To investigate whether hepatic Exo70 expression was regulated by HNF4α, the most important and abundant transcription factor in liver, we knocked down endogenous HNF4α in human hepatic cancer cell line Hep G2, and a dramatic decrease in the protein and mRNA expression level of Exo70 was observed (Figure 1A–1B). The gene discussed is HNF4A; the disease is liver cancer.