2-cyano-3-12-dioxooleana-1-9(11)-dien-28-oic-acid-ethyl-amide and Adenomatous-Polyposis-Coli

Proton radiotherapy is becoming more common as protons induce more precise DNA damage at the tumor site with reduced side effects to adjacent normal tissues. However, the long-term biological effects of proton irradiation in cancer initiation compared with conventional photon irradiation are poorly characterized. In this study, using a human familial adenomatous polyposis syndrome susceptible mouse model, we show that whole-body irradiation with protons are more effective in inducing senescence-associated inflammatory responses (SIRs), which are involved in colon cancer initiation and progression. After proton irradiation, a subset of SIR genes (Troy, Sox17, Opg, Faim2, Lpo, Tlr2 and Ptges) and a gene known to be involved in invasiveness (Plat), along with the senescence-associated gene (P19Arf), are markedly increased. Following these changes, loss of Casein kinase Iα and induction of chronic DNA damage and TP53 mutations are increased compared with X-ray irradiation. Proton irradiation also increases the number of colonic polyps, carcinomas and invasive adenocarcinomas. Pretreatment with the non-steroidal anti-inflammatory drug, 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid-ethyl amide (CDDO-EA), reduces proton irradiation-associated SIR and tumorigenesis. Thus exposure to proton irradiation elicits significant changes in colorectal cancer initiation and progression that can be mitigated using CDDO-EA.

Topics: Adenomatous Polyposis Coli; Aging; Animals; Colorectal Neoplasms; Disease Models, Animal; Disease Progression; DNA Damage; Gene Expression Regulation, Neoplastic; Humans; Inflammation; Mice, Inbred C57BL; Mice, Knockout; Mutation; Oleanolic Acid; Oxidative Stress; Proton Therapy; Reverse Transcriptase Polymerase Chain Reaction; Survival Analysis; Tumor Suppressor Protein p53; Whole-Body Irradiation