Alteration of the fragile histidine triad gene early in carcinogenesis: an update

[Epigenetic changes in the promoter of the fragile histidine triad (FHIT) gene in human sebocytes under the influence of in vitro culture]

BACKGROUND

Due to the lack of tumor suppressor function of the fragile histidine triad (FHIT) gene product, sebaceous gland carcinomas can develop.

OBJECTIVE

The model of the sebocyte cell line SZ95 was used to identify methylated CpG islands at the 5'-end of the FHIT gene and the decrease of gene expression as well as the increase of double-stranded (ds) DNA breaks were examined.

MATERIAL AND METHODS

Methylation, immunofluorescence analysis, promotor sequencing and treatment of SZ95 cells with 5‑azacytidine/trichostatin A (TSA).

RESULTS

The cultivation was accompanied by an increasing methylation of the CpG islands, a decrease of the FHIT gene expression and an accumulation of ds-DNA breaks. Treatment with 5‑azacytidine/TSA showed a decrease in DNA methylation and a re-expression of FHIT transcripts.

DISCUSSION

Epigenetic changes in the cellular genome are caused by in vitro cell culture. Consequently, a positive selection of sebocytes with an epigenetically inactivated FHIT locus occurs.

Impact of decitabine on immunohistochemistry expression of the putative tumor suppressor genes FHIT, WWOX, FUS1 and PTEN in clinical tumor samples

BACKGROUND

Since tumor suppressor gene function may be lost through hypermethylation, we assessed whether the demethylating agent decitabine could increase tumor suppressor gene expression clinically. For fragile histidine triad (FHIT), WW domain-containing oxidoreductase (WWOX), fused in sarcoma-1 (FUS1) and phosphatase and tensin homolog (PTEN), immunohistochemistry scores from pre- and post-decitabine tumor biopsies (25 patients) were correlated with methylation of the long interspersed nuclear element-1 (LINE-1) repetitive DNA element (as a surrogate for global DNA methylation) and with tumor regression.

RESULTS

With negative staining pre-decitabine (score = 0), the number of patients converting to positive staining post-decitabine was 1 of 1 for FHIT, 3 of 6 for WWOX, 2 of 3 for FUS1 and 1 of 10 for PTEN. In tumors with low pre-decitabine tumor suppressor gene scores (≤150), expression was higher post-treatment in 8 of 8 cases for FHIT (P = 0.014), 7 of 17 for WWOX (P = 0.0547), 7 of 12 for FUS1 (P = 0.0726), and 1 of 16 for PTEN (P = 0.2034). If FHIT, WWOX and FUS1 were considered together, median pre- versus post-decitabine scores were 60 versus 100 (P = 0.0002). Overall, tumor suppressor gene expression change did not correlate with LINE-1 demethylation, although tumors converting from negative to positive had a median decrease in LINE-1 methylation of 24%, compared to 6% in those not converting (P = 0.069). Five of 15 fully evaluable patients had reductions in tumor diameter (range 0.2% to 33.4%). Of these, three had simultaneous increases in three tumor suppressor genes (including the two patients with the greatest tumor regression) compared to 2 of 10 with tumor growth (P = 0.25).

CONCLUSIONS

In tumors with low tumor suppressor gene expression, decitabine may be associated with increased expression of the tumor suppressor genes FHIT, FUS1, and WWOX, but not PTEN.

Expression of WWOX and FHIT is downregulated by exposure to arsenite in human uroepithelial cells

Ecological studies in Taiwan, Chile, Argentina, Bangladesh, and Mexico have confirmed significant dose-dependent associations between ingestion of arsenic-contaminated drinking water and the risk of various human malignancies. The FHIT and WWOX genes are active in common fragile sites FRA3B and FRA16D, respectively. Reduced expression of FHIT or WWOX is known to be an early indicator of carcinogen-induced cancers. However, the effect of arsenite on the expressions and molecular mechanisms of these markers is still unclear. The aims of this study were (i) to observe the expression of ATR, WWOX and FHIT proteins in urothelial carcinoma (UC) between endemic and non-endemic areas of blackfoot disease (BFD) by immunohistochemical analyses; (ii) to compare expression of these genes between arsenite-treated SV-HUC-1 human epithelial cells and rat uroepithelial cells; and (iii) to determine the role of DNMT and MEK inhibitors on expressions of WWOX and FHIT in response to arsenite in SV-HUC-1. The experiments revealed that expressions of ATR, WWOX and FHIT in UC significantly differed between BFD areas and non-BFD areas (p=0.003, 0.009 and 0.021, respectively). In fact, the results for the arsenite-treated groups showed that ATR, WWOX and FHIT are downregulated by arsenite in SV-HUC-1. However, the inhibitors suppressed the effects of arsenite on WWOX and FHIT proteins and mRNA expression. In conclusion, arsenite decreased expressions of ATR, WWOX and FHIT via ERK1/2 activation in SV-HUC-1 cells. These findings confirm that dysregulations of these markers may contribute to arsenite-induced carcinogenesis.

