Hepatocellular carcinoma is a common malignant tumor of extremely high malignancy, with the highest incidence in Asia and Africa where hepatitis virus is endemic; however, the incidence of hepatocellular carcinoma in North America and Europe has been increasing in recent years. Although some patients have only very small tumors that are completely removed surgically, the prognosis for long-term postoperative survival is still poor. In recent years, there has been a proliferation of molecular markers of biological prognosis combined with clinical indicators, and there is still no study comparing the predictive ability of these molecular markers, so this review provides a detailed review of current predictive models and molecular labels.
1. Hepatocellular carcinoma staging system and prognosis
Currently, staging systems based on clinical parameters have limited predictive value for prognosis. In order to improve the predictive ability of clinical staging systems, many researchers have explored different predictors integrated into the models, and about 10 prognostic staging systems have emerged, mainly including: TNM staging, Vauthey simple liver cancer staging, Izumi tumor metastasis improvement staging, CLIP system staging, CUPI prognostic index system staging, and CUPI prognostic index system staging. CUPI prognostic index system staging, JIS staging, BCLC staging, French staging and so on.
The Okuda staging system has been widely used for its simplicity and reliability and is still considered the most successful staging system, while the TNM staging has been very successful in staging cancers other than hepatocellular carcinoma. Thus, different research groups have developed various improved staging systems, for example, CUPI has added clinical features such as ascites and symptoms to TNM staging, but this model is based on Chinese patients with liver cancer, most of whom are co-infected with HBV virus, and such features limit its wide application.
Takanishi compared the currently available staging systems and found that CLIP has good performance for prognosis prediction, but some investigators believe that CLIP staging is not significant for postoperative treatment guidance.Jorge A compared seven staging systems through prognostic follow-up of 239 patients with postoperative hepatocellular carcinoma and found that clinical status, tumor size, liver function and treatment were independent factors affecting tumor prognosis. They found that the BCLC system included all the factors and performed best for this cohort.
In conclusion, the advantages of different staging systems, the combination of different prognostic influencing factors and the search for more effective prognostic factors are still promising for clinical work.
2. Local hepatic microenvironment and prognosis
The local microenvironment of the liver is a complex tissue structure, including a variety of cells, Ito cells, Kupffer cells, endothelial cells, immune cells, etc.; including a variety of molecules, cytokines, extracellular matrix components, growth factors, etc.. All cells and molecules form a complex network of interactions, and many of these factors may become prognostic factors.
2.1 Hepatocellular carcinoma infiltrating lymphocytes and metastatic recurrence
Patients with hepatocellular carcinoma often have a history of HBV or HCV infection, a history of cirrhosis, and other backgrounds. There is often a large infiltration of lymphocytes in the paracancerous tissues, while the infiltration of lymphocytes in the tumor is often less than in the peri-tumor. Other studies have found that patient tumor or peripheral blood regulatory T cells (Treg) are associated with tumor invasion, and that regulatory T cells reduce effector T cell action and facilitate tumor immune escape. Imbalance of regulatory T cells and cytotoxic T cells within hepatocellular carcinoma tumors is also expected to be an effective prognostic factor.
Kobayashi et al. found that Treg cells were significantly higher in cancerous tissue than in non-cancerous liver tissue in HCC patients, suggesting that Treg infiltration in hepatocellular carcinoma can suppress tumor immunity and that high Treg cell infiltration in tumors is a predictor of poorer prognosis.
2.2 Immunoinflammatory factors and metastatic recurrence
In 2006, Budhu A et al. used the gene expression profile of hepatocellular carcinoma paraneoplastic tissue to screen a set of inflammatory immune-related genes that could accurately predict tumor metastasis with an accuracy of more than 90%. imbalance has important implications for tumor prognosis prediction.
The 17 cytokine expression profiles could be used as independent prognostic factors compared with other clinical prognostic indicators, and they suggested that there are distinct dominant cytokine expression profiles in different metastatic potential liver microenvironments, and the shift of microenvironment from anti-inflammatory state to immunosuppression may promote tumor metastasis. However, this result has not been validated at the protein level in large samples. Meanwhile, some studies have also revealed the relationship between cytokine alterations and tumor recurrence and metastasis. TNF-α and IL-1β are both higher in HCC patients than in normal subjects, and these two factors are also increased in the peri-cancerous period.
3. Genetic factors and genomic alterations and prognosis
3.1 Single or combined multiple gene prediction
Mann CD [16] summarized the current physiological alterations associated with the malignancy or prognosis of hepatocellular carcinoma: oncogenes, oncogenes, proliferation index, telomerase, apoptosis regulators, angiogenesis, adhesion molecules, stroma-associated proteins, etc. It has been proven that it is impossible to accurately predict the prognosis of hepatocellular carcinoma by single gene expression, and only by combining multiple genes together to construct a prediction model can we improve the accuracy of prognosis.
3.2 Genomic instability and DNA methylation
From chromosomal instability and microsatellite instability to single nucleotide polymorphism (SNP), genetic instability has become an important tool for clinical prognosis, and SNPs are widely present in the genome and are mostly dimorphic changes, which have great advantages as predictors. pan et al. applied comparative genomic hybridization to study the whole chromosome changes in 158 HBV-related liver cancer patients, and they found that 1q21-23 and 8q copy number acquisition were associated with early progression of hepatocellular carcinoma, and 3q acquisition as a late genomic change was associated with tumor recurrence and poor overall prognosis.
