Tumour-associated isoenzymes of gamma-glutamyl transferase in the serum of patients with hepatocellular carcinoma

Guide for diagnosis and treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is ranked as the 5^th common type of cancer worldwide and is considered as the 3^rd common reason for cancer-related deaths. HCC often occurs on top of a cirrhotic liver. The prognosis is determined by several factors; tumour extension, alpha-fetoprotein (AFP) concentration, histologic subtype of the tumour, degree of liver dysfunction, and the patient’s performance status. HCC prognosis is strongly correlated with diagnostic delay. To date, no ideal screening modality has been developed. Analysis of recent studies showed that AFP assessment lacks adequate sensitivity and specificity for effective surveillance and diagnosis. Many tumour markers have been tested in clinical trials without progressing to routine use in clinical practice. Thus, surveillance is still based on ultrasound (US) examination every 6 mo. Imaging studies for diagnosis of HCC can fall into one of two main categories: routine non-invasive studies such as US, computed tomography (CT), and magnetic resonance imaging, and more specialized invasive techniques including CT during hepatic arteriography and CT arterial portography in addition to the conventional hepatic angiography. This article provides an overview and spotlight on the different diagnostic modalities and treatment options of HCC.

Combined analysis of serum γ-glutamyl transferase isoenzyme II, α-L-fucosidase and α-fetoprotein detected using a commercial kit in the diagnosis of hepatocellular carcinoma

γ-glutamyl transferase isoenzyme II (GGT-II) is a sensitive biomarker of hepatocellular carcinoma (HCC). However, numerous disadvantages of the traditional manual method affected its application. The commercial kit provided a convenient and fast method for the determination of GGT-II levels. The purposes of the present study were to compare the reproducibility and sensitivity between the manual and commercial kit methods and to evaluate the diagnostic efficiency for HCC with the combined analysis of GGT-II, α-L-fucosidase (AFU) and α-fetoprotein (AFP). In patients with various liver diseases (HCC, liver cirrhosis and chronic hepatitis) and normal subjects, GGT-II was detected by manual and commercial polyacrylamide gel electrophoresis (PAGE). The levels of AFU and AFP were assayed by colorimetry and a chemiluminescence immunoassay, respectively. The commercial PAGE had equal diagnostic efficiency with traditional manual PAGE and no significant differences were observed in intra- and average-gel reproducibility and GGT-II sensitivities between the manual and commercial PAGE (P>0.05). The incidence of GGT-II detected by commercial PAGE in HCC patients was 84.1% and <8% in benign liver disease. The levels of AFU and AFP in the benign liver diseases and normal subjects were lower than those in HCC. According to the cut-off value obtained by receiver operating characteristic curves, a total of 56.6 and 59.3% of HCC patients (64 out of 113 and 67 out of 113) had AFU >636.5 μmol/l h and AFP >44.0 μg/l, respectively. There were no significant correlations between GGT-II and AFU or AFP. Combined detection of GGT-II with AFU or AFP increased the diagnostic sensitivity to 92.9 and 93.8%, respectively. These results suggest that commercial PAGE provides a simple and reproducible method for GGT-II detection. Combined determination of GGT-II with AFU or AFP exhibited superior sensitivity and specificity for the diagnosis of HCC.

Surveillance programmes for early detection of hepatocellular carcinoma

Primary hepatocellular carcinoma (HCC) is the most commonly diagnosed primary malignancy of the liver. The number of new diagnosed cases of HCC seems to be on a rise worldwide. HCC is typically diagnosed in patients with underlying liver cirrhosis (> 90% cases) regardless of aetiology; over a five-year follow-up period HCC develops in 15–20% of patients with cirrhosis. Patients who are at a high risk of HCC development (i.e. individuals with liver cirrhosis, especially/or chronically infected with HBV or HCV) should undergo regular screening for HCC; the current screening standard comprises liver ultrasonography and determination of α-fetoprotein (AFP) concentration in blood serum at ca. 6 months’ intervals (now has been excluded from current diagnostic standards). Only such diagnostic methods are capable of detecting HCC early, and thus make it possible to treat the cancer effectively.

