Biomarkers for risk assessment in molecular epidemiology of cancer

Association of FHIT expression and FHIT gene hypermethylation with liver cancer risk: a PRISMA-compliant meta-analysis

Background

There have been suggestions that fragile histidine triad protein (FHIT) expression and FHIT gene hypermethylation were crucial to the pathogenesis of liver cancer. However, the conclusions remained unclear because of small sample size, disease subtype, and different detection techniques. Therefore, we performed a meta-analysis to estimate the associations of FHIT expression and FHIT gene hypermethylation with liver cancer pathogenesis.

Methods

Studies that were published in electronic databases, such as PubMed, Web of Knowledge, China National Knowledge Infrastructure (CNKI), VIP, and WanFang, were retrieved and selected for the meta-analysis. Relative risk (RR) and 95% confidence interval (CI) were calculated to determine the correlations of FHIT expression and FHIT gene hyper-methylation with liver cancer pathogenesis with Stata 12.0 software.

Results

A total of 17 papers that evaluated the associations of FHIT expression (14 articles) and FHIT gene methylation (3 articles) with liver cancer pathogenesis were included in this meta-analysis. In the overall analysis, the pooled relative risk was 1.93 (95% CI =1.72–2.17), which indicated a significant association between FHIT low expression and liver cancer risk. According to the results of clinical information, there were significant associations of FHIT expression with TNM-stage (RR =2.13, 95% CI =1.72–2.64), tumor size (RR =1.67, 95% CI =1.36–2.05), and merger of cirrhosis (RR =1.34, 95% CI =1.06–1.69) of liver cancer in the Chinese population. In addition, the FHIT gene hypermethylation was significantly associated with the risk of liver cancer (RR =1.45, 95% CI =1.08–1.93).

Conclusion

The FHIT expression and hypermethylation of FHIT gene were significantly associated with the risk of liver cancer, especially in the Chinese population. Furthermore, the results indicated significant associations between FHIT low expression and TNM-stage, tumor size, and merging of cirrhosis of liver cancer in the Chinese population.

The Role of Epigenomics in the Study of Cancer Biomarkers and in the Development of Diagnostic Tools

Epigenetics plays a key role in cancer development. Genetics alone cannot explain sporadic cancer and cancer development in individuals with no family history or a weak family history of cancer. Epigenetics provides a mechanism to explain the development of cancer in such situations. Alterations in epigenetic profiling may provide important insights into the etiology and natural history of cancer. Because several epigenetic changes occur before histopathological changes, they can serve as biomarkers for cancer diagnosis and risk assessment. Many cancers may remain asymptomatic until relatively late stages; in managing the disease, efforts should be focused on early detection, accurate prediction of disease progression, and frequent monitoring. This chapter describes epigenetic biomarkers as they are expressed during cancer development and their potential use in cancer diagnosis and prognosis. Based on epigenomic information, biomarkers have been identified that may serve as diagnostic tools; some such biomarkers also may be useful in identifying individuals who will respond to therapy and survive longer. The importance of analytical and clinical validation of biomarkers is discussed, along with challenges and opportunities in this field.

Epigenetic biomarkers in liver cancer

Liver cancer (hepatocellular carcinoma or HCC) is a major cancer worldwide. Research in this field is needed to identify biomarkers that can be used for early detection of the disease as well as new approaches to its treatment. Epigenetic biomarkers provide an opportunity to understand liver cancer etiology and evaluate novel epigenetic inhibitors for treatment. Traditionally, liver cirrhosis, proteomic biomarkers, and the presence of hepatitis viruses have been used for the detection and diagnosis of liver cancer. Promising results from microRNA (miRNA) profiling and hypermethylation of selected genes have raised hopes of identifying new biomarkers. Some of these epigenetic biomarkers may be useful in risk assessment and for screening populations to identify who is likely to develop cancer. Challenges and opportunities in the field are discussed in this chapter.

