Clinical Relevance of Dominant-Negative p73 Isoforms for Responsiveness to Chemotherapy and Survivalin Ovarian Cancer: Evidence for a Crucial p53-p73 Cross-talk In vivo Nicole Concin, 1 Gerda Hofstetter, 1 AstridBerger, 1 Adriana Gehmacher, 1 Daniel Reimer, 1 RafalWatrowski, 2 DanTong, 2 Eva Schuster, 2 Lukas Hefler, 2 Kurt Heim, 1 ElisabethMueller-Holzner, 1 Christian Marth, 1 Ute M. Moll, 3 Alain G. Zeimet, 1 and Robert Zeillinger 2 Abstract Purpose: We aimed to determine the clinical role of the p53 family members p53 and p73 in the responsiveness to platinum-based chemotherapy and survivalinovarian cancer, considering their cross-talk and the p53 polymorphismatcodon 72. ExperimentalDesign: Adetailedanalysisof p53 and p73 inaseriesof122ovariancancerswas done.We used a functional yeast-based assay to determine the p53 mutational status. Red yeast colonies, indicating mutant p53, were subsequently sequenced to determine the specific p53 alteration. p53 mutations were divided into two groups according to their previous characteriza- tion in the literature: those that efficiently inhibit transcriptionally activeTAp73 function and those that do not. A p53 polymorphism at codon 72 was determinedin corresponding normal tissue or bloodofovariancancerpatients.Isoform-specific p73 expressionanalysisusingreal-timereverse transcription-PCR has previously been done in the majority of ovarian cancers included in this study. In a retrospective chart review, responsiveness to chemotherapy was assessed, and survival data with long follow-up times were collected. Results: Eighty of122 (65.6%) of ovarian cancers harbored p53 mutations. p53 mutational status was an important determinant of responsiveness to platinum-based chemotherapy in all patients with a residual tumor of <2 cm in diameter after initial surgery (wild-type versus mutant, P =0.029).Inaddition, p53 mutationalstatuswasastrongprognosticator forrecurrence-freeand overall survival ( P < 0.0001and P = 0.003, respectively) in univariate analyses. High expression levels of dominant-negative p73 isoforms (DNp73 and DNV p73) significantly correlated with chemotherapeutic failure (P = 0.048) and with worse recurrence-free and overall survival in patients with p53 mutant cancers ( P =0.048and P =0.005,respectively).Eight p53 mutations, present in 19 cases, were found that efficiently inhibitTAp73 (i.e., 175H, 220C, 245S, 245D, 248W, 248Q, 266E, and 273H). Patients with p53 mutations that efficiently inhibitTAp73 function had a significantly shorter overall survival than patients with p53 mutations of unknown effect on TAp73 (P = 0.044).The p53 polymorphism at codon 72 had no influence on respon- siveness to chemotherapy or survival. Conclusion: We provide the first clinical evidence that dominant-negative p73 isoforms con- tribute to drug resistance in vivo, underscoring the importance of a p53-p73 cross-talk. NH 2 - terminally truncated p73 isoforms were of significant clinical effect by providing an additional unfavorable factor for response to platinum-based chemotherapy and survival in p53 mutant ovariancancers. Innate or acquired resistance to chemotherapy is a crucial obstacle to treatment success in human cancer in general and in ovarian cancer in particular. The majority of ovarian cancer patients present with advanced disease at the time of diagnosis. In this stage of disease, cytoreductive surgery alone proves to be an insufficient treatment and prognosis mainly depends on Imaging, Diagnosis, Prognosis Authors’Affiliations: 1 DepartmentofObstetricsandGynecology,InnsbruckMedical University, Innsbruck, Austria; 2 Molecular Oncology Group, Department of Obstetrics and Gynecology, Medical University ofVienna,Vienna, Austria; and 3 Department ofPathology,StateUniversityofNew YorkatStonyBrook,StonyBrook,New York Received 4/25/05; revised 8/27/05; accepted 9/8/05. Grant support: NIH grant R01 (U.M. Moll) and Fond zur Foerderung Wissens- chaftlicher Forschung (N. Concin). The costs of publication of this article were defrayed in part by the payment of page charges.This article must therefore be hereby marked advertisement in accordance with18 U.S.C. Section1734 solely to indicate this fact. Note: N. Concin and G. Hofstetter contributed equally to the article. Requestsforreprints: NicoleConcin,DepartmentofObstetrics andGynecology, Innsbruck Medical University, A-6020 Innsbruck, Austria. Phone: 43-512-504- 81433; E-mail: nicole.concin@uibk.ac.at. F 2005 American Association for Cancer Research. doi:10.1158/1078-0432.CCR-05-0899 www.aacrjournals.org Clin Cancer Res 2005;11(23) December15, 2005 8372 Research. on June 6, 2020. © 2005 American Association for Cancer clincancerres.aacrjournals.org Downloaded from