APC promoter methylation and protein expression in hepatocellular carcinoma

Circulating tumor DNA in management of primary liver malignancy: A review of the literature and future directions

Primary liver malignancies are a serious and challenging global health concern. The most common primary tumors are hepatocellular carcinoma and cholangiocarcinoma. These diseases portend poor prognosis when presenting with progressive, extensive disease. There is a critical need for improved diagnosis, therapeutic intervention, and monitoring surveillance in liver-related malignancies. Liquid biopsy using ctDNA provides an opportunity for growth within these domains for liver-related malignancy. However, ctDNA is relatively understudied in this field compared with other solid tumor types, possibly due to the complex nature of the pathology. In this review, we aim to discuss ctDNA, the current literature, and future directions of this technology within primary liver malignancies.

Adenomatous Polyposis Coli (APC) Promoter Gene Methylation in Urine-Derived DNA: A Non-invasive Biomarker for Early Bladder Cancer Detection and Tumor Aggressiveness

Background Bladder urothelial carcinoma (BLCA) is a major cause of morbidity and mortality worldwide, largely due to the high frequency of disease relapse and the lack of efficient endoscopic diagnostic methods. This study aimed to address this clinical gap by evaluating the potential of using adenomatous polyposis coli (APC) gene promoter methylation as a biomarker detectable in urine DNA of individuals with BLCA. Methods Methylation-specific PCR was used to determine the methylation status of the APC promoter gene in 50 bladder carcinoma patients and 50 apparently healthy individuals. Electrophoresis on agarose gel was performed for the detection of PCR products. Statistical analysis was conducted using Excel, SPSS, and Python to assess correlations and significance. Results APC promoter methylation was detected in 34 (68%) of bladder cancer cases but in only eight (16%) of healthy controls, indicating a strong association between APC promoter methylation and bladder cancer (p < 0.001). High-grade tumors were found to have significantly higher levels of APC promoter methylation, suggesting a link between APC methylation and tumor aggressiveness (p = 0.048). Smoking was identified as a significant risk factor for BLCA (p < 0.001), but no correlation was observed with the tumor stage. Conclusion APC promoter gene methylation shows a diagnostic value for BLCA and may be useful as a non-invasive marker for early detection. This study highlights the clinical utility of using a simple urine test to detect bladder cancer, particularly in early stages, and suggests that combining APC methylation with other specific biomarkers could enhance diagnostic accuracy.

Measuring the differential expression of the major hypermethylated tumor suppressor genes in tissues of primary hepatocellular carcinoma

BACKGROUND

Hepatocarcinogenesis is a multifactorial process that arises from a integration of genetic and epigenetic anomalies leading to abnormal gene expression and function. It is difficult to characterize HCC with a single biomarker. Our study aimed at detecting the expression of a panel of 8 methylated genes (SOCS1, APC, Gadd45b, CDKN1B, P15, PAX6, STAT1 and MSH2) as regulatory factors among Egyptian patients with HCC.

METHODS

This study was conducted on HCC tissue samples of 30 Egyptian patients in comparison with their non-cancerous adjacent cirrhotic tissue as a control. Tissue samples were obtained from patients who have undergone living donor liver transplantation (LDLT) or liver resection at El Sahel Teaching Hospital (Cairo, Egypt). A special Custom designed PCR Arrays was used to analyze the expression profiles of chosen methylated genes associated with HCC.

RESULTS

Expression of SOCS1, APC, Gadd45b, CDKN1B, P15, PAX6, STAT1 and MSH2 were lower in the HCC tissue compared to the cirrhotic tissue (pvalue = 0.015, 0.081, 0.004, 0.027, 0.211, 0.015, 0.025 and 0.0001 respectively). 5 genes (SOCS1, APC, GAdd45b, CDKN1B, and MSH2) showed the ability to be used as diagnostic biomarkers for HCC with high sensitivity and specificity values at cut off values: 1.05, 1.17, 0.995, 0.546, and 0.125 respectively. As for the other 3 genes (P15, PAX6, STAT1), PAX6 gene has the highest sensitivity at a cut off value of 0.3364. A significant negative correlation was shown between alpha fetoprotein (AFP) and 5 of the studied genes (SOCS1, APC, Gadd45b, STAT1, and MSH2).

CONCLUSIONS

Expression of the selected hypermethylated genes (SOCS1, APC, Gadd45b, CDKN1B, P15, PAX6, STAT1 and MSH2) in HCC tissue samples was lower than adjacent tissue. Their role should be further studied to solve the mystery that surrounds the pathogenesis of HCC.

Plasma Cell-Free Adenomatous Polyposis Coli Gene Promoter Methylation as a Prognostic Biomarker for Hepatocellular Carcinoma

INTRODUCTION

Hepatocellular carcinoma (HCC) is a leading cause of cancer death worldwide. Lack of biomarkers for follow-up after treatment is a clinical challenge. DNA methylation has been proposed to be a potential biomarker in HCC. However, there is still a lack of evidence of its clinical use. This study aimed to evaluate the value of using plasma Adenomatous Polyposis Coli promoter methylation level (APC-MET) as a potential biomarker in HCC treatment.

METHOD

A total of 96 patients with HCC at BCLC stage B who underwent local tumor ablation treatment were prospectively included in this study. APC-MET was examined in the plasma of each patient before and 1 month after treatment. The prediction value of APC-MET for survival outcome and disease status after treatment was analyzed and adjusted with alpha-fetoprotein and protein induced by vitamin K absence-II using Cox regression analysis.

RESULTS

Univariate Cox regression analysis showed preoperative APC-MET >0 (HR, 2.9, 95% CI: 1.05-8.05, p = 0.041) and postoperative APC-MET >0 (HR, 3.47, 95% CI: 1.16-10.4, p = 0.026) were both predictors of death, and preoperative APC-MET >0 was a predictor of disease progression after treatment (HR, 2.04, 95% CI: 1.21-3.44, p = 0.007). In multivariate models, preoperative APC-MET >0 was a significant predictor of disease progression after adjusting with the other two traditional biomarkers (HR, 1.82, 95% CI: 1.05-3.17, p = 0.034).

CONCLUSIONS

Hypermethylation of APC promoter appears to be a potential biomarker that could predict patient survival and disease progression outcomes in patients with intermediate-stage HCC after local ablation treatment.

