Controversy over the role of antioxidants in cancer has persisted for decades. Here, we demonstrate that synthesis of the antioxidant glutathione (GSH), driven by GCLM, is required for cancer initiation. Genetic loss of Gclm prevents a tumor's ability to drive malignant transformation. Intriguingly, these findings can be replicated using an inhibitor of GSH synthesis, but only if delivered prior to cancer onset, suggesting that at later stages of tumor progression GSH becomes dispensable potentially due to compensation from alternative antioxidant pathways. Remarkably, combined inhibition of GSH and thioredoxin antioxidant pathways leads to a synergistic cancer cell death in vitro and in vivo, demonstrating the importance of these two antioxidants to tumor progression and as potential targets for therapeutic intervention.

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The emerging field of sphingolipidomics calls for accurate quantitative analyses of sphingolipidome. Existing analytical methods for sphingolipid (SPL) profiling often suffer from isotopic/isomeric interference, leading to the low-abundance, but biologically important SPLs being undetected. In the current study, we have developed an improved sphingolipidomic approach for reliable and sensitive quantification of up to 10 subclasses of cellular SPLs. By integratively utilizing high efficiency chromatographic separation, quadrupole time-of-flight (Q-TOF) and triple quadrupole (QQQ) mass spectrometry (MS), our approach facilitated unambiguous identification of several groups of potentially important but low-abundance SPLs that are usually masked by isotopic/isomeric species and hence largely overlooked in many published methods. The methodology, which featured a modified sample preparation and optimized MS parameters, permitted the measurement of 86 individual SPLs in PC12 cells in a single run, demonstrating great potential for high throughput analysis. The improved characterization, along with increased sensitivity for low-abundance SPL species, resulted in the highest number of SPLs being quantified in a single run in PC12 cells. The improved method was fully validated and applied to a lipidomic study of PC12 cell samples with or without amyloid β peptide (Aβ) treatment, which presents a most precise and genuine sphingolipidomic profile of the PC12 cell line. The adoption of the metabolomics protocol, as described in this study, could avoid misidentification and bias in the measurement of the analytically challenging low-abundance endogenous SPLs, hence achieving informative and reliable sphingolipidomics data relevant to discovery of potential SPL biomarkers for Aβ-induced neurotoxicity and neurodegenerative disease.

Melioidosis is an emerging, potentially fatal disease caused by Burkholderia pseudomallei, which requires prolonged antibiotic treatment to prevent disease relapse. However, difficulties in laboratory diagnosis of melioidosis may delay treatment and affect disease outcomes. Isolation of B. pseudomallei from clinical specimens has been improved with the use of selective media. However, even with positive cultures, identification of B. pseudomallei can be difficult in clinical microbiology laboratories, especially in non-endemic areas where clinical suspicion is low. Commercial identification systems may fail to distinguish between B. pseudomallei and closely related species such as Burkholderia thailandensis. Genotypic identification of suspected isolates can be achieved by sequencing of gene targets such as groEL which offer higher discriminative power than 16S rRNA. Specific PCR-based identification of B. pseudomallei has also been developed using B. pseudomallei-specific gene targets such as Type III secretion system and Tat-domain protein. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry, a revolutionary technique for pathogen identification, has been shown to be potentially useful for rapid identification of B. pseudomallei, although existing databases require optimization by adding reference spectra for B. pseudomallei. Despite these advances in bacterial identification, diagnostic problems encountered in culture-negative cases remain largely unresolved. Although various serological tests have been developed, they are generally unstandardized "in house" assays and have low sensitivities and specificities. Although specific PCR assays have been applied to direct clinical and environmental specimens, the sensitivities for diagnosis remain to be evaluated. Metabolomics is an uprising tool for studying infectious diseases and may offer a novel approach for exploring potential diagnostic biomarkers. The metabolomics profiles of B. pseudomallei culture supernatants can be potentially distinguished from those of related bacterial species including B. thailandensis . Further studies using bacterial cultures and direct patient samples are required to evaluate the potential of metabolomics for improving diagnosis of melioidosis.