Silence of ATAD2 inhibits proliferation of colorectal carcinoma via the Rb-E2F1 signaling.

Abstract

This study aims to clarify the potential function of ATAD2 (ATPase family, AAA domain containing 2) in regulating proliferative and apoptotic abilities of colorectal carcinoma (CRC). ATAD2 levels in CRC specimens and cell lines were detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). Overall survival in CRC patients with high or low level of ATAD2 was assessed by Kaplan-Meier method. The correlation between ATAD2 level and clinical characteristics of CRC patients was analyzed by χ2 test. Univariable and multivariable Cox regression models were generated to illustrate potential risk factors for the overall survival of CRC. After knockdown of ATAD2 in SW620 cells, relative levels of Cyclin D1, ppRb, pRb, E2F1, Cyclin E and cleaved Caspase 3 were detected by Western blot. Regulatory effects of ATAD2 on viability, clonality, cell cycle distribution, and apoptosis in SW620 and HCT15 cells were examined by a series of functional experiments. Upregulated ATAD2 in CRC was correlated to tumor size, tumor node metastasis (TNM) staging, and histological classification of CRC. High level of ATAD2 predicted poor prognosis in CRC patients. Cox regression test suggested that ATAD2 level, tumor size, TNM staging and histological classification were independent factors influencing overall survival in CRC. Knockdown of ATAD2 reduced viability and clonality in SW620 and HCT15 cells. In addition, cell cycle was arrested in G1 phase and apoptosis was stimulated in CRC cells with ATAD2 knockdown. In SW620 cells transfected with ATAD2 shRNA, protein levels of Cyclin D1, ppRb, E2F1 and Cyclin E were downregulated, and cleaved Caspase 3 was upregulated. ATAD2 is upregulated in CRC tissues and correlated to poor prognosis of CRC patients. It exerts an anti-proliferation role in CRC by arresting cell cycle in G1/S phase and triggering apoptosis via the Rb-E2F1 signaling.