FOS and neoplasm of esophagus: Since functional AP-1 complex is constituted either by homo or hetrodimerization between different members of Jun and Fos family of proteins, we analyzed the composition of AP-1 complex in esophageal tumor tissues both in the presence and absence of HPV infection in a gel supershift assays by adding specific antibodies to all 7 members of AP-1 e.g. cJun, JunB, JunD, cFos, FosB, Fra-1 and Fra-2 (Figure 4A &4B).