FHIT alterations in breast cancer

rs73092672 allele T is significantly associated with the higher risk of breast cancer incidence

Breast cancer is the most common cancer in women worldwide with remarkable proportion of the patients in advanced stage. Recently the importance of genetic mutations in cancers are well established and also the role of tumor suppressor genes such as FHIT gene in both heritable and non-heritable cancer. MicroRNAs are a class of non-coding RNAs which can interfere with cellular regulation. In this study, the association of rs73092672 which is located within the FHIT gene and the 3'UTR of hsa-miR-509-5p with the susceptibility to breast cancer risk has been studied in the Iranian population. By using the PCR_RFLP, the genotype rs73092672 was determined in 90 patients and 100 control subjects. The genotypes of the individuals were analyzed statistically to find the association between rs73092672 and the breast cancer incidence. The results revealed that due to the dominance of the C allele, the frequency of CC + CT genotypes, as compared with TT, had a significant correlation with the incidence of this disease in controls and cases (p = 0.02; OR= 3.6). Moreover, Bioinformatics analysis suggests rs73092672 as a polymorphism in the 3'UTR of hsa-miR-509-5p with higher binding affinity in the presence of T allele than C allele.

Interplay between promoter methylation and chromosomal loss in gene silencing at 3p11-p14 in cervical cancer

Loss of 3p11-p14 is a frequent event in epithelial cancer and a candidate prognostic biomarker in cervical cancer. In addition to loss, promoter methylation can participate in gene silencing and promote tumor aggressiveness. We have performed a complete mapping of promoter methylation at 3p11-p14 in two independent cohorts of cervical cancer patients (n = 149, n = 121), using Illumina 450K methylation arrays. The aim was to investigate whether hyperm-ethylation was frequent and could contribute to gene silencing and disease aggressiveness either alone or combined with loss. By comparing the methylation level of individual CpG sites with corresponding data of normal cervical tissue, 26 out of 41 genes were found to be hypermethylated in both cohorts. The frequency of patients with hypermethylation of these genes was found to be higher at tumor stages of 3 and 4 than in stage 1 tumors. Seventeen of the 26 genes were transcriptionally downregulated in cancer compared to normal tissue, whereof 6 genes showed a significant correlation between methylation and expression. Integrated analysis of methylation, gene dosage, and expression of the 26 hypermethylated genes identified 3 regulation patterns encompassing 8 hypermethylated genes; a methylation driven pattern (C3orf14, GPR27, ZNF717), a gene dosage driven pattern (THOC7, PSMD6), and a combined methylation and gene dosage driven pattern (FHIT, ADAMTS9, LRIG1). In survival analysis, patients with both hypermethylation and loss of LRIG1 had a worse outcome compared to those harboring only hypermethylation or none of the events. C3orf14 emerged as a novel methylation regulated suppressor gene, for which knockdown was found to promote invasive growth in human papilloma virus (HPV)-transformed keratinocytes. In conclusion, hypermethylation at 3p11-p14 is common in cervical cancer and may exert a selection pressure during carcinogenesis alone or combined with loss. Information on both events could lead to improved prognostic markers.

Promoter methylation status of the FHIT gene and Fhit expression: association with HER2/neu status in breast cancer patients

Aberrant DNA methylation has been recognized to contribute to breast carcinogenesis, and promoter hypermethylation of several tumor suppressor genes has been correlated with decreased gene expression. The fragile histidine triad (FHIT) gene is a putative tumor suppressor gene in breast and other types of cancer, and loss of Fhit expression has been observed in breast cancer. The aim of the present study was to evaluate the association between methylation of the FHIT gene and its expression in breast cancer, and to investigate whether methylation and expression of the FHIT gene correlates with clinicopathological characteristics in relation to human epidermal growth factor receptor 2 (HER2) status. Pyrosequencing of bisulfite-treated DNA was performed to study the methylation status of the FHIT gene in 60 breast cancer samples. We examined the expression of Fhit using tissue microarrays by immunohistochemical staining. FHIT methylation was detected in 96.7% and the positive expression rate of Fhit was 87.3% of the patients. The mean methylation level of the FHIT gene was associated with intratumoral inflammation. Methylation level of the FHIT gene had no significant differences according to molecular subtypes. Loss of Fhit expression was associated with large tumor size, basal-like subtype and positive expression of EGFR. In HER2-negative breast cancer, loss of Fhit expression was significantly associated with tumor size, estrogen receptor status and Ki-67 proliferation index. No significant correlation between methylation of the FHIT gene and its expression was observed in the present study. Our results suggest that loss of Fhit expression in breast cancer is associated with poor prognostic features, and it is also relevant to the results in HER2-negative breast cancer. Further studies with larger sample sizes and longer follow-up are required to clarify the predictive and prognostic value of Fhit expression and the FHIT gene methylation status in breast cancer.

