Expression and Effect of CTCF in Pediatric Acute Lymphoblastic Leukemia

Abstract 4298

Acute lymphoblastic leukemia (ALL) is the most frequent-occurring malignant neoplasm in children, but the pathogenesis of the disease remains unclear. In a microarray assay using samples from 100 Chinese children with ALL, CTCF was found to be up-regulated. DNA-binding nuclear protein CTCF (encoded by CTCF gene) is a highly conserved zinc finger protein involved in multiple cellular processes including transcriptional activation/repression, insulation, imprinting and × chromosome inactivation. It has been shown to be associated with cell apoptosis and differentiation in tumors; however, the biological function of CTCF in pediatric ALL is presently unknown.

To investigate the expression features of CTCF in pediatric ALL cells, matched newly diagnosis (ND), complete remission (CR) and relapse (RE) bone marrow samples from 24 patients were collected. Ten ND-CR paired samples (n=20) were selected to detect the mRNA levels of CTCF by Q-PCR. Besides, the protein levels of CTCF at different stages of disease progression were measured by western blot in all patients (20 ND-CR paired samples, n=40; 4 ND-CR-RE matched samples, n=12). To further explore the role of CTCF in the pathogenesis of leukemia, the potential effect of CTCF on the cell apoptosis in lymphoblastic cells was investigated by flow cytometry.

We identified significant up-regulation of CTCF in the ND samples. Importantly, the expression of CTCF returned to normal level after CR, but rebounded in the RE samples. Knock-down of CTCF resulted in nearly 3–fold and 15–fold increases in early and late apoptosis of leukemic cells respectively, which indicated that CTCF is an anti-apoptotic factor and plays an anti-apoptotic role in lymphoblastic cells.

Our results indicate that CTCF may represent a promising indicator of disease progression as well as reflecting the ongoing therapeutic effects of treatment. Furthermore, CTCF serves as an anti-apoptotic factor and potentially contributes to leukemogenesis in pediatric ALL patients.