A rat normal expressing cDNA library was established and subsequently its whole DNA was transfected into CBRH-7919 rat hepatoma cell cultures. With neomycin selection and morphological distinction, several reversed colonies were isolated and subcloned. All these colonies showed decreased growth rates, reduced capacity for foci formation on soft agar and tumorigenicity in nude mice compared to CBRH-7919. Analysis of rescued plasmid cDNA from these colonies is under way.