Lung cancer is the leading cause of cancer deaths worldwide. Expression of the p53 tumor suppressor protein is
frequently altered in tobacco-associated lung cancers. We studied chemopreventive effects of p53-modulating
agents, namely, CP-31398 and Prima-1, on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)–induced lung
adenoma and adenocarcinoma formation in female A/J mice. Seven-week-old mice were treated with a single dose
of NNK (10 μmol/mouse) by intraperitoneal injection and, 3 weeks later, were randomized to mice fed a control
diet or experimental diets containing 50 or 100 ppm CP-31398 or 150 or 300 ppm Prima-1 for either 17 weeks
(10 mice/group) or 34 weeks (15 mice/group) to assess the efficacy against lung adenoma and adenocarcinoma.
Dietary feeding of 50 or 100 ppm CP-31398 significantly suppressed (P < .0001) lung adenocarcinoma by 64% and
73%, respectively, after 17 weeks and by 47% and 56%, respectively, after 34 weeks. Similarly, 150 or 300 ppm Prima-1
significantly suppressed (P < .0001) lung adenocarcinoma formation by 56% and 62%, respectively, after 17 weeks
and 39% and 56%, respectively, after 34 weeks. Importantly, these results suggest that both p53 modulators cause a
delay in the progression of adenoma to adenocarcinoma. Immunohistochemical analysis of lung tumors from mice
exposed to p53-modulating agents showed a significantly reduced tumor cell proliferation and increased accumulation
of wild-type p53 in the nucleus. An increase in p21- and apoptotic-positive cells was also observed in lung tumors of
mice exposed to p53-modulating agents. These results support a chemopreventive role of p53-modulating agents in
tobacco carcinogen–induced lung adenocarcinoma formation