Family history of gastric cancer correlates with decreased expression of HINT1 tumor suppressor gene in gastric mucosa of dyspeptic patients

Gastric cancer (GC) is the fourth most common cancer and the second most common cause of cancer-associated mortality worldwide. Approximately 10% of gastric cancers are hereditary and a small percentage of these cases (1-3%) have been classified as a single hereditary syndrome (hereditary diffuse gastric cancer). We previously demonstrated that a family history of gastric cancer (FHGC) contributes to a predisposition towards the development of gastric cancer. Our data revealed that for dyspeptic patients whose first-degree relative(s) succumbed to GC, the levels of the fragile histidine triad pro-apoptotic protein in gastric mucosa were decreased. Another member of the histidine triad protein superfamily is histidine triad nucleotide-binding protein 1 (HINT1), a novel tumor suppressor that plays an inhibitory role in the control of gene transcription. The study comprised 38 ethnically homogeneous patients with dyspeptic symptoms without concomitant chronic diseases (18 controls/20 patients with FHGC). The results showed that the samples from the control patients predominantly exhibited non-atrophic changes (approximately 90%), whereas atrophic changes occurred more frequently in patients with FHGC. Notably, the expression levels of the HINT1 gene were markedly higher in the samples with atrophy taken from the antrum of FHGC patients compared to the non-atrophic samples. Moreover, the levels of HINT1 mRNA in samples obtained from the antrum of patients with FHGC were lower compared to analogous samples from the control individuals. The decreased levels of HINT1 mRNA in the antrum samples of patients with the FHGC indicate that it is a factor predisposing those patients to the development of gastric cancer.

Inverse correlation of aberrant expression of fragile histidine triad (FHIT) protein with cyclin D1 protein and prognosis in Chinese patients with cholangiocarcinoma

BACKGROUND

This is the first study to explore the relationship between the expression of fragile histidine triad, FHIT and cyclin D1 proteins, and the clinicopathological significance of the two proteins in Chinese patients with cholangiocarcinoma.

MATERIAL AND METHODS

Immunohistochemistry was used to study 53 cases of cholangiocarcinoma, 30 para-neoplastic and 20 normal bile ducts for their expression status of FHIT and cyclin D1 and then the results were analyzed with the patient's age, sex, tumour site, histological grade and clinical stage as well as overall median survival time.

RESULTS

Compared with the para-neoplastic and normal cholangiocytes, the expression of FHIT was obviously decreased (p=0.0001), whereas that of cyclin D1 was significantly increased (p=0.0001) in carcinoma cells. The expression of FHIT was found to be correlated with the histological grade (p=0.007) and the clinical stage (p=0.004), but not with age (p=0.776), sex (p=0.246) or tumour site (p=0.347). The expression of cyclin D1 was also showed statistically associated with the histological grade (p=0.043) and clinical stage (p=0.047), but not with age (p=0.965), sex (p=0.751) or tumour site (p=0.948). Further, the expression of FHIT was found to be inversely correlated with the expression of cyclin D1 (p=0.0001). The loss of expression of FHIT and the expression of cyclin D1 were significantly related to the cancers with shorter median survival time (p=0.0001, p=0.0081). The expression of FHIT was an independent prognostic factor (p=0.005).

DISCUSSION

The expression of FHIT may be inversely correlated with the expression of cyclin D1. It is suggested that the loss of FHIT protein and overexpression of cyclin D1 protein may play an important role in carcinogenesis and prognosis of cholangiocarcinoma.

