FOXO3 and cancer: In the same cellular system, another FoxO3A mutant, FoxO3A-Δ242-271, in which we deleted the nuclear localization signal (NLS)32, was unable to enter the nucleus (Fig. 4n) and bind p21/p27 FHRE sites (Fig. 4o), but was still capable of entering the mitochondria and bind FHRE sites at the D-Loop of mtDNA in metabolically stressed cancer cells (Fig. 4p).