Utility of plasma circulating mRNA as a marker to detect hepatic injury

Albumin and apolipoprotein H mRNAs in human plasma as potential clinical biomarkers of liver injury: analyses of plasma liver-specific mRNAs in patients with liver injury

CONTEXT

Plasma liver-specific mRNAs are useful biomarkers of hepatotoxicity in rats.

OBJECTIVE

To investigate the potential application of liver-specific mRNAs as biomarkers for liver injury in humans.

METHODS

We determined the plasma levels of liver-specific mRNAs by real-time qRT-PCR in healthy donors and patients with liver injury.

RESULTS

Plasma levels of albumin (ALB) and apolipoprotein H (APOH) mRNAs increased in patients with elevated serum alanine aminotransferase. These mRNAs also increased in plasma after transcatheter arterial chemoembolization, which induces specific injury to liver.

CONCLUSIONS

We demonstrated the potential application of plasma ALB and APOH mRNAs as clinical biomarkers for liver injury.

Injured hepatocyte-released microvesicles induce bone marrow-derived mononuclear cells differentiation

The ability of bone marrow-derived mononuclear cells (BMMCs) to differentiate into hepatocyte-like cells under different conditions has been demonstrated previously. In the present study, we investigated the effect of CCl4-injured hepatocytes on the differentiation of the non-adherent (NAD) fraction of BMMCs. Differentiation (cell fate) was analyzed after 2, 6 and 24h of co-culture by gene and protein expression and by urea production. We also evaluated the presence of microvesicles (MVs) in the supernatant of differentiated cells, their content and the ability of these cells to absorb them. Hepatocyte-like characteristics were observed in the NAD cells after 24h of co-culture with injured hepatocytes. Cells that were co-cultured with healthy hepatocytes did not present signs of differentiation at any analyzed time point. Analysis of the supernatant from differentiated cells revealed the presence of MVs carrying hepatocyte-specific mRNAs, including Albumin, Coagulation factor V, Alpha-fetoprotein, and Cytokeratin 18. The incorporation of injured hepatocyte-derived MVs by NAD cells was shown at 24h, suggesting a possible role for MVs in the induction of cell plasticity.

Development of blood biomarkers for drug-induced liver injury: an evaluation of their potential for risk assessment and diagnostics

Drug-induced liver injury (DILI) remains a rare but serious complication in drug therapy that is a primary cause of drug failure during clinical trials. Conventional biomarkers, particularly the serum transaminases and bilirubin, serve as useful indicators of hepatocellular or cholestatic liver injury, respectively, but only after substantial and sometimes irreversible tissue damage. Ideally, more sensitive biomarkers that respond very early before irreversible injury has occurred would offer improved outcomes. Novel biomarkers are initially being developed in animal models exposed to intrinsically hepatotoxic stimuli. However, the eventual translation to human populations, even those with known risk factors that predispose the liver to drug toxicity, would be the fundamental goal. Ultimately, some might even be applicable for the early identification of individuals predisposed to idiosyncratic hepatotoxicity potential. This article reviews recent progress in the discovery and qualification of novel biomarkers for DILI and delineates the path to eventual utilization for risk assessment. Some major categories of plasma or serum biomarkers surveyed include proteins, cytokines, circulating mRNAs, and microRNAs.

Identification of novel liver-specific mRNAs in plasma for biomarkers of drug-induced liver injury and quantitative evaluation in rats treated with various hepatotoxic compounds

Circulating liver-specific mRNAs such as albumin (Alb) and α-1-microglobulin/bikunin precursor (Ambp) have been reported to be potential biomarkers for drug-induced liver injury (DILI). We identified novel circulating liver-specific mRNAs and quantified them, together with the two previously reported mRNAs, in plasma from rats treated with various hepatotoxicants to validate circulating liver-specific mRNAs as biomarkers for DILI. Among six genes selected from the database, high liver specificity of apolipoprotein h (Apoh) and group-specific component (Gc) mRNAs were confirmed by reverse transcription (RT)-PCR and the copy numbers of these mRNAs elevated in plasma from rats treated with thioacetamide. Liver-specific mRNAs (Alb, Ambp, Apoh, and Gc) were quantified by real-time RT-PCR in plasma from rats with single dosing of seven hepatotoxicants. There were noticeable interindividual and intercompound variabilities in the severity of liver injury. The levels of four mRNAs increased almost in parallel and correlated with changes in the alanine aminotransferase (ALT) values and the hepatocellular necrosis scores at 24h after dosing. It was noteworthy that the magnitude of the increases in mRNA levels was greater than that in the ALT value. Time course analysis within 24h after dosing revealed that the timing of the increase was different among mRNA species, and the plasma levels of Alb and Gc mRNAs increased substantially earlier than the ALT values, suggesting that patterns of changes in circulating liver-specific mRNAs indicate the progression of liver injury. These results strongly support the reliability and usefulness of the four circulating liver-specific mRNAs as biomarkers for DILI.