National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines for use of tumor markers in liver, bladder, cervical, and gastric cancers

BACKGROUND

Updated National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines for the use of tumor markers in the clinic have been developed.

METHODS

Published reports relevant to use of tumor markers for 4 cancer sites--liver, bladder, cervical, and gastric--were critically reviewed.

RESULTS

Alpha-fetoprotein (AFP) may be used in conjunction with abdominal ultrasound for early detection of hepatocellular carcinoma (HCC) in patients with chronic hepatitis or cirrhosis associated with hepatitis B or C virus infection. AFP concentrations >200 microg/L in cirrhotic patients with typical hypervascular lesions >2 cm in size are consistent with HCC. After a diagnosis of HCC, posttreatment monitoring with AFP is recommended as an adjunct to imaging, especially in the absence of measurable disease. Although several urine markers have been proposed for bladder cancer, none at present can replace routine cystoscopy and cytology in the management of patients with this malignancy. Some may, however, be used as complementary adjuncts to direct more effective use of clinical procedures. Although carcinoembryonic antigen and CA 19-9 have been proposed for use gastric cancer and squamous cell carcinoma antigen for use in cervical cancer, none of these markers can currently be recommended for routine clinical use.

CONCLUSIONS

Implementation of these recommendations should encourage optimal use of tumor markers for patients with liver, bladder, cervical, or gastric cancers.

Present and future possibilities for early diagnosis of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) represents the fifth most common cancer in the world, and the third most frequent oncological cause of death. The incidence of HCC is on the increase. HCC typically develops in patients with chronic liver diseases, and cirrhosis, usually with viral etiology, is the strongest predisposing factor. Nowadays HCC diagnosis is a multistage process including clinical, laboratory, imaging and pathological examinations. The prognosis of HCC is mostly poor, because of detection at an advanced, non-resectable stage. Potentially curative treatment (surgery) is limited and really possible only for cases with small HCC malignancies. For this reason, more effective surveillance strategies should be used to screen for early occurrence of HCC targeted to the population at risk. So far, the generally accepted serological marker is α-fetoprotein (AFP). Its diagnostic accuracy is unsatisfactory and questionable because of low sensitivity, therefore there is a strong demand by clinicians for new HCC-specific biomarkers. In this review, we will focus on other biomarkers that seem to improve HCC diagnosis, such as AFP-L3, des-γ-carboxyprothrombin, α-l-fucosidase, γ-glutamyl transferase, glypican-3, squamous cell carcinoma antigen, a new generation of immunoglobulin M-immunocomplexes, and very promising gene-expression profiling.

Clinical application of an enzyme-linked immunosorbent assay detecting hepatoma-specific gamma-glutamyltransferase

AIM

To develop a sandwich enzyme-linked immunosorbent assay (ELISA) measuring hepatoma-specific datura stramonium agglutinin-tightly bounding gamma-glutamyltransferase (DSA-GGT) and evaluate its clinical application for hepatocellular carcinoma (HCC) diagnosis.

METHODS

Serum DSA-GGT concentrations were measured with the sandwich ELISA system in 96 patients with HCC, 240 patients with chronic liver diseases and 119 healthy subjects. The diagnostic performance of DSA-GGT for HCC was assessed using receiver operating characteristic (ROC) curves. The diagnostic accuracy of DSA-GGT was compared with serum alpha-fetoprotein (AFP).

RESULTS

The area under the ROC curve of DSA-GGT in discriminating patients with HCC from non-HCC was 0.865 (95% confidence interval: 0.818-0.915, P < 0.001). Serum DSA-GGT was positive in 67 out of 96 patients with HCC and 23 out of 240 patients with non-HCC diseases. The sensitivity and specificity of DSA-GGT and AFP for the diagnosis of HCC were 69.8% and 90.5%, and 72.9% and 89.1%, respectively. A higher sensitivity (93.8%) in the identification of HCC was observed by combining DSA-GGT and AFP.

