Tumour-initiating activities on mouse skin of dihydrodiols derived from benzo[a]pyrene

Abstract

Three dihydrodiols that are metabolites of benzo[a]pyrene and benzo[a]-pyrene itself have been tested in a comparative experiment for their activities as initiators of tumours in mouse skin. A single application (25 mug) of 4,5-dihydro-4,5-dihydroxybenzo[a]pyrene, of 7,8-dihydro-7,8-dihydroxybenzo[a]pyrene, of 9,10-dihydro-9,10-dihydroxybenzo[a]pyrene, or of benzo[a]pyrene was made to the shaved dorsal skin of adult female CDI mice; this was followed 2 weeks later by multiple thrice-or twice-weekly applications (1 mug) of 12-O-tetradecanoyl-phorbol-13-acetate as promoting agent. A control group of 30 mice received the promoting agent alone. The experiments were terminated 52 weeks after initiation. At this stage, all the groups contained mice bearing skin papillomas, some of which had progressed to malignancy. Quantitatively the results show that the 7,8-dihydrodiol is almost as active an initiator of mouse skin tumours as benzo[a]pyrene itself; the 4,5- and 9,10-dihydrodiols were significantly less active. The significance of these results is discussed in relation to the hypothesis that diol-epoxides are important in the metabolic activation of polycyclic hydrocarbons like benzo[a]pyrene. Images Fig. 1 Fig. 2 Fig. 3

Biological activities of dihydrodiols derived from two polycyclic hydrocarbons in rodent test systems

“…The results reported here for dihydrodiols derived from 7-methylbenz[a] anthracene and those obtained previously for diols derived from benzo[a]pyrene (Slaga et al, 1976;Chouroulinkov et al, 1976;Levin et al, 1976) and from benz [a] anthracene (Levin et al, 1978) show that comparative tests for mouse-skin tumourinitiating activity can assist in the identification of the dihydrodiols that are involved in the metabolic activation of the parent hydrocarbons.…”

“…Papillomas, the predominant tumour type, started to appear about 10 weeks after initiation, as in previous experiments (Chouroulinkov et al, 1976), and they appeared first in the group of mice initiated with the 3,4-dihydrodiol. Only 5 malignant neoplasms were found, 4 of which were squamous-cell carcinomas, and the earliest examples of this type oftumour were detected in mice initiated with the 3,4-dihydrodiol.…”

“…In these shortterm mouse skin tests (Table II) (Malaveille et al, 1975;Slaga et al, 1976;Chouroulinkov et al, 1976;Marquardt et al, 1976), was clearly less active than the parent hydrocarbon. The activities of a range of polycyclic hydrocarbons in inducing hyperplasia and in suppressing sebaceous glands have been reported to correlate with their carcinogenic potencies (Bock & Mund, 1958;Gue'rin & Cuzin, 1961;Lazar & Chouroulinkov, 1974).…”

“…The particular dihydrodiols that are the precursors of reactive diolepoxides have been identified, partly through the activities that they show as mutagens (Wood et al, 1976;Malaveille et al, 1977Malaveille et al, , 1978Levin et al, 1978) and as transforming agents (Marquardt et al, 1977(Marquardt et al, , 1978 in in vitro tests, partly by the examination of the nucleic-acid adducts that are formed when the parent hydrocarbons are activated by metabolism in tissues or in cultured cells (Sims et al, 1974;Jeffrey et al, 1976Jeffrey et al, , 1977Tierney et al, 1977;Bigger et al, 1978) and partly by comparative in vivo tests for biological activity (Slaga et al, 1976;Chouroulinkov et al, 1976;Levin et al, 1976). Since the non-K-region dihydrodiols are often available only in small amounts, many of the in vivo tests have been of tumour-initiating activity on mouse skin using a phorbol ester as a promoter, but other in vivo test procedures may merit investigation.…”

Comparison of mutagenesis and malignant transformation by dihydrodiols from benz[a]anthracene and 7,12-dimethylbenz[a]anthracene

“…Although the results of these biochemical and biophysical investigations have often provided strong circumstantial evidence implicating one particular dihydrodiol, additional evidence that this dihydrodiol is more biologically active than other dihydrodiols derived from the same hydrocarbon has usually been sought from test systems in which dihydrodiols are expected to be metabolically converted in situ into the related vicinal diolepoxides. Such studies on mutagenicity (Malaveille et al, 1975(Malaveille et al, , 1977Wislocki et al, 1976) and on the abilities of non-Kregion dihydrodiols to induce malignant transformation in mammalian cells (Marquardt et al, , 1977b and to initiate tumours in mouse skin (Chouroulinkov et al, 1976(Chouroulinkov et al, , 1977Slaga et at., 1976;Levin et at., 1976) have been useful in helping to identify those dihydrodiols that are the precursors of the vicinal diol-epoxides involved in the metabolic activation of benzo[a]pyrene and 7-methylbenz[a]anthracene. Attention has now been turned towards the metabolic activation of other hydrocarbons, and efforts are beinig made to identify the dihydrodiols concerned in the activation of, for example, benz [a]anthracene (BA) (Wood et at., 1976(Wood et at., , 1977aanthracene (DMBA) (Moschel et al, 1977;Vigny et al, 1977b;Ivanovic et al, 1978) and 3-methylcholanthrene (King et al, 1977;Thakker et al, 1978 (II), are known to be converted into a variety of K-region and non-K-region dihydrodiols by rat-liver preparations (Boyland & Sims, 1964, 1965Sims, 1970;Tierney et al, 1978b (Marquardt et al, 1974) are described.…”