The assessment of circulating tumor DNA associated with Wnt/β-catenin signaling pathway as a diagnostic tool for liver cancer: a systematic review and meta-analysis

BACKGROUND

Circulating tumor DNA (ctDNA) in peripheral blood has become a promising noninvasive biomarker. However, the diagnostic potential of Wnt/β-catenin signaling pathway-related ctDNA for liver cancer is controversial. Here, we aimed to access the diagnostic potential and clinicopathological features of Wnt/β-catenin signaling pathway-related ctDNA in liver cancer and provide data support for its clinical diagnosis and treatment.

METHODS

A comprehensive literature search was conducted to identify the relevant studies. The methodological quality of the included studies was evaluated using the QUADAS-2 tool. The bivariate linear mixed models were used.

RESULTS

The AUC (area under the curve), pooled sensitivity and specificity were 0.77, 0.42 and 0.98, respectively. The findings suggested that control type, sample source, research methods and thresholds were the potential sources of heterogeneity (p < 0.05). Additionally, this study also found that there were significant correlations between the hypermethylation of Wnt/β-catenin signaling pathway-related ctDNA and tumor size, TNM stage, distant metastasis, and HBV infection(p < 0.05).

CONCLUSION

This study confirmed that Wnt/β-catenin signaling pathway-related ctDNA had the better diagnostic potential for liver cancer and might be an effective complementary tool for serum AFP assays in the early diagnosis of liver cancer.

PROSPERO

(No. CRD42023404984).[Figure: see text].

APC-driven actin nucleation powers collective cell dynamics in colorectal cancer cells

Cell remodeling relies on dynamic rearrangements of cell contacts powered by the actin cytoskeleton. The tumor suppressor adenomatous polyposis coli (APC) nucleate actin filaments (F-actin) and localizes at cell junctions. Whether APC-driven actin nucleation acts in cell junction remodeling remains unknown. By combining bioimaging and genetic tools with artificial intelligence algorithms applied to colorectal cancer cell, we found that the APC-dependent actin pool contributes to sustaining levels of F-actin, as well as E-cadherin and occludin protein levels at cell junctions. Moreover, this activity preserved cell junction length and angle, as well as vertex motion and integrity. Loss of this F-actin pool led to larger cells with slow and random cell movement within a sheet. Our findings suggest that APC-driven actin nucleation promotes cell junction integrity and dynamics to facilitate collective cell remodeling and motility. This offers a new perspective to explore the relevance of APC-driven cytoskeletal function in gut morphogenesis.

Distinct phenotypic spectra of hepatocellular carcinoma in liver-specific tumor suppressor-deficient hepatitis B virus transgenic mice

The hepatitis B virus (HBV) transgenic mouse model was used to interrogate the origins of HCC heterogeneity. HBV biosynthesis was used as a marker of liver tumor heterogeneity. Principal component and correlation analysis of HBV and cellular transcript levels demonstrated major differences within and between the gene expression profiles of Apc-deficient, Apc-deficient Pten-deficient, and Pten-deficient HCC. Hence, both oncogenic stimuli and zonal hepatocyte properties determine heterogeneous HCC phenotypes. Additionally, Apc-deficient HCC display decreased expression of Apob, Otc and Tet2 relative to Pten-deficient HCC and control liver tissue suggesting their gene products may represent markers of Apc-deficient HCC. A subset of human HCC with mutations in the β-catenin gene (CTNNB1) displayed a gene expression profile similar to that observed in the mouse Apc-deficient HCC indicating this model of liver cancer may be useful for interrogating the molecular properties of these tumors and their potential therapeutic vulnerabilities.

Methylation site APC112043544 as a potential biomarker for post-transplant hepatocellular carcinoma recurrence

Objective: To investigate the prognostic value of DNA methylation of tumor suppressor genes for hepatocellular carcinoma (HCC) recurrence after liver transplantation. Methods: APC gene was selected according to The Cancer Genome Atlas dataset. Tumor tissues and clinical data of 85 HCC patients who received a liver transplantation were retrospectively enrolled and next-generation methylation sequencing was performed. Risk factors were determined using the Cox proportional-hazard-regression model. Results: The APC methylation site (chromosome 5, position 112043544) was an independent predictor of post-transplant HCC recurrence. Patients with hyper-methylated APC112043544 experienced superior recurrence-free survival (p = 0.021) and had a decreased proportion of microvascular invasion (p = 0.017). APC112043544 also predicted recurrence risk in patients beyond selection criteria. Conclusions: APC112043544 methylation may serve as a potential biomarker for post-transplant HCC recurrence.

Targeting Wnt Signaling in Endometrial Cancer

Simple Summary

Wnt has diverse regulatory roles at multiple cellular levels and numerous targeting points, and aberrant Wnt signaling has crucial roles in carcinogenesis, metastasis, cancer recurrence, and chemotherapy resistance; based on these facts, Wnt represents an appealing therapeutic target for cancer treatment. Although preclinical data supports a role for the Wnt signaling pathway in uterine carcinogenesis, this area remains understudied. In this review, we identify the functions of several oncogenes of the Wnt/β-catenin signaling pathway in tumorigenesis and address the translation approach with potent Wnt inhibitors that have already been established or are being investigated to target key components of the pathway. Further research is likely to expand the potential for both biomarker and cancer drug development. There is a scarcity of treatment choices for advanced and recurrent endometrial cancer; investigating the sophisticated connections of Wnt signaling networks in endometrial cancer could address the unmet need for new therapeutic targets.

Abstract

This review presents new findings on Wnt signaling in endometrial carcinoma and implications for possible future treatments. The Wnt proteins are essential mediators in cell signaling during vertebrate embryo development. Recent biochemical and genetic studies have provided significant insight into Wnt signaling, in particular in cell cycle regulation, inflammation, and cancer. The role of Wnt signaling is well established in gastrointestinal and breast cancers, but its function in gynecologic cancers, especially in endometrial cancers, has not been well elucidated. Development of a subset of endometrial carcinomas has been attributed to activation of the APC/β-catenin signaling pathway (due to β-catenin mutations) and downregulation of Wnt antagonists by epigenetic silencing. The Wnt pathway also appears to be linked to estrogen and progesterone, and new findings implicate it in mTOR and Hedgehog signaling. Therapeutic interference of Wnt signaling remains a significant challenge. Herein, we discuss the Wnt-activating mechanisms in endometrial cancer and review the current advances and challenges in drug discovery.

