215P - 53BP1 loss induces the chemoresistance of colorectal cancer cells to 5-fluorouracil by inhibiting ATM-CHK2-P53 pathway

Date 17 December 2016
Event ESMO Asia 2016 Congress
Session Poster lunch
Topics Anticancer agents
Colon and Rectal Cancer
Rectal Cancer
Translational Research
Presenter Hong Ma
Citation Annals of Oncology (2016) 27 (suppl_9): ix53-ix67. 10.1093/annonc/mdw581
Authors H. Ma, J. Yao, A. Huang, T. Zhang
  • Cancer Center, Wuhan Union Hospital (of Tongji Medical College of HUST), 430022 - Wuhan/CN

Abstract

Background

P53 binding protein 1 (53BP1) is a key component in DNA repair to maintain genetic stability and preventing tumors. Our previous study indicated that 53BP1 loss is an adverse prognostic factor of colorectal cancer, but its effect on the sensitivity of colorectal cancer to 5-fluorouracil (5-FU) is unknown. This study aimed to examine the effect of 53BP1 expression on the sensitivity of colorectal cancer to 5-FU.

Methods

Immunohistochemical analysis of was performed in 30 metastatic colorectal cancer (mCRC) samples to investigate the association of 53BP1 expression level with clinical therapeutic effect and prognosis. IC50 values for 5-FU and 53BP1 expression were determined by MTT assay and Western blotting in 5 colorectal cancer cell lines. 53BP1 knockdown was also performed in HCT116 and HT29 cells with relatively high 5BP1 expression, and the effects on cell proliferation, apoptosis and cell cycle were evaluated. In addition, the protein expressions of ATM-CHK2-P53 pathway components and Bcl-2 family were measured by Western blotting. Finally, the effect of 53BP1 knockdown on tumor growth and 5-FU chemoresistance was investigated in vivo.

Results

53BP1 expression was closely related to time to progress (TTP) after the first-line chemotherapy based on downregulation of 53BP1 resulting in a reduction of TTP. In vitro, downregulated 53BP1 induced S-phase arrest of HCT116 and HT29 cells, increased the proliferation, inhibited apoptosis after 5-FU treatment, and inhibiting relative proteins expression in ATM-CHK2-P53 apoptotic pathway, as well as apoptotic proteins capase9, capase3 and upregulating Bcl-2 expression. In addition, the in vivo study further confirmed that 53BP1 downregulation accelerated the proliferation of implanted tumor cells in nude mice and enhanced resistance to 5-FU.

Conclusions

Our studies showed the 53BP1 loss served as a negative factor to affecting chemotherapy efficacy, and could promote cell proliferation and inhibit apoptosis through inhibition of the pathway of ATM-CHK2-P53 to induce 5-FU resistance. Our study provides a new prospect for the research in this field.

Clinical trial indentification

The tumor tissues from 30 mCRC patients who have received first-line chemotherapy were collected from March 2012 to December 2014.The study was approved by the Human Ethics Review Board from the Union Hospital of Tongji Medical College of Huazhong University of Science and Technology (Hubei, China).

Legal entity responsible for the study

N/A

Funding

Supported by Natural Science Foundation of Hubei Province of China, No2015CFB659

Disclosure

All authors have declared no conflicts of interest.