Polymorphisms of hemochromatosis, and alpha-1 antitrypsin genes in Egyptian HCV patients with and without hepatocellular carcinoma
Introduction
Hepatocellular carcinoma (HCC) is ranked to be the most common cancer in many countries. HCC was reported to be the fifth most common cancer in males, the eighth common cancer in females and about 560,000 cases are discovered per year, more than 80% of which occur in the developing countries (Levrero, 2006).
In Egypt, HCC was reported to account for about 4.7% of chronic liver disease (CLD) patients. The rising trend of HCC has been associated with increased prevalence of hepatitis C virus (HCV) infection. However, it seems that cirrhosis is the common pathway by which several risk factors exert their carcinogenic effect (El-Zayadi et al., 2005). So the search for epidemiologic, biologic, or genetic factors that could help to select patients at higher risk and thus to modulate the indications of screening procedures is necessary (Llovet et al., 2004). Moreover, identification of predictive factors could lead to a better diagnosis and planning of new prevention strategies in these patients (Lodato et al., 2006).
Hereditary hemochromatosis is an autosomal recessive condition characterized by excessive iron deposition in hepatocytes due to an increased intestinal absorption. HFE gene, the name assigned to the hemochromatosis locus in the genome database, has been identified on the short arm of chromosome 6, about 4 megabases telomeric to the major histocompatibility complex (MHC). This gene encodes 343 amino acid protein that exhibits significant similarity to human leucocytes antigen (HLA) class Ι molecules. The two missense mutations C282Y and H63D in the HFE gene explain most of the cases of hemochromatosis (Feder et al., 1996). Eighty percent to 100% of these patients are homozygotes for the C282Y mutation, and approximately 5% are compound heterozygotes (Fargion et al., 1992, Kew, 1990).
Among hemochromatotic patients, 6% of men and 1.5% of women are at absolute risk of liver cancer (Elmberg et al., 2003). However, a cross-sectional study showed that progression to HCC among hemochromatotic patients is mostly variable from one population to another, depending mainly on exposure to environmental factors that synergize the current underlying gene mutation (Willis et al., 2005).
Alpha-1 antitrypsin (A1AT) is an acute phase 52 kDa serine protease inhibitor that is primarily synthesized and secreted by the hepatocytes in the liver [Rogers et al., 1983]. It is present in all tissues of the body with its primary role being to inhibit the enzyme neutrophil elastase (NE) (Travis et al., 1985).
The A1AT gene is located on the q arm of chromosome 14 at position 14q32.1 (De Serres et al., 2002). It is a 12.2-kilobase pair gene composed of seven exons and six introns. The protein is encoded by the protease inhibitor (Pi) locus. The Pi locus is highly polymorphic, resulting in different A1AT isotypes that can be detected by electrophoresis (Kok et al., 2007).
The normal gene is designated PiM, and at least 100 additional normal and deficiency alleles have been described (Crystal et al., 1989). The two most common variant or deficient alleles are S and Z. The S mutation resulted from a single base-pair substitution in exon 3 of thymidine for adenine (Glu264 GAA/ValGTA). The Z mutation resulted from a single base-pair substitution in exon 5 of adenine for guanine (Glu342 GAG/Lys AAG) (Brantly et al., 1988). These mutations interfere with protein conformation in such a way that it is retained in the ER of hepatocytes rather than secreted into the blood and body fluids (McLean et al., 2009).
The liver damage occurs through a gain-of-function mechanism, unlike the lung disease, which is due to loss of function. The retention of the mutant ZA1AT molecules in the endoplasmic reticulum (ER) triggers a series of events (ER stress responses) which are mainly protective, however when they are ineffective hepatotoxicity eventually occurs (Carlson et al., 1989).
Taking into consideration the fact that both hereditary hemochromatosis and alpha-1 antitrypsin deficiencies are liver diseases characterized by ER stress (Carlson et al., 1989, Lawless et al., 2007), this work was planned to estimate the frequency of HFE gene common mutant alleles (C282Y and H63D) and Z/S A1AT variants among Egyptian cirrhotic patients and in patients with hepatocellular carcinoma, to investigate the role of these mutations in the development of cirrhosis and/or hepatocellular carcinoma.
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Material and methods
This work included 200 Egyptian patients with HCV (100 patients complicated with cirrhosis, 100 patients with HCC). The HCV cirrhosis patients were selected according to the clinical and laboratory examination (36 child B and 64 child C according to Child–Pugh classification). Hepatic malignancies in those patients were excluded by both abdominal US and AFP. All patients were recruited from cases admitted and followed in Tropical Medicine Department, Faculty of Medicine, Zagazig University. 100
Characteristic of the studied group (Table 1)
Patients with cirrhosis and HCC had a significantly higher level of ALT, AST and AFP compared with healthy controls. Moreover patients with HCC had a significantly higher AST and AFP levels than patients with cirrhosis.
HFE (H63D and C282Y) polymorphism genotypes in all studied groups (Table 2)
The genotype distributions in patients with cirrhosis, HCC and healthy controls were consistent with the Hardy–Weinberg equilibrium.
For HFE polymorphisms in cirrhotic patients, there were no significant differences between genotypes and allele frequencies of H63D polymorphism (HH
Discussion
Worldwide, HCC is one of the most common malignancies associated with poor prognosis (Okano et al., 2001) complicating liver cirrhosis in most cases. Its incidence is increasing worldwide ranging between 3% and 9% annually depending on the geographic location (Velazquez et al., 2003) with a specially high incidence in Egypt (Wagida et al., 2008).
Due to the alarming increase in the incidence of HCC in Egypt, there is a need to further investigate the contribution of other risk factors to the
Conflict of interest
None.
Acknowledgment
This study was funded with the support of academic research in Zagazig University Projects, Zagazig University Postgraduate & Research Affairs.
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