Molecular and immunological paradigms of hepatocellular carcinoma: Special reference to therapeutic approaches

The development of hepatocellular carcinoma (HCC) is a multistep process with a complex interaction of various genetic backgrounds and the tumor microenvironment. In addition to the development of rational approaches to epidemiologic research, early detection, and diagnosis, considerable progress has been made in systemic treatment with molecular-targeted agents for patients with advanced HCC. Moreover, encouraging reports of recent clinical trials of combination therapy with immune-checkpoint inhibitors (ICIs) has raised high hopes. Each HCC is the result of a unique combination of somatic alterations, including genetic, epigenetic, transcriptomic, and metabolic events, leading to conclusive tumoral heterogeneity. Recent advances in comprehensive genetic analysis have accelerated molecular classification and defined subtypes with specific characteristics, including immune-associated molecular profiles reflecting the immune reactivity in the tumor. In considering the development of therapeutic strategies in combination with immunotherapy, proper interpretation of molecular pathological characterization could lead to effective therapeutic deployment and enable individualization of the management of HCC. Here, we review distinctive molecular alterations in the subtype classification of HCC, current therapies, and representative clinical trials with alternative immune-combination approaches from a molecular pathological point.

Casein Kinase 1α as a Regulator of Wnt-Driven Cancer

Wnt signaling regulates numerous cellular processes during embryonic development and adult tissue homeostasis. Underscoring this physiological importance, deregulation of the Wnt signaling pathway is associated with many disease states, including cancer. Here, we review pivotal regulatory events in the Wnt signaling pathway that drive cancer growth. We then discuss the roles of the established negative Wnt regulator, casein kinase 1α (CK1α), in Wnt signaling. Although the study of CK1α has been ongoing for several decades, the bulk of such research has focused on how it phosphorylates and regulates its various substrates. We focus here on what is known about the mechanisms controlling CK1α, including its putative regulatory proteins and alternative splicing variants. Finally, we describe the discovery and validation of a family of pharmacological CK1α activators capable of inhibiting Wnt pathway activity. One of the important advantages of CK1α activators, relative to other classes of Wnt inhibitors, is their reduced on-target toxicity, overcoming one of the major impediments to developing a clinically relevant Wnt inhibitor. Therefore, we also discuss mechanisms that regulate CK1α steady-state homeostasis, which may contribute to the deregulation of Wnt pathway activity in cancer and underlie the enhanced therapeutic index of CK1α activators.

Regulation of Wnt Signaling through Ubiquitination and Deubiquitination in Cancers

The Wnt signaling pathway plays important roles in embryonic development, homeostatic processes, cell differentiation, cell polarity, cell proliferation, and cell migration via the β-catenin binding of Wnt target genes. Dysregulation of Wnt signaling is associated with various diseases such as cancer, aging, Alzheimer’s disease, metabolic disease, and pigmentation disorders. Numerous studies entailing the Wnt signaling pathway have been conducted for various cancers. Diverse signaling factors mediate the up- or down-regulation of Wnt signaling through post-translational modifications (PTMs), and aberrant regulation is associated with several different malignancies in humans. Of the numerous PTMs involved, most Wnt signaling factors are regulated by ubiquitination and deubiquitination. Ubiquitination by E3 ligase attaches ubiquitins to target proteins and usually induces proteasomal degradation of Wnt signaling factors such as β-catenin, Axin, GSK3, and Dvl. Conversely, deubiquitination induced by the deubiquitinating enzymes (DUBs) detaches the ubiquitins and modulates the stability of signaling factors. In this review, we discuss the effects of ubiquitination and deubiquitination on the Wnt signaling pathway, and the inhibitors of DUBs that can be applied for cancer therapeutic strategies.

Progress in research on association between cell signal transduction pathways and hepatocellular carcinoma

Cell signal transduction refers to the process by which a signal molecule induces signal transduction in a cell by stimulating the cell membrane or intracellular receptor, thereby affecting the biological function of the cell. In recent years, studies have found that the activation or inhibition of certain cell signal transduction pathways plays an important role in the development and progression of hepatocellular carcinoma. This article will review the recent research progress in the understanding of the role of some common signal transduction pathways in hepatocellular carcinoma.

Genomic Medicine and Implications for Hepatocellular Carcinoma Prevention and Therapy

The pathogenesis of hepatocellular carcinoma (HCC) is poorly understood, but recent advances in genomics have increased our understanding of the mechanisms by which hepatitis B virus, hepatitis C virus, alcohol, fatty liver disease, and other environmental factors, such as aflatoxin, cause liver cancer. Genetic analyses of liver tissues from patients have provided important information about tumor initiation and progression. Findings from these studies can potentially be used to individualize the management of HCC. In addition to sorafenib, other multi-kinase inhibitors have been approved recently for treatment of HCC, and the preliminary success of immunotherapy has raised hopes. Continued progress in genomic medicine could improve classification of HCCs based on their molecular features and lead to new treatments for patients with liver cancer.

Screening the key genes of hepatocellular adenoma via microarray analysis of DNA expression and methylation profiles

The aim of the present study was to identify the biomarkers involved in the development of hepatocellular adenoma (HCA) through integrated analysis of gene expression and methylation microarray. The microarray dataset GSE7473, containing HNF1α-mutated HCA and their corresponding non-tumor livers, 5 HNF1α-mutated HCA and 4 non-related non-tumor livers, was downloaded from the Gene Expression Omnibus (GEO) database. The DNA methylation profile GSE43091, consisting of 50 HCA and 4 normal liver tissues, was also downloaded from the GEO database. Differentially expressed genes (DEGs) were identified by the limma package of R. A t-test was conducted on the differentially methylated sites. Functional enrichment analysis of DEGs was performed through the Database for Annotation, Visualization and Integrated Analysis. The genes corresponding to the differentially methylated sites were obtained by the annotation files of methylation chip platform. A total of 182 DEGs and 3,902 differentially methylated sites were identified in HCA. In addition, 238 enriched GO terms, including organic acid metabolic process and carboxylic acid metabolic process, and 14 KEGG pathways, including chemical carcinogenesis, were identified. Furthermore, 12 DEGs were identified to contain differentially methylated sites, among which, 8 overlapped genes, including pregnancy zone protein and solute carrier family 22 member 1 (SLC22A1), exhibited inverse associations between gene expression levels and DNA methylation levels. The DNA methylation levels may be potential targets of HCA. The present study revealed that the 8 overlapped genes, including annexin A2, chitinase 3-like 1, fibroblast growth factor receptor 4, mal, T-cell differentiation protein like, palladin, cytoskeletal associated protein, plasmalemma vesicle associated protein and SLC22A1, may be potential therapeutic targets of HCA.

