Hypermethylated DAPK in serum DNA of women with uterine leiomyoma is a biomarker not restricted to cancer

Abstract

ObjectiveOvarian cancer is most frequently diagnosed at a late stage with a poor prognosis. No markers for early diagnosis have been established. Aberrantly methylated DNA appears as a promising molecular cancer marker. The aim of this study was to analyze the methylation status of the proapoptotic cancer related gene death-associated protein kinase (DAPK) in ovarian cancer patients, healthy controls and in patients suffering from a benign proliferative disease such as uterine leiomyoma. MethodsMethylation-specific PCR (MSP) was used to detect DAPK methylation in primary tumor tissue and serum of both ovarian cancer (n=32) and uterine leiomyoma patients (n=17 primary tissue, n=30 serum). Serum samples from healthy women served as controls (n=20). MSP results were confirmed by restriction digest and sequencing analyses of cloned PCR products. ResultsDAPK methylation was detected in 50% and 35.3% of primary tissue and 56% and 23.8% of serum samples from ovarian cancer and leiomyoma patients, respectively. However, the association of methylation frequencies in tissue and serum was low (kappa=−0.053). Sequencing experiments revealed fully methylated MSP products in sera of both ovarian cancer and leiomyoma patients. In contrast sera from control patients showed only partially methylated DAPK sequences. ConclusionDAPK hypermethylation was neither specific for the tissue of origin nor for cancer. The high prevalence of leiomyoma compromises the utility of this gene as a serum marker for early ovarian cancer detection. These data emphasize the necessity to co-analyze controls presenting with non-cancer proliferative disease in the quest for molecular cancer markers.