Evaluation of FHIT gene alterations in ovarian cancer

Candidate tumor-suppressor gene DLEC1 is frequently downregulated by promoter hypermethylation and histone hypoacetylation in human epithelial ovarian cancer

Suppression of ovarian tumor growth by chromosome 3p was demonstrated in a previous study. Deleted in Lung and Esophageal Cancer 1 (DLEC1) on 3p22.3 is a candidate tumor suppressor in lung, esophageal, and renal cancers. The potential involvement of DLEC1 in epithelial ovarian cancer remains unknown. In the present study, DLEC1 downregulation was found in ovarian cancer cell lines and primary ovarian tumors. Focus-expressed DLEC1 in two ovarian cancer cell lines resulted in 41% to 52% inhibition of colony formation. No chromosomal loss of chromosome 3p22.3 in any ovarian cancer cell line or tissue was found. Promoter hypermethylation of DLEC1 was detected in ovarian cancer cell lines with reduced DLEC1 transcripts, whereas methylation was not detected in normal ovarian epithelium and DLEC1-expressing ovarian cancer cell lines. Treatment with demethylating agent enhanced DLEC1 expression in 90% (9 of 10) of ovarian cancer cell lines. DLEC1 promoter methylation was examined in 13 high-grade ovarian tumor tissues with DLEC1 downregulation, in which 54% of the tumors showed DLEC1 methylation. In addition, 80% of ovarian cancer cell lines significantly upregulated DLEC1 transcripts after histone deacetylase inhibitor treatment. Therefore, our results suggested that DLEC1 suppressed the growth of ovarian cancer cells and that its downregulation was closely associated with promoter hypermethylation and histone hypoacetylation.

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.

Impaired FHIT expression characterizes serous ovarian carcinoma

The FHIT (fragile histidine triad) gene on chromosome 3p14.2 is a candidate tumour suppressor gene. To define the role of the FHIT gene in the development of ovarian cancer, we have examined 33 ovarian carcinomas, 2 borderline tumours and 10 benign adenomas for the presence of FHIT gene alterations. FHIT transcripts were analysed by RT-PCR and sequencing. Aberrant FHIT transcripts were observed in 5/33 carcinomas (15%) and in 1 of 2 borderline tumours. Loss of normal FHIT transcript was observed in 5/33 carcinomas (15%) but not in 2 borderline tumours or 10 benign adenomas. Allelic losses at D3S1300 and D3S4103, both located within intron 5 of FHIT, were detected in 5/24 (21%) and 5/25 (20%) informative ovarian carcinomas, respectively. Expression of Fhit protein was analysed by immunohistochemistry in 44 carcinomas, 19 borderline tumours and 16 benign adenomas. Loss or significantly reduced expression of Fhit protein was observed in 6/44 (14%) ovarian carcinomas but not in any of 19 borderline tumours or 16 benign adenomas. The impaired Fhit protein expression was significantly correlated with the loss of normal FHIT transcription. Most notably, loss of normal FHIT transcript and impaired expression of Fhit protein occurred only in serous adenocarcinomas of grade 2 and 3 (5/15; 33% and 6/19; 32%, respectively). The present data suggest that inactivation of the FHIT gene by loss of expression is one of the important molecular events associated with the genesis of ovarian carcinoma, especially of high-grade serous carcinoma.

The prevalence of loss of heterozygosity in chromosome 3, including FHIT, in bladder cancer, using the fluorescent multiplex polymerase chain reaction

OBJECTIVE

To determine some of the genetic alterations involved in the pathogenesis and progression of transitional cell carcinoma of the bladder. Materials and methods In a population-based study, freshly frozen tissue was collected from all patients newly diagnosed with urinary bladder cancer in the Stockholm region during 1995-1996. The prevalence of loss of heterozygosity (LOH) was assessed at seven sites on chromosome 3, analysed in 151 patients, using a fluorescent multiplex polymerase chain reaction based on DNA from the tumour and peripheral blood.

RESULTS

LOH was detected in 12.1% (at 3q25-26.2) to 22.1% (at 3p11-12) of the informative cases. Relatively frequent LOH was detected at 3p22-24.2 (21.6%), at 3p14.2 within FHIT (21.5%), and at 3p11-12 (22.1%). Of 151 tumours, 72 (47.7%) showed LOH at one or more loci on chromosome 3. LOH on chromosome 3 was weakly associated with tumour grade (P = 0.095), but not with tumour stage (P = 0.701). However, when the frequency of LOH was analysed individually at each site, the prevalence of LOH at 3p11-12 was closely correlated with higher tumour stage (P = 0.011). Replication errors were detected in only four of 151 (2.6%) tumours. Conclusion These findings suggest that the 3p11-12 locus may involve a putative candidate tumour-suppressor gene which might be associated with bladder tumour invasiveness. The FHIT gene locus showed a relatively high frequency of LOH even in Ta tumours.

Loss of heterozygosity at chromosomes 3, 6, 8, 11, 16, and 17 in ovarian cancer: correlation to clinicopathological variables

Tumor specimens from 78 epithelial ovarian cancer patients were examined for loss of heterozygosity (LOH) at 11 microsatellite markers at chromosomes 3p14.2, 6q27, 8p12, 11p15.5, 11q23.1-q24, 16q24.3, and 17p13.1, to evaluate the involvement, possible clustering, and prognostic significance of these lesions in the progression of the disease. The LOH analysis was performed on polymerase chain reaction (PCR)-amplified DNA from sections of paraffin-embedded tumor and normal tissue pairs. In addition to primary tumors, specimens of metastatic tissues were studied from 19 patients. In the combined results from primary and metastatic tumors, LOH frequencies varied between 31% (6q27) and 69% (17p13.1). Only LOH at chromosomal regions 3p14.2 (D3S1300), 11p15.5 (D11S1318), 11q23.3-q24 (D11S1340 and D11S912), 16q24.3 (D16S476 and D16S3028), and 17p13.1 (D17S938) was associated with an adverse disease course. Our results indicate that LOH at 17p13.1 occurs independently from the other chromosomal sites studied, and is an early event in ovarian tumorigenesis. The LOH at 16q24.3, 11q23.3/q24, and 11p15.5 seems to occur later. The LOH at 11p15.5 and 11q23.3 was associated with reduced cancer-specific survival time; therefore, the studied markers could be located close to genes with influence on patient survival. Of the studied chromosomal regions, the most important tumor suppressor genes involved in the evolution of ovarian cancer appear to be located on chromosomes 11, 16, and 17. The genetic heterogeneity observed in primary and metastatic specimens demonstrates that there are multiple pathways involved in the progression of ovarian cancer.