A pilot study was perfonned to examine the potential of stable isotope tiques for monitoring the impact of a harmfil substance on the cellular nitrogen metabolism in the ciliate species Tenra/mnayfornnis. After identical cultivation periods ofcontrol cals and toluene-exposed cells in a defined culture medium enriched with (guanidino5N2]L-argnine, a number of nitrogen-contaning pools were analyzech 1) quantity and 15N abundance of ammonia as the end product of nitrogen metabolism in the sytem; 2) pattem and 15N abundances of the protein-bound amino acids in thecells; 3) patten and 15N abundancesoffreeamino acids inthe clls; and 4) pattern and 15N abundances of the amino acids in the culture medium. In addition to 15N emission spectometry, a new gas chromatogrhybcombuston interace-iotope ratio mass spectrometry/mass spectrometry an cal stem was used. The production and 15N content of ammonia were higher in the toluene-exposed sysem by 30% and 43%, respectily, indig higher demination rates and greater argnie consumptont The toluene-exposed cells exhibited increased 15N abundances ofprotein-bound amino acids in alanine, aspartic acid, gluhtmic acid, and tyrosine. Furthermore, strctural anals revealed the presence of N0-acelarginine and pyrrolidonecarboxylic acid-compounds dtat had not previously been detcted in Tena4ym aprfni. Differences in the '5N-enrichment of fee amino acids were also evident. This new effect-monitoring stem designed to investigte the impact ofa pollut on protein metabolism by using a stable isotope-labeled cell cuture is a powerfil tool for environmentl medical rsach. Key worux amino acids, GC-C-IRMS, GC-MS, nitro- Cell culture has been used frequently as a test system for toxicity assessment in pharmacology (4,6,7) and ecotoxicology (8,9). By observing end points such as growth impairment (10), modification of motility (7,11), and inner and outer morphology (6,12,13)

The anti-malaria drug Artesunate (ART) shows strong anti-cancer effects in vitro; however, it shows only marginal treatment results in clinical cancer studies. In this study, ART was tested in preclinical 3D cancer models of increasing complexity using clinically relevant peak plasma concentrations to obtain further information for translation into clinical use. ART reduced cell viability in HCT-116 and HT-29 derived cancer spheroids (p < 0.001). HCT-116 spheroids responded dose-dependently, while HT-29 spheroids were affected more strongly by ART than by cytostatics (p < 0.001). HCT-116 spheroids were chemo-sensitized by ART (p < 0.001). In patient-derived cancer spheroids (PDCS), ART led to inhibition of cell viability in 84.62% of the 39 samples tested, with a mean inhibitory effect of 13.87%. Viability reduction of ART was 2-fold weaker than cytostatic monotherapies (p = 0.028). Meanwhile, tumor-stimulation of up to 16.30% was observed in six (15.38%) PDCS-models. In 15 PDCS samples, ART modulated chemotherapies in combined testing, eight of which showed chemo-stimulation (maximum of 36.90%) and seven chemo-inhibition (up to 16.95%). These results demonstrate that ART’s anti-cancer efficacy depends on the complexity of the tumor model used. This emphasizes that cancer treatment with ART should be evaluated before treatment of the individual patient to ensure its benefits and prevent unwanted effects.

A pilot study was performed to examine the potential of stable isotope techniques for monitoring the impact of a harmful substance on the cellular nitrogen metabolism in the ciliate species Tetrahymena pyriformis. After identical cultivation periods of control cells and toluene-exposed cells in a defined culture medium enriched with [guanidino-15N2]l-arginine, a number of nitrogen-containing pools were analyzed: 1) quantity and 15N abundance of ammonia as the end product of nitrogen metabolism in the system; 2) pattern and 15N abundances of the protein-bound amino acids in the cells; 3) pattern and 15N abundances of free amino acids in the cells; and 4) pattern and 15N abundances of the amino acids in the culture medium. In addition to 15N emission spectrometry, a new gas chromatography/combustion interface-isotope ratio mass spectrometry/mass spectrometry analytical system was used. The production and 15N content of ammonia were higher in the toluene-exposed system by 30% and 43%, respectively, indicating higher deamination rates and greater arginine consumption. The toluene-exposed cells exhibited increased 15N abundances of protein-bound amino acids in alanine, aspartic acid, glutamic acid, and tyrosine. Furthermore, structural analyses revealed the presence of N[Omega]-acetylarginine and pyrrolidonecarboxylic acid--compounds that had not previously been detected in Tetrahymena pyriformis. Differences in the 15N-enrichment of free amino acids were also evident. This new effect-monitoring system designed to investigate the impact of a pollutant on protein metabolism by using a stable isotope-labeled cell culture is a powerful tool for environmental medical research.