Building Classification Models with Combined Biomarker Tests: Application to Early Detection of Liver Cancer

Early detection of hepatocellular carcinoma (HCC) is critical for the effective treatment. Alpha fetoprotein (AFP) serum level is currently used for HCC screening, but the cutoff of the AFP test has limited sensitivity (~50%), indicating a high false negative rate. We have successfully demonstrated that cancer derived DNA biomarkers can be detected in urine of patients with cancer and can be used for the early detection of cancer (Jain et al., 2015; Lin et al., 2011; Song et al., 2012; Su, Lin, Song, & Jain, 2014; Su, Wang, Norton, Brenner, & Block, 2008). By combining urine biomarkers (uBMK) values and serum AFP (sAFP) level, a new classification model has been proposed for more efficient HCC screening. Several criterions have been discussed to optimal the cutoff for uBMK score and sAFP score. A joint distribution of sAFP and uBMK with point mass has been fitted using maximum likelihood method. Numerical results show that the sAFP data and uBMK data are very well described by proposed model. A tree-structured sequential test can be optimized by selecting the cutoffs. Bootstrap simulations also show the robust classification results with the optimal cutoff.

Association between Hepatitis C Virus Infection, p53 Phenotypes, and Gene Variants of Adenomatous Polyposis Coli in Hepatocellular Carcinomas

OBJECTIVE

To investigate the clinical value of p53 codon 72 single nucleotide polymorphisms (SNPs) and variants of adenomatous polyposis coli (APC) in hepatocellular carcinomas (HCCs).

METHODS

DNA and RNA from 51 HCCs and their matching, uninvolved liver tissues were analyzed for p53 mutations, and the methylation and expression of APC variants were determined. Proliferation of each HCC was assessed by Ki67 immunohistochemistry. The results were correlated with the demographic and clinicopathologic features and patient survival.

RESULTS

Of 51 HCCs, 12% exhibited missense p53 mutations. SNP analysis of p53 codon 72 demonstrated the highest prevalence of the Arg/Arg (56%) phenotype, followed by Arg/Pro (33%) and Pro/Pro (11%). Four of five cases with the Pro/Pro phenotype were African Americans (AAs). All five cases with the Pro/Pro phenotype had hepatitis C virus (HCV) infections, a high Ki67 index, and lower median survival (15.5 months) compared to those with Arg/Arg or Arg/Pro phenotypes (32 months). The overall frequency of APC methylation was 31%, which was found predominantly in Caucasians. There was lower mRNA expression of APC variants-2 and -3 in both HCCs and corresponding adjacent, uninvolved liver tissues as compared to APC variant-1. The expression of APC variant-3, but not variants-1 and -2, was lower in HCCs relative to uninvolved tissues. Expression of all APC variants was lower in HCCs with APC methylation relative to HCCs without APC methylation, and low expression of APC variant-2 was associated with the Pro/Pro phenotype.

CONCLUSIONS

These findings suggest that, for AA patients with HCCs, the p53 Pro/Pro phenotype and low expression of APC variant-2 are associated with aggressive tumor behavior, HCV infection, and poor clinical outcome.

Hepatocellular carcinoma mouse models: Hepatitis B virus-associated hepatocarcinogenesis and haploinsufficient tumor suppressor genes

The multifactorial and multistage pathogenesis of hepatocellular carcinoma (HCC) has fascinated a wide spectrum of scientists for decades. While a number of major risk factors have been identified, their mechanistic roles in hepatocarcinogenesis still need to be elucidated. Many tumor suppressor genes (TSGs) have been identified as being involved in HCC. These TSGs can be classified into two groups depending on the situation with respect to allelic mutation/loss in the tumors: the recessive TSGs with two required mutated alleles and the haploinsufficient TSGs with one required mutated allele. Hepatitis B virus (HBV) is one of the most important risk factors associated with HCC. Although mice cannot be infected with HBV due to the narrow host range of HBV and the lack of a proper receptor, one advantage of mouse models for HBV/HCC research is the numerous and powerful genetic tools that help investigate the phenotypic effects of viral proteins and allow the dissection of the dose-dependent action of TSGs. Here, we mainly focus on the application of mouse models in relation to HBV-associated HCC and on TSGs that act either in a recessive or in a haploinsufficient manner. Discoveries obtained using mouse models will have a great impact on HCC translational medicine.

DNA methyltransferase 3b silencing affects locus-specific DNA methylation and inhibits proliferation, migration and invasion in human hepatocellular carcinoma SMMC-7721 and BEL-7402 cells

DNA methylation is an important regulator of gene transcription, and its role in carcinogenesis has been a topic of considerable interest in previous years. The present study examined the influence of DNA methyltransferase 3b (DNMT3b) on cell proliferation, migration and invasion, and the methylation status of identified tumor suppressor genes in hepatoma SMMC-7721 and BEL-7402 cells. DNMT3b was silenced by small interfering RNA (siRNA) in human hepatocellular carcinoma cell lines. Transfection efficiency was verified using a fluorescent imaging system, reverse transcription polymerase chain reaction (RT-PCR) and western blotting. A cell proliferation assay was performed to evaluate cell viability. Cell cycle distribution and apoptosis were analyzed by flow cytometry. The migratory and invasive ability of cells was measured using a Transwell assay. Methylation-specific PCR (MSP) was performed to assess methylation in the promoter region of genes. The present data revealed that DNMT3b siRNA successfully inhibited expression of the DNMT3b gene in these two liver cancer cell lines and therefore inhibited the proliferation of the transfected cells, stimulated apoptosis in the cells, led to an accumulation of cells in the G2/M phase and decreased cell migration and invasion. It was also found that silencing DNMT3b expression results in hypomethylation of specific sets of gene promoters and increases the expression of distinct set of genes in HCC cell lines. The present study is therefore useful for assessing the specificity of emerging action based on the altered expression of associated regulatory genes, particularly in methylation-silenced genes.

