FOXO (forkhead box O) transcription factors are crucial regulators of cell fate. This function of FOXO proteins relies on their ability to control diverse and at times, opposing cellular functions, such as proliferation, differentiation, DNA repair, defence against oxidative stress damage and apoptosis, in response to hormones, growth factors and other environmental cues. This review discusses our current understanding of the regulation and role of FOXO transcription factors in determining cell fate and highlights their relevance to tumorigenesis and drug resistance.

Together with the chromatin immunoprecipitation and biotinylated oligonucleotide pulldown data, the co-immunoprecipitation results also suggest the possibility that FoxM1 and FoxO3a cooperate to regulate ER␣ gene transcription.