Using CGH, Qin Lunxiu et al. compared 10 pairs of genomic changes in primary tumors and metastases and found that 8p deletion was an important event in HCC patients prone to metastasis. Kusano et al. also demonstrated that 8p copy number reduction and 11q13 amplification were associated with poor prognosis in hepatocellular carcinoma patients and that DNA copy number alteration could be an independent prognostic factor.
Chan et al. found chromosome 8p allele deletion in 60 patients with hepatocellular carcinoma, suggesting that there must be loss or inactivation of tumor suppressor genes in this region. Further, the investigators found that heterozygous deletions located at this locus such as D8S298 and D1S199 were associated with postoperative recurrence in early stage patients and could be a new predictor.
3.3 Single nucleotide polymorphisms and prognosis
In 2007, Wu Liming et al. found that three polymorphic loci C1236T, G2677A/T and C3435T of MDR1 (Multi-drug resistance gene) were associated with recurrence in patients after liver transplantation for hepatocellular carcinoma. .
SNP692CG carriers of the AFP promoter had significantly higher serum AFP levels, and this genotype was associated with HCC progression. dharel et al. 2006 analyzed 435 MDM2 SNP309 genotypes in HCV-associated Japanese liver cancer patients and found that SNP309 GG was an independent correlate of HCC progression.
In addition, Kato found that certain SNP loci were associated with hepatocellular carcinoma susceptibility by study, and SNPs and haplotypes of SCYB14, GFA1, and CRHR2 could be used as biomarkers to predict progression to HCC in HCV infected patients.
3.4 Gene expression profile and prognosis of hepatocellular carcinoma
Molecular prediction of tumor recurrence allows clinicians to more accurately identify patients with different prognosis types and decide which patients to give adjuvant therapy. Several studies have identified expression profiles related to the prediction of metastatic recurrence of liver cancer, the earliest being Iizuka et al. Other representative studies have emerged but there is still great disagreement between molecular models to overlap and validate each other .
In 2006, Ho et al. obtained a 14-gene expression profile that accurately distinguished 18 hepatocellular carcinomas in the training group, 10 of which had vascular invasion and 8 without; this model also had an independent predictive effect on prognosis in 35 patients with stage I disease.
For example, if a patient’s tumor molecular phenotype is similar to the expression profile of fetal hepatoblasts, it suggests a poor prognosis. Lee et al. found that liver precursor cell expression profiles could identify a group of patients with poor prognosis, suggesting that this subset of patients may have originated from liver precursor cells.
In addition attempts at tumor prognosis prediction are becoming widespread, and studies of expression profiles of different subtypes may suggest the search for new tumor predictive markers that may accelerate the clinical translation of test results.
3.5 Metastasis-related MicroRNAs
In 2008, Anu and Jia HL et al [27] firstly applied microRNA microarray to construct a metastatic expression profile containing 20 miRNAs, which was validated in 110 additional HCC cases and confirmed to be significantly associated with tumor survival and recurrence, and this expression profile could easily identify those hepatocellular carcinoma patients prone to metastasis or recurrence. In 2009, Sun et al. found that microRNA-26 could be used as a prognostic label for postoperative metastasis of hepatocellular carcinoma and its expression could predict the prognosis of patients on interferon therapy.
4. Protein expression, protein profile and prognosis
Protein microarrays or antibody microarrays, quantitative proteomics and multidimensional protein quantitative identification technologies have greatly enriched protein expression, modification and function studies. In the past few years, proteomics has further applications in the screening of HCC diagnostic and prognostic markers. Hsp70, Hsp27 and GRP78 were identified as HCC diagnostic markers; HSPA9 was associated with HCC metastasis, suggesting that it could be used as a marker to predict early tumor recurrence (sensitivity 90.9%; specificity 71.4%).
5. Intra-serum molecular labeling and prognosis
To date, AFP remains the most important biomolecule as a predictor of postoperative recurrence, while several indicators are available to complement or replace it. Due to the limited reproducibility of microarrays, indicators screened by gene chips or proteomics still need further validation before being applied in the clinic. Detection of molecular labels in blood is more acceptable to patients and is not limited in number, and serological molecular markers are promising to enable relapse detection to take the lead in clinical application.
Blood components mainly include blood component cells, various proteins and other small molecules of circulating DNA, RNA, miRNA, etc. Studies have shown that serum C-reactive protein, interleukin 18 levels, and serum free DNA levels are significantly elevated in HCC patients, and their levels correlate with overall patient survival, and all of these molecules may be effective predictors. 2006 Renning found that by testing circulating plasma DNA in 79 HCC cases, 20 cirrhotic patients, and 20 healthy controls before surgery, circulating plasma DNA levels and D8S258 microsatellite could be used as a prognostic indicator for HCC, almost simultaneously Wong et al. reported a higher recurrence rate in patients with high levels of peripheral blood albumin concentration and AFP mRNA.
Many environmental or genetic risk factors associated with the development of hepatocellular carcinoma have been elucidated, but the molecular mechanisms of HCC metastasis and recurrence are still unclear. However, these newly discovered indicators are still far from clinical application, and how to improve screening methods and select stable and specific prognostic markers is still the main task of current liver cancer research.