Global increase of p16INK4a in APC-deficient mouse liver drives clonal growth of p16INK4a-negative tumors

Reduction of β-catenin (CTNNB1) destroying complex components, for example, adenomatous polyposis coli (APC), induces β-catenin signaling and subsequently triggers activation of genes involved in proliferation and tumorigenesis. Though diminished expression of APC has organ-specific and threshold-dependent influence on the development of liver tumors in mice, the molecular basis is poorly understood. Therefore, a detailed investigation was conducted to determine the underlying mechanism in the development of liver tumors under reduced APC levels. Mouse liver at different developmental stages was analyzed in terms of β-catenin target genes including Cyp2e1, Glul, and Ihh using real-time RT-PCR, reporter gene assays, and immunohistologic methods with consideration of liver zonation. Data from human livers with mutations in APC derived from patients with familial adenomatous polyposis (FAP) were also included. Hepatocyte senescence was investigated by determining p16(INK4a) expression level, presence of senescence-associated β-galactosidase activity, and assessing ploidy. A β-catenin activation of hepatocytes does not always result in β-catenin positive but unexpectedly also in mixed and β-catenin-negative tumors. In summary, a senescence-inducing program was found in hepatocytes with increased β-catenin levels and a positive selection of hepatocytes lacking p16(INK4a), by epigenetic silencing, drives the development of liver tumors in mice with reduced APC expression (Apc(580S) mice). The lack of p16(INK4a) was also detected in liver tumors of mice with triggers other than APC reduction.

IMPLICATIONS

Epigenetic silencing of p16(Ink4a) in selected liver cells bypassing senescence is a general principle for development of liver tumors with β-catenin involvement in mice independent of the initial stimulus.

DNA markers in molecular diagnostics for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the one of the leading causes of cancer mortality in the world, mainly due to the difficulty of early detection and limited therapeutic options. The implementation of HCC surveillance programs in well-defined, high-risk populations were only able to detect about 40-50% of HCC at curative stages (Barcelona Clinic Liver Cancer stages 0 & 1) due to the low sensitivities of the current screening methods. The advance of sequencing technologies has identified numerous modifications as potential candidate DNA markers for diagnosis/surveillance. Here we aim to provide an overview of the DNA alterations that result in activation of cancer pathways known to potentially drive HCC carcinogenesis and to summarize performance characteristics of each DNA marker in the periphery (blood or urine) for HCC screening.

TALEN-mediated somatic mutagenesis in murine models of cancer

Cancer genome sequencing has identified numerous somatic mutations whose biologic relevance is uncertain. In this study, we used genome-editing tools to create and analyze targeted somatic mutations in murine models of liver cancer. Transcription activator-like effector nucleases (TALEN) were designed against β-catenin (Ctnnb1) and adenomatous polyposis coli (Apc), two commonly mutated genes in hepatocellular carcinoma (HCC), to generate isogenic HCC cell lines. Both mutant cell lines exhibited evidence of Wnt pathway dysregulation. We asked whether these TALENs could create targeted somatic mutations after hydrodynamic transfection into mouse liver. TALENs targeting β-catenin promoted endogenous HCC carrying the intended gain-of-function mutations. However, TALENs targeting Apc were not as efficient in inducing in vivo homozygous loss-of-function mutations. We hypothesized that hepatocyte polyploidy might be protective against TALEN-induced loss of heterozygosity, and indeed Apc gene editing was less efficient in tetraploid than in diploid hepatocytes. To increase efficiency, we administered adenoviral Apc TALENs and found that we could achieve a higher mutagenesis rate in vivo. Our results demonstrate that genome-editing tools can enable the in vivo study of cancer genes and faithfully recapitulate the mosaic nature of mutagenesis in mouse cancer models. Cancer Res; 74(18); 5311-21. ©2014 AACR.

Dysregulated expression of dickkopfs for potential detection of hepatocellular carcinoma

The prognosis for hepatocellular carcinoma (HCC) remains dismal due to the lack of diagnostic markers for early detection. This review will discuss the clinical potential of the dickkopf (DKK) family members as diagnostic and/or prognostic markers for HCC. In comparison to serum α-fetoprotein (AFP) level, which remains the gold standard for HCC diagnosis, high serum DKK1 levels have higher diagnostic value for HCC, especially for AFP-negative HCC, and can distinguish HCC from non-malignant chronic liver diseases. Additionally, the combination of serum DKK1 and AFP levels enhances diagnostic accuracy for HCC compared to serum DKK1 or AFP levels alone. Although DKK1 offers potential for its use in HCC diagnosis this review will discuss the challenges facing DKK1 and also shed some light on recent developments on the remaining DKK family members: DKK2, DKK3 and DKK4.

Quantitative analysis of APC promoter methylation in hepatocellular carcinoma and its prognostic implications

The present study aimed to quantitatively determine the aberrant methylation signal of the adenomatous polyposis coli (APC) gene in hepatocellular carcinoma (HCC), and to evaluate whether hypermethylation of the APC promoter could be a prognostic biomarker for HCC. Taqman probe-based quantitative methylation-specific polymerase chain reaction was performed to identify the APC promoter methylation levels in 57 HCC and corresponding non-tumorous liver tissues. In the present study, the methylation level of the APC promoter was upregulated by 4.51-fold in the HCC tissues compared with the non-cancerous tissues (P=0.0003). With regard to the clinicopathological data, the methylation level of the APC promoter in the HCC samples was higher in the patients with larger tumors when the cut-off was set at 4 cm (P=0.0008), and in the older patients when the cut-off was set at 60 years old (P=0.0438). However, the methylation status in the HCC samples appeared not to affect the overall patient survival rate (P=0.1684). The findings of the present study showed that APC promoter hypermethylation accumulates during the development of HCC, but that it may not be a promising prognostic biomarker for HCC.

Expression profile and function of Wnt signaling mechanisms in malignant mesothelioma cells

Malignant mesothelioma (MM) is an uncommon and particularly aggressive cancer associated with asbestos exposure, which currently presents an intractable clinical challenge. Wnt signaling has been reported to play a role in the neoplastic properties of mesothelioma cells but has not been investigated in detail in this cancer. We surveyed expression of Wnts, their receptors, and other key molecules in this pathway in well established in vitro mesothelioma models in comparison with primary mesothelial cultures. We also tested the biological response of MM cell lines to exogenous Wnt and secreted regulators, as well as targeting β-catenin. We detected frequent expression of Wnt3 and Wnt5a, as well as Fzd 2, 4 and 6. The mRNA of Wnt4, Fzd3, sFRP4, APC and axin2 were downregulated in MM relative to mesothelial cells while LEF1 was overexpressed in MM. Functionally, we observed that Wnt3a stimulated MM proliferation while sFRP4 was inhibitory. Furthermore, directly targeting β-catenin expression could sensitise MM cells to cytotoxic drugs. These results provide evidence for altered expression of a number of Wnt/Fzd signaling molecules in MM. Modulation of Wnt signaling in MM may prove a means of targeting proliferation and drug resistance in this cancer.

