P53 activation suppresses irinotecan metabolite SN-38-induced cell damage in non-malignant but not malignant epithelial colonic cells

Nutlin-3a is a p53 activator and potential cyclotherapy approach that may also mitigate side effects of chemotherapeutic drugs in the treatment of colorectal cancer. We investigated cell proliferation in a panel of colorectal cancer (CRC) cell lines with wild-type or mutant p53, as well as a non-tumorigenic fetal intestinal cell line following Nutlin-3a treatment (10 mu M). We then assessed apoptosis at 24 and 48 h following administration of the active irinotecan metabolite, SN-38 (0.001 mu M - 1 mu M), alone or following pre-treatment with Nutlin-3a (10 mu M). Nutlin-3a treatment (10 mu M) significantly reduced proliferation in wild-type p53 expressing cell lines (FHS 74 and HCT116(+/+)) at 72 and 96 h, but was without effect in cell lines with mutated or deleted p53 (Caco-2, SW480, and HCT 116(-/-)). SN-38 treatment induced significant apoptosis in all cell lines after 48 h. Nutlin-3a unexpectedly increased cell death in the p53 wild-type CRC cell line, HCT116(+/+), while Nutlin-3a pre-treatment provided protection from SN-38 in the p53 wild-type normal cell line, FHs 74. These results demonstrate Nutlin-3a's selective growth-arresting efficacy in p53 wild-type non-malignant intestinal cell lines, enabling the selective targeting of malignant cells with chemotherapy drugs. These studies highlight the potential of Nutlin-3a to minimise intestinal mucosal damage following chemotherapy.