title: Activation of p53 by MDM2 antagonists can protect proliferating cells from mitotic inhibitors.
abstract: Recent studies have shown that activation of cell cycle checkpoints can protect normal proliferating cells from mitotic inhibitors by preventing their entry into mitosis. These studies have used genotoxic agents that act, at least in part, by activation of the p53 pathway. However, genotoxic drugs are known also to have p53-independent activities and could affect the sensitivity of tumor cells to antimitotic agents. Recently, we have developed the first potent and selective small-molecule inhibitors of the p53-MDM2 interaction, the nutlins, which activate the p53 pathway only in cells with wild-type but not mutant p53. Using these compounds, we show that p53 activation leads to G1 and G2 phase arrest and can protect cells from mitotic block and apoptosis caused by paclitaxel. Pretreatment of HCT116 and RKO colon cancer cells (wild-type p53) or primary human fibroblasts (1043SK) with nutlins for 24 hours followed by incubation with paclitaxel for additional 48 hours did not increase significantly their mitotic index and protected the cells from the cytotoxicity of paclitaxel. Cancer cells with mutant p53 (MDA-MB-435) responded to the same treatment with mitotic arrest and massive apoptosis. These results have two major implications for cancer therapy. First, p53-activating therapies may have antagonistic effect when combined with mitotic poisons. Second, pretreatment with MDM2 antagonists before chemotherapy of tumors with mutant p53 may offer a partial protection to proliferating normal tissues.
authors.affiliation: Discovery Oncology, Roche Research Center, Hoffmann-La Roche Inc., Nutley, New Jersey 07110, USA.
authors.forename: Daisy
authors.initials: D
authors.lastname: Carvajal
authors.forename: Christian
authors.initials: C
authors.lastname: Tovar
authors.forename: Hong
authors.initials: H
authors.lastname: Yang
authors.forename: Binh T
authors.initials: BT
authors.lastname: Vu
authors.forename: David C
authors.initials: DC
authors.lastname: Heimbrook
authors.forename: Lyubomir T
authors.initials: LT
authors.lastname: Vassilev
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000009:adverse effects; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects*; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000473:pathology; D005260:Female; D016193:G1 Phase / Q000187:drug effects; D016195:G2 Phase / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D008938:Mitosis / Q000187:drug effects; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017239:Paclitaxel / Q000009:adverse effects; D010879:Piperazines / Q000494:pharmacology*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D014407:Tumor Cells, Cultured / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D007093:Imidazoles; D009687:Nuclear Proteins; D010879:Piperazines; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; C482203:nutlin 1; C482205:nutlin 3; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D017239:Paclitaxel