Human hepatocyte carcinogenesis (review)

Hepatocellular carcinoma is the third most frequent cause of cancer-related death worldwide; and its incidence rate is increasing. Clinical and molecular medical analyses have revealed substantial information on hepatocarcinogenesis. Hepatocarcinogenesis is a stepwise process during which multiple genes are altered. Genetic changes and their biological consequences in human HCC can be divided into at least 4 groups: i) tumor suppressor genes (p53, retinoblastoma, phosphatase tensin homolog and runt-related transcription factor 3), ii) oncogenes (myc, K-ras, BRAF), iii) reactivation of developmental pathways (Wnt, hedgehog), and iv) growth factors and their receptors (transforming growth factor-α, insulin-like growth factor-2 receptor). An experimental model of human hepatocarcinogenesis such as in vitro neoplastic transformation of human hepatocytes has not been successfully achieved yet, but several immortalized human hepatocyte cell lines have been established. These immortalized human hepatocytes will become useful tools for the elucidation of hepatocarcinogenesis, especially for the initial step of multistep hepatocarcinogenesis.

Inhibition of DNA methyltransferase activity and expression by treatment with the pan-deacetylase inhibitor panobinostat in hepatocellular carcinoma cell lines

BACKGROUND

Hepatocellular carcinoma (HCC) still represents an unmet medical need. Epigenetic inactivation of tumor suppressor genes like RASSF1A or APC by overexpression of DNA methyltransferases (DNMTs) has been shown to be common in HCC and to be linked to the overall prognosis of patients. Inhibitors of protein and histone deacetylases (DACi) have been demonstrated to possess strong anti-tumor effects in HCC models.

METHODS

We therefore investigated whether DACi also has any influence on the expression and activity of DNMTs and methylated target genes in HepG2 and Hep3B cell culture systems and in a xenograft model by immunohistochemistry, westernblotting, RT-qPCR and methylation-specific PCR.

RESULTS

Our findings demonstrate a rapid inhibition of DNMT activity 6 h after treatment with 0.1 μM of the pan-DACi panobinostat. A downregulation of DNMT mRNAs and protein were also observed at later points in time. This loss of DNMT activity and expression was paralleled by a diminished methylation of the target genes RASSF1A and APC and a concomitant re-expression of APC mRNA and protein. Analysis of HepG2 xenograft specimens confirmed these results in vivo.

CONCLUSION

We suggest a dual mode of action of DACi on DNA methylation status: a rapid inhibition of enzyme activity due to interference with posttranslational acetylation and a delayed effect on transcriptional control of DNMT genes by HDAC or miRNA mechanisms.

Transcriptional regulators in hepatocarcinogenesis--key integrators of malignant transformation

Hepatocellular carcinoma (HCC) is one of the most frequent human malignancies with poor prognosis and increasing incidence in the Western world. Only for a minority of HCC patients, surgical treatment options offer potential cure and therapeutic success of pharmacological approaches is limited. Highly specific approaches (e.g., kinase inhibitors) did not significantly improve the situation so far, possibly due to functional compensation, genetic heterogeneity of HCC, and development of resistance under selective pressure. In contrast, transcriptional regulators (especially transcription factors and co-factors) may integrate and process input signals of different (oncogenic) pathways and therefore represent cellular bottlenecks that regulate tumor cell biology. In this review, we want to summarize the current knowledge about central transcriptional regulators in human hepatocarcinogenesis and their potential as therapeutic target structures. Genomic and transcriptomic data of primary human HCC revealed that many of these factors showed up in subgroups of HCCs with a more aggressive phenotype, suggesting that aberrant activity of transcriptional regulators collect input information to promote tumor initiation and progression. Therefore, expression and dysfunction of transcription factors and co-factors may gain relevance for diagnostics and therapy of HCC.

DNA methyltransferases 1 and 3b expression in Huh-7 cells expressing HCV core protein of different genotypes

BACKGROUND

Hepatitis C virus infects ~3% of the population and it is a risk factor for hepatocarcinogenesis. The epigenetic mechanisms of HCV-induced hepatocyte transformation towards malignancy in this context are unclear.

AIMS

The purpose of this study was to evaluate the effect of HCV core proteins of different genotypes on DNA methyltransferases (DNMTs) induction.

MATERIALS/METHODS

We investigated DNMT1, DNMT3b and E-Cadherin (CDH1) mRNA and protein expression levels in an in vitro model of Huh-7 cells expressing the HCV core protein of different genotypes: 1b, 2a, 3a, 4h and 5a.

RESULTS

We found that both mRNA and protein expression levels of DNMT1 and 3b were upregulated in genotype 1b HCV core expressing cells as compared to control cells. DNMT3b mRNA levels did not change in genotypes 2a, 3a, 4h and 5a, but were upregulated at the protein level by genotype 1b, 2a, 3a. CDH1 mRNA expression was downregulated only in genotype 1b, whereas its protein expression resulted in downregulation by the HCV core of genotypes 1b, 2a and 3a. Conversely, no significant changes were observed for DNMTs and CDH1 investigated in Huh-7 cells expressing the genotypes 4h and 5a. Furthermore, we present evidence that HCV core 1b protein expression induces DNMTs overexpression through STAT3 protein as demonstrated by NSC74859 treatment. Moreover, SIRT1 inhibition affected DNMT1 and 3b expression only in HCV core protein genotype 1b expressing cells as demonstrated by treatment with its inhibitor sirtinol.

CONCLUSIONS

Our findings suggest that HCV core protein could play a role in HCC development at least in part by altering DNMTs expression.

