PRIMA-1 stabilize p53 by altering phosphorylation in human lung cancer cells

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Restoration of p53 function in tumor cells is an important approach for cancer therapy because p53 mutations are found in many cancer cells. The small molecule PRIMA-1 (p53-dependent reactivation and induction of massive apoptosis) has been shown to induce apoptosis in human tumor cells containing mutant p53 by restoration of the tumor suppressor function of p53. This is believed to be mediated by a change in the conformation of mutated p53 protein, restoring DNA binding and activation of p53 target genes. The efficiency of PRIMA-1 to restore mutant p53 proteins to wild-type conformation may be correlated to p53 mutational types.
 We investigated the effects of PRIMA-1 in apoptosis with Western blot analysis, immunoprecipitation and MTT assay using human lung cancer cell lines A549 (wild type p53), H1299 (p53 null), H23 (mutant p53, 246I), H211 (mutant p53, 248Q), and H1155 (mutant p53, 273H).
 We found that this compound selectivelyinduced apoptosis in the H1155 and H211 cells, but was less toxic to the A549, H1299, and H23 cells. Western blot analysis also showed the mutant p53 protein was phosphorylated in the H211 and H1155 cell lines.
 In addition, p53 degradation was reduced in the H1155 and H211 post PRIMA-1 treatment. Thus PRIMA-1 can not only induce apoptosis but also increase the protein level in the mutant p53-expressing human lung cancer cells.
 The above results suggest PRIMA-1 is a highly selective small molecule toxic to p53 mutantcells which could serve as a prototype for the development of effective systemicp53-targeting agents. Given the high prevalence of p53 mutations in Codon 273 and 248 in human lung cancer, development of related compounds for lung cancer therapy deserves consideration. Further understanding the relationships between PRIMA-1 induced p53 phosphorylation and mutational types in vitro and in vivo may lead to effective strategies for p53 related pharmacological therapeutic intervention in human lung cancers.