Alternatively, Gharavi and El-Kadi (2005) showed in murine hepatoma cell lines that Cyp1a1 is down-regulated by the proinflammatory cytokines interleukin 1β (Il-1β), IL-6, and tumor necrosis factor α in an AHR-dependent manner. This evidence concerns the gene CYP1A1 and hepatocellular carcinoma.