Methylation of the CpG sites only on the sense strand of the APC gene is specific for hepatocellular carcinoma

Hypermethylation of the promoter of the tumor suppressor gene, adenomatous polyposis coli (APC), occurs in various malignancies, including hepatocellular carcinoma (HCC). However, reports on the specificity of the methylation of the APC gene for HCC have varied. To gain insight into how these variations occur, bisulfite PCR sequencing was performed to analyze the methylation status of both sense and antisense strands of the APC gene in samples of HCC tissue, matched adjacent non-HCC liver tissue, hepatitis, cirrhosis, and normal liver tissues. DNA derived from fetal liver and 12 nonhepatic normal tissue was also examined. These experiments revealed liver-specific, antisense strand-biased CpG methylation of the APC gene and suggested that, although methylation of the antisense strand of the APC gene exists in normal liver and other non-HCC disease liver tissue, methylation of the sense strand of the APC gene occurs predominantly in HCC. To determine the effect of the DNA strand on the specificity of the methylated APC gene as a biomarker for HCC detection, quantitative methylation-specific PCR assays for sense and antisense strand DNA were developed and performed on DNA isolated from HCC (n = 58), matched adjacent non-HCC (n = 58), cirrhosis (n = 41), and hepatitis (n = 39). Receiver operating characteristic curves were constructed. With the cutoff value set at the limit of detection, the specificity of sense and antisense strand methylation was 84% and 43%, respectively, and sensitivity was 67.2% and 72.4%, respectively. This result demonstrated that the identity of the methylated DNA strand impacted the specificity of APC for HCC detection. Interestingly, methylation of the sense strand of APC occurred in 40% of HCCs from patients with serum AFP levels less than 20 ng/mL, suggesting a potential role for APC as a biomarker to complement AFP in HCC screening.

Clinical implications of DNA methylation in hepatocellular carcinoma

BACKGROUND

Epigenetics is a rapidly evolving field of genetic study applicable to nearly every aspect of genome-related research. The importance of epigenetics has been recognised in human hepatocellular carcinoma (HCC). Changes in DNA methylation patterns, including global hypomethylation and promoter hypermethylation, are thought to be early events in hepatocarcinogenesis.

OBJECTIVES

This review aimed to summarise the role of epigenetics in HCC, to describe the mechanisms of epigenetic changes in HCC and to examine the clinical relevance of epigenetics in HCC.

METHODS

This review examines the role of CpG-rich regions and DNA methylation, and describes an epigenetic model of cancer, tumour type-specific methylation, the relationships among methylation, cirrhosis and hepatocarcinogenesis, and the role of DNA methylation in HCC. The clinical implications of epigenetics in HCC are discussed.

RESULTS

A multivariate predictor model based on traditional clinical factors and DNA methylation profile may have important applications in the early detection of neoplastic transformation in populations at high risk for HCC. CpG methylation may be valuable in HCC prognostics. DNA methylation profiles may enable clinical prediction in pre-therapy patient biopsies, paraffin-embedded samples or plasma DNA.

CONCLUSIONS

Epigenetic changes and profiles may correlate to the biological behaviour of tumours and clinical outcome of HCC patients. The use of DNA methylation profiles as a surrogate biomarker remains an active area of clinical cancer research.

Hypermethylated levels of E-cadherin promoter in Huh-7 cells expressing the HCV core protein

BACKGROUND AND AIM

The mechanisms of hepatocarcinogenesis induced by hepatitis C virus remain unclear. Our aim was to investigate the effect of the HCV core protein on the promoter methylation status of selected genes potentially involved in the hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

We evaluated the promoter methylation levels of the E-cadherin (CDH1), the glutathione S-transferase p1 (GSTP1), adenomatosis polyposis coli (APC), tissue inhibitor of metalloproteinase 3 (TIMP3), catenin (cadherin-associated protein) beta 1 (CNNTB1) genes by a quantitative methylation-specific polymerase chain reaction (QMSP) in the in vitro model of Huh-7 cells expressing the HCV core protein of genotype 1b.

RESULTS

We found that CDH1 promoter was hypermethylated in genotype 1b HCV core protein-positive cells as compared to control cells expressing the GFP protein alone (HCV core 1b vs GFP p=0.00; HCV core 1b vs Huh-7 p=0.03). This resulted in reduced levels of CDH1 protein as evaluated by immunoblot and by immunofluorescence. On the other hand no significant changes were observed for the other genes investigated. Furthermore, we present evidence that genotype 1b HCV core protein expression induces SIRT1 upregulation and that treatment with SIRT1 inhibitor sirtinol decreases the methylation levels of CDH1 promoter (1b+sirtinol vs 1b p=0.05; 1b+sirtinol vs GFP+sirtinol p=NS) resulting in 1.7-fold increased CDH1 mRNA expression (1b+sirtinol vs 1b p=0.05).

CONCLUSIONS

Our findings suggest that HCV core protein could play a role in HCC at least in part by altering the methylation status of CDH1 promoter. These findings could also suggest a novel therapeutic approach for HCC.

Prognostic value of Wnt inhibitory factor-1 expression in hepatocellular carcinoma that is independent of gene methylation

Recently, Wnt inhibitory factor-1 (WIF-1) was found to be epigenetically inactivated in several solid tumors, but the biological and clinical relevance of WIF-1 methylation and expression status in hepatocellular carcinoma (HCC) are still unclear. In the present study, reverse transcription polymerase chain reaction (PCR) and methylation-specific PCR were used to examine the WIF-1 expression and methylation in HCC cell lines. In addition, methylation and expression status of WIF-1 in 105 HCC cases were correlated with clinicopathological parameters and prognosis after tumor resection. WIF-1 was expressed in one HCC cell line and L02, both of which were not methylated in promoter region. DNA hypermethylation of WIF-1 promoter was identified in the other four HCC cell lines without WIF-1 expression. In neoplastic and non-neoplastic tissue samples, the rates of WIF-1 methylation were 61.9% and 37.1% (P = 0.001), respectively. WIF-1 was significantly downregulated in neoplastic tissues at messenger ribonucleic acid (mRNA) level, as compared to adjacent non-neoplastic tissues (P = 0.006). A significant inverse association was observed between WIF-1 methylation of and WIF-1 expression (P  0.017, R = -0.232). Methylation of WIF-1 was not associated with patient survival. In contrast, patients whose tumors exhibited negative WIF-1 mRNA expression had lower rates of overall survival. These findings suggested that aberrant methylation of WIF-1 is a common event in hepatocarcinogenesis. In addition, expression, but not methylation, of WIF-1 is a predictor of good outcome in patients undergoing resection of HCC.