Liver extracellular vesicles in health and disease

Extracellular vesicles (EVs) play an important role in cell-to-cell communication. Although there are different kinds of vesicles, each with their own secretion and capture biology, all of them carry a cargo of proteins, lipids, metabolites and nucleic acids. They act as vehicles for exchange of biological materials and signals and are involved in the regulation of various physiological processes. Liver is an essential organ containing different cell populations fulfilling various functions, which need to be strictly controlled and coordinated. There are a few articles showing the role of liver-derived EVs. On the basis of them, we present here a hypothesis of the implication of such vesicles in the physiology of the liver. Different liver cell types, including hepatocytes, cholangiocytes and stellate cells, secrete and capture EVs and interact with them. Liver injury changes the abundance and cargo of EVs; these changes are likely to be important for the outcome of stress response. Although a substantial effort has been put into the characterization of EVs in isolated populations, it is only recently that some more comprehensive information has begun to appear. In this article, we hypothesize about the role of EVs in liver microenvironment and their possible function using published data from both hepatic and non-hepatic systems.

Frontiers in preclinical safety biomarkers: microRNAs and messenger RNAs

The measurement of plasma microRNAs (miRNAs) and messenger RNAs (mRNAs) is the most recent effort to identify novel biomarkers in preclinical safety. These genomic markers often display tissue-specific expression, may be released from the tissues into the plasma during toxic events, change early and with high magnitude in tissues and in the blood during specific organ toxicities, and can be measured using multiplex formats. Their validation as biomarkers has been challenged by the technical difficulties. In particular, the concentration of miRNAs in the plasma depends on contamination by miRNAs originating from blood cells and platelets, and the relative fraction of miRNAs in complexes with Argonaute 2, high-density lipoproteins, and in exosomes and microvesicles. In spite of these hurdles, considerable progress has recently been made in assessing the potential value of miRNAs in the clinic, especially in cancer patients and cardiovascular diseases. The future of miRNAs and mRNAs as biomarkers of disease and organ toxicity depends on our ability to characterize their kinetics and to establish robust collection and measurement methods. This review covers the basic biology of miRNAs and the published literature on the use of miRNAs and mRNAs as biomarkers of specific target organ toxicity.

Circulating cell-free human telomerase reverse transcriptase mRNA in plasma and its potential diagnostic and prognostic value for gastric cancer

BACKGROUND

Our aims were to detect circulating cell-free human telomerase reverse transcriptase (hTERT) mRNA in the plasma of gastric cancer patients and evaluate its potential diagnostic and prognostic value.

METHODS

Real-time quantitative reverse transcription-polymerase chain reaction was employed to detect circulating cell-free hTERT mRNA from 118 gastric cancer patients, 40 chronic atrophic gastritis (CAG) patients, and 58 healthy controls.

RESULTS

Circulating cell-free hTERT mRNA was detected in all gastric cancer patients, 39 (97.5 %) CAG patients and 56 (96.6 %) healthy control individuals, respectively. However, it was higher in gastric cancer than in CAG and healthy controls (all at P < 0.05). Moreover, its high level was significantly correlated with clinical stages (P < 0.001) and lymph nodes metastasis (P < 0.001). There was no difference between circulating cell-free mRNA and other parameters. The area under the receiver operating characteristic (ROC) curve was 0.891, and the optimal cut-off point was 0.18, providing a sensitivity of 66 % and a specificity of 87 %. The ROC analysis showed that the diagnosis capability of circulating cell-free mRNA was statistically significantly higher than that of carcinoembryonic antigen (CEA) and cancer antigen 19-9 (CA19-9), alone [CEA (0.656); CA19-9 (0.722)] or in combination (0.756). Kaplan-Meier analysis demonstrated a correlation between increased circulating cell-free hTERT mRNA and reduced disease-free survival (P < 0.001) and overall survival (P < 0.001). Cox analysis indicated that it was an independent prognostic factor for disease-free survival and overall survival.

CONCLUSIONS

We concluded that circulating cell-free hTERT mRNA might serve as a potential and useful noninvasive tumor marker for gastric cancer.

