A method of cancer treatment is provided that includes administering an effective amount of an endogenous ligand for the aryl hydrocarbon (Ah) receptor (AhR) named ITE or one of its structural analogs (the active ingredient) to a subject with cancer is disclosed. An effective dose and dosing frequency of the active ingredient are determined by measuring its blood levels of the subject after dosing. The active ingredient formulated with a carrier system is applied topically, enterally, or parenterally to the subject. An oral dose of water, in addition to normal water drinking, is administered to help alleviate feces hardening, a complication of ITE dosing. Subjects with cancers of skin, colon (or rectum), stomach, pancreas, kidney, bladder, soft tissue, and cervix, are preferably accepted for treatment or intervention.