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Growth reduction of a xenotransplanted human soft tissue sarcoma by MDM2 antisense therapy via implanted osmotic
Peter Würl1, Frank Bartel, Axel Meye
1Clinic of Surgery 1, University of Leipzig, Germany.
Abstract:
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.
Insights
MDM2-antisense ODNs reduce soft tissue sarcoma tumor mass and number in a preclinical model. This gene therapy approach shows promise for treating MDM2-expressing tumors, irrespective of P53 gene status.
Area of Science:
- Oncology
- Gene Therapy
- Molecular Biology
Background:
- MDM2 oncogene overexpression is linked to poor prognosis in soft tissue sarcomas (STS).
- MDM2 antisense (AS ODN) therapy has shown potential in reducing MDM2 protein levels.
- Previous studies were confounded by wild-type P53 (wt-P53) mediated effects, necessitating models with mutated P53 (mt-P53).
Purpose of the Study:
- To evaluate the efficacy of MDM2-AS ODN in a xenotransplanted STS model with mutated P53 (mt-P53).
- To assess the impact of MDM2-AS ODN on tumor mass, tumor number, and protein expression in vivo.
- To determine if MDM2-AS ODN exerts therapeutic effects independent of P53 status.
Main Methods:
- A xenotransplanted STS model with mt-P53 was established in nude rats.
- Continuous intraperitoneal administration of MDM2-AS ODNs, MDM2-sense ODN (SE ODN), or saline via osmotic pumps for one week.
- Tumor mass, tumor number, and protein expression (MDM2 and P53) were analyzed post-treatment.
Main Results:
- MDM2-AS ODN treatment significantly reduced tumor mass compared to SE ODN and saline controls (p=0.018 or p=0.007).
- A significant reduction in tumor number was observed with MDM2-AS ODN treatment compared to controls (p=0.009).
- Western blot and immunohistochemistry confirmed reduced MDM2 and unexpectedly, mt-P53 protein expression in tumors treated with MDM2-AS ODN.
Conclusions:
- MDM2-AS ODN therapy effectively reduces tumor mass and number in a preclinical STS model with mutated P53.
- The treatment also decreases both MDM2 and mt-P53 protein expression in vivo.
- These findings suggest MDM2-AS ODN therapy may be a viable strategy for treating MDM2-expressing tumors, regardless of P53 mutational status, with broad implications for cancer gene therapy.