Prognostic value of CDH2 and CDT2 expression levels in the peripheral blood (PB) specimens of patients with Ewing family of tumors (EFTs).

Abstract

e22046 Background: EFTs are characterized by oncogenic EWSR1-FLI1 fusion gene, which can be detected in 85-90% of tumors and in 20-70% of peripheral blood specimens. It has been previously reported that downregulation of CDH2 (encoding N-cadherin) and overexpression of CDT2 [also known as DTL, encoding denticleless homolog (Drosophila)]in EFTs tumors are associated with poor prognosis. The aim of the study was to evaluate the expression levels of these markers in the circulating tumor cells and assess their utility as prognostic markers in EFTs. Methods: 10mL of PB was collected from 24 untreated adult EFTs patients at the diagnosis (period: 2009-2011, median age 30 years). 9 blood specimens from healthy individuals, and 5 untreated frozen EFTs tumor samples were used as controls. 8 EFTs patients presented metastatic disease (M1) at the diagnosis and 5 patients died during the follow-up period. Median follow-up was 22 months. Quantitative reverse transcription PCR (qRT-PCR) for CDH2 and CDT2 expression were performed in triplicate using the TaqMan Gene Expression Assays (Applied Biosystems). Mean expression level of 2 reference genes PSMC4 and EIF2B1 served as endogenous control. The fold change was calculated using ddCt method with pooled healthy individuals as calibrator. Results: At least 2-fold decrease (range 2.11-16.35) of CDH2 expression level in PB has been observed in 79% (n=19) of EFTs patients (p=0.04) as compared to healthy control. In general, CDH2 expression level in PB of EFTs patients was 3.08-fold lower compared with healthy individuals (p=0.07). All of the patients who had M1 at diagnosis (n=8) and who died during the follow-up (n=5) had CDH2 gene underexpression. CDT2 overexpression (FC range 3.28-6.97) has been observed in 17% (n=4) of EFTs patients (p=0.01). Three of these patients had M1 at diagnosis and two of these patients died during the follow-up. PB specimens presenting CDT2 overexpression clustered together with the tumor specimens. Conclusions: Abnormalities in the expression of CDH2 and CDT2 genes in PB specimens are associated with aggressive clinical course of EFTs. Diagnostic and prognostic significance of these biomarkers warrants further studies.