PARP1 and colorectal carcinoma: To further decipher the role of PARP-1 in CRC, we transiently overexpressed PARP- 1 in two human colorectal cancer cell lines with different status of p53: HCT-116 (p53 wild-type) and HCT-116 p53 null (p53 −/−) (Figure 3).