Guan Z, et al. – The expression of exchange protein directly activated by cAMP1 (Epac1), PDE4, and PKC was tested in esophageal cancer tissues, as well as, the association of each protein with the pathological parameters of the samples was probed. As compared to the rates in para–carcinoma tissues, the expression rates of Epac1, PDE4, and PKC protein in esophageal cancer tissues were significantly higher. This finding indicated an association between these proteins and the development and progression of esophageal cancer.