Suppression of the tumorigenicity of human hepatoma hep3B cells by long-term retinoic acid treatment

We cultured human hepatoma Hep3B cells in the presence of RA (10−5 M) for 30 days; the expression of both α fetoprotein and hepatitis B virus surface antigen were suppressed over 70% at the transcriptional level by RA treatment. The doubling time of RA treated Hep3B cells was slightly different from the control cells when they were cultured in 5% fetal calf serum/DMEM medium. However, cultured under serum-free conditions, the control Hep3B cells still grow, but the RA treated cells could not attach to the substratum of the culture plate and stopped growing. In vivo assay indicated that RA treatment completely suppressed the tumorigenicity of Hep3B cells in nude mice.