Fhit tumor suppressor: guardian of the preneoplastic genome

Environmental agents induce intragenic alterations in the FRA3B/FHIT chromosome fragile site, resulting in fragile FHIT allele loss early in cancer development. Fhit knockout mice are predisposed to tumor development and Fhit gene therapy reduces tumor burden. Repair-deficient cancers are likely to be Fhit-deficient and Fhit-deficient cells show enhanced resistance to ultraviolet C, mitomycin C, camptothecin and oxidative stress-induced cell killing. Loss of Fhit leads to alterations in the DNA damage response checkpoint and contributes to DNA instability. Hsp60/Hsp10 are Fhit interactors, suggesting a direct role for Fhit in stress responses. Fhit also interacts with and stabilizes ferrodoxin reductase (Fdxr), a mitochondrial flavoprotein that transfers electrons from NADPH to cytochrome P450, suggesting a role for Fhit in the modulation of reactive oxygen species production and of genomic damage.

Deletions of BRCA1/2 and p53 R248W gain-of-function mutation suggest impaired homologous recombination repair in fragile histidine triad-negative sebaceous gland carcinomas

BACKGROUND

Sebaceous gland carcinomas represent rare malignancies of the skin and some 60% of them demonstrate high-grade microsatellite instability on the background of a defective mismatch repair system. However, a significant fraction of periocular sebaceous gland carcinomas exhibits microsatellite stability associated with a frequent loss of the candidate tumour suppressor fragile histidine triad (FHIT).

OBJECTIVES

We hypothesized that in those sebaceous gland carcinomas with microsatellite stability and loss of FHIT, effector molecules participating in homologous recombination repair (HRR), such as BRCA1/2, could be somatically inactivated.

METHODS

A pilot series of 10 paraffin-embedded sebaceous gland carcinoma specimens with a defined FHIT status was studied for loss of heterozygosity (LOH) events in the genes BRCA1, BRCA2, FHIT and WWOX. We sequenced the coding exons 5-8 of the p53 gene.

RESULTS

Sebaceous gland carcinomas with FHIT negativity displayed LOH and biallelic deletions of the BRCA1 gene in five of 10 (50%) of the sebaceous gland carcinoma specimens analysed. Tumour-specific genomic losses close to BRCA2 were also uncovered. A homozygous p53 R248W gain-of-function mutation as the result of a CGG to TGG transition was identified in one of seven sebaceous gland carcinomas. It has been demonstrated previously that p53 R248W mutants inactivate ATM-directed HRR. This particular sebaceous gland carcinoma presented with concomitant genomic deletions at the BRCA1 and BRCA2 loci, and also at the constitutively fragile sites FRA3B/FHIT and FRA16D/WWOX.

CONCLUSIONS

Our study demonstrates for the first time that microsatellite-stable FHIT-negative sebaceous gland carcinomas accumulate mutations that target central components of the HRR network. This observation will prompt investigations in synthetic lethality of BRCA-deficient sebaceous gland carcinomas by therapeutic poly(ADP-ribose) polymerase inhibitors.

Effect of fragile histidine triad gene transduction on proliferation and apoptosis of human hepatocellular carcinoma cells

AIM: To evaluate the inhibitory effects of human fragile histidine triad (FHIT) gene on cell proliferation and apoptosis in human hepatocellular carcinoma line Hep3B in vitro.

METHODS: A recombinant pcDNA3.1 (+)/FHIT including the functional region of FHIT gene was constructed and transferred into human hepatocellular carcinoma cells in vitro. mRNA and protein expression of the FHIT gene in the transfected cells was detected by RT-PCR and Western blot, respectively. The effect of FHIT on proliferation was detected by MTT assay. Changes in cell cycle and apoptosis were assayed by flow cytometry. Five mice received subcutaneous transplantation of Hep3B-FHIT; 5 mice received subcutaneous transplantation of normal Hep3B and Hep3B-C as controls. The body weight of nude mice and tumor growth were measured.

RESULTS: RT-PCR and Western blot analysis showed that the expression level of FHIT-mRNA and FHIT protein was higher in Hep3B cells after infection with pcDNA3.1 (+)/FHIT. The growth of Hep3B cells treated with pcDNA3.1 (+)/FHIT was significantly inhibited. The pcDNA3.1 (+)/FHIT-transfected Hep3B cells showed a significantly higher cell rate at G₀-G₁ phase and increased apoptosis in comparison with controls (P < 0.05). The growth of transplanted tumor was inhibited markedly by FHIT. Tumors arising from the Hep3B-FHIT cells occurred much later than those arising from the Hep3B and Hep3B-C cells. The growth of Hep3B-FHIT cells was slow and the tumor volume was low.

