FOS and cancer: Several transcription factors were identified through microarray analysis as downstream targets of FoxO in response to tumor-burden, including the atrophy-related bZIP transcription factors, Cebpb and Fos. The identification of Cebpb as a downstream target of FoxO in skeletal muscle during cancer is of particular interest, since the protein expression of C/EBPβ is increased in muscles of tumor bearing mice, and mice lacking C/EBPβ are resistant to LLC cancer-induced muscle wasting [13].