Damaged DNA Binding Protein 2 Plays a Role in Breast Cancer Cell Growth

Zilal Kattan,Philippe Becuwe,Michel Dauça,Emilie Brunner,Sophie Marchal,Lionel Domenjoud,Carole Ramacci,Jean Louis Merlin,Agnès Leroux,Mikhail V Blagosklonny

doi:10.1371/journal.pone.0002002

Abstract

The Damaged DNA binding protein 2 (DDB2), is involved in nucleotide excision repair as well as in other biological processes in normal cells, including transcription and cell cycle regulation. Loss of DDB2 function may be related to tumor susceptibility. However, hypothesis of this study was that DDB2 could play a role in breast cancer cell growth, resulting in its well known interaction with the proliferative marker E2F1 in breast neoplasia. DDB2 gene was overexpressed in estrogen receptor (ER)-positive (MCF-7 and T47D), but not in ER-negative breast cancer (MDA-MB231 and SKBR3) or normal mammary epithelial cell lines. In addition, DDB2 expression was significantly (3.0-fold) higher in ER-positive than in ER-negative tumor samples (P = 0.0208) from 16 patients with breast carcinoma. Knockdown of DDB2 by small interfering RNA in MCF-7 cells caused a decrease in cancer cell growth and colony formation. Inversely, introduction of the DDB2 gene into MDA-MB231 cells stimulated growth and colony formation. Cell cycle distribution and 5 Bromodeoxyuridine incorporation by flow cytometry analysis showed that the growth-inhibiting effect of DDB2 knockdown was the consequence of a delayed G1/S transition and a slowed progression through the S phase of MCF-7 cells. These results were supported by a strong decrease in the expression of S phase markers (Proliferating Cell Nuclear Antigen, cyclin E and dihydrofolate reductase). These findings demonstrate for the first time that DDB2 can play a role as oncogene and may become a promising candidate as a predictive marker in breast cancer.

Highlights

Damaged DNA Binding protein 2 (DDB2) is a 48-kDa protein originally identified as a component of the damage-specific DNAbinding heterodimeric complex DDB, which is involved in nucleotide excision repair of UV-induced DNA damage through interaction with DDB1 (127- kDA protein) or CSA proteins [1]
Previous studies showed that mutations in the DDB2 gene, which lead to a deficiency in the NER system, increased susceptibility to develop cancer [21] and a DDB2 deficiency promoted spontaneous malignant tumors in mice [17,22]
These results provided evidence that DDB2 could play a role as a tumor suppressor in normal cells

Summary

Introduction

Damaged DNA Binding protein 2 (DDB2) is a 48-kDa protein originally identified as a component of the damage-specific DNAbinding heterodimeric complex DDB, which is involved in nucleotide excision repair of UV-induced DNA damage through interaction with DDB1 (127- kDA protein) or CSA proteins [1]. It works in association with other proteins of the repair system, including the XPC-hHR23B heterodimer, XPA and replication protein A [2,3]. Human DDB2 is involved in other cellular processes, including transcription and cell cycle regulation. The cell cycleregulation of DDB2 levels involves ubiquitin-proteasome pathway-mediated proteolysis, through the interaction between DDB2 and cullin 4A [7,12,13]

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