G6PC1 and hepatocellular carcinoma: While dibutyryl cAMP alone did not significantly stimulate transcription of a luciferase reporter gene under control of 1.2 kb of the human glucose-6-phosphatase promoter in H4IIIE hepatoma cells [6], a later report by the same group described a ≈ 2-fold stimulation of glucose-6-phosphatase promoter activity with dibutyryl cAMP [7].