CONCLUSION: Transduction of FHIT gene inhibits the growth of human hepatocellular carcinoma cells and induces cell apoptosis in vivo and in vitro.

The tumor suppressor Fhit acts as a repressor of beta-catenin transcriptional activity

The Fra3B locus on chromosome 3p14.2 targeting the fragile histidine triad (Fhit) gene represents one of the most common fragile sites of the human genome and is associated with early preneoplastic and malignant disorders in multiple human tumors. Fhit was classified as a tumor suppressor; however, the molecular mechanisms of its function are not well established. Here, we report that Fhit associates with the lymphoid enhancer-binding factor 1/T cell factor/beta-catenin complex by directly binding to beta-catenin, a major player in the canonical Wnt pathway that is deregulated in numerous forms of human cancer. In binding to the beta-catenin C-terminal domain, Fhit represses transcription of target genes such as cyclin D1, axin2, MMP-14, and survivin. Knockdown of Fhit reversed this effect, whereas this reversal was not detectable when beta-catenin was knocked down simultaneously. The Fhit enzymatic activity as a diadenosine-polyphosphate hydrolase is not required for the down-regulation of beta-catenin-mediated transcription as examined with an enzymatic inactive Fhit-H96N protein. ChIPs revealed recruitment of Fhit/beta-catenin complexes to target gene promoters. In soft agar assays Fhit and beta-catenin are involved in regulation of anchorage-independent growth. These observations assign to the tumor suppressor Fhit an unexpected role in the regulation of beta-catenin-mediated gene transcription.

Fragile Histidine Triad Expression in Oral Squamous Cell Carcinoma and Precursor Lesions

PURPOSE

Fragile histidine triad (FHIT) expression in precursor oral lesions (POL) and oral squamous cell carcinomas (OSCC) was studied with regard to (a) the frequency of loss of FHIT expression, (b) whether loss of FHIT expression correlates with degree of dysplasia in POLs, (c) whether FHIT loss predicts high-risk POLs that are more likely to transform, and (d) whether FHIT loss in OSCCs correlates with survival.

EXPERIMENTAL DESIGN

Ninety-four POLs and 86 OSCCs were immunostained for FHIT. Survival analysis was done for cases with validated clinical outcomes.

RESULTS

By optimizing the immunostaining protocol, we found that FHIT is expressed in a distinctive strong nuclear and weak cytoplasmic pattern in oral tissues. Loss of FHIT expression was found in 42 of 94 (45%) POLs and in 66 of 86 (77%) OSCCs. We observed a statistically significant positive correlation between frequency of FHIT loss and increasing grade of dysplasia (chi2=13.8; degrees of freedom=4; P=0.008). Loss of FHIT expression in POLs that progressed to malignancy was more frequent than in those that did not [17 of 25 (68%) versus 12 of 29 (41.4%), respectively]. This difference was statistically significant (chi2=3.8; degrees of freedom=1; P=0.046). In OSCCs, loss of FHIT staining indicated a worse prognosis (survival rate, 36.2%) than when positive FHIT staining was observed (survival rate, 50%), but the difference was not statistically significant (P=0.546, Kaplan-Meier, log-rank).

CONCLUSIONS

FHIT seems to localize to both nuclear and cytoplasmic domains. FHIT inactivation occurs early in oral carcinogenesis and may be useful molecular marker for progressive dysplastic oral lesions.

Aberrant FHIT protein expression in classical Hodgkin’s lymphoma: a potential marker

AIMS

The fragile histidine triad (FHIT) gene is frequently inactivated in human cancers; however, the FHIT gene remains unexplored in Hodgkin's lymphoma. The aim of this study was to investigate the role of FHIT expression in classical Hodgkin's lymphoma.

METHODS

Classical Hodgkin's lymphomas were analysed for FHIT gene expression by two-step non-biotin immunohistochemical method and Western blotting.

RESULTS

Thirty of the 33 (91%) cases of Hodgkin's lymphoma tested were positive for FHIT protein by immuohistochemistry. The expression of FHIT was mainly located in cytoplasm of Reed-Sternberg (HRS) cells. The protein expression was also documented by Western blotting. The non-Hodgkin's lymphomas were negative for FHIT protein.

CONCLUSIONS

The results indicate that abnormal FHIT expression is noted frequently in classical Hodgkin's lymphoma and the expression can give insight into the pathogenesis of the disease. The protein may serve as a marker to localise HRS cells in classical Hodgkin's lymphoma.

