated by C18×HILIC, HILIC×C18, and HILIC×PFP were 1784, 1059, and 1123, respectively. Therefore, it was evident that the performance of comprehensive 2DLC, especially the C18×HILIC method, considerably exceeded 1DLC. Interestingly, a comparison of the HILIC×C18 and C18×HILIC approaches showed, under the optimized conditions, similar orthogonality, but the effective separation power of the C18×HILIC was much higher. A comparison of the HILIC×C18 and the HILIC×PFP methods demonstrated that the HILIC×PFP separation had superior orthogonality with a small increase on its effective peak capacity, indicating that the HILIC×PFP combination maybe a promising platform for untargeted lipidomics in complex samples. Finally, from the comprehensive lipid profiling respective, the C18×HILIC was selected for further studies.

Keywords:  Comprehensive two-dimensional liquid chromatography; Conventional one-dimensional liquid chromatography; Untargeted lipidomics; Zebrafish

DOI:  https://doi.org/10.1007/s00216-020-02661-1