1. Embryonic Antigen
1.1. Alpha-Fetoprotein (AFP)
AFP, the most available tumor biomarker, is currently used for early detection of HCC. Serum AFP had a sensitivity of 41% - 65% and specificity of 80% - 94% (13). Alpha-Fetoprotein has a positive rate ranging from 60% to 80%. Furthermore, AFP is positive during pregnancy, embryonic tumors and some gastrointestinal tumors. It is a major biomarker in benign liver diseases and exists in the serum and liver of patients with HCC. When total AFP is 10 - 200 ng/mL, the diagnostic specificity for HCC reaches 100%. Moreover, AFP does not correlate with other biomarkers, thus it can be used as an independent factor for the early diagnosis of HCC (14-16).
2. Proteantigen
2.1. Glypican-3 (GPC3)
GPC3 is a potential marker for HCC. It links to the cell membrane by a glycosylphosphatidylinositol anchor. It is a heparan sulfate proteoglycans that is involved in regulating cell growth. Furthermore, GPC3 can remove tumorigenic growth factors (such as hepatocyte growth factor and vascular endothelial growth factor) from the cell surface and inhibit the growth of HCC (17, 18). There is no correlation between GPC3 expression and AFP level, tumor size and stage (19).
2.2. Heat Shock Protein 70 (HSP70)
HSP70 is a potential marker for HCC. It is expressed when someone is exposed to carcinogens. It is a conserved stress response protein and can promote cells to repair damages. Immunohistochemical staining, showed that the positive rate of HSP70 was 56.3 in HCC (20). Its stain intensity was associated with tumor size and stage. The sensitivity and specificity of HSP70 in detecting HCC was 57.5 and 85%, respectively (21, 22).
3. Cytokines
3.1. Transforming Growth Factor-β1 (TGF-β1)
TGF-β1 is a growth factor involved in the regulation of cell proliferation and immune function. It is expressed in tumor cells. It can inhibit the proliferation of Cytotoxic T Lymphocytes (CTL) and promote the growth of tumor cells. Furthermore, TGF-β1 may be used as an indicator to diagnose HCC related to HBV with sensitivity and specificity of 89.5 and 94.0%, respectively (23-25).
3.2. Vascular endothelial growth factor (VEGF)
VEGF has a vital role in tumor angiogenesis. It can induce new vessel formation and promote tumor metastasis. The level of VEGF is higher in HCC patients than healthy individuals. It has been revealed that the expression of VEGF is correlated with tumor prognosis and recurrence. It seems that overexpression of VEGF is a useful biological marker of tumors (26, 27).
4. Genetic Biomarkers
4.1. Alpha-Fetoprotein mRNA
This is a marker for spreading of HCC in the blood in active HCC cells. It is a predictor for HCC recurrence and has a positive rate of 82.4% in recrudescent patients (14).
4.2. MicroRNAs
These are non-coding RNAs that block translation by inducing the degradation of target mRNAs. MiR-500 is a new biomarker for HCC. It could downregulate liver development and then upregulate cirrhosis (28). Thus, MiR-500 is a promising biomarker of HCC.
5. Enzymes and Isozymes
5.1. Des-γ-Carboxyprothrombin (DCP)
DCP is induced by the absence of vitamin K. Vitamin K-dependent carboxylation system fails and causes the production of DCP in malignant liver cells. Its level is associated with a larger tumor. It is an accurate tumor marker compared with AFP (29, 30).
5.2. Gamma-Glutamyl Transferase (GGT)
This enzyme is secreted by endothelial cells of the bile duct and hepatic Kupffer cells. Its activity increases in HCC tumors. In addition, cholestasis and inflammation can improve the level of GGT. Gamma-Glutamyl Transferase mRNA is widely distributed in liver tissues of HCC patients. Therefore, GGT can be a biomarker for diagnosis of HCC.
5.3. Glutamine Synthetase (GS)
GS induces the synthesis of glutamine. Glutamine is an important energy source for tumor cells. The level of GS increases in patients with precancerous lesions, which can change to advanced-HCC. It has been reported that GS is a new target in development of HCC (specificity 89%; sensitivity 100%) (31, 32).
6. New Discoveries
6.1. Hepatocyte Paraffin 1 (HepPar 1)
This antigen can differentiate between normal and malignant hepatocytes. It is expressed in normal human liver cells. Decreasing expression of HepPar 1 is seen in HCC. It seems that reduction of HepPar 1-positive cells is associated with HCC (33). Therefore, HepPar 1 can be considered as a new valuable marker for the diagnosis of HCC.
7. Multi-Marker Panel
The use of panels with multiple biomarkers increases the accuracy of the diagnosis. Findings have indicated that concomitant use of GS, GPC3 and HSP70 has sensitivity and specificity of 70% and 100%, respectively in HCC diagnosis. This panel has an accuracy of 57% and specificity of 100% in grade 1 HCC patients (34, 35). In addition, a four-marker panel has been introduced, which has a diagnostic accuracy of 84.3% in small HCC tumors (36). It seems that multi-marker panels need to be further investigated to achieve valuable detective methods.
As mentioned above, there are some biomarkers for HCC detection. Hepatocellular Carcinoma can be diagnosed by analysis of the expression of specific genes by quantitative methods such as Reverse transcription polymerase chain reaction (qRT-PCR). In this regard, different expression levels of genes have been associated with protein levels, which are related to HCC development. In addition, immunohistochemical techniques are useful in HCC diagnosis. Hepatocellular Carcinoma is able to synthesize tumor-related proteins. Therefore, biomarkerrelated researches are needed.
Regarding the relationship between biomarkers and HCC, selecting useful biomarkers in HCC detection is essential. Despite limitations, it seems that AFP is the most important tumor marker for HCC. The results indicated that AFP and DCP were better than AFP alone in detecting early HCC. In addition, some biomarkers including GPC3, GS, HepPar 1 and HSP70 could be supplementary to AFP in HCC detection. In addition, in some HCC patients, DCP or AFP may be negative while other biomarkers may be positive; therefore, multi-marker panels can modify the precision of the diagnosis.
Considering the importance of this lethal cancer in the world and considering the mortality rate of HCC, it is essential to introduce better methods for diagnosis and prognosis of HCC patients. Medical researches have primarily affected public health and have an important role in all human activities. One of the most important aspects of medicine is proper interpretation of data. However, medical decision-making is difficult because processing a lot of data is a difficult task. In this regard, diagnosis is very important. Error at this level can have considerable consequences. One of the main problems related to HCC patients, is the lack of proper diagnosis of disease. As a result of wrong diagnosis or no diagnosis at an early stage, a person may even develop complications that lead to death. Rapid and correct diagnosis of HCC should be determined based on a predetermined pattern. In this regard, molecular biology-related researches in regards to HCC could reveal valuable information about the natural history of HCC including metastasis and recurrence. In the recent years, specific biomarkers have been reported that have diagnostic values. However, some of them can’t diagnose the disease at early stages. Thus, studies should be focused on prognostic values of such biomarkers. These biomarkers not only lead to the prediction of HCC in patients but also provide useful information for selection of appropriate treatment, leading to increased survival of patients.
