Growth reduction of a xenotransplanted human soft tissue sarcoma by MDM2 antisense therapy via implanted osmotic minipumps

Int J Oncol. 2002 May;20(5):1087-93.


The MDM2 oncogene plays an important role in tumorigenesis and especially in soft tissue sarcomas (STS). Overexpression of the MDM2 protein is associated with a poorer prognosis for STS patients. An MDM2 antisense approach to reduce MDM2 protein levels has been successfully applied on several carcinomas in vitro and used on a few in vivo cases. However, antisense treatment not only resulted in an MDM2 protein reduction but also in a wild-type P53 gene (wt-P53) mediated tumor growth suppression due to its genetic wt-P53 status. In this study, we used a clinically relevant xenotransplanted STS model with a mutated P53 gene (mt-P53) in order to exclude the influence of wt-P53. The human STSs were surgically implanted and one week later osmotic pumps were implanted intraperitoneally into nude rats releasing MDM2-antisense ODNs (AS ODNs) continuously for one week. As controls MDM2-sense ODN (SE ODN) or a 0.9% NaCl solution (saline solution) were administered. After one week animals treated with MDM2-AS ODN (100 or 200 microg) showed a reduction in tumor mass in comparison to animals treated with MDM2-SE ODN. The reduction in tumor mass was significant in animals treated with MDM2-AS ODNs in comparison to the saline solution treated ones (p=0.018 or p=0.007). Furthermore, a significant reduction in macroscopically visible tumor number with MDM2-AS ODN treatments (100 or 200 microg) in comparison to MDM2-SE ODN or saline solution treatment (both p=0.009) was observed for the first time. As expected a reduction in MDM2 protein expression in the MDM2-AS ODN treated tumors when compared to the MDM2-SE ODN or saline solution treated tumors was detected in Western blot analyses and immunohistochemically. In addition, an unexpected reduction in mt-P53 protein expression after AS ODN therapy was also observed. In short, we have demonstrated in vivo for the first time that MDM2-AS ODN treatment of xenotransplanted STS (mt-P53) reduces tumor mass, tumor number, MDM2 protein and mt-P53 protein expression. Our findings support the hypothesis that MDM2-AS ODN treatment may exert a tumor inhibiting effect on all MDM2 expressing tumors regardless of the P53-status, this in turn may be of general importance in gene therapy of cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Western
  • Genetic Therapy / methods*
  • Humans
  • Immunohistochemistry
  • Infusion Pumps, Implantable
  • Nuclear Proteins*
  • Oligonucleotides, Antisense / pharmacology*
  • Proto-Oncogene Proteins / genetics*
  • Proto-Oncogene Proteins / pharmacology*
  • Proto-Oncogene Proteins c-mdm2
  • Rats
  • Sarcoma / therapy*
  • Transplantation, Heterologous / methods*
  • Tumor Cells, Cultured
  • Tumor Suppressor Protein p53 / biosynthesis


  • Nuclear Proteins
  • Oligonucleotides, Antisense
  • Proto-Oncogene Proteins
  • Tumor Suppressor Protein p53
  • MDM2 protein, human
  • Mdm2 protein, rat
  • Proto-Oncogene Proteins c-mdm2