Comparative analysis of promoter methylation and gene expression endpoints between tumorous and non-tumorous tissues from HCV-positive patients with hepatocellular carcinoma

Transcriptional silencing of tumor suppressor genes and other cancer-related genes induced by promoter CpG island hypermethylation is an important epigenetic mechanism of hepatocarcinogenesis. Previous studies have established methylation profiles of hepatocellular carcinomas (HCCs) and demonstrated that methylation of several candidate genes in resected tissues may be associated with time to recurrence. The goals of our study were to test whether specific promoter methylation and mRNA levels of candidate genes, as well as global changes in DNA methylation, can be linked with time to recurrence and clinicopathological variables in a homogenous study group of HCC patients. Forty-three tumorous and 45 non-tumorous liver tissue samples from the surgical margin were obtained from HCV-positive, HBV-negative HCC patients who underwent tumor resection surgery and who were monitored for tumor recurrence thereafter (median follow-up time: 16 months (range, 0-79 months)). Methylation-specific PCR was used to assess the promoter methylation status of P16(INK4a), SOCS-1, RASSF1A, APC, GSTP1, RIZ1, and MGMT genes, while the level of LINE-1 methylation was used as marker of global DNA methylation levels. Methylation frequencies in P16(INK4a), RASSF1A, APC, GSTP1, and RIZ1 genes were significantly greater in tumorous versus non-tumorous tissues. Methylation of RIZ1 in non-tumorous tissues was significantly associated with time to recurrence. Additionally, genomic DNA was significantly more hypomethylated in tumorous tissues, and this change was associated with shorter recurrence, but not with clinicopathological features. In conclusion, this study supports the role of aberrant methylation in the pathobiology of HCV-positive HCCs. The finding that RIZ1 methylation and increased levels of LINE-1 hypomethylation in non-tumorous tissues are associated with time to recurrence underscores the importance of assessing the epigenetic state of the liver remnant.

Epigenetic mechanisms involved in the pathogenesis of hepatobiliary malignancies

Primary tumors of the liver and biliary tree are increasing in frequency and portend a miserable prognosis. Epigenetic regulation of gene expression has emerged as a fundamental aspect of cancer development and progression. The molecular mechanisms of carcinogenesis in hepatocellular carcinoma and cholangiocarcinoma involve a complex interplay of both genetic and epigenetic factors. Recent studies investigating the possible epigenetic mechanisms induced in the disease have shed new light on the molecular underpinnings of hepatobiliary cancers. In addition, epigenetic modifications of DNA in cancer and precancerous lesions offer hope and the promise of novel biomarkers for early cancer detection, prediction, prognosis and response to treatment. Furthermore, the reversal of epigenetic changes represents a potential target for novel therapeutic strategies and medication design.

High-throughput assessment of CpG site methylation for distinguishing between HCV-cirrhosis and HCV-associated hepatocellular carcinoma

Methylation of promoter CpG islands has been associated with gene silencing and demonstrated to lead to chromosomal instability. Therefore, some postulate that aberrantly methylated CpG regions may be important biomarkers indicative of cancer development. In this study we used the Illumina GoldenGate Methylation BeadArray Cancer Panel I for simultaneously profiling methylation of 1,505 CpG sites in order to identify methylation differences in 76 liver tissues ranging from normal to pre-neoplastic and neoplastic states. CpG sites for ESR1, GSTM2, and MME were significantly differentially methylated when comparing the pre-neoplastic tissues from patients with concomitant hepatocellular carcinoma (HCC) to the pre-neoplastic tissues from patients without HCC. When comparing paired HCC tissues to their corresponding pre-neoplastic non-tumorous tissues, eight CpG sites, including one CpG site that was hypermethylated (APC) and seven (NOTCH4, EMR3, HDAC9, DCL1, HLA-DOA, HLA-DPA1, and ERN1) that were hypomethylated in HCC, were identified. Our study demonstrates that high-throughput methylation technologies may be used to identify differentially methylated CpG sites that may prove to be important molecular events involved in carcinogenesis.

Folate rescues lithium-, homocysteine- and Wnt3A-induced vertebrate cardiac anomalies

Elevated plasma homocysteine (HCy), which results from folate (folic acid, FA) deficiency, and the mood-stabilizing drug lithium (Li) are both linked to the induction of human congenital heart and neural tube defects. We demonstrated previously that acute administration of Li to pregnant mice on embryonic day (E)6.75 induced cardiac valve defects by potentiating Wnt-beta-catenin signaling. We hypothesized that HCy may similarly induce cardiac defects during gastrulation by targeting the Wnt-beta-catenin pathway. Because dietary FA supplementation protects from neural tube defects, we sought to determine whether FA also protects the embryonic heart from Li- or HCy-induced birth defects and whether the protection occurs by impacting Wnt signaling. Maternal elevation of HCy or Li on E6.75 induced defective heart and placental function on E15.5, as identified non-invasively using echocardiography. This functional analysis of HCy-exposed mouse hearts revealed defects in tricuspid and semilunar valves, together with altered myocardial thickness. A smaller embryo and placental size was observed in the treated groups. FA supplementation ameliorates the observed developmental errors in the Li- or HCy-exposed mouse embryos and normalized heart function. Molecular analysis of gene expression within the avian cardiogenic crescent determined that Li, HCy or Wnt3A suppress Wnt-modulated Hex (also known as Hhex) and Islet-1 (also known as Isl1) expression, and that FA protects from the gene misexpression that is induced by all three factors. Furthermore, myoinositol with FA synergistically enhances the protective effect. Although the specific molecular epigenetic control mechanisms remain to be defined, it appears that Li or HCy induction and FA protection of cardiac defects involve intimate control of the canonical Wnt pathway at a crucial time preceding, and during, early heart organogenesis.

Adenomatous polyposis coli 1A is likely to be methylated as a passenger in human gastric carcinogenesis

Many promoter CpG islands (CGIs) are methylated as a consequence of or in association with carcinogenesis (passenger), in addition to being a cause of carcinogenesis (driver). In gastric cancers, promoter 1A of the adenomatous polyposis coli (APC) gene is frequently methylated, and is often discussed as a driver. However, the actual role of 1A methylation is unclear because the same APC protein is coded by two transcripts from two promoters, 1A and 1B, and their relative expression levels in gastric mucosae have not been quantified. To clarify this issue, we first identified detailed transcription start sites of 1A and 1B transcripts. We then confirmed that, among nine gastric cancer cell lines, 1A methylation, if present, could repress 1A transcription while 1B was expressed and not methylated. In primary samples, 1B expression was 15-fold higher than 1A expression in gastric mucosae of healthy volunteers, and was decreased markedly in non-cancerous gastric mucosae of cancer patients. Quantitative methylation analysis showed that promoter 1A was methylated at similar levels (20-40%) in healthy individuals and non-cancerous gastric mucosae of cancer patients, and promoter 1B was never methylated in any samples, including gastric cancers. These findings strongly indicated that methylation of APC promoter 1A is a passenger, and suggested that marked down-regulation of 1B expression could be related to formation of a field predisposed to gastric cancers.