Implications of genomic instability in the diagnosis and treatment of breast cancer

Tumorigenesis is a multistep process resulting from DNA mutations observed at the DNA sequence and chromosome level as well as epigenetic changes, which affect expression of oncogenes and tumor suppressor genes. Breast cancer is a very heterogeneous disease that manifests in various histological and clinical types. Defects in the biological action of the genome driven by various alterations, such as point mutations and chromosomal rearrangements, lead to the collapse of genome integrity, uncontrolled cell proliferation and failure in apoptotic cell death. Detailed profiling of breast cancer-associated genomic alterations is indispensable for the design of individualized anticancer therapy, by suggesting diagnostic and prognostic criteria as well as the outcome of applied treatment. Among various directions of cancer research, identification of genomic alterations in breast cancer and their translation into clinical applications is at the forefront.

FHIT gene and flanking region on chromosome 3p are subjected to extensive allelic loss in Egyptian breast cancer patients

The fragile histidine triad gene (FHIT) is a candidate tumor suppressor gene at chromosome 3p14.2. Deletions in FHIT gene were reported in different types of cancer including breast cancer. In this study, we investigated the loss of heterozygosity (LOH) incidence that target FHIT genomic structure and chromosome 3p in cancerous and pre-neoplastic lesions of Egyptian breast patients. Genomic DNA was isolated from tumor tissues and their normal counterparts of 55 Egyptian patients diagnosed with breast cancer and 11 patients diagnosed with preneoplastic breast lesions. LOH was detected in 51% of breast cancer cases in at least one microsatellite marker of the four investigated markers. While, none of the markers showed LOH among the pre-neoplastic breast lesions. We also observed a significant association between LOH and invasive ductal carcinoma (IDC) histopathological type while no association observed between LOH and patients' age, tumor grade, or lymph node involvement. We also investigated FHIT gene expression profiles in breast cancer using Oncomine database. We found that FHIT is significantly reduced in all investigated studies. We conclude that, FHIT is underexpressed in breast cancer tissues compared to their normal counterparts due to the extensive allelic loss that is observed in its gene structure.

Alterations of tumour suppressor gene PPP2R1B in hepatocellular carcinoma

To evaluate whether the tumour suppressor gene, PPP2R1B, is involved in pathogenesis of hepatocellular carcinoma (HCC), reverse transcription-polymerase chain reaction (RT-PCR) and cDNA sequencing were performed. Eleven of 38 (29%) tumours and 1 of 34 (3%) corresponding non-tumour tissues showed coexpression of wild-type and aberrant mRNA. Various deletions were found in aberrant transcripts. Southern blot analysis did not show gene deletion in tumours, suggesting abnormal RNA splicing may be involved. These data suggest the possibility that aberrant transcripts of PPP2R1B might be associated with the development of HCC.

Hint1 is a haplo-insufficient tumor suppressor in mice

The HINT1 protein, a member of the histidine triad (HIT) family, is highly conserved in diverse species and ubiquitously expressed in mammalian tissues. However, its precise function in mammalian cells is not known. As a result of its structural similarity to the tumor-suppressor protein FHIT, we used homozygous-deleted Hint1 mice to study its role in tumorigenesis. We discovered that after 2 to 3 years of age the spontaneous tumor incidence in Hint1 -/- mice was significantly greater than that in wild-type Hint1 +/+ mice (P < 0.05). Using a well-established mouse model of 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary carcinogenesis we found a marked and significant (P < 0.05) increase in the incidence of mammary and ovarian tumors in both, Hint1 -/- and +/- mice versus +/+ mice. The Hint1 -/- and +/- mice had similar tumor incidence and similar tumor histologies. Therefore, deletion of Hint1 in mice enhances both spontaneous tumor development and susceptibility to tumor induction by DMBA. In addition, since the Hint1 +/- tumors retained expression of the unmutated wild-type allele, Hint1 is haplo-insufficient with respect to tumor suppression in this model system.

Loss of heterozygosity of the BRCA1 and FHIT genes in patients with sporadic breast cancer from Southern Brazil

AIM

The evaluation of allelic losses at the FHIT and the BRCA1 genes and at three other loci at the 17q region in a series of 34 sporadic breast cancer cases from Southern Brazil.