CONCLUSION

The sandwich ELISA system showed good reliability and reproducibility, and using the measurement, we found that serum DSA-GGT was a valuable marker of HCC, as a usable complementary to AFP. The sensitivity for identifying HCC could be significantly improved by combining DSA-GGT and AFP, and the combination could be used in large-scale screening for HCC in susceptible individuals.

Diagnostic value of protein induced by vitamin K absence (PIVKAII) and hepatoma-specific band of serum gamma-glutamyl transferase (GGTII) as hepatocellular carcinoma markers complementary to alpha-fetoprotein

Serum protein induced by vitamin K absence or antagonist II (PIVKAII), hepatoma-specific band of serum gamma-glutamyl transferase (GGTII), and alpha-fetoprotein (AFP) levels were determined in 120 patients with hepatocellular carcinoma (HCC) and 90 patients with cirrhosis. The mean serum concentration of PIVKAII in HCC patients was higher than that in cirrhotic patients. A total of 53.3% of patients (64 out of 120) with HCC had PIVKAII levels above 40 mAU ml(-1). However, only 13 patients with cirrhosis had higher PIVKA II levels. Of 32 small HCC patients, 13 (40.6%) had PIVKAII values above 40 mAU ml(-1). An increased concentration of AFP (i.e. 20 ng ml(-1)) was observed in 70 out of 120 (58.3%) patients with HCC and in 33 out of 90 (36.7%) patients with cirrhosis. Positive GGTII was found in 74.0% (89 out of 120) cases of HCC (sensitivity), in 16 of 90 cases of cirrhosis, and 14 of 32 (43.8%) small HCC patients had GGTII positive. No significant correlation was found between serum levels of AFP and PIVKAII. Combining the information from PIVKAII, AFP, and GGTII significantly increases the sensitivity over AFP alone. PIVKAII and GGTII are useful tumour markers complementary to AFP for diagnosis of HCC.

Evaluation of the albumin-gamma-glutamyltransferase isoenzyme as a diagnostic marker of hepatocellular carcinoma-complicating liver cirrhosis

AIM

The present study aimed to evaluate the usefulness of albumin-gamma-glutamyltransferase isoenzyme in the diagnosis of hepatocellular carcinoma.

METHODS

Electrophoretic assays of gamma-glutamyltransferase isoenzymes were performed on sera from 190 cirrhotics with (n = 131) or without (n = 59) hepatocellular carcinoma, 36 patients with chronic active hepatitis, 17 patients with liver metastases, and 16 control subjects. In the group of cirrhotic patients, the serum level of alpha-fetoprotein was also assessed.

RESULTS

Albumin-gamma-glutamyltransferase was found in 88 of 131 cirrhotics with hepatocellular carcinoma, 14 of 59 cirrhotics without hepatocellular carcinoma, nine of 17 patients with liver metastases, and in none of the chronic active hepatitis or control patients. Within the cirrhotic subgroup, albumin-gamma-glutamyltransferase was effective in detecting hepatocellular carcinoma in general (sensitivity: 67%; specificity: 76%; diagnostic accuracy: 70%), and small hepatocellular carcinoma (< 3 cm; corresponding figures: 58, 76, and 69%). The best alpha-fetoprotein value discriminating between hepatocellular carcinoma and non-hepatocellular carcinoma cirrhotics was 20 ng/mL (sensitivity: 54%; specificity 85%; accuracy: 64%). The combined use of albumin-gamma-glutamyltransferase and alpha-fetoprotein, > 20 ng/mL, was associated with greater sensitivity and accuracy (84 and 74%, respectively) than those observed with either of the two markers considered alone.

CONCLUSIONS

Albumin-gamma-glutamyltransferase appears to be a sensitive diagnostic marker of both advanced and small hepatocellular carcinoma-complicating liver cirrhosis.

