NOS2 and colorectal carcinoma: To further investigate whether NO synthesized from iNOS acts as an intermediate in the regulation of stem cell properties by PARP-1 in CRC, we used the pCMV6-PARP1 plasmid to stably overexpress PARP-1 in HCT-116 (p53 wild-type) and HT-29 (p53 mutated) cell lines.