cp-31398 and Lung-Neoplasms

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.

Topics: Adenocarcinoma; Animals; Anticarcinogenic Agents; Apoptosis; Aza Compounds; Bridged Bicyclo Compounds, Heterocyclic; Cell Transformation, Neoplastic; Chemoprevention; Cyclin-Dependent Kinase Inhibitor p21; Female; Lung Neoplasms; Mice; Mice, Inbred A; Nicotiana; Nitrosamines; Pyrimidines; Random Allocation; Tumor Suppressor Protein p53

CP-31398, a styrylquinazoline, emerged from a high throughput screen for therapeutic agents that restore a wild-type-associated epitope (monoclonal antibody 1620) on the DNA-binding domain of the p53 protein. We found that CP-31398 can not only restore p53 function in mutant p53-expressing cells but also significantly increase the protein level and promote the activity of wild-type p53 in multiple human cell lines, including ATM-null cells. Cells treated with CP-31398 undergo either cell cycle arrest or apoptosis. Further investigation showed that CP-31398 blocks the ubiquitination and degradation of p53 but not in human papillomavirus E6-expressing cells. Of note, CP-31398 does not block the physical association between p53 and MDM2 in vivo. Moreover, unlike the DNA-damaging agent adriamycin, which induces strong phosphorylation of p53 on serines 15 and 20, CP-31398 exposure leads to no measurable phosphorylation on these sites. We found that CP-31398 could also stabilize exogenous p53 in p53 mutant, wild-type, and p53-null human cells, even in MDM2-null p53(-/-) mouse embryonic fibroblasts. Our results suggest a model wherein CP-31398-mediated stabilization of p53 may result from reduced ubiquitination, leading to high levels of transcriptionally active p53. Further understanding of this mechanism may lead to novel strategies for p53 stabilization and tumor suppression in cancers, even those with absent ARF or high MDM2 expression.

Topics: Adenocarcinoma; Animals; Ataxia Telangiectasia Mutated Proteins; Carcinoma, Non-Small-Cell Lung; Cell Cycle Proteins; Colonic Neoplasms; Cyclin-Dependent Kinase Inhibitor p21; Cyclins; DNA Damage; DNA-Binding Proteins; Doxorubicin; Female; Fibroblasts; Gene Expression Regulation; Genes, p53; Humans; Lung Neoplasms; Lymphocytes; Mice; Mice, Knockout; Neoplasm Proteins; Nuclear Proteins; Oncogene Proteins, Viral; Ovarian Neoplasms; Phosphorylation; Phosphoserine; Protein Binding; Protein Processing, Post-Translational; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-mdm2; Pyrimidines; Receptors, TNF-Related Apoptosis-Inducing Ligand; Receptors, Tumor Necrosis Factor; Repressor Proteins; Transcription, Genetic; Tumor Cells, Cultured; Tumor Suppressor Protein p53; Tumor Suppressor Proteins; Ubiquitin