Relationship between DNA strand breaks and inhibition of poly(ADP-ribosylation): enhancement of carcinogen-induced transformation

Abstract
Inhibition of poly(ADP-Rib) by benzamide (BA) or 3-aminobenzamide (3AB) for a limited period (i.e., when ADP-ribosylation is elevated) during and shortly following X-ray or MNNG-induced DNA damage of BALB/3T3 cells significantly (3- to 30-fold) enhanced transformation frequency by these agents. Individual Type III foci isolated from benzamide, X-ray, or X-ray plus benzamide treated cultures were established and characterized for growth in soft agar and for tumor induction in nude mice. DNA isolated from representative transformed lines established as a result of BA, X-ray or X-ray and BA treatments was transfected onto NIH/3T3 cells. Transformation efficiencies ranging from 0.17 to 0.28 foci/ μg of DNA were observed suggesting the possibility that dominant transforming gene(s) were responsible for the oncogenic phenotype of radiation and benzamide transformed DNA.