Figure 4.
Exogenous expression of 53BP1 partially restored the sensitivity of poly(ADP‐ribose) polymerase inhibitors (PARPi)‐resistant variants to PARPi. A, Levels of DNA repair‐related proteins in the parental and resistant U251 cells determined by western blotting. B, After U251/OP, U251/TP and U251/SP cells were transfected with the full‐length 53BP1 cDNA, the levels of 53BP1 protein were determined by western blotting (upper) and immunofluorescence (lower). Scale bar: 5 μm. C, Accumulation of γH2AX triggered by olaparib was increased in U251/OP+53BP1 cDNA cells relative to U251/OP cells. D,E, Exogenous expression of 53BP1 in U251/OP cells partially restored olaparib sensitivity. D, Survival curves of olaparib‐treated U251, U251/OP and U251/OP+53BP1 cDNA cells. E, IC 50 in the log scale. **P < .01