METHODS

The samples were evaluated for loss of heterozygosity (LOH) at the FHIT and the BRCA1 genes and at three other microsatellite markers at 17q, and the findings were correlated with clinicopathological parameters.

RESULTS

The BRCA1 intragenic marker, D17S855, had the highest frequency of LOH, detected in 10 of 24 informative cases, followed by the D17S579 (six of 23 informative cases), D17S806 (five of 21 informative cases), and D17S785 markers (five of 21 informative cases). LOH at the FHIT intragenic marker, D3S1300, was found in six of 25 informative cases. In four of the six cases with LOH of the FHIT gene, there was concomitant loss of the BRCA1 intragenic marker.

CONCLUSIONS

The frequency of allelic losses in the FHIT and BRCA1 loci in the Southern Brazilian population is similar to that described in the general population. No correlations were found when the total LOH frequency was compared with tumour size, grade, or presence of axillary lymph node metastasis. Further studies using larger sporadic breast cancer samples and additional markers would be useful to confirm these findings, in addition to establishing more specific associations with clinicopathological parameters in this specific population.

Chromosome arm 8p and cancer: a fragile hypothesis

Chromosome arm 8p is one of the most frequently altered regions in human cancers. Several potential oncogenes and tumour suppressor genes have been identified but further investigations are needed to confirm which are bona fide oncogenic targets. In cancer cells, chromosome breaks may occur at fragile sites throughout the genome. Some fragile sites lie within genes that may have a role in cancer; the best example is FHIT at 3p14, which contains the fragile site FRA3B. We have found that chromosome breaks disrupt the NRG1 gene at 8p12 in breast and pancreatic cancers. We hypothesise that alteration of the NRG1 gene could occur through breakage at a non-common fragile site.

Primary and Secondary Prevention of Non–Small-Cell Lung Cancer: The SPORE Trials of Lung Cancer Prevention

The aims of chemoprevention in lung cancer are to prevent the appearance of disease (primary prevention) and to stop or reverse the progression of premalignant lesions (secondary prevention). Until recently, there was little hope that these goals could be attained. However, the results achieved with tamoxifen in the prevention of breast cancer, and the emergence of new therapies specifically targeted to molecules involved in the pathogenesis of lung cancer have set the stage for investigation of these agents for chemoprevention of lung cancer. Two of these new molecular targeted agents are gefitinib, an inhibitor of epidermal growth factor receptor-tyrosine kinase activity, and tipifarnib (R115777, Zarnestra ), an inhibitor of the farnesyltransferase enzyme, which is required for the proper localization and function of the ras oncogene. Tumor responses and disease stabilization have been achieved with both agents in clinical trials. In the Iressa Dose Evaluation in Advanced Lung Cancer (IDEAL)-1 and IDEAL-2 phase II trials, gefitinib was demonstrated to be effective for disease control in patients with advanced non-small-cell lung cancer. The SPORE (Specialized Program of Research Excellence) Trials of Lung Cancer Prevention (STOP) are 2 parallel studies that will investigate the potential effectiveness of gefitinib and tipifarnib in preventing the appearance and progression of premalignant lesions in former or current smokers with a history of smoking-related cancer. These trials should provide information not only about the potential role of gefitinib and tipifarnib in lung cancer chemoprevention, but also about the molecular changes that underlie tumorigenesis and that may serve as markers of disease progression. The STOP trial objectives are to evaluate the effect of gefitinib and tipifarnib on histologic and biologic parameters in patients with evidence of sputum atypia, to evaluate various parameters as potential predictors of the effectiveness of these agents, and to evaluate the tolerability of these agents over a 6-month course of treatment. Histologic response, defined as prevention of appearance or progression of premalignant lesions, is the primary endpoint of these trials. New targeted molecular therapies such as gefitinib and tipifarnib may offer the opportunity to make chemoprevention a viable treatment modality in lung cancer as well as in other human solid tumors.

