Consistently, we observed that the activation of HSF1 by heat shock stress, the actions of a pharmacological activator (geldanamycin), and the ectopic overexpression of HSF1 significantly promoted mevalonate pathway- and cholesterol biosynthesis-related genes, in particular HMGCS1 expression in hepatocellular carcinoma cells. The gene discussed is HMGCS1; the disease is hepatocellular carcinoma.