AP-1: a double-edged sword in tumorigenesis

The AP-1 transcription factor is a dimeric complex that contains members of the JUN, FOS, ATF and MAF protein families. AP-1 proteins are primarily considered to be oncogenic, but recent studies have challenged this view — some AP-1 proteins, such as JUNB and c-FOS, have been shown to have tumour-suppressor activity. Here, we focus on the JUN and FOS proteins and aim to offer a new perspective on the molecular mechanisms that regulate the oncogenic and anti-oncogenic effects of AP-1 in tumour development.