Establishment of a human hepatoma cell line, HLE/2E1, suitable for detection of p450 2E1-related cytotoxicity

Integrated multi-omics data analysis identifying novel drug sensitivity-associated molecular targets of hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the most common type of liver cancer and the third-leading cause of malignancy-associated mortality worldwide. HCC cells are highly resistant to chemotherapeutic agents. Therefore, there are currently only two US Food and Drug Administration-approved drugs available for the treatment of HCC. The objective of the present study was to analyze the results of previously published high-throughput drug screening, and in vitro genomic and transcriptomic data from HCC cell lines, and to integrate the obtained results to define the underlying molecular mechanisms of drug sensitivity and resistance in HCC cells. The results of treatment with 225 different small molecules on 14 different HCC cell lines were retrieved from the Genomics of Drug Sensitivity in Cancer database and analyzed. Cluster analysis using the treatment results determined that HCC cell lines consist of two groups, according to their drug response profiles. Continued analyses of these two groups with Gene Set Enrichment Analysis method revealed 6 treatment-sensitive molecular targets (epidermal growth factor receptor, mechanistic target of rapamycin, deoxyribonucleic acid-dependent protein kinase, the Aurora kinases, Bruton's tyrosine kinase and phosphoinositide 3-kinase; all P<0.05) and partially effective drugs. Genetic and genome-wide gene expression data analyses of the determined targets and their known biological partners revealed 2 somatically mutated and 13 differentially expressed genes, which differed between drug-resistant and drug-sensitive HCC cells. Integration of the obtained data into a short molecular pathway revealed a drug treatment-sensitive signaling axis in HCC cells. In conclusion, the results of the present study provide novel drug sensitivity-associated molecular targets for the development of novel personalized and targeted molecular therapies against HCC.

CYP2E1 and oxidative liver injury by alcohol

Ethanol-induced oxidative stress seems to play a major role in mechanisms by which ethanol causes liver injury. Many pathways have been suggested to contribute to the ability of ethanol to induce a state of oxidative stress. One central pathway seems to be the induction of cytochrome P450 2E1 (CYP2E1) by ethanol. CYP2E1 metabolizes and activates many toxicological substrates, including ethanol, to more reactive, toxic products. Levels of CYP2E1 are elevated under a variety of physiological and pathophysiological conditions and after acute and chronic alcohol treatment. CYP2E1 is also an effective generator of reactive oxygen species such as the superoxide anion radical and hydrogen peroxide and, in the presence of iron catalysts, produces powerful oxidants such as the hydroxyl radical. This review article summarizes some of the biochemical and toxicological properties of CYP2E1 and briefly describes the use of cell lines developed to constitutively express CYP2E1 and CYP2E1 knockout mice in assessing the actions of CYP2E1. Possible therapeutic implications for treatment of alcoholic liver injury by inhibition of CYP2E1 or CYP2E1-dependent oxidative stress will be discussed, followed by some future directions which may help us to understand the actions of CYP2E1 and its role in alcoholic liver injury.

Toxicity of ethanol and acetaldehyde in hepatocytes treated with ursodeoxycholic or tauroursodeoxycholic acid

In hepatocytes ethanol (EtOH) is metabolized to acetaldehyde and to acetate. Ursodeoxycholic acid (UDCA) and tauroursodeoxycholic acid (TUDCA) are said to protect the liver against alcohol. We investigated the influence of ethanol and acetaldehyde on alcohol dehydrogenase (ADH)-containing human hepatoma cells (SK-Hep-1) and the protective effects of UDCA and TUDCA (0.01 and 0.1 mM). Cells were incubated with 100 and 200 mM ethanol, concentrations in a heavy drinker, or acetaldehyde. Treatment with acetaldehyde or ethanol resulted in a decrease of metabolic activity and viability of hepatocytes and an increase of cell membrane permeability. During simultaneous incubation with bile acids, the metabolic activity was better preserved by UDCA than by TUDCA. Due to its more polar character, acetaldehyde mostly damaged the superficial, more polar domain of the membrane. TUDCA reduced this effect, UDCA was less effective. Damage caused by ethanol was smaller and predominantly at the more apolar site of the cell membrane. In contrast, preincubation with TUDCA or UDCA strongly decreased metabolic activity and cell viability and led to an appreciable increase of membrane permeability. TUDCA and UDCA only in rather high concentrations reduce ethanol and acetaldehyde-induced toxicity in a different way, when incubated simultaneously with hepatocytes. In contrast, preincubation with bile acids intensified cell damage. Therefore, the protective effect of UDCA or TUDCA in alcohol- or acetaldehyde-treated SK-Hep-1 cells remains dubious.

Increased cytotoxicity of carbon tetrachloride in a human hepatoma cell line overexpressing cytochrome P450 2E1

Cytotoxic free radicals generated during the metabolism of carbon tetrachloride by cytochrome P450 2E1 (CYP2E1) are thought to cause hepatotoxicity. Here, the cytotoxic effects of carbon tetrachloride in a liver cell line expressing CYP2E1 (HLE/2E1) are compared with those in the mother cell line (HLE). The effects of carbon tetrachloride on the gene expression of HSP70, a potential marker of oxidative stress, were also examined. The viability of HLE/2E1 cells after exposure to carbon tetrachloride was significantly decreased compared with that of HLE cells. Northern blot analysis revealed that the HSP70 mRNA level was significantly increased after carbon tetrachloride treatment in both cell lines, while the magnitude of its increase was much greater in HLE/2E1 cells than in HLE cells. These results suggest that the oxidative stress induced by CYP2E1 plays an important role in the increase in cytotoxicity of carbon tetrachloride in CYP2E1-overexpressing cells.