Plasma hemoglobin: A method comparison of six assays for hemoglobin and hemolysis index measurement.

INTRODUCTION: Plasma hemoglobin (Hb) is measured for assessment of in vivo and in vitro hemolysis. The objective of the present investigation was to conduct a method comparison of five quantitative and one semi-quantitative Hb and H-index (hemolysis index) assays to evaluate their performance measuring plasma Hb in clinical specimens. METHODS: One hundred and fourteen clinical specimens previously tested for plasma Hb using a laboratory-developed spectrophotometric assay were also tested for Hb using a HemoCue Plasma/Low Hb assay (azide methemoglobin), a laboratory-modified Pointe Scientific Hb assay (cyanmethemoglobin), tested for H-index measurements using a Roche cobas c501, an Abbott Architect c8000, and a semi-quantitative (binned) H-index measurement on a Beckman AU5800. The reference result was defined as the median Hb score (median of all Hb or H-index results). RESULTS: The laboratory-developed spectrophotometric Hb assay and Roche H-index methods mostly closely matched the median Hb score across all data, as well as for lower range median Hb score results ≤2.0 g/L. Two-way frequency table analysis using an Hb (or H-index) cutoff of 0.5 g/L (or 0.5 H-index units) was then performed to compare methods to the median Hb score cutoff. The Beckman method had the highest accuracy at this cutoff, the Roche and Abbott methods had the highest positive predictive value (PPV), and the Beckman, HemoCue, and Pointe methods had the highest negative predictive value (NPV). CONCLUSIONS: Plasma Hb and H-index results vary by method. Laboratories should evaluate the performance characteristics of their respective assays when considering adoption of spectrophotometric or chemical methods for plasma Hb assessment.

Evaluating Percentage-Based Reporting of Glucose-6-Phosphate Dehydrogenase (G6PD) Enzymatic Activity.

OBJECTIVES: The World Health Organization recommends measurement of glucose-6-phosphate dehydrogenase (G6PD) activity before initiation of 8-aminoquinoline therapy. A new drug for malaria prophylaxis and treatment (tafenoquine) is contraindicated in patients with G6PD deficiency or unknown G6PD status given its prolonged half-life. Assessments of percentage of normal G6PD activity using laboratory-specific result distributions are not widely available, making tafenoquine-eligibility decisions potentially challenging. METHODS: Using an institutional review board-exempt protocol, a data set of quantitative G6PD results was retrieved from a national reference laboratory. G6PD testing was previously performed at 37 °C using an automated enzymatic assay configured on a Roche cobas c501 chemistry analyzer. RESULTS: Overall, 52,216 results from patients 18 years and older and 6,397 results from patients younger than 18 years were obtained. A modified adjusted male median of 12.7 U/g Hb was derived for adult males in this assay configuration. Result distributions showed higher G6PD activity in neonates. CONCLUSIONS: Retrospective data analysis can be used to determine laboratory-specific normal G6PD activity values in clinical populations and thus can assist in clinical-eligibility considerations for 8-aminoquinoline treatment.

Synthesis and biological evaluation of non-glucose glycoconjugated N-hydroyxindole class LDH inhibitors as anticancer agents.

Inhibitors of human lactate dehydrogenase A (LDH-A) are promising therapeutic agents against cancer. The development of LDH-A inhibitors that possess cellular activities has so far proved to be particularly challenging, since the enzyme's active site is narrow and highly polar. In the recent past, we were able to develop a glucose-conjugated N-hydroxyindole-based LDH-A inhibitor designed to exploit the sugar avidity expressed by cancer cells (the Warburg effect). Herein we describe a structural modulation of the sugar moiety of this class of inhibitors, with the insertion of α-D-mannose, ß-D-gulose, or ß-N-acetyl-D-glucosamine portions in their structures. Their stereospecific chemical synthesis, which involves a substrate-dependent stereospecific glycosylation step, and their biological activity in reducing lactate production and proliferation in cancer cells are reported. Interestingly, the α-D-mannose conjugate displayed the best properties in the cellular assays, demonstrating an efficient antiglycolytic and antiproliferative activity in cancer cells.

Dual targeting of the Warburg effect with a glucose-conjugated lactate dehydrogenase inhibitor.

Effective glucose diet: We report the development and activity of glucose-conjugated LDH-A inhibitors designed for dual targeting of the Warburg effect (elevated glucose uptake and glycolysis) in cancer cells. Glycoconjugation could be applied to inhibitors of many enzymes involved in glycolysis or tumor metabolism.

Glucose conjugation for the specific targeting and treatment of cancer.

Cancers of diverse origins exhibit marked glucose avidity and high rates of aerobic glycolysis. Increased understanding of this dysfunctional metabolism known as the Warburg effect has led to an interest in targeting it for cancer therapy. One promising strategy for such targeting is glycoconjugation, the linking of a drug to glucose or another sugar. This review summarizes the most salient examples of glycoconjugates, in which known cytotoxins or targeted anticancer therapeutics have been linked to glucose (or another glucose transporter substrate sugar) for improved cancer targeting and selectivity. Building on these examples, this review also provides a series of guidelines for the design and mechanistic evaluation of future glycoconjugates.

Assessing the differential action on cancer cells of LDH-A inhibitors based on the N-hydroxyindole-2-carboxylate (NHI) and malonic (Mal) scaffolds.

A head-to-head study of representative examples of N-hydroxyindole-2-carboxylates (NHI) and malonic derivatives (Mal) as LDH-A inhibitors was conducted, comparing the enzyme inhibition potency, cellular uptake, reduction of lactate production in cancer cells and anti-proliferative activity. Among the compounds tested, methyl 1-hydroxy-6-phenyl-4-(trifluoromethyl)-1H-indole-2-carboxylate (2, NHI-2), a methyl ester belonging to the NHI class, displayed optimal properties in the cell-based assays, proving to be an efficient anti-glycolytic agent against cancer cells.

Discovery of N-hydroxyindole-based inhibitors of human lactate dehydrogenase isoform A (LDH-A) as starvation agents against cancer cells.

Highly invasive tumor cells are characterized by a metabolic switch, known as the Warburg effect, from "normal" oxidative phosphorylation to increased glycolysis even under sufficiently oxygenated conditions. This dependence on glycolysis also confers a growth advantage to cells present in hypoxic regions of the tumor. One of the key enzymes involved in glycolysis, the muscle isoform of lactate dehydrogenase (LDH-A), is overexpressed by metastatic cancer cells and is linked to the vitality of tumors in hypoxia. This enzyme may be considered as a potential target for new anticancer agents, since its inhibition cuts cancer energetic and anabolic supply, thus reducing the metastatic and invasive potential of cancer cells. We have discovered new and efficient N-hydroxyindole-based inhibitors of LDH-A, which are isoform-selective (over LDH-B) and competitive with both the substrate (pyruvate) and the cofactor (NADH). The antiproliferative activity of these compounds was confirmed on a series of cancer cell lines, and they proved to be particularly effective under hypoxic conditions. Moreover, NMR experiments showed that these compounds are able to reduce the glucose-to-lactate conversion inside the cell.