WWOX Gene Methylation, WWOX and FHIT Protein Expression in Primary Breast Tumors and Breast Parenchymal Tissues and Their Relationship to Prognostic and Epidemiological Data.
Cigdem Himmetoglu Ussakli, Kay Huebner, Gulnur Guler. Hacettepe University Faculty of Medicine, Ankara, Turkey; The Ohio State University Medical Center, Columbus
Background: Tumor suppressor genes,FHIT and WWOX,are encoded by fragile loci FRA3B and FRA16D at chromosomes 3p14.2 and 16q23.3,and lost concordantly in breast cancer.These genes are frequently inactivated due to loss of heterozygosity and hypermethylation at their control sites.The expression of their protein products has been shown to decrease in the neighbouring breast parenchyma of tumor tissues as well.This concordant loss of expression suggest that these common fragile regions of the genome,where certain environmental/chemical factors result in damage, have important functions in carcinogenesis.The aim of this study was to determine the methylation status of invasive tumor tissues as well as benign breast parenchyma and correlate these results with the epidemiological and prognostic parameters.
Design: Fresh frozen tumor tissues from 26 patients and formaldehyde fixed paraffin embedded tumor tissues from 50 patients with a diagnosis of primary breast cancer and follow-up of at least 5 years were selected from the archives of Hacettepe University.In addition to benign parenchymas within 4 cm of invasive tumor and more than 4 cm away,24 controls from reduction mammoplasties were selected for analysis.Expression of Wwox, Fhit, ER, PR and HER2 proteins were determined by immunohistochemistry.Methylation status of 34 CpG islands in promoter and exon 1 region of WWOX gene was analysed quantitatively by pyrosequencing.
Results: Wwox hypermethylated tumors were significantly more in patients younger than 40 years old (p=0.024) as well as in patients with a family history for breast cancer (p=0.05).Hypermethylation in tumor tissues was significantly more in patients with systemic metastasis (p=0.05) on follow-up.Methylation in breast parenchyma was correlated with lymphovascular invasion (p=0.002) and family history (p=0.015).
Conclusions: These results support the hypothesis that WWOX gene hypermethylation is associated with hereditary and early breast cancer development via abnormal DNA damage response. Epigenetic alterations such as hypermethylation are thought to promote mutations in genome by silencing tumor suppressor genes.These epigenetic alterations are proving to be consistent and early events in neoplastic progression and the reversible nature of methylation offers the potential to revert aspects of the cancer phenotype with the appropriate therapy.
Tuesday, March 1, 2011 1:00 PM
Poster Session IV # 30, Tuesday Afternoon