CASP3 and breast cancer: However, proteolytic activation of pro-caspase-3, typical of the apoptotic program, leads to the active protease caspase-3,58 which cuts the 116-kDa form of PARP1 at the DEVD site in two small pieces, of 85 and 24 kDa.59 As consequence, the cleaved PARP is not able to repair DNA damage.60 We observed that pH2AX increases in all cells, regardless of the treatment, according to our results with pH2AX foci in BC cell line.