Carcinogens, including aflatoxin Bi,
benzo(a)pyrene, acetylaminofluorene, benzidine, and dimethylamino-
trans-stilbene, are shown to be activated by
liver homogenates to form potent frameshift mutagens.
We believe that these carcinogens have in common a ring
system sufficiently planar for a stacking interaction with
DNA base pairs and a part of the molecule capable of being
metabolized to a reactive group: these structural features
are discussed in terms of the theory of frameshift mutagenesis.
We propose that these carcinogens, and many
others that are mutagens, cause cancer by somatic mutation.
A simple, inexpensive, and extremely sensitive test for
detection of carcinogens as mutagens is described. It consists
of the use of a rat or human liver homogenate for
carcinogen activation (thus supplying mammalian metabolism)
and a set ofSalmonella histidine mutants for mutagen
detection. The homogenate, bacteria, and a TPNHgenerating
system are all incubated together on a petri
plate. With the most active compounds, as little as a few
nanograms can be detected