Prevalence of Fragile Histidine Triad Expression in Tumors from Saudi Arabia: A Tissue Microarray Analysis

AIM

The fragile histidine triad (FHIT) gene was discovered and proposed as a tumor suppressor gene for most human cancers. It encodes the most active common human chromosomal fragile region, FRA3B. We studied the prevalence of loss of FHIT expression in various tumors and correlated its loss with various clinicopathologic features.

METHODS

To determine whether the absence of FHIT expression correlates with clinical variables such as grade, stage, and survival time, we assessed FHIT expression using immunohistochemistry. More than 1,800 tumors from more than 75 tumor categories were analyzed by immunohistochemistry in a tissue microarray format.

RESULTS

Loss of FHIT expression ranged from 19% in ovarian tumors to 67% in lung cancers. Clinical and pathologic features like grade, stage, tumor size, and lymph node metastasis showed correlation with loss of FHIT expression in some tumors. No difference was seen in the survival patterns and loss of FHIT expression in any of the tumor groups studied.

CONCLUSIONS

Loss of FHIT expression is an ubiquitous event in the multistep, multifactorial carcinogenesis process. FHIT may be altered at different stages in different types of cancers. Most of the tumors with a wider prevalence of loss of FHIT expression as an early event show a correlation with clinicopathologic features. However, in some of the tumors, FHIT expression is lost as a late event and is only seen in a fraction of the tumors.

Early loss of Fhit in the respiratory tract of rodents exposed to environmental cigarette smoke

The Fhit gene, encompassing the most active common human chromosomal fragile region, FRA3B, has been shown to act as a tumor suppressor. Several studies have shown significant Fhit alterations or Fhit protein loss in lung cancers from smokers compared with lung cancers from nonsmokers. To evaluate the role of Fhit under controlled experimental conditions, we exposed rodents to environmental cigarette smoke (ECS) and evaluated Fhit expression or Fhit protein in the respiratory tract. After 14 days of exposure to ECS, loss of Fhit protein in the bronchial/bronchiolar epithelium affected half of the tested B6-129(F(1)) mice, either wild type or Fhit(+/-). After 28 days, it affected the vast majority of the tested SKH-1 hairless mice and of A/J mice and all (UL53-3 x A/J)F(1) mice, either wild type or P53(+/-). In Sprague-Dawley rats, exposure to ECS for up to 30 days caused a time-dependent loss of Fhit in pulmonary alveolar macrophages. Moreover, ECS down-regulated Fhit expression and significantly decreased Fhit protein in the rat bronchial epithelium. The oral administration of N-acetylcysteine attenuated the ECS-related loss of Fhit, whereas oltipraz, 5,6-benzoflavone, phenethyl isothiocyanate, and indole 3-carbinol, and their combinations had no significant effect. Parallel studies evaluated a variety of molecular, biochemical, and cytogenetic alterations in the respiratory tract of the same animals. In conclusion, there is unequivocal evidence that Fhit is an early, critical target in smoke-related lung carcinogenesis in rodents, and that certain chemopreventive agents can attenuate the occurrence of this gene alteration.

FHIT is up-regulated by inflammatory stimuli and inhibits prostaglandin E2-mediated cancer progression

The FHIT gene is known to be susceptible to environmental carcinogens. Formation of prostaglandin E(2) (PGE(2)) is catalyzed by cyclooxygenase-2 (COX-2) and may influence malignant phenotype in colorectal cancer. We explored whether FHIT might play a role in progression of colorectal cancer through inflammation-associated PGE(2) activity. Immunohistochemical study of COX-2 and FHIT expression was done in 92 colorectal cancer tumors. We also used a FHIT-expressing cancer cell line (H460) induced by ponasterone A and two FHIT small interfering RNA-treated colorectal cancer cell lines (CCK81 and DLD1). After PGE(2) stimulation, we compared synthesis of PGE(2) (ELISA assay) and cell proliferation [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay]. Immunohistochemistry showed a significant association between COX-2 and FHIT expression in colorectal cancers (P < 0.01). In a subset of 41 COX-2-expressing tumors, 12 FHIT(-) tumors showed deeper cancer invasion than 29 FHIT(+) tumors (P < 0.01). Experimental study, however, showed there was no direct interaction between FHIT and COX-2. Considered with results from another experiment with epidermal growth factor receptor (EGFR), we hypothesize that FHIT and COX-2 might be regulated by a common molecule, such as EGFR. Additionally, there was an inverse and direct correlation between PGE(2) synthesis and FHIT in vitro, suggesting that FHIT's postulated antiaggressive effect on tumor goes through PGE(2) but not COX-2. Loss of FHIT expression in colorectal cancer suggests higher malignant potential. We conclude that FHIT suppressed cancer cell proliferation in this malignancy by directly inhibiting synthesis of PGE(2) but not affecting that of COX-2.

