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Published on: March 10, 2017
Cell-based small-molecule compound screen identifies fenretinide as potential therapeutic for translocation-positive
David Herrero Martín1, Aleksandar Boro, Beat W Schäfer
1Department of Oncology and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland.
Abstract:
A subset of paediatric sarcomas are characterized by chromosomal translocations encoding specific oncogenic transcription factors. Such fusion proteins represent tumor specific therapeutic targets although so far it has not been possible to directly inhibit their activity by small-molecule compounds. In this study, we hypothesized that screening a small-molecule library might identify already existing drugs that are able to modulate the transcriptional activity of PAX3/FOXO1, the fusion protein specifically found in the pediatric tumor alveolar rhabdomyosarcoma (aRMS). Towards this end, we established a reporter cell line based on the well characterized PAX3/FOXO1 target gene AP2ß. A library enriched in mostly FDA approved drugs was screened using specific luciferase activity as read-out and normalized for cell viability. The most effective inhibitor identified from this screen was Fenretinide. Treatment with this compound resulted in down-regulation of PAX3/FOXO1 mRNA and protein levels as well as in reduced expression of several of its direct target genes, but not of wild-type FOXO1, in a dose- and time-dependent manner. Moreover, fenretinide induced reactive oxygen species and apoptosis as shown by caspase 9 and PARP cleavage and upregulated miR-9. Importantly, it demonstrated a significant anti-tumor effect in vivo. These results are similar to earlier reports for two other pediatric tumors, namely neuroblastoma and Ewing sarcoma, where fenretinide is under clinical development. Our results suggest that fenretinide might represent a novel treatment option also for translocation-positive rhabdomyosarcoma.
Insights
Fenretinide, an existing drug, effectively inhibits the PAX3/FOXO1 fusion protein in alveolar rhabdomyosarcoma. This pediatric cancer drug shows promise for treating translocation-positive rhabdomyosarcoma by inducing apoptosis and reducing tumor growth.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Paediatric sarcomas often involve oncogenic transcription factor fusions, like PAX