FOS and cancer: Also required for the atrophy phenotype during cancer are the transcription factors, Signal Transducer and Activator of Transcription 3 (STAT3), which acts downstream of IL-6 [11, 12], CCAAT/enhancer-binding protein beta (C/EBPβ), which is activated by p38 mitogen activated protein kinase (MAPK) [13], and activator protein-1 (AP-1) [14], which is activated through extracellular regulated kinase 1 and 2 (ERK 1/2) MAPK [15].