title: A modified p53 enhances apoptosis in sarcoma cell lines mediated by doxorubicin.
abstract: Mdm2 is frequently overexpressed in sarcoma cells and may contribute to drug resistance by increasing p53 degradation. We investigated the induction of apoptosis in sarcoma cells via adenovirus-mediated gene transfer of wild-type p53 and two modified p53 genes, p53 14/19 and p53 22/23, whose protein products are resistant to Mdm2-mediated degradation. We found that adenovirus-wt p53 (Ad-wt p53) induces significant apoptosis in HT1080 fibrosarcoma cells expressing low levels of Mdm2, but fails to induce apoptosis in SJSA osteosarcoma cells expressing high levels of Mdm2. In contrast, Ad-p53 14/19 induces significant apoptosis in both cell lines. Interestingly, Ad-p53 22/23, a vector encoding a transcription-defective p53 mutant, causes limited apoptosis in both cell lines. We demonstrate that doxorubicin induces phosphorylation of both wt p53 and p53 14/19 protein at multiple sites. We tested the efficacy of doxorubicin and cisplatin with either Ad-wt p53, Ad-p53 22/23 or Ad-p53 14/19. SJSA cells, although harbouring endogenous wt p53, did not undergo significant apoptosis following doxorubicin or cisplatin exposure alone or combined with Ad-wt p53. In contrast, doxorubicin or cisplatin plus Ad-p53 14/19 induced significant apoptosis. Gene transfer of p53 14/19 in combination with the administration of doxorubicin or cisplatin is a potential therapeutic approach for cancers expressing high levels of Mdm2.
authors.affiliation: Department of Obstetrics and Gynecology, University of Michigan Comprehensive Cancer Center, Ann Arbor, MI 48109, USA.
authors.forename: H-J
authors.initials: HJ
authors.lastname: Tang
authors.forename: D
authors.initials: D
authors.lastname: Qian
authors.forename: V K
authors.initials: VK
authors.lastname: Sondak
authors.forename: S
authors.initials: S
authors.lastname: Stachura
authors.forename: J
authors.initials: J
authors.lastname: Lin
mesh_terms: D000256:Adenoviridae; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002945:Cisplatin / Q000494:pharmacology*; D004317:Doxorubicin / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic; D018014:Gene Transfer Techniques; D016158:Genes, p53; D005822:Genetic Vectors; D006801:Humans; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D051736:Proto-Oncogene Proteins c-mdm2; D012509:Sarcoma / Q000235:genetics* / Q000473:pathology*; D014407:Tumor Cells, Cultured; D016335:Zinc Fingers
chemical_list: D000903:Antibiotics, Antineoplastic; D000970:Antineoplastic Agents; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D004317:Doxorubicin; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D002945:Cisplatin