Modifying effects of dietary exposure of protocatechuic acid (PCA), a natural monophenolic
compound, S-methylmethanethiosulfonate (MMTS), an organosulfur compound newly isolated
from cauliflower, and 5-hydroxy-4-(2-phenyl-(E)ethenyl)-2(5H)-furanone (KYN-54), a
novel retinoidal butenolide compound, on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone
(NNK) (10 micromol, [corrected] single i.p. injection)-induced pulmonary carcinogenesis
were examined in female A/J mice. Each of the test chemicals was given in diets during
initiation or post-initiation phases (PCA, 1000 ppm; MMTS, 100 ppm; KYN-54, 200 ppm).
All of these which had been proved to be chemopreventive mainly in digestive-organs
carcinogenesis did not exert any preventive effect in this model when the incidence
or multiplicity of pulmonary tumors (adenomas) of mice given NNK and the test chemical
at the termination of the experiment (4 months) was compared to that of mice exposed
to the carcinogen alone. In contrast, the multiplicity of lung tumors of mice receiving
KYN-54 during the post-initiation phase was significantly larger than of the animals
with NNK alone (P < 0.05), showing that KYN-54 has a promoting effect on pulmonary
carcinogenesis in mice. These data indicate an organotropic activity of these compounds
and suggest that candidate compounds for cancer chemoprevention need to be carefully
examined for effectiveness in multiple organs by different models.