Pancreatic cancer biomarkers and their implication in cancer diagnosis and epidemiology

Pancreatic cancer is the fourth most common cause of cancer-related mortality in the United States. Biomarkers are needed to detect this cancer early during the disease development and for screening populations to identify those who are at risk. In cancer, “biomarker” refers to a substance or process that is indicative of the presence of cancer in the body. A biomarker might be either a molecule secreted by a tumor or it can be a specific response of the body to the presence of cancer. Genetic, epigenetic, proteomic, glycomic, and imaging biomarkers can be used for cancer diagnosis, prognosis, and epidemiology. A number of potential biomarkers have been identified for pancreatic cancer. These markers can be assayed in non-invasively collected biofluids. These biomarkers need analytical and clinical validation so that they can be used for the purpose of screening and diagnosing pancreatic cancer and determining disease prognosis. In this article, the latest developments in pancreatic cancer biomarkers are discussed.

Epigenetic mechanisms in cancer

After the completion of the human genome, a need was identified by scientists to look for a functional map of the human genome. Epigenomics provided functional characteristics of genes identified in the genome. Epigenetics is the alteration in gene expression (function) without changing the nucleotide sequence. Both activation and inactivation of cancer-associated genes can occur by epigenetic mechanisms. The major players in epigenetic mechanisms of gene regulation are DNA methylation, histone deacetylation, chromatin remodeling, small noncoding RNA expression and gene imprinting. In the last few years, epigenetic mechanisms have been studied in a number of tumor types and epigenetic markers have been identified that are suitable for cancer detection, diagnosis, follow-up of treatment and screening high-risk populations. One interesting aspect of epigenetics is the reactivation of genes by successful reversion of some epigenetic changes using chemicals. The reversibility of epigenetic aberrations has made them attractive targets for cancer treatment with modulators that demethylate DNA and inhibit histone deacetylases, leading to the reactivation of silenced genes. In this article, we have described the current status of this powerful science and discussed the challenges in the clinical fields where epigenetic approaches in cancer are applied.

Cancer biomarkers: are we ready for the prime time?

A biomarker is a characteristic that is objectively measured and evaluated as an indicator of normal biologic processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention. In cancer, a biomarker refers to a substance or process that is indicative of the presence of cancer in the body. A biomarker might be either a molecule secreted by a tumor or it can be a specific response of the body to the presence of cancer. Genetic, epigenetic, proteomic, glycomic, and imaging biomarkers can be used for cancer diagnosis, prognosis and epidemiology. These markers can be assayed in non-invasively collected biofluids. However, few cancer biomarkers are highly sensitive and specific for cancer detection at the present time. Consequently, biomarkers are not yet ready for routine use due to challenges in their clinical validation for early disease detection, diagnosis and monitoring to improve long-term survival of patients.

Proteomics and cancer epidemiology

Profiling of differentially expressed proteins is perhaps the most important and useful approach in developing tools for risk assessment in a population, diagnostic screening, and therapeutics. Proteomic markers have potential for identifying individuals at high risk of developing cancer; however, these markers have not been extensively used in cancer epidemiologic studies. Several markers have to be clinically validated. In this chapter, methods used in proteomic analysis of clinical samples, challenges in the proteomics and cancer epidemiology, and their potential solutions are discussed.

Plasma haptoglobin and immunoglobulins as diagnostic indicators of deoxynivalenol intoxication

This study aimed to discover potential biomarkers for dioxynivalenol (DON) intoxication. B6C3F1 male mice were orally exposed to 0.83, 2.5 and 7.5 mg/kg body weight (bw) DON for 8 days and the differential protein expressions in their blood plasma were determined by SELDI - Time-of-Flight/Mass Spectrometry (TOF/MS) and the immunoglobulins (Igs) G, A, M and E in the serum were investigated. 11.7 kDa protein was significantly highly expressed according to DON administration and this protein was purified by employing a methyl ceramic HyperD F column with using optimization buffer for adsorption and desorption. The purified protein was identified as a haptoglobin precursor by peptide mapping with using LC/Q-TOF/MS and MALDI-TOF/MS and this was confirmed by western blotting and ELISA. IgG and IgM in serum were decreased in a dose-dependent manner and IgA was decreased at 7.5 mg/kg bw DON administration, but the IgE level was not changed. To compare the expressions of haptoglobin and the Igs patterns between aflatoxin B1 (AFB1), zearalenone (ZEA) and DON intoxications, rats were orally administered with AFB1 1.0, ZEA 240 and DON 7.5 mg/kg bw for 8 days. Haptoglobin was increased only at DON 7.5 mg/kg bw, while it was slightly decreased at ZEA 240 mg/kg bw and it was not detected at all at AFB1 1.0 mg/kg bw. IgG and IgA were decreased by DON, but IgG, IgA, IgM and IgE were all increased by AFB1. No changes were observed by ZEA administration. These results show that plasma haptoglobin could be a diagnostic biomarker for DON intoxication when this is combined with examining the serum Igs.