Screening for hepatocellular carcinoma

To determine the role of screening and to screen in a cost-effective manner, it is important to define the high-risk patient population that is most likely to benefit from screening and to identify a readily available diagnostic modality that is sensitive, specific, and inexpensive. Moreover, to have a major effect on the outcome of hepatocellular carcinoma, the test should be applicable in the majority of high-risk subjects. Herein, we identify the high-risk patient population, discuss various diagnostic modalities, and recommend a practical and cost-effective strategy for screening.

Gamma glutamyl transferase

Serum gamma-glutamyl transferase (GGT) has been widely used as an index of liver dysfunction and marker of alcohol intake. The last few years have seen improvements in these areas and advances in understanding of its physiological role in counteracting oxidative stress by breaking down extracellular glutathione and making its component amino acids available to the cells. Conditions that increase serum GGT, such as obstructive liver disease, high alcohol consumption, and use of enzyme-inducing drugs, lead to increased free radical production and the threat of glutathione depletion. However, the products of the GGT reaction may themselves lead to increased free radical production, particularly in the presence of iron. There have also been important advances in the definition of the associations between serum GGT and risk of coronary heart disease, Type 2 diabetes, and stroke. People with high serum GGT have higher mortality, partly because of the association between GGT and other risk factors and partly because GGT is an independent predictor of risk. This review aims to summarize the knowledge about GGT's clinical applications, to present information on its physiological roles, consider the results of epidemiological studies, and assess how far these separate areas can be combined into an integrated view.

Repetitive 5-azacytidine treatments of Fao cells induce a stable and strong expression of gamma-glutamyl transpeptidase

The role of DNA methylation in the expression of the rat gamma-glutamyl transpeptidase (GGT) gene was assessed in the Fao cell line using a hypomethylating agent, 5-azacytidine. Ten repetitive treatments of the cells, with 8 microM 5-azacytidine for 24 h, led to 13- and 80-fold increases, respectively, in GGT activity and in GGT mRNA level. The DNA methylation patterns generated by the isoschizomeric restriction enzymes Hpa II and Msp I indicated that the GGT gene, highly methylated in Fao cells, became strongly demethylated after 5-azacytidine treatments. Thus, DNA demethylation increases the expression of the GGT gene. 5-Azacytidine treatments also increased, but to a lesser extent, mRNAs level for actin, albumin, mitochondrial aspartate aminotransferase, aldolase B mRNAs (12- to 16-fold) as well as for tubulin, gluthathione transferase, and tyrosine aminotransferase mRNAs (2- to 5-fold). The GGT gene expression was further studied in B4 cells, cloned from the demethylated Fao cell population. This clone B4 exhibited a stable and strong GGT activity and a highly demethylated GGT gene. Among the three GGT mRNA I, II, or III, transcribed from three different promoters of the single rat GGT gene, only mRNA III was detected in Fao cells and was increased in clone B4, indicating that the demethylation acts on the promoter for mRNA III. The analysis of the differentiation state of B4 cells, as compared to Fao cells, showed a loss of the regulation of GGT and aspartate aminotransferase genes by dexamethasone, as well as a loss of the gluconeogenic pathway. Interestingly, B4 cells have retained many other specific functions of hepatic differentiation and have acquired alpha-fetoprotein expression; thus this clone exhibits the characteristics of a hepatic fetal phenotype.

Electrophoretic behavior and partial characterization of disease-associated serum forms of gamma-glutamyltransferase