Promoter methylation and loss of coding exons of the fragile histidine triad (FHIT) gene in intrahepatic cholangiocarcinomas

AIMS

About 10-30% of primary liver cancers represent intrahepatic cholangiocarcinomas (IHCC). Since chromosomal losses of 3p are detectable in about 40% of cholangiocarcinomas our study aimed at the identification of mechanisms leading to functional deletion of tumor suppressor genes in this region. Our efforts focussed on genomic losses and epigenetic inactivation of two tumor suppressor genes, the fragile histidine triad (FHIT) and the ras association domain family 1 (RASSF1A) genes, both located on the short arm of chromosome 3.

METHODS

Methylation-specific PCR (MSP) and combined bisulfite-dependent restriction analysis (COBRA) were applied to detect epigenetic silencing of gene promoters. Genomic duplex PCR was used to identify exon losses of the FHIT gene. Nineteen paraffin-embedded samples of intrahepatic cholangiocarcinomas were studied.

RESULTS

Here we report for the first time that in addition to frequent losses of the exons 5 and 6, hypermethylation of the FHIT promoter occured in a significant portion of IHCC. Methylation specific PCR (MSP) detected epigenetic inactivation of the FHIT/FRA3B locus in 8 of 19 (42%) cases. Combined bisulfite restriction analysis (COBRA) revealed that high levels of methylated FHIT promoter sequences were present in 6 of the 8 methylation positive samples. In agreement with previous reports MSP identified hypermethylation of the RASSF1A gene in 13 of 19 (68%) IHCC specimens examined.

CONCLUSIONS

Epigenetic silencing of the FHIT tumor suppressor gene is a novel inactivation mechanism to be considered in the development of intrahepatic cholangiocarcinomas. However, a statistically significant inverse correlation between K-Ras activation and RASSF1A inactivation was not found.

Common chromosomal fragile sites and cancer: focus on FRA16D

A growing body of experimental evidence supports the view that certain human chromosomal fragile sites have roles to play in cancer. The principle lines of evidence are at the level of mutation mechanism and gene function. Most research in this area has previously focussed on the FRA3B common fragile site and the FHIT gene that spans this site. Here we review recent progress in characterising the second most readily observed common fragile site, FRA16D, and the WWOX gene that spans it. Comparative analyses of FRA3B/FHIT and FRA16D/WWOX reveal some striking similarities suggesting that these sites and their associated genes may play a part in a normal protective response of cells to environmental stress.

Differential roles of E-type cyclins during transformation of murine E2F-1-deficient cells

Deregulation of retinoblastoma gene product (pRB) is a hallmark of cancer, which acts as a transcriptional repressor by targeting E2F transcription factors. A transcription factor E2F-1 is not only important for S phase entry of cell cycle, but also stimulates gene expression of pro-apoptotic molecules. To investigate roles of E2F-1 and its target genes in cellular transformation, we studied murine E2F-1-deficient embryonic fibroblasts. Compared with control wild-type cells, E2F-1-deficient cells at early passages were less sensitive to exposure to gamma-radiation and showed an increase of colony formation, while their growth was slow. After sequential passages, the growth of E2F-1-deficient cells reached closely to that of wild-type cells. Immunoblot study of E2F target genes showed that multiple passages of E2F-1-deficient cells resulted in preferential increase of cyclin E2 expression. Furthermore, carcinogenicity study using N-nitrosomethylbenzylamine demonstrated that, compared to wild-type mice, fore-stomach tumors in E2F-1-deficient mice expressed an increased amount of cyclin E2, but not cyclin E1. Taken together, the present study shows that differential roles of E-type cyclins are involved at least partially in the process of cellular transformation, supporting the concept of important roles of the E2F regulatory pathway in carcinogenesis.

Loss of FHIT expression in gastric mucosa of patients with family histories of gastric cancer and Helicobacter pylori infection

AIM: To answer the question whether FHIT gene expression is affected by the family history of gastric carcinoma and the presence of Helicobacter pylori (H pylori) in the gastric mucosa of patients with dyspepsia.

