The effect of the timing of iron administration on the outcome of photodynamic therapy using photolon in the CT26 colorectal cancer mouse model

Photodynamic therapy (PDT) is a minimally invasive cancer treatment undergoing research to in-crease its therapeutic effect. This study investigated the effect of iron administration time on the anticancer effects of PDT. Inflammation-related gene expression in tumor tissue was measured using RNA sequencing. Comparison of the PDT and Fe groups revealed that tumor volume increased 2.75 times in the PDT group after 14 d of PDT, with no difference between the PDT and 24hFe+PDT groups, while in the 1hFe+PDT group tumor vol-ume decreased 0.49 times. After 24 h of PDT, the 8-OHdG and TBARS content in the tumor tissue increased by 60% and 68% respectively in the 1hFe+PDT group compared with the PDT group, with no difference observed between the PDT and 24hFe+PDT groups. Gene expression was significantly increased in the 1hFe+PDT group 24 h after PDT and included Ccl12, Cxcl1, Cxcl2, Cxcl5, IL1b, and Il6, which are related to the inflammatory response in tumor tissues. Iron administration 1 h before PDT increased the anticancer effect of PDT probably as a result of in-creased oxidative damage.