Genetic and epigenetic biomarkers in cancer : improving diagnosis, risk assessment, and disease stratification

Gene expression patterns change during the initiation, progression, and development of cancer, as a result of both genetic and epigenetic mechanisms. Genetic changes arise due to irreversible changes in the nucleotide sequence, whereas epigenetic changes occur due to changes in chromatin conformation, histone acetylation, and methylation of the CpG islands located primarily in the promoter region of a gene. Both genetic and epigenetic markers can potentially be utilized to identify different stages of tumor development. Several such markers exhibit high sensitivity and specificity for different tumor types and can be assayed in biofluids and other specimens collected by noninvasive technologies. In spite of the availability of large numbers of diagnostic markers, only a few have been clinically validated so far. The current status and the challenges in the field of genetic and epigenetic markers in cancer diagnosis, risk assessment, and disease stratification are discussed.

Path Analysis of Biomarkers of Exposure and Early Biological Effects among Coke-Oven Workers Exposed to Polycyclic Aromatic Hydrocarbons

Many host factors or biomarkers are involved in the process of early DNA damage induced by occupational exposure to polycyclic aromatic hydrocarbons (PAH) as seen in coke-oven workers. This paper aimed to identify complicated causal interrelationship of various biomarkers using the path analysis. In this analysis, we included 235 subjects (166 coke-oven workers and 69 nonexposed controls) whose data on the comet assay (e.g., Olive tail moment) and cytogenetic analysis of peripheral blood lymphocytes as well as urinary 1-hydroxypyrene (1-OHP) were available. The path analysis showed that coke-oven exposure and tobacco smoke were both significant predictors of the concentrations of urinary 1-OHP (P < 0.05), with a coefficient of determination of 0.75. The factors having significant influence on the Olive tail moment were in the following order: urinary 1-OHP > XRCC1-exon 9 variant genotype > ERCC2-exon 10 variant genotype > XRCC1-exon 6 variant genotype, with a coefficient of determination of 0.22. The variables of relative importance in influencing on cytokinesis-block micronucleus frequencies were in the following order: coke-oven exposure > urinary 1-OHP > age > mEH3 variant genotype > ERCC2-exon 10 variant genotype > XRCC1-exon 6 variant genotype, with a coefficient of determination of 0.27. These results indicated that exogenous agents, especially the coke-oven exposure, played a more important role than the genotypes in the induction of early genetic damage. In conclusion, the path analysis seemed to be an alternative statistical approach for the ascertainment of complicated association among related biomarkers for the assessment of occupational exposure.

Pancreatic cancer epidemiology

Carcinoma of the exocrine pancreas remains a challenging disease mainly due to advanced stage diagnosis, the early systemic dissemination, aggressive local tumor progression, and subsequent short patient survival. Thus, assessment of incidence markers instead of prevalence indicators is recommended because the time between diagnosis and death is usually very short. Investigations to date have led to the discovery of many rare genes and environmental factors that contribute to pancreatic cancer. However, common genes involved in genetic polymorphisms, and specific risk factors have not been identified. Furthermore, the role of gene-environment interactions on the tumorogenesis and progression of pancreatic cancer need to be further investigated. Given current therapeutic modalities, only early detection of cancer of the pancreas, followed by surgical resection, offers the possibility of lengthening survival time.