METHODS: FHIT gene expression in two different topographic sites of the gastric mucosa of twenty-one patients with dyspepsia and with or without familial gastric carcinoma, infected or not infected with H pylori, was evaluated by reverse transcription-PCR (RT-PCR) and IMAGE QUANT methods. A rapid urease test and histopathological examination were used to determine H pylori colonization.

RESULTS: In the gastric mucosa of patients with family histories of gastric carcinoma, the amount of FHIT protein mRNA was reduced down to 32%, and for patients with H pylori colonization, to 24% in comparison to controls with dyspepsia and without cancer in the family. FHIT expression was independent of the topography of specimens (corpus vs antrum), and for the control patients it was less sensitive to infection with H pylori. A considerable statistical difference in FHIT levels was observed in the gastric mucosa from the corpus of patients with family histories of gastric carcinoma in respect to H pylori colonization (P = 0.06). Macroscopic evaluation of the gastric mucosa demonstrated that pathologic changes classified according to the Sydney system had no significant influence on FHIT expression within each tested group of patients.

CONCLUSION: Loss of FHIT expression was observed in patients with dyspepsia and family histories of gastric carcinoma, especially those infected with H pylori. Such results may constitute an early indication of the development of gastric carcinoma, which is associated with family factors including heredity and H pylori infection. The loss of the FHIT gene may serve as a marker for early diagnosis and prevention of gastric carcinoma, especially in context of early monitoring of H pylori infection in individuals with a record of familial stomach cancer.

Unique patterns of gene expression changes in liver after treatment of mice for 2 weeks with different known carcinogens and non-carcinogens

Previously we demonstrated that the mouse liver tumor response to the non-genotoxic carcinogens oxazepam and Wyeth-14,643 involved more differences than similarities in changes in early gene expression. In this study we used quantitative real-time PCR and oligonucleotide microarray analysis to identify genes that were up- or down-regulated in mouse liver early after treatment with different known carcinogens, including oxazepam (125 and 2500 p.p.m.), o-nitrotoluene (1250 and 5000 p.p.m.) and methyleugenol (75 mg/kg/day), or the non-carcinogens p-nitrotoluene (5000 p.p.m.), eugenol (75 mg/kg/day) and acetaminophen (6000 p.p.m.). Starting at 6 weeks of age, mice were treated with the different compounds for 2 weeks in the diet, at which time the livers were collected. First, expression of 12 genes found previously to be altered in liver after 2 weeks treatment with oxazepam and/or Wyeth-14,643 was examined in livers from the various chemical treatment groups. These gene expression changes were confirmed for the livers from the oxazepam-treated mice in the present study, but were not good early markers for all the carcinogens in this study. In addition, expression of 20 842 genes was assessed by oligonucleotide microarray [n = 4 livers/group, 2 hybridizations/liver (with fluor reversals)] and the results were analyzed using the Rosetta Resolver System and GeneSpring software. The analyses revealed that several cancer-related genes, including Fhit, Wwox, Tsc-22 and Gadd45b, were induced or repressed in unique patterns for specific carcinogens and not altered by the non-carcinogens. The data indicate that even if the tumor response, including molecular alterations, is similar, such as for oxazepam and methyleugenol, early gene expression changes appear to be carcinogen specific and seem to involve apoptosis and cell cycle-related genes.

Effect of exogenous E2F-1 on the expression of common chromosome fragile site genes, FHIT and WWOX

The expression of two tumor suppressor genes, fragile histidine triad (FHIT) and WW domain containing oxidoreductase (WWOX), encompassing common chromosome fragile regions, FRA3B at 3p14.2 and FRA16D at 16q23, is altered in many epithelial tumors. Since DNA sequence search shows that the FHIT gene has the E2F-1 recognition site in 5'] region, which regulates cell cycle, we tested the effect of E2F-1 overexpression in tumor cells. Ectopic E2F-1 expression led to an increase of Fhit and Wwox expression in allele remaining tumor cells and resulted in induction of apoptosis. Reporter assay showed that the E2F-1 site in FHIT 5' region was involved in the down-stream transcription after exogenous E2F-1 introduction. Chromatin immunoprecipitation detected exogenous E2F-1 binding to the recognition site in FHIT 5' region. The data suggest that E2F-1 overexpression plays a role in suppression of tumor, at least in part trough transcriptional regulation of FHIT and relevant activation of WWOX.