O2-O3 triggers tumoricidal immune response after application of a repetitive highly oxidative stimulus by insufflation of a medical O3/O2 gas mixture into the peritoneal cavity in animal model. O3/O2-PP treatment, indicates an enhanced activation of the innate and adaptive arms of the immune system, implicating a role of activated TILs In the anti cancer effects of the O3. Interestingly, COX2 expression was decreased.