Background: Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide, its prognosis is poor, and early detection is of utmost importance. Although alpha-fetoprotein (AFP) is a useful marker for detecting and monitoring HCC development, the false-negative or false-positive rates with AFP alone may be as high as 30%-40% for patients with small HCCs. To enhance the specificity and accuracy of AFP measurements for HCC, we analyzed AFP expression states in livers, detected the hepatoma-specific AFP (HS-AFP) fraction and AFP-mRNA from peripheral blood mononuclear cells, and explored their clinical implications for HCC diagnosis.
Methods: AFP expression and hepatocyte distributions in liver specimens were investigated by an immunohistochemical assay. Total RNAs were extracted from circulating blood, synthesized to cDNA through random primers and reverse transcriptase, and fragments of the AFP gene were amplified by a nested-PCR assay. The HS-AFP fraction was separated by lectin-affinity chromatography and its level was detected by radioimmunoassay.
Results: The incidence of AFP was 73.3% in HCC tissues and its expression in HCCs with moderate or low differentiation was significantly stronger than that of HCCs with high differentiation (P<0.05). The incidence of AFP gene fragments was 100% in HCCs, and 60% in paracancerous tissues (P<0.01). In the HCC and liver cirrhosis groups, the incidence of HS-AFP was 91.7% and 18% (P<0.01), and of AFP-mRNA was 56.7% and 16% (P<0.01), respectively, and neither was found in controls. HS-AFP or AFP-mRNA was not significantly related to size or number of HCC, but to its differentiation, metastasis, and relapse (P<0.05).
Conclusions: Different AFP expression is present in different parts of HCC tissues. HS-AFP and AFP-mRNA fragments improve sensitivity and specificity, and both are useful markers to diagnose HCC or monitor metastasis and relapse.