p53 expression in hepatocellular carcinoma in Greece. Correlation with epidemiological and histopathological data

p53 immunocytochemistry and TP53 gene mutations in patients with chronic hepatitis C virus (HCV) infection

Chronic infection with hepatitis C virus (HCV) is regarded as a risk factor for hepatocellular carcinoma (HCC), mostly in patients with liver cirrhosis. Present study aimed at evaluation of cellular expression of p53 protein, genetic TP53 changes in liver samples and anti-p53 in serum of patients with chronic hepatitis C virus infection. The expression of p53 protein were analysed by immunocytochemistry in liver biopsies from adult patients with chronic, long-lasting hepatitis C. In order to detect TP53 mutations, PCR/SSCP and sequencing were performed. Antibodies against p53 in serum were determined using enzyme immunoassay (ELISA).In two out of 14 examined patients TP53 point mutations were detected in the liver samples. In the first patient, a substitution of C to T was demonstrated in position 1 of the codon 250, resulting in substitution of proline by serine. The other patient carried a substitution of C to G in position 13274 of the intron 6. The patient carrying mutation in the codon 250 demonstrated morphological traits of liver cirrhosis and had high number of p53-immunoreactive cell nuclei in tissue. None of the patients manifested elevated titres of serum anti-p53. In the liver, significant positive correlations were disclosed between expression of p53 on one hand and grading and staging on the other. A negative correlation was disclosed between cellular expression of p53 and duration time of infection. In conclusions, genetic changes in TP53 can be detected also in non-neoplastic lesions linked to chronic HCV infection.

Chromosome instability in human hepatocellular carcinoma depends on p53 status and aflatoxin exposure

Hepatocellular carcinoma (HCC) is a heterogeneous disease triggered by various risk factors and frequently characterized by chromosome instability. This instability is considered to be caused primarily by Hepatitis B virus (HBV), although aflatoxin B1 (AFB1), a potent fungal mutagen is also suspected to influence chromosomal repair. We studied 90 HCCs from Italy, the country with the highest incidence of hepatocellular carcinoma in Europe, 81 samples from France and 52 specimens from Shanghai, in a region where intake of AFB1 via the diet is known to be high. All 223 tumours were characterized for 15 different genomic targets, including allelic loss at 13 chromosome arms and mutations of beta-catenin and p53 genes. Despite disparity in risk-factor distribution, Italian and French cases did not significantly differ for 14 of the 15 targets tested. beta-Catenin and p53 displayed moderate and similar mutation rates (18-29% of cases) in European series. By contrast, tumours from Shanghai were significantly different, with a lower mutation rate for beta-catenin (4% vs. 26%, p<0.0003) and a higher mutation rate for p53 (48% vs. 22%, p<0.0001) when compared with tumours of European origin. The Arg249Ser mutation, hallmark of exposure to AFB1, represented half of the changes in p53 in Shanghai. Furthermore, when stratified for the presence of HBV or p53 mutations, chromosome instability was always higher in Chinese than in European patients. This difference was particularly strong in p53-wildtype tumours (fractional allelic loss, 29.4% vs. 16.7%, p<0.0001). We suggest that AFB1-associated mutagenesis represents a plausible cause for the higher chromosome instability observed in Chinese HCCs, when compared with European primary liver carcinomas.

Hepatic expression of the proliferative marker Ki-67 and p53 protein in HBV or HCV cirrhosis in relation to dysplastic liver cell changes and hepatocellular carcinoma

To evaluate hepatic expression of the nuclear proliferative marker Ki-67 and the p53 oncoprotein in hepatitis B virus (HBV)/HCV cirrhosis in relation to dysplastic liver cell changes and hepatocellular carcinoma (HCC). We studied needle liver biopsies from 107 patients with cirrhosis and no HCC (52 HBV, 55 HCV) who had been assessed for protocol studies, and 57 cirrhotic patients with HCC (40 HBV, 17 HCV). We evaluated small and large cell dysplastic changes along with the expression of Ki-67 and p53 by immunohistochemistry. The labelling index (LI) was defined as the proportion (%) of positive-stained nuclei of the 500 measured. Large and small cell dysplastic changes were observed in 12 and 9% of specimens respectively. Only small cell changes were associated with Ki-67 expression. Ki-67 LI was 5.50 +/- 5.7 in cirrhosis (13.90 +/- 3.84 in those with small cell dysplastic changes vs 4.64 +/- 4.98 in those without, P < 0.01), 10.2 +/- 5.95 in cirrhosis with HCC (P < 0.05) and 18.56 +/- 10 in HCC (P < 0.01). Neither the presence of small cell dysplastic changes nor the expression of Ki-67 was related to severity or aetiology of cirrhosis. Expression of p53 was observed in 30% of the non-tumorous and in 53% of the neoplastic tissue obtained from patients with HCC, with no differences between HCV and HBV. Ki-67 and p53 expression was associated with the tumour grade (P < 0.001). Our observations clearly demonstrate the association between the proliferation activity and the morphological changes in the cirrhotic liver from the non-dysplastic to dysplastic lesion to HCC. They also support the hypothesis that p53 alterations are a rather late event in carcinogenesis and related to HCC grade. And finally, they suggest that the final steps of hepatocarcinogenesis are common and independent of the aetiology of the chronic viral infection.

Overexpression of p53 protein is not directly related to hepatitis B x protein expression and is associated with neoplastic progression in hepatocellular carcinomas rather than hepatic preneoplasia

p53 mutations and binding of p53 to hepatitis B virus (HBV) x protein (HBx) have been suggested as alternative mechanisms of development of hepatocellular carcinomas (HCCs) in man, both processes resulting in intracellular accumulation of the protein which is detectable by immunohistochemical approaches. We have examined p53 expression in 149 explanted human livers, including 39 cases infected with HBV and 35 bearing HCC. p53 was demonstrated immunohistochemically in 51% of HCC samples (18/35), localized mainly in fast growing poorly differentiated areas. Accumulation of mutant p53 was verified by immunoprecipitation in most of the positive HCC samples (14/15), implying occurrence of p53 mutations. No cells positive for p53 were found in 354 preneoplastic hepatocellular lesions examined. This indicates that p53 mutation is associated with progression, rather than early development, of HCC in the low-aflatoxin B(1)-exposed region. The intracellular distribution patterns of p53 and HBx were different, with the former within nuclei and the latter confined to cytoplasmic compartment. HBx did not coimmunoprecipitate with p53. These data indicate that p53-HBx binding is infrequent, if it really occurs, in HBV-infected human liver, and that it cannot be a common mechanism of HBV-associated hepatocarcinogenesis. In addition, p53 accumulation was also observed in some parenchymal and ductular (oval) cells in cirrhotic livers and, more frequently, in fulminant hepatitis, being independent of HBx expression, and seemingly associated with the damage and/or regeneration of liver parenchyma, perhaps merely reflecting a cellular stress response.