Loss of FHIT protein expression is a marker of adverse evolution in good prognosis localized breast cancer

The FHIT tumor suppressor gene, which encompasses the fragile site FRA3B at 3p14.2, is altered frequently in many types of human cancers. To determine its importance as a prognostic marker in breast cancer, the expression of the FHIT protein was studied in a series of 452 breast carcinomas by using immunohistochemistry on sections of tissue microarrays. Three distinct levels of FHIT expression were observed: in 154 cases (34.1%) expression was unchanged as compared to normal level; in 78 (17.2%) no expression was found; in the remaining 220 cases (48.7%), expression was intermediate. Overall, two-thirds of the cases had abnormal levels of the protein. Absence of FHIT was significantly associated with a higher grade (p < 0.01) and absence of hormone receptors (p < 0.001). The patients were separated into Group I (153 node-negative good prognosis patients who did not receive adjuvant chemotherapy) and Group II (226 high-risk patients treated by adjuvant chemotherapy) according to the St.-Gallen conference consensus. The median follow-up was 48 months. Among Group I but not Group II patients, a multivariate analysis showed that FHIT expression was significantly associated with disease-free survival. The relative risk of recurrence for FHIT-negative Group I patients was 2.37 (1.21-4.64; p = 0.03). Thus, among the patients who present with tumors of apparent good prognosis, FHIT is an independent prognostic factor that distinguishes a subgroup of patients who could benefit from adjuvant treatment.

Reciprocal translocations in breast tumor cell lines: cloning of a t(3;20) that targets the FHIT gene

All molecular alterations that lead to breast cancer are not precisely known. We are evaluating the frequency and consequences of reciprocal translocations in breast cancer. We surveyed 15 mammary cell lines by multicolor fluorescence in situ hybridization (M-FISH). We identified nine apparently reciprocal translocations. Using mBanding FISH and FISH with selected YAC clones, we identified the breakpoints for four of them, and cloned the t(3;20)(p14;p11) found in the BrCa-MZ-02 cell line. We found that the breakpoint targets the potential tumor-suppressor gene FHIT (fragile histidine triad) in the FRA3B region; it is accompanied by homozygous deletion of exon 5 of the gene and absence of functional FHIT and fusion transcripts, which leads to the loss of FHIT protein expression. Additional experiments using comparative genomic hybridization provided further information on the genomic context in which the t(3;20)(p14;p11) reciprocal translocation was found.

DNA methylation and breast carcinogenesis

Knowledge about breast carcinogenesis has accumulated during the last decades but has barely been translated into strategies for early detection or prevention of this common disease. Changes in DNA methylation have been recognized as one of the most common molecular alterations in human neoplasia and hypermethylation of gene-promoter regions is being revealed as one of the most frequent mechanisms of loss of gene function. The heritability of methylation states and the secondary nature of the decision to attract or exclude methylation support the idea that DNA methylation is adapted for a specific cellular memory. According to Hanahan and Weinberg, there are six novel capabilities a cell has to acquire to become a cancer cell: limitless replicative potential, self-sufficiency in growth signals, insensitivity to growth-inhibitory signals, evasion of programmed cell death, sustained angiogenesis and tissue invasion and metastasis. This review highlights how DNA-methylation contributes to these features and offers suggestions about how these changes could be prevented, reverted or used as a 'tag' for early detection of breast cancer or, preferably, for detection of premalignant changes.

High frequency of LOH, MSI and abnormal expression of FHIT in gastric cancer

The FHIT gene is a putative tumour suppressor gene. In this study, we analysed a set of 50 gastric tumours for alterations of FHIT, and found 38 of 45 tumours (84%) exhibiting loss of heterozygosity (LOH) within the FHIT gene. We used both nested Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) and single step RT-PCR to analyse the FHIT transcripts and found 34 of 39 (87%) tumours and seven of the 11 (64%) corresponding non-cancerous tissues showed low or aberrant expression of FHIT mRNA and the appearance of the aberrant FHIT transcripts depended on the conditions of the RT-PCR. In these aberrant transcripts, frequent deletions and/or insertions were detected by direct sequencing. All breakpoints for deletions and insertions were at splicing sites. All insertions came from the adjacent introns, whose appearance was completely in accordance with the 'GU-AG' rule for pre-mRNA splicing. It may be suggested that an alternative splicing mechanism functions in the formation of these aberrant transcripts. The fragile nature of FRA3B within the FHIT gene could be responsible for the formation of the aberrant mRNA. Negative or reduced Fhit expression was detected in 39 of 50 tumours (78%). Moreover, an association was found between abnormal Fhit expression and positive node status (P=0.012). Thirteen of 48 tumours (27%) displayed microsatellite instability (MSI), among which 10 tumours also showed MSI within the FHIT gene. Furthermore, we detected an association between MSI and negative node status (P=0.02). We conclude that the abnormalities of FHIT, presumably associated with the unstable nature of FRA3B within the FHIT gene, are involved in the carcinogenesis of gastric cancer, and lack of mismatch repair (MMR) could possibly promote its alteration in a subset of gastric tumours.