title: Correlation of TP53 and MDM2 genotypes with response to therapy in sarcoma.
abstract: BACKGROUND
  Relatively few sarcomas harbor TP53 (tumor protein p53) mutations, but in many cases, amplification of MDM2 (murine double minute 2) effectively inactivate p53. The p53 pathway activity can also be affected by normal genetic variation.
  
  
  METHODS
  The mutation status of TP53 and expression of MDM2, TP53, and their genetic variants SNP309 and R72P (Arg72Pro) were investigated in 125 sarcoma patient samples and 18 sarcoma cell lines. Association of the different genotypes and gene aberrations with chemotherapy response and survival, as well as response to MDM2 antagonists in vitro was evaluated.
  
  
  RESULTS
  Twenty-two percent of the tumors had mutant TP53 and 20% MDM2 gene amplification. Patients with wild-type TP53 (TP53(Wt) ) tumors had improved survival (P < .001) and TP53(Wt) was an independent prognostic factor (hazard ratio = 0.41; 95% confidence interval = 0.23-0.74; P = .03). Interestingly, there was a trend toward longer time to progression after chemotherapy for tumors with the apoptosis-prone p53 variant R72 (P = .07), which was strongest with doxorubicin/ifosfamide-based regimens (P = .01). Liposarcomas had low R72 frequency (33% versus 56%), but increased levels of MDM2 and MDM4 (51% and 11%, P < .001). MDM2 overexpression on a TP53(Wt) background predicted better response to MDM2 antagonist Nutlin-3a, irrespective of R72P or SNP309 status.
  
  
  CONCLUSIONS
  Improved survival after chemotherapy was found in patients with TP53(Wt) tumors harboring the R72 variant. MDM2 overexpression in TP53(Wt) tumors predicted good response to MDM2 antagonists, irrespective of R72P or SNP309 status. Thus, detailed TP53 and MDM2 genotype analyses prior to systemic therapy are recommended.
authors.affiliation: Department of Tumor Biology, Oslo University Hospital, Norwegian Radium Hospital, Oslo, Norway.
authors.forename: Hege O
authors.initials: HO
authors.lastname: Ohnstad
authors.forename: Russell
authors.initials: R
authors.lastname: Castro
authors.forename: Jinchang
authors.initials: J
authors.lastname: Sun
authors.forename: Karen-Marie
authors.initials: KM
authors.lastname: Heintz
authors.forename: Lyubomir T
authors.initials: LT
authors.lastname: Vassilev
authors.forename: Bodil
authors.initials: B
authors.lastname: Bjerkehagen
authors.forename: Stine H
authors.initials: SH
authors.lastname: Kresse
authors.forename: Leonardo A
authors.initials: LA
authors.lastname: Meza-Zepeda
authors.forename: Ola
authors.initials: O
authors.lastname: Myklebost
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D045744:Cell Line, Tumor; D002648:Child; D005260:Female; D016158:Genes, p53; D005838:Genotype; D006801:Humans; D007093:Imidazoles / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010879:Piperazines / Q000627:therapeutic use; D020641:Polymorphism, Single Nucleotide; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors / Q000235:genetics*; D012509:Sarcoma / Q000188:drug therapy / Q000235:genetics* / Q000401:mortality; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D007093:Imidazoles; D010879:Piperazines; C482205:nutlin 3; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2