We have recently devised an improved procedure for the rapid electrophoretic separation of multiple forms of serum gamma-glutamyltransferase (GGT). This procedure is based on the separation on cellulose acetate strips, usually employed for lipoprotein electrophoresis, followed by visualization with a fluorescent reagent. The method is highly sensitive and the fractions are more clearly resolved than with other procedures. Reference intervals have been evaluated in the sera from 142 healthy subjects and the patterns (two GGT forms comigrating with alpha 1 and alpha 2-globulin) are reproducible. In 150 sera from patients with various hepatobiliary diseases (including neoplasias), acute pancreatitis and non liver-involving neoplasias, we observed some disease-specific GGT forms: an albumin comigrating enzyme (Alb-GGT) specific of liver neoplasia; a gamma-globulin comigrating GGT (gamma-GGT) and a nonmigrating isoform (dep-GGT) both specifically associated to extrahepatic jaundice. Multiple lipoprotein fraction precipitation showed that beta-, gamma- and dep-GGT are complexes between GGT and low density lipoprotein and very low density lipoproteins (LDL + VLDL), and that some of the alpha 1-GGT from cirrhotic patients is a complex between GGT and high density lipoprotein (HDL). GGT fractions from normal subjects and Alb-GGT from patients with liver neoplasia do not appear to be complexed with lipoproteins.(ABSTRACT TRUNCATED AT 250 WORDS)

The prevalence of variant alkaline phosphatase in hepatocellular carcinoma in southern African blacks

The prevalence of variant alkaline phosphatase in the serum of 335 southern African blacks with hepatocellular carcinoma was determined using polyacrylamide gel electrophoresis. The isoenzyme was detected in 2% (seven of 335) of the patients: it could not be found in the serum of 300 matched, healthy individuals or in 56 patients with various benign hepatic diseases. Variant alkaline phosphatase is thus of little use as a diagnostic marker of hepatocellular carcinoma in southern African blacks. The reported prevalence of this isoenzyme in hepatocellular carcinoma ranges between 3% and 31%. Higher frequencies usually are recorded in populations with a low incidence of the tumor, and the lowest frequencies have been found in Chinese patients. Our finding of variant alkaline phosphatase in only 2% of another high incidence population fits this trend. Patients with tumors that secreted the variant isoenzyme had a significantly higher serum total alkaline phosphatase activity than those with tumors lacking this property.

Tumour markers in diagnosis and management

The 20-year period since the discovery of AFP by Abelev has seen the introduction of a wide range of new tumour markers and it is now clear that PLC is biologically heterogeneous. Hepatoblastomas, fibrolamellar carcinomas, hepatocellular carcinomas and cholangiocarcinomas may secrete a variety of distinctive markers which are predominantly glycoproteins, and may resemble those found in placenta or fetal liver. Diagnostically, AFP remains the best marker for HCC, both in sensitivity and specificity; it is known to consist of isoforms. In patients with elevated serum AFP and filling defects on liver scan, Con A reactive AFP may differentiate PLC from hepatic metastases, whilst fucosylated AFP may distinguish PLC from benign disorders when AFP is non-diagnostically elevated. With this recognition of tumour heterogeneity the value of a multiple-marker approach has become apparent. The measurement of vitamin B12 binding protein and neurotensin should lead to the detection of most patients with the fibrolamellar variant of HCC and many of these should be resectable. In patients with normal serum AFP levels, HCC-associated GGTP is of major value whilst in low-incidence areas for HCC, patients should also be screened for H-ALP; using a multiple marker approach in high-risk groups, 90% of clinically diagnosed hepatocellular carcinomas are serologically positive. The Chinese and Alaskan studies, in which small, potentially resectable tumours were detected, suggest that it is now possible to achieve 5-year survival figures of up to 60% in HCC patients detected by screening. The value of such a strategy in low-incidence countries is currently under study. In patient monitoring, as in diagnosis, AFP remains the outstanding marker. In AFP-negative patients, other markers including vitamin B12-binding protein, neurotensin, HCC-specific isoenzymes, des-gamma-carboxy-prothrombin and alpha-fucosidase, are of undoubted diagnostic value, but their value as indicants of disease progression remains to be established. In monitoring the response of hepatic metastases, CEA remains the least unsatisfactory marker but should always be used in conjunction with serial ultrasound scans. Tumour markers now play an important role in the diagnosis and monitoring of PLC but a role is also emerging in tumour imaging and drug targeting. The next 20 years should see the introduction of tumour markers of high sensitivity and specificity which make a fundamental contribution not only to detection and monitoring, but also to the effective treatment of liver cancer.