IGF2 polymorphisms are associated with hepatitis B virus clearance and hepatocellular carcinoma

Genome-wide association study of disease resilience traits from a natural polymicrobial disease challenge model in pigs identifies the importance of the major histocompatibility complex region

Infectious diseases cause tremendous financial losses in the pork industry, emphasizing the importance of disease resilience, which is the ability of an animal to maintain performance under disease. Previously, a natural polymicrobial disease challenge model was established, in which pigs were challenged in the late nursery phase by multiple pathogens to maximize expression of genetic differences in disease resilience. Genetic analysis found that performance traits in this model, including growth rate, feed and water intake, and carcass traits, as well as clinical disease phenotypes, were heritable and could be selected for to increase disease resilience of pigs. The objectives of the current study were to identify genomic regions that are associated with disease resilience in this model, using genome-wide association studies and fine-mapping methods, and to use gene set enrichment analyses to determine whether genomic regions associated with disease resilience are enriched for previously published quantitative trait loci, functional pathways, and differentially expressed genes subject to physiological states. Multiple quantitative trait loci were detected for all recorded performance and clinical disease traits. The major histocompatibility complex region was found to explain substantial genetic variance for multiple traits, including for growth rate in the late nursery (12.8%) and finisher (2.7%), for several clinical disease traits (up to 2.7%), and for several feeding and drinking traits (up to 4%). Further fine mapping identified 4 quantitative trait loci in the major histocompatibility complex region for growth rate in the late nursery that spanned the subregions for class I, II, and III, with 1 single-nucleotide polymorphism in the major histocompatibility complex class I subregion capturing the largest effects, explaining 0.8–27.1% of genetic variance for growth rate and for multiple clinical disease traits. This single-nucleotide polymorphism was located in the enhancer of TRIM39 gene, which is involved in innate immune response. The major histocompatibility complex region was pleiotropic for growth rate in the late nursery and finisher, and for treatment and mortality rates. Growth rate in the late nursery showed strong negative genetic correlations in the major histocompatibility complex region with treatment or mortality rates (−0.62 to −0.85) and a strong positive genetic correlation with growth rate in the finisher (0.79). Gene set enrichment analyses found genomic regions associated with resilience phenotypes to be enriched for previously identified disease susceptibility and immune capacity quantitative trait loci, for genes that were differentially expressed following bacterial or virus infection and immune response, and for gene ontology terms related to immune and inflammatory response. In conclusion, the major histocompatibility complex and other quantitative trait loci that harbor immune-related genes were identified to be associated with disease resilience traits in a large-scale natural polymicrobial disease challenge. The major histocompatibility complex region was pleiotropic for growth rate under challenge and for clinical disease traits. Four quantitative trait loci were identified across the class I, II, and III subregions of the major histocompatibility complex for nursery growth rate under challenge, with 1 single-nucleotide polymorphism in the major histocompatibility complex class I subregion capturing the largest effects. The major histocompatibility complex and other quantitative trait loci identified play an important role in host response to infectious diseases and can be incorporated in selection to improve disease resilience, in particular the identified single-nucleotide polymorphism in the major histocompatibility complex class I subregion.

Meta-analysis of the correlation between the rs17401966 polymorphism in kinesin family member 1B and susceptibility to hepatitis B virus related hepatocellular carcinoma

Background/Aims

The association between the kinesin family member 1B (KIF1B) gene polymorphism and the risk of hepatitis B virus-related hepatocellular carcinoma (HCC) has been investigated in many peer-reviewed studies. However, scholars have failed to replicate these results in validation tests. The purpose of the present study was to explore whether the KIF1B rs17401966 polymorphism was associated with susceptibility to HCC.

Methods

The results of case-controlled studies on the correlation between the KIF1B rs17401966 polymorphism and HCC susceptibility were collected using Google Scholar and the EMBASE, PubMed and CNKI databases. Based on inclusion and exclusion criteria, 5 papers with a total of 12 cohorts were included in this study.

