FOS and neoplasm: It has been also found that AP-1 induces transcriptionally the expression of co-inhibitory immune checkpoints (PD-1, PD-L1) and the expression of the FOXP3 gene locus, which is a key modulator of regulatory T cells (Treg); therefore, AP-1 is implicated in the efficacy of anti-tumor T-cell responses and immunotherapy [49].