Targeting ABCB1 (MDR1) in multi-drug resistant osteosarcoma cells using the CRISPR-Cas9 system to reverse drug resistance

// Tang Liu 1, 2 , Zhihong Li 1 , Qing Zhang 1 , Karen De Amorim Bernstein 2 , Santiago Lozano-Calderon 2 , Edwin Choy 2 , Francis J. Hornicek 2 , Zhenfeng Duan 2 1 Department of Orthopaedics, The 2 nd Xiangya Hospital of Central South University, Changsha, Hunan, 410011, P.R. China 2 Sarcoma Biology Laboratory, Department of Orthopaedic surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA Correspondence to: Tang Liu, email: liutang1204@csu.edu.cn Zhenfeng Duan, email: zduan@mgh.harvard.edu Keywords: osteosarcoma, CRISPR-Cas9, meta-analysis, ABCB1, P-glycoprotein Received: June 06, 2016     Accepted: October 16, 2016     Published: November 7, 2016 ABSTRACT Background: Multi-drug resistance (MDR) remains a significant obstacle to successful chemotherapy treatment for osteosarcoma patients. One of the central causes of MDR is the overexpression of the membrane bound drug transporter protein P-glycoprotein (P-gp), which is the protein product of the MDR gene ABCB1 . Though several methods have been reported to reverse MDR in vitro and in vivo when combined with anticancer drugs, they have yet to be proven useful in the clinical setting. Results: The meta-analysis demonstrated that a high level of P-gp may predict poor survival in patients with osteosarcoma. The expression of P-gp can be efficiently blocked by the clustered regularly interspaced short palindromic repeats (CRISPR)-associated Cas9 system (CRISPR-Cas9). Inhibition of ABCB1 was associated with reversing drug resistance in osteosarcoma MDR cell lines (KHOSR2 and U-2OSR2) to doxorubicin. Materials and Methods: We performed a meta-analysis to investigate the relationship between P-gp expression and survival in patients with osteosarcoma. Then we adopted the CRISPR-Cas9, a robust and highly efficient novel genome editing tool, to determine its effect on reversing drug resistance by targeting endogenous ABCB1 gene at the DNA level in osteosarcoma MDR cell lines. Conclusion: These results suggest that the CRISPR-Cas9 system is a useful tool for the modification of ABCB1 gene, and may be useful in extending the long-term efficacy of chemotherapy by overcoming P-gp-mediated MDR in the clinical setting.