Quantification of BCR-ABL mRNA in plasma/serum of patients with chronic myelogenous leukemia

Quantification of tumor-associated mRNA extracted from blood cells/tissues containing tumor cells is used for evaluation of treatment efficacy or residual tumor cell burden in tumors including leukemia. However, this method using tumor cell-containing blood/tissue is difficult to evaluate the whole tumor cell burden in the body. In order to establish an efficient method to evaluate the whole tumor cell burden in the body, we tried to quantify tumor-associated mRNA existing in plasma/serum instead of leukemia cell-containing blood cells in patients with chronic myelogenous leukemia (CML) and compared the levels of BCR-ABL mRNA between plasma/serum and peripheral blood cells. mRNA of BCR-ABL, WT1 or GAPDH (control molecule) was detected by real-time RT-PCR using RNA extracted from plasma/serum of almost all the patients with CML. Copy numbers of BCR-ABL mRNA were significantly correlated between plasma/serum and peripheral blood cells. However, levels of BCR-ABL mRNA extracted from serum were low compared with those extracted with peripheral blood cells. The present findings suggest that although real-time RT-PCR of mRNA existing in plasma/serum could be used for evaluating the whole tumor cell burden in the body, it's required to establish an efficient method to quantify plasma/serum mRNA by nature without degrading during the procedure.

Genomic indicators in the blood predict drug-induced liver injury

Genomic biomarkers for the detection of drug-induced liver injury (DILI) from blood are urgently needed for monitoring drug safety. We used a unique data set as part of the Food and Drug Administration led MicroArray Quality Control Phase-II (MAQC-II) project consisting of gene expression data from the two tissues (blood and liver) to test cross-tissue predictability of genomic indicators to a form of chemically induced liver injury. We then use the genomic indicators from the blood as biomarkers for prediction of acetaminophen-induced liver injury and show that the cross-tissue predictability of a response to the pharmaceutical agent (accuracy as high as 92.1%) is better than, or at least comparable to, that of non-therapeutic compounds. We provide a database of gene expression for the highly informative predictors, which brings biological context to the possible mechanisms involved in DILI. Pathway-based predictors were associated with inflammation, angiogenesis, Toll-like receptor signaling, apoptosis, and mitochondrial damage. The results show for the first time and support the hypothesis that genomic indicators in the blood can serve as potential diagnostic biomarkers predictive of DILI.

Biomarkers for drug-induced liver injury

Of the estimated 10,000 documented human drugs, more than 1000 have been associated with drug-induced liver injury (DILI), although causality has not always been established clearly. Numerous biomarkers for DILI have been explored, but less than ten are adopted or qualified as valid by the US FDA. The biomarkers for DILI are individual or a panel of proteins, nucleic acids or metabolites from various sources, such as the liver, blood and urine. While most DILI biomarkers are drug independent, some possibly 'drug-specific' DILIs have been explored, but specificity and sensitivity of both types need to be improved for the diagnosis of DILI during drug development and in clinical practice. Novel approaches for DILI biomarkers have been actively investigated recently, but produced mainly animal-based biomarkers, which are possibly useful for drug development, but are not suitable or have not been validated for clinical applications. This review summarizes the current practice and future perspectives for DILI biomarkers.

Aberrant concentrations of liver-derived plasma albumin mRNA in liver pathologies

BACKGROUND

We hypothesized that liver-derived mRNA, such as ALB (albumin) mRNA, would be released into human plasma with liver cell death.

METHODS

We genotyped ALB mRNA molecules in samples of plasma and whole blood from liver and bone marrow transplant recipients by RNA single-nucleotide polymorphism analysis. Plasma and whole blood ALB mRNA genotypes were compared with the DNA genotypes of the recipients and donors. A reverse-transcription quantitative real-time PCR assay was used to measure plasma ALB mRNA concentrations in 107 patients [hepatocellular carcinoma (HCC), cirrhosis, or chronic hepatitis B (CHB)] and 207 healthy controls.

RESULTS

The RNA genotype data revealed ALB mRNA in plasma to be liver derived, whereas tissue compartments other than the liver also contributed to the ALB mRNA detected in whole blood. Statistically significant increases in plasma ALB mRNA concentrations were observed for HCC, cirrhosis, and active CHB, compared with controls. A cutoff of 835 copies/mL of plasma ALB mRNA identified by ROC curve analysis showed 85.5% diagnostic sensitivity and 92.8% diagnostic specificity for the detection of liver pathologies. Only 21.5% of patients with liver pathologies had increased alanine aminotransferase (ALT) activities, whereas 73.8% had increased plasma ALB mRNA concentrations. Only 48.6% of the HCC patients had increased serum alpha-fetoprotein concentrations, whereas 91.4% had increased plasma ALB mRNA concentrations.

CONCLUSIONS

ALB mRNA is liver specific in plasma, but not in whole blood. Plasma ALB mRNA is increased in some liver pathologies and may be more diagnostically sensitive than alpha-fetoprotein and ALT.