TFAP4 and lung carcinoma: In addition to a role in the development of CRPC, AP4 was found to be associated with other types of cancer, including colorectal cancer,17 hepatocellular cancer,34 gastric cancer35, 36 and lung cancer.37 The transcription factor AP4 was first identified as a cellular factor that activated late SV40 transcription in vitro by synergistically interacting with AP-1.38 Large amounts of evidence support the hypothesis that AP4 preferentially binds to the E-box motif CAGCTG to activate the expression of its downstream target genes.