Given the ability of CD4 Tregs to adapt their metabolism to survive and proliferate in the hostile TME,11 with FOXP3 driving this adaptation,13 and the suggestive findings about the putative role of FOXP3+ CD8 T cells as tumor-specific effector T cells,21,22 we decided to overexpress FOXP3 in mature CD8 T cells and study how this affected their metabolic competences and antitumor efficacy in adoptive immunotherapy for melanoma. The gene discussed is FOXP3; the disease is melanoma.