An Improved Diagnostic Method for Chronic Hepatic Disorder: Analyses of Metallothionein Isoforms and Trace Metals in the Liver of Patients with Hepatocellular Carcinoma as Determined by Capillary Zone Electrophoresis and Inductively Coupled Plasma-Mass Spectrometry

Abstract

Metallothionein (MT) is a low molecular weight and cysteine-rich protein that binds to several heavy metals. The suggested functions of MT are detoxification of heavy metals, maintenance of trace element homeostasis, and scavenging of free radicals via the thiol groups present in the protein.1,2) Hepatocellular carcinoma (HCC) is one of the most common human tumors that occurs globally, and generally develops from chronic hepatitis (CH) and liver cirrhosis (LC). [3][4][5] It is, therefore, very important to detect and evaluate the progressing state of chronic hepatic disorder in order to diagnose the diseases.We have previously reported that abnormal accumulations of both copper (Cu) and total MT occur in the livers of Long Evans Cinnamon (LEC) rats and that these accumulations are directly related to the development of jaundice and hepatoma.6-10) Similar observations have been reported with regard to the livers of HCC patients, although the concentrations of metals and total MT accumulations differed among the studies. [11][12][13][14] Many researchers have reported that the serum copper/zinc (Cu/Zn) ratio is sufficiently sensitive to diagnose various diseases. [15][16][17] The serum Cu/Zn ratio in the patients with different hepatic diseases has been confirmed to be significantly higher than that of patients without hepatic disorders (Ctrl). [18][19][20] However, during our study, some patients with congestive heart failure, diabetes mellitus, and hypertension exhibited markedly high Cu/Zn ratio, indicating that the ratio could not be considered selective for diagnosing the diseases. On the other hand, we also reported that Cu concentrations in the human liver cytosol increased with the development of HCC. [18][19][20] The increase in Cu concentrations in the hepatic tissues were due to the distribution of Cu in MT rather than in superoxide dismutase (SOD) in the hepatic tissues.21) Based on these observations, we attempted to determine whether monitoring of MT isomers and metal concentrations in human liver is a better approach for diagnosing human liver disorder.It is well known that MT occurs in several isoforms, 22) among which MT-1 and MT-2 are induced in most organs by specific stimuli such as exposure to toxic metals and glucocorticoids. 23) Although the biological functions and physiological role of MT are not yet known, based on the results of the analysis of hepatic MT-1 and MT-2 in LEC rats we recently proposed that MT-1 is related to the metabolism or detoxification of toxic metals such as cadmium, and, MT-2 is responsible for the homeostasis of essential metals such as Cu.24) Since the pathophysiological feature of hepatic disorders in LEC rats has been reported to be very similar to that of human hepatic diseases involving HCC, 25,26) we attempted to determine MT-1 and MT-2 in the liver cytosol of humans by using a capillary zone electrophoresis (CZE). Previously, It is desirable to diagnose hepatocellular carcinoma (HCC) in the early stages during its development since its treatment is usually d...

The status of zinc in the development of hepatocellular cancer

“…Beginning with Danielsen and Steinnis in 1970, 3 ten reported population studies [3][4][5][6][7][8][9][10][11][12] have consistently demonstrated a marked decrease (~55-75%) in zinc levels in HCC tissue compared with normal liver tissue. The "typical" results are represented in Figure 1 from Kew and Mallet, 7 who concluded that "the zinc concentration in the liver cancer tissue was significantly less than that in the non-cancerous tissues, whether cirrhotic or non-cirrhotic in the HCC patients or normal from the noncancerous patients (P < 0.001 in each instance)."…”

“…Similarly, Tashiro et al studies 4 concluded that "the Zn concentration in cancerous liver was lower (55% decrease) than in noncancerous liver tissue for all twenty-three subjects." Only one study (Ebara et al 13 ) had reported a zinc increase in HCC, which was subsequently reversed by pursuant studies of the Ebara group 5,6 that showed a consistent significant decrease in zinc in HCC. In addition, our studies 14 with tissue samples from 26 HCC cases identifies the specific zinc decrease in the hepatoma cells in well-differentiated and advancing malignancy, as compared to the higher zinc in the normal hepatocytes (Fig.…”

Emerging Roles of Cadmium and Heme Oxygenase in Type-2 Diabetes and Cancer Susceptibility

“…Excessive liver copper and iron accumulations are known risk factors for liver cancer. Indeed, greater copper levels with lower MT levels were noted in neoplastic liver samples, compared with surrounding non-neoplastic liver portions (Kawata et al 2006). The MT sequestration of cadmium is considered to provide protection against acute toxicity.…”

Recent trends in CE of inorganic ions: From individual to multiple elemental species analysis

“…Cadmium, bound to the different rabbit-liver MT isoforms separated by CE, was postcapillary transformed into volatile species and online detected by ICP-MS. An ICPsector field-mass spectrometer was used for the determination of the stoichiometric Zn/protein ratio by monitoring both Zn and S after the CE separation of free Zn ions and the zinc bound to a metalloprotein [182]. Kawata et al [183] have presented a new diagnostic method for chronic hepatic disorder based on CE determination of MT isoforms and trace metals in the liver of patients. Other applications to real biological material (but with UV detection) encompassed the separation and determination of MT isoforms in rat liver cytosol [184] and horse kidney preparations [185] using polyacrylamide coated capillaries, and measuring induction of MTs in maize plantlets by chromium(VI) exposure [186].…”