Correlation of inducibility of aryl hydrocarbon hydroxylase with susceptibility to 3-methylcholanthrene-induced lung cancers.

C57BL/6Cum, DBA/2Cum, first filia (F1), and backcross progeny from these 2 parental strains of mice were evaluated for their susceptibility to 3-methylcholanthrene-induced lung cancers. In the crosses among these mice, aryl hydrocarbon hydroxylase (AHH) responsiveness segregated as a single autosomal dominant gene (the Ah locus). AHH responsive mice (Ahb allele) expressed 40-60 units AHH activity/g wet wt liver following intraperitoneal treatment with 3-methylcholanthrene (MCA) compared to AHH non-responsive mice (Ahd allele) which expressed 7-11 units AHH activity/g wet wt liver after MCA treatment. Intratracheal administration of 500 microgram MCA for a total of 4 times at weekly intervals yielded a variety of pulmonary cancers, including squamous cell carcinomas, alveolar adenocarcinomas, and adeno-squamous cell carcinomas among mice that survived 1 year after the carcinogen treatment. The AHH responsive C57BL/6Cum, F1, and C57BL/6Cum X F1 animals were much more susceptible to MCA-induced lung cancers than the AHH non-responsive DBA/2Cum mice. The lung cancers were also not randomly distributed in DBA/2Cum X F1 backcross progeny since significantly more lung cancers were found in AHH-responsive progeny than in AHH non-responsive mice. Data support genetic linkage between susceptibility to MCA-induced lung carcinomas and the Ahb allele.