Results

The 12 cohorts were integrated, and the results showed that the rs17401966 polymorphism reduced the risk for HCC under the allele, heterozygous, homozygous, and dominant models but not under the additive or recessive models. Moreover, the merged results showed strong heterogeneity, and the cumulative meta-analysis results were unreliable. A genetic differentiation analysis of the 12 cohorts found different degrees of genetic differentiation between the 5 cohorts in Zhang et al.’s study and the cohorts in the other studies. We further divided the 12 study cohorts into 2 subgroups based on fixation index value; however, the results of that analysis were inconsistent.

Conclusions

The results of this meta-analysis were not able to verify the association between the KIF1B rs1740199 polymorphism and HCC risk. Therefore, a well-designed, large-scale, multicenter validation study is needed to confirm the relationship.

Lin28 and let-7: roles and regulation in liver diseases

The diagnosis and treatment of liver disease remain a major health concern worldwide because of the diverse etiologies of this disease. For this reason, new therapeutic targets are greatly needed to halt the progression of this damaging disease. Upon initiation of liver injury by viral infection, autoimmune disease or toxin, and/or hepatitis, chronic disease may develop, which can progress to cirrhosis, hepatocellular carcinoma (HCC), cholangiocarcinoma, liver failure, or death. The Lin28/lethal-7 (let-7) molecular switch has emerged as a central regulator of multiorgan injuries and cancer development. Lin28 is a stem cell marker vital to initiation or maintenance of a stem cell phenotype. Lin28 has not been extensively studied in the liver, despite its ability to induce tissue regeneration via reprogramming of oxidative enzymes in other tissues and its involvement with numerous upstream regulators and downstream targets in liver disease. Theoretically, overexpression of Lin28 in certain forms of liver disease could be a potential treatment that aids in liver regeneration. Alternatively, Lin28 has been implicated numerous times in the progression of diverse cancer types and is associated with increased severity of disease. In this case, Lin28 could be a potential inhibitory target to prevent malignant transformation in the liver. This review seeks to characterize the role of Lin28 in liver disease.

Epigenetic regulation of Newborns' imprinted genes related to gestational growth: patterning by parental race/ethnicity and maternal socioeconomic status

BACKGROUND

Children born to parents with lower income and education are at risk for obesity and later-life risk of common chronic diseases, and epigenetics has been hypothesised to link these associations. However, epigenetic targets are unknown. We focus on a cluster of well-characterised genomically imprinted genes because their monoallelic expression is regulated by DNA methylation at differentially methylated regions (DMRs), are critical in fetal growth, and DNA methylation patterns at birth have been associated with increased risk of birth weight extremes and overweight status or obesity in early childhood.

METHODS

We measured DNA methylation at DMRs regulating genomically imprinted domains (IGF2/H19, DLK1/MEG3, NNAT and PLAGL1) using umbilical cord blood leucocytes from 619 infants recruited in Durham, North Carolina in 2010-2011. We examined differences in DNA methylation levels by race/ethnicity of both parents, and the role that maternal socioeconomic status (SES) may play in the association between race/ethnic epigenetic differences.

RESULTS

Unadjusted race/ethnic differences only were evident for DMRs regulating MEG3 and IGF2; race/ethnic differences persisted in IGF2/H19 and NNAT after accounting for income and education.

CONCLUSIONS

Results suggest that parental factors may not only influence DNA methylation, but also do so in ways that vary by DMR. Findings support the hypothesis that epigenetics may link the observed lower SES during the prenatal period and poor outcomes such as low birth weight; lower birth weight has previously been associated with adult-onset chronic diseases and conditions that include cardiovascular diseases, diabetes, obesity and some cancers.

