Metabolism of a novel antitumor agent, crisnatol, by a human hepatoma cell line, Hep G2, and hepatic microsomes. Characterization of metabolites

Metabolite Profiling in Anticancer Drug Development: A Systematic Review

Drug metabolism is one of the most important pharmacokinetic processes and plays an important role during the stage of drug development. The metabolite profile investigation is important as the metabolites generated could be beneficial for therapy or leading to serious toxicity. This systematic review aims to summarize the research articles relating to the metabolite profile investigation of conventional drugs and herb-derived compounds for cancer chemotherapy, to examine factors influencing metabolite profiling of these drugs/compounds, and to determine the relationship between therapeutic efficacy and toxicity of their metabolites. The literature search was performed through PubMed and ScienceDirect databases up to January 2019. Out of 830 published articles, 78 articles were included in the analysis based on pre-defined inclusion and exclusion criteria. Both phase I and II enzymes metabolize the anticancer agents/herb-derived compounds . The major phase I reactions include oxidation/hydroxylation and hydrolysis, while the major phase II reactions are glucuronidation, methylation, and sulfation. Four main factors were found to influence metabolite formation, including species, gender, and route and dose of drug administration. Some metabolites were identified as active or toxic metabolites. This information is critical for cancer chemotherapy and anticancer drug development.

Modulation by extracellular matrices of monooxygenase and CYP1A1 induction in Hep G2 cells in serum-free culture

The in vitro cellular functions of differentiated cells are influenced by culture conditions. Effects of several extracellular matrices (ECMs) on cytochrome P450-dependent monooxygenases (MFOs) induction and cytochrome P4501A1 (CYP1A1) gene expression were estimated in Hep G2 cells cultured in a serum-free medium. The cells were cultured on collagen type I- and II-, fibronectin-, and matrigel-coated dishes and MFO activities were induced by the addition of 3-methylcholanthrene (MC). The induction of ethoxycoumarin O-deethylase (ECOD) and alkoxyresorufin O-dealkylase activities as well as the expression of CYP1A1 mRNA were also determined. ECOD and methoxy- and ethoxyresorufin O-dealkylase activities in Hep G2 cells were enhanced by culturing the cells using a serum-free medium on fibronectin- or matrigel-coated dishes. ECOD activity on fibronectin-coated dishes was about 3-fold higher than that using a serum-supplemented medium on untreated dishes. Furthermore, both immobilized and soluble fibronectin enhanced the induction of MFOs. The expression of CYP1A1 mRNA using fibronectin-coated dishes was about 2-fold higher than that using a serum-supplemented medium on untreated dishes. These findings suggest that the gene expression in cultured cells is greatly influenced by ECMs. By using fibronectin-coated dishes to cell culture in a serum-free medium, reproducible and highly sensitive results can be obtained in experiments using cultured cells.

Induction of cytochrome P450-dependent monooxygenase in serum-free cultured Hep G2 cells

We examined the induction of cytochrome P450-dependent mixed-function monooxygenase (MFO) in the human hepatoma cell line Hep G2 by means of several factors. The MFO activities induced in the cells cultured in medium containing five commercial sera varied significantly, and the activity in the cells cultured in the absence of serum was about twice as high as that in cells supplemented with serum. The activity of ethoxycoumarin O-deethylase was highest 12 hr after adding 3-methylcholanthrene, and it was induced by several polycyclic aromatic hydrocarbons such as benzo(a)anthracene and benzo(a)pyrene, which are usually found in urban air as environmental contaminants. Furthermore, an extract from the total suspended particles collected using a high volume air sampler, which was mutagenic in the Ames assay using Salmonella typhimurium TA98, induced the same enzyme activities in Hep G2 cells. These findings suggest that serum-free culture allows the stable and highly sensitive measurement of induced MFO activity, and that studies of MFO induction by environmental samples using human hepatoma Hep G2 cells should provide helpful information regarding the risk associated with environmental contaminants.

Response of the human hepatic tissue cultures Hep-G2 and WRL-68 to cocaine

The hydrolytic metabolism of cocaine into benzoylecgonine, ecgonine methyl ester, and ecgonine was studied in the human hepatoma cell line Hep-G2 and in the nontumorigenic fetal hepatic cell line WRL-68. Also, the toxicological response of these cells to cocaine was compared to previously published results obtained with perfused liver cells and in vivo systems. Our experiments indicated that Hep-G2 appear to have similar metabolic and toxicological patterns to in vivo and perfused cell systems. The WRL-68 tissue culture system was found to be less similar. These results suggest Hep-G2 cells can be utilized to study cocaine metabolism and toxicology, and possibly in studies involving other xenobiotic compounds.

Comparison of sulfur amino acid utilization for GSH synthesis between HepG2 cells and cultured rat hepatocytes

HepG2 cells are widely used as a model of human hepatocytes for studies of drug metabolism and toxicity. However, GSH metabolism in HepG2 cells is poorly characterized. This report describes the utilization of sulfur amino acids for GSH synthesis in HepG2 cells. In contrast to primary cultures of rat hepatocytes, which rely mostly on methionine for GSH synthesis, HepG2 cells use cystine. Their inability to utilize methionine for GSH synthesis was not due to lack of methionine uptake or low cellular ATP levels, but rather to the lack of S-adenosyl-methionine synthetase activity. When HepG2 cells were cultured overnight in medium containing cystine as the only sulfur amino acid, addition of glutamate or acivicin had minimal to no effect on cell GSH; however, addition of threonine significantly depleted cell GSH. When cystine (0.18 mM) uptake was measured, glutamate (2.5 mM), which inhibited cystine uptake in cultured rat hepatocytes, had a minimal effect in HepG2 cells. Instead, threonine (20 mM) strongly inhibited the apparent uptake of cystine by HepG2 cells. Strong inhibition by threonine of apparent cystine uptake was actually due to inhibition of cysteine uptake, which resulted from GSH-cystine mixed disulfide exchange. Radio-HPLC confirmed this. After incubating cells with [35S]cystine (0.18 mM) for 10 min, the total counts inside the cell matched the counts in the uptake medium in the form of GSH-cysteine mixed disulfide. Finally, HepG2 cells took up cysteine by both Na(+)-dependent and -independent mechanisms. The former exhibited high affinity and low capacity, whereas the latter exhibited the opposite. At a physiologic concentration of cysteine (10 microM), 68% of cysteine uptake occurred via the Na(+)-dependent system and 32% via system L1.

Hep G2 cell line as a human model for sulphate conjugation of drugs

1. The objective of this study was to examine the usefulness of the hepatoma cell line Hep G2 as a model for human sulphoconjugation of drugs, in particular stereoselective conjugation. 2. Using the substrates p-nitrophenol and dopamine, we found sulphation activities consistent with the presence of both the phenol (P) and the monoamine (M) form of the human phenolsulphotransferases in these cells. 3. The Kmapp was 3.0 microM for the sulphation of p-nitrophenol. This activity was inhibited selectively by 2,6-dichloro-4-nitrophenol, IC50 6 microM. The Kmapp was 39 microM for the sulphation of dopamine. This activity was selectively inhibited by elevated temperature. 4. The chiral adrenergic drugs (+/-)-terbutaline and (+/-)-4-hydroxypropranolol were both sulphated stereoselectively with Kmapp and Vmaxapp values for each enantiomer virtually identical to previous observations with human liver cytosol. 5. In a direct comparison, the estimated activity of the P form of phenolsulphotransferase in the Hep G2 cell line was 30% of that in human liver, whereas, surprisingly, the activity of the M form of phenolsulphotransferase was 4.5 times higher in the Hep G2 cells than in the liver.