Spleens of EG7 (syngeneic lymphoma)-bearing C57BL/6 mice were collected and analyzed 20 days after tumor inoculation and a dose-dependent decrease in the ratio of Treg cells (CD4+CD25+)/total CD4+ and in the number of FoxP3+ cells among CD4+CD25+ Treg cells was detected as a consequence of RES treatment. This evidence concerns the gene FOXP3 and neoplasm.