Products of ingested fat metabolism and also products of lipid peroxidation influenced on genes expression being natural ligands for nuclear receptors functioning as a transcription factors. This situation creates possibilities of diet modification by type and amount of fat as an important element of cancer prevention and cancer therapy. Functioning and activity of PPARs indicating the way of controlling their activity by another ligands than that included in the diet. This is a base for pharmacologic synthesis of a new class of specific drugs as an agonists for nuclear receptors of precisely defined histologic type of cancer.