IGF2 and cancer

Insulin-like growth factor 2 (IGF2) is a 7.5  kDa mitogenic peptide hormone expressed by liver and many other tissues. It is three times more abundant in serum than IGF1, but our understanding of its physiological and pathological roles has lagged behind that of IGF1. Expression of the IGF2 gene is strictly regulated. Over-expression occurs in many cancers and is associated with a poor prognosis. Elevated serum IGF2 is also associated with increased risk of developing various cancers including colorectal, breast, prostate and lung. There is established clinical utility for IGF2 measurement in the diagnosis of non-islet cell tumour hypoglycaemia, a condition characterised by a molar IGF2:IGF1 ratio >10. Recent advances in understanding of the pathophysiology of IGF2 in cancer have suggested much novel clinical utility for its measurement. Measurement of IGF2 in blood and genetic and epigenetic tests of the IGF2 gene may help assess cancer risk and prognosis. Further studies will determine whether these tests enter clinical practice. New therapeutic approaches are being developed to target IGF2 action. This review provides a clinical perspective on IGF2 and an update on recent research findings.

MicroRNA-196A-2 polymorphisms and hepatocellular carcinoma in patients with chronic hepatitis B

Single nucleotide polymorphisms (SNPs) in microRNA (miR)-196a-2 have been suggested to contribute to susceptibility to various human cancers. The aim of this study was to determine whether polymorphisms of miRNA-196a-2 affect the clinical outcomes of hepatitis B virus (HBV) infection in Korean patients. Genotyping was performed for 1,439 Korean patients with either past or present HBV infection, including 404 control subjects who underwent spontaneous recovery and 1,035 subjects with chronic HBV (313 cases of chronic hepatitis B, 305 cases of cirrhosis of the liver, and 417 cases of hepatocellular carcinoma [HCC]). Genotyping results revealed that the polymorphism rs12304647A>C, which lies in the pri-miRNA region of miR-196a-2, has a significant minor allele frequency (0.210). Logistic analysis revealed that the rs12304647A>C SNP was associated with a significant protective effect against HCC in patients with chronic hepatitis (odds ratio [OR] = 0.70, P = 0.005 in a codominant model; OR = 0.73, P = 0.03 in a dominant model; OR = 0.31, P = 0.004 in a recessive model), and in the patients with cirrhosis (OR = 0.63, P = 0.0009 in a codominant model; OR = 0.66, P = 0.01 in a dominant model; OR = 0.25, P = 0.001 in a recessive model). A Cox relative hazards model with adjustments for age, gender, HBeAg status, and cirrhosis revealed that rs12304647A>C retained its association with HCC in a codominant model (relative hazards [RH] = 1.14, P = 0.05) and in a recessive model (RH = 1.44, P = 0.03). However, the miR-196a-2 rs12304647A>C SNP had no association with HBV clearance. In conclusion, the miR-196a-2 rs12304647 CC genotype had a protective effect against development of HCC in comparison to the AA or AC genotypes in patients with chronic hepatitis and cirrhosis.

Polymorphisms near interleukin 28B gene are not associated with hepatitis B virus clearance, hepatitis B e antigen clearance and hepatocellular carcinoma occurrence

BACKGROUND

Polymorphisms near the IL28B gene have been proposed to be strongly associated with treatment response and the rate of spontaneous clearance of hepatitis C virus infection, and treatment response of hepatitis B virus (HBV) infection. In this study, we aimed to determine whether these polymorphisms could affect natural courses of HBV infection.

METHODS

Genetic variations were identified through direct DNA sequencing using TaqMan assay in 1,439 patients with past or present HBV infection. Subjects included 404 spontaneously recovered patients, 313 chronic hepatitis B (CHB) patients, 305 liver cirrhosis (LC) patients and 417 hepatocellular carcinoma (HCC) patients. Three polymorphisms near the IL28B gene, rs8099917T>G, rs12979860C>T and rs12980275A>G, were identified. Associations between these polymorphisms and HBV clearance, hepatitis B e antigen (HBeAg) clearance as well as HCC occurrence among patients were analyzed using logistic regression analyses adjusted for age and gender.

RESULTS

There were no significant associations between these polymorphisms and the HBV clearance both in CHB and LC groups. Similarly, these polymorphisms showed no significant associations with HBeAg clearance and the occurrence of HCC either.

DISCUSSION

No significant association was identified between polymorphisms near the IL28B gene and the natural courses of chronic HBV infection, including the HBV clearance and HCC occurrence.

Clinical significance of insulin-like growth factor gene polymorphisms with survival in patients with gastrointestinal stromal tumors

Purpose

Insulin-like growth factors (IGFs) regulate a wide range of biological functions including cell proliferation, differentiation, and apoptosis through paracrine and autocrine mechanisms. Accordingly, the present study analyzed polymorphisms of IGF genes and their impact on the prognosis for patients with gastrointestinal stromal tumors (GISTs).

Methods

Two hundred-thirteen consecutive patients with GISTs who underwent curative surgery from 5 medical centers were enrolled in the present study. The genomic DNA was extracted from paraffin-embedded tumor tissue, and four IGF-1 (+2995C/A, +533C/T, IVS2-16540A/G, Ex4-177G/C) and one IGF-2 (IVS1+1280A/G) gene polymorphisms were determined using a Sequenom MassARRAY system.

Results

With a median follow-up of 18.4 months, the estimated 5-year relapse-free survival and overall survival rates were 69.9% and 86.7%, respectively. In a multivariate analysis including age, gender, primary site of disease, pathology, and risk stratification, no significant association was observed between the polymorphism of the IGF-1 and IGF-2 genes and survival.

Conclusion

None of the five IGF-1 and IGF-2 gene polymorphisms investigated in this study was found to be an independent prognostic marker for Korean patients with surgically resected GIST. However, further studies on a larger scale are warranted to clarify the role of IGF-1 and IGF-2 gene polymorphisms as a prognostic biomarker for GIST patients.

Smoking, green tea consumption, genetic polymorphisms in the insulin-like growth factors and lung cancer risk

Insulin-like growth factors (IGFs) are mediators of growth hormones; they have an influence on cell proliferation and differentiation. In addition, IGF-binding protein (IGFBP)-3 could suppress the mitogenic action of IGFs. Interestingly, tea polyphenols could substantially reduce IGF1 and increase IGFBP3. In this study, we evaluated the effects of smoking, green tea consumption, as well as IGF1, IGF2, and IGFBP3 polymorphisms, on lung cancer risk. Questionnaires were administered to obtain the subjects' characteristics, including smoking habits and green tea consumption from 170 primary lung cancer cases and 340 healthy controls. Genotypes for IGF1, IGF2, and IGFBP3 were identified by polymerase chain reaction. Lung cancer cases had a higher proportion of smoking, green tea consumption of less than one cup per day, exposure to cooking fumes, and family history of lung cancer than controls. After adjusting the confounding effect, an elevated risk was observed in smokers who never drank green tea, as compared to smokers who drank green tea more than one cup per day (odds ratio (OR) = 13.16, 95% confidence interval (CI) = 2.96-58.51). Interaction between smoking and green tea consumption on lung cancer risk was also observed. Among green tea drinkers who drank more than one cup per day, IGF1 (CA)(19)/(CA)(19) and (CA)(19)/X genotypes carriers had a significantly reduced risk of lung cancer (OR = 0.06, 95% CI = 0.01-0.44) compared with IGF1 X/X carriers. Smoking-induced pulmonary carcinogenesis could be modulated by green tea consumption and their growth factor environment.

Hepatocellular carcinoma and other liver disease among Greenlanders chronically infected with hepatitis B virus: a population-based study

BACKGROUND

In Greenland, the prevalence of hepatitis B surface antigen carriers, reflecting chronic hepatitis B virus (HBV) infection, is 5%-10%. However, the incidence of cirrhosis and hepatocellular carcinoma in this population has been reported to be low. We investigated this discrepancy in a large population-based cohort study.

METHODS

In total, 8879 Greenlanders (16% of the population) were recruited for population-based surveys performed from May 5 to July 7, 1987, and from November 1 to November 21, 1998, with follow-up until March 31, 2010. HBV status was based on serological testing, supplemented by data from all available HBV registries in Greenland to determine changes in HBV status over time. Information on morbidity and mortality was obtained from the Patient Discharge Registry, the Cancer Registry, and the Central Registration System. Sex, age, ethnicity, and period-adjusted incidence rate ratios (IRRs) were estimated using Poisson regression. World standardized rates were derived from these and World Health Organization data.

RESULTS

The 650 chronically HBV-infected persons had higher rates of hepatocellular carcinoma (adjusted IRR = 8.70; 95% CI = 2.06 to 36.7), liver disease (adjusted IRR = 5.73, 95% CI = 3.52 to 9.34), and all-cause mortality (adjusted IRR = 1.47; 95% CI = 1.21 to 1.79) than the 5160 HBV-negative persons. However, the world standardized incidence rates of hepatocellular carcinoma (38.5 cancers per 100 000 person-years) and cirrhosis (24 cases per 100 000 person-years) among chronically HBV-infected persons were low compared with results from population-based studies from countries with low, intermediate, and high rates of endemic HBV infection.

CONCLUSION

The relatively low incidence of hepatocellular carcinoma and other HBV-related morbidity among chronic HBV-infected persons in Greenland suggest a more benign course of HBV among the Greenlandic Inuit than in populations in other parts of the world.

Viral hepatitis: human genes that limit infection

Treatment response and susceptibility to chronic viral hepatitis C and B may be modified by host genetic factors. The majority of genetic variants that confer a significant risk have been localized in genes involved in immune response. However, many findings could not be replicated and almost none of the identified risk factors had a noticeable impact on clinical decisions. In contrast, recent findings in independent large genome wide association studies confirmed genetic variants in the interferon gamma gene locus as strong predictors of outcome with outstanding clinical relevance. This review gives an overview on significant genetic susceptibility factors for susceptibility and treatment outcome in chronic viral hepatitis C and B that have been identified by the classical candidate gene approach and genome wide studies and also highlights some recent findings on genetic factors for common adverse drug reactions.

Putative association of transforming growth factor-alpha polymorphisms with clearance of hepatitis B virus and occurrence of hepatocellular carcinoma in patients with chronic hepatitis B virus infection

Previous studies showed that several genetic polymorphisms might influence the clinical outcome of chronic hepatitis B virus (HBV) infection, including HBV clearance or development of hepatocellular carcinoma (HCC). The aim of this study was to determine whether polymorphisms of the transforming growth factor-alpha (TGF-alpha) gene are associated with clinical outcome of HBV infection. A total of 1096 Korean subjects having either present or past evidence of HBV infection were prospectively enrolled between January 2001 and August 2003. Among 16 genetic variants in TGFA gene, nine variants were genotyped using TaqMan assay and the genetic association with HBV clearance and HCC occurrence was analysed. Statistical analyses revealed that TGFA+103461T>C, TGFA+106151C>G and TGFA-ht2 were marginally associated with clearance of HBV infection. However, only TGFA-ht2 retained significance after multiple correction (OR = 0.39, P(corr) = 0.007 in recessive model). Although no variants were significant after multiple correction, TGFA+88344G>A and TGFA+103461T>C were weakly associated in recessive model in the analysis of HCC occurrence. In addition, Cox relative hazards model also revealed that TGFA+88344G>A was associated with onset age of HCC occurrence in subjects (RH = 1.46, P(corr) = 0.04). TGF-alpha polymorphisms might be an important factor in immunity, progression of inflammatory process and carcinogenesis, which explains the variable outcome of HBV infection at least in part. Further biological evidence is warranted in the future to support these suggestive associations.

CCND2 polymorphisms associated with clearance of HBV infection

Cyclin D2s (CCND2s) are members of the D-type cyclin family. They interact and construct complexes with cyclin-dependent kinase (CDK)4 or 6. The cyclin D2/CDK4 or CDK6 complexes have key roles in controlling the progression of cell cycle from the Gap 1 (G1) phase to the synthesis (S) phase. Overexpression of cyclin D2 is associated with the development of tumors. In this study, we identified 16 sequence variants of CCND2 polymorphisms through direct DNA sequencing in 24 individuals, and 5 common variants were selected for genotyping in larger-scale subjects (n=1100). Genetic associations of those polymorphisms with hepatitis B virus (HBV) clearance and hepatocellular carcinoma (HCC) outcome among patients with HBV were analyzed. Although no significant association was observed between the polymorphisms and HCC outcome among HBV patients, one common polymorphism in the 5'-untranslated region (that is, rs1049606) and the most common haplotype (CCND-ht1 [T-C-T-A-T]), however, were significantly associated with HBV clearance (odds ratio=0.69, P=0.0002, Pcorr=0.001 and odds ratio=1.37, P=0.0009, Pcorr=0.004, respectively). The minor allele frequency of rs1049606 among the spontaneously recovered (SR) group was significantly higher than that of the chronic carrier (CC) group (frequency=0.403 vs 0.336, P=0.0002). In contrast, the frequency of CCND-ht1 was higher among the CC group than among the SR group (frequency=0.429 vs 0.374, P=0.0009). The information identified in this study might provide valuable insights into generating strategies for control of HBV.

[Genetic epidemiological study on single nucleotide polymorphisms associated with hepatocellular carcinoma in patients with chronic HBV infection]

Hepatocellular carcinoma (HCC) is associated with hepatitis B virus (HBV) as an etiologic agent in 80% of cases, and is the major cause of death among HBV carriers. Family history of HCC is a known risk factor for the development of HCC among chronically HBV infected patients; therefore, genetic factors are likely to modify the risk of HCC. However, the genetic factors that determine progression to HCC remain mostly to be recovered. It is estimated that there are millions of single nucleotide polymorphisms (SNPs) within human genome and they are likely to explain much of the genetic diversity of individuals. In this review, the natural history of HBV infection and host genetic factors related to HCC, study design and target gene selection for the detection of SNPs related to the occurrence of HCC were discussed. Also, several SNPs or haplotypes, which were reportedly associated with increased or reduced risk of HCC occurrence in patients with chronic HBV infection, were reviewed. Especially, recent studies in Korea, one of the HBV endemic areas, were discussed. Screening of these polymorphisms might be useful in clinical practice to stratify the lower or higher risk group for HCC and might modify the design of HCC surveillance programs in patients with chronic HBV infection, if further genetic susceptibilities are identified. The ongoing studies of the distributions and functions of the implicated allele polymorphisms will not only provide insight into the pathogenesis of HCC, but may also provide a novel rationale for new methods of diagnosis and therapeutic strategies.

Integrin alpha V polymorphisms and haplotypes in a Korean population are associated with susceptibility to chronic hepatitis and hepatocellular carcinoma

BACKGROUND/AIMS

Integrins are cell surface receptors for extracellular matrix (ECM) proteins that initiate signalling pathways that modulate proliferation, survival, invasion or metastasis. Consequently, integrins are potential targets for the treatment of cancer. In this study, we investigated whether single nucleotide polymorphisms (SNPs) in integrin alpha(V) (ITGAV) in a Korean population were associated with chronic hepatitis B virus (HBV) infection and HBV-infected hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

Thirteen ITGAV SNPs in 111 cases of chronic HBV infection, 86 cases of HBV-infected HCC and 107 cases of acute self-limited HBV infection were genotyped using Illumina's Sentrix array matrix (SAM) chip.

RESULTS

The ITGAV intron SNPs rs9333289 and rs11685758, the 3'-untranslated region SNP rs1839123 and haplotype 3 (T-T-A) were associated with enhanced susceptibility to HBV-infected HCC (OR=1.75-2.42; P=0.02-0.05), while the intron SNP rs2290083 was associated with both chronic infection and HBV-infected HCC (OR=1.73-2.01; P=0.01-0.04). In addition, both rs2290083 and ht1 (C-C-G) were associated with the age at which chronic infection occurred, as determined by Cox relative hazard analysis (RH=1.39-1.62, P=0.04-0.01)

CONCLUSION

ITGAV SNPs and haplotypes may be genetic factors that increase the susceptibility of Koreans to chronic HBV infection and HBV-infected HCC.

Effect of insulin-like growth factor gene polymorphisms alone or in interaction with diabetes on the risk of pancreatic cancer

Insulin-like growth factors (IGF) have been associated with risk of common human cancers, but the association between IGFs and pancreatic cancer risk is unclear. To determine whether genetic variations of IGF modify pancreatic cancer risk, we compared the frequency of six single nucleotide polymorphisms of IGF1 and IGF2 in a large-scale case control study. Single nucleotide polymorphisms were investigated using the TaqMan method in 892 patients with pancreatic ductal adenocarcinoma and 783 healthy controls who were recruited from The University of Texas M. D. Anderson Cancer Center from 2000 to 2007. Cases and controls were frequency matched by age (+/-5 years), race, and sex. Risk factor information was collected using direct interviews. We estimated odds ratios (OR) and 95% confidence intervals (95% CI) using unconditional multivariate logistic regression models. A haplotype of IGF1 gene containing the 3'-UTR Ex4 -177 G>C G allele had a significantly lower frequency in cases (0.027) than in controls (0.041; P = 0.039). A statistically significant joint effect of the IGF1 3'-UTR Ex4 -177 G>C C allele and diabetes on pancreatic cancer risk was observed. The OR (95% CI) were 1.07 (0.81-1.42), 2.12 (1.53-2.93), and 5.69 (2.63-12.3) for individuals who had the CC/CG genotype alone, diabetes alone, or both factors, respectively, compared with subjects without either of the two factors with adjustment for other risk factors. The IGF2 3'-UTR Ex4 -233C>T TT genotype was significantly associated with a reduced risk of pancreatic cancer (OR = 0.07; 95% CI = 0.01-0.57; P = 0.013). The polymorphic variants of the IGF genes may serve as a susceptibility factor for pancreatic cancer.

[Molecular mechanisms of hepatitis B virus-associated hepatocellular carcinoma]

Hepatocellular carcinoma (HCC) is one of the most common malignant diseases in the world. The hepatitis B virus (HBV) replicates non-cytopathically in hepatocytes, and most of the liver injury associated with this infection reflects the immune response. Epidemiological studies have clearly demonstrated that a chronic HBV infection is a major etiological factor in the development of HCC. The pathogenesis of HBV-associated HCC has been studied extensively, and the molecular changes during the malignant transformation have been identified. The main carcinogenic mechanism of HBV-associated HCC is related to the long term-inflammatory changes caused by a chronic hepatitis B infection, which might involve the integration of the HBV. Integration of the HBV DNA into the host genome occurs at the early steps of clonal tumorous expansion. The hepatitis B x protein (HBx) is a multifunctional regulatory protein that communicates directly or indirectly with a variety of host targets, and mediates many opposing cellular functions, including its function in cell cycle regulation, transcriptional regulation, signaling, encoding of the cytoskeleton and cell adhesion molecules, as well as oncogenes and tumor suppressor genes. Continued study of the mechanisms of hepatocarcinogenesis will refine our current understanding of the molecular and cellular basis for neoplastic transformations in the liver. This review summarizes the current knowledge of the mechanisms involved in HBV-associated hepatocarcinogenesis.

Molecular Pathogenesis of Hepatitis-B-virus-associated Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most frequent and malignant diseases worldwide. Epidemiological studies have clearly demonstrated that chronic hepatitis B virus (HBV) infection is a major etiological factor in the development of HCC. The pathogenesis of HBV-associated HCC has been studied extensively, and the molecular changes associated with malignant transformation have been identified. The predominant carcinogenic mechanisms of HBV-associated HCC are chronic inflammation and the effects of cytokines in the development of fibrosis and liver cell proliferation. An important role is also played by the integration of HBV DNA into host cellular DNA, which disrupts or promotes the expression of cellular genes that are important in cell growth and differentiation. Especially, HBx protein is a transactivating protein that promotes cell growth, survival, and the development of HCC. Continued investigation of the mechanisms underlying hepatocarcinogenesis will refine our current understanding of the molecular and cellular basis for neoplastic transformation in the liver. Prevention of HBV infections and effective treatments for chronic hepatitis B are still needed for the global control of HBV-associated HCC. This review summarizes the current knowledge on the mechanisms involved in HBV-associated hepatocarcinogenesis.

Molecular genetics of human growth hormone, insulin-like growth factors and their pathways in common disease

The human growth hormone gene (GH1) and the insulin-like growth factor 1 and 2 genes (IGF1 and IGF2) encode the central elements of a key pathway influencing growth in humans. This "growth pathway" also includes transcription factors, agonists, antagonists, receptors, binding proteins, and endocrine factors that constitute an intrincate network of feedback loops. GH1 is evolutionarily coupled with other genes in linkage disequilibrium in 17q24.2, and the same applies to IGF2 in 11p15.5. In contrast, IGF1 in 12q22-24.1 is not in strong linkage disequilibrium with neighbouring genes. Knowledge of the functional architecture of these regions is important for the understanding of the combined evolution and function of GH1, IGF2 and IGF1 in relation to complex diseases. A number of mutations accounting for rare Mendelian disorders have been described in GH-IGF elements. The constellation of genes in this key pathway contains potential candidates in a number of complex diseases, including growth disorders, metabolic syndrome, diabetes (notably IGF2BP2) cardiovascular disease, and central nervous system diseases, and in longevity, aging and cancer. We review these genes and their associations with disease phenotypes, with special attention to metabolic risk traits.

Insulin, insulin-like growth factors and colon cancer: a review of the evidence

Insulin and insulin-like growth factor (IGF) axes are major determinants of proliferation and apoptosis and thus may influence carcinogenesis. In various animal models, modulation of insulin and IGF-1 levels through various means, including direct infusion, energy excess or restriction, genetically induced obesity, dietary quality including fatty acid and sucrose content, inhibition of normal insulin secretion and pharmacologic inhibition of IGF-1, influences colonic carcinogenesis. Human evidence also associates high levels of insulin and IGF-1 with increased risk of colon cancer. Clinical conditions associated with high levels of insulin (noninsulin-dependent diabetes mellitus and hypertriglyceridemia) and IGF-1 (acromegaly) are related to increased risk of colon cancer, and increased circulating concentrations of insulin and IGF-1 are related to a higher risk of colonic neoplasia. Determinants and markers of hyperinsulinemia (physical inactivity, high body mass index, central adiposity) and high IGF-1 levels (tall stature) are also related to higher risk. Many studies indicate that dietary patterns that stimulate insulin resistance or secretion, including high consumption of sucrose, various sources of starch, a high glycemic index and high saturated fatty acid intake, are associated with a higher risk of colon cancer. Although additional environmental and genetic factors affect colon cancer, the incidence of this malignancy was invariably low before the technological advances that rendered sedentary lifestyles and obesity common, and increased availability of highly processed carbohydrates and saturated fatty acids. Efforts to counter these patterns are likely to have the most potential to reduce colon cancer incidence, as well as cardiovascular disease and diabetes mellitus.