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Oncotarget. 2018 May 25;9(40):25833-25841. doi: 10.18632/oncotarget.25383. eCollection 2018 May 25.

VX-984 is a selective inhibitor of non-homologous end joining, with possible preferential activity in transformed cells.

Author information

Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY 10011, USA.
Department of Radiation Oncology, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
Department of Molecular Biology and Biochemistry, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA.



DNA double-strand breaks (DSBs) can be repaired by non-homologous end joining (NHEJ) or homologous recombination (HR). We demonstrate the selectivity of VX-984, a DNA-PK inhibitor, using assays not previously reported.

Experimental Design:

The class switch recombination assay (CSR) in primary B cells was used to measure efficiency of NHEJ. A cellular reporter assay (U2OS EJ-DR) was used to assess the efficiency of HR and NHEJ in cells treated with VX-984. Immunofluorescence assays (IF) evaluated γ-H2AX foci for DSB repair kinetics in human astrocytes and T98G glioma cells. Western blotting was used to evaluate phosphorylation of DNA-PKcs substrates.


We found a dose-dependent reduction in CSR efficiency with VX-984, and through the EJ-DR assay, dramatic dose-dependent increases in HR and mNHEJ. Immunofluorescence assays showed an inability of malignant cells to resolve γ-H2AX foci in the presence of VX-984. Radiation-induced phosphorylation of DNA-PK substrates was further reduced by treatment with VX-984.


VX-984 efficiently inhibits NHEJ, resulting in compensatory increases in alternative repair pathways, increases DSBs, and appears to affect transformed cells preferentially.


DNA repair; DNA-PK; double-strand break repair; non-homologous end joining; radiation therapy

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