H2AX and breast carcinoma: These data could be controversial due to previous results that showed that high VRK1 expression was associated with an ability to confer resistance to DNA-damaging agents in human breast cancer [24]; however, recent results suggest a potentially contradictory role of VRK1 in the DDR to ionizing radiation [17], through its ability to phosphorylate histone H2AX at Ser 139, which could be directly associated with DNA ladder formation in apoptosis [32].