Inhibition of 7,12-dimethylbenzanthracene-induced rat mammary tumorigenesis by 2,5-di-O-acetyl-D-glucaro-1,4:6,3-dilactone, an in vivo beta-glucuronidase inhibitor.

2,5-Di-O-acetyl-D-glucaro-1,4:6,3-dilactone ( DAGDL ) is a slow release form of D-glucaro-1,4-lactone (GL), a non-toxic natural inhibitor of beta-glucuronidase. When administered orally to female rats in conjunction with a carcinogenic dose of 7,12-dimethylbenzanthracene (DMBA), this compound caused a 70% reduction in the number of rats with mammary tumors and 72% reduction in the number of mammary tumors per rat. Co-administration also reduces the induction by DMBA of a 60 kd oncofetal protein, previously shown to be associated with carcinogenesis and tumorigenesis. DAGDL administration depressed beta-glucuronidase activity both in the absence and presence of concurrent treatment with DMBA and also markedly reduced binding of DMBA to organ DNA. The anti-carcinogenic effect of DAGDL appears to be independent of route of administration of DMBA. It is proposed that inhibition of beta-glucuronidase increases the proportion of DMBA which is sequestered and excreted as the glucuronide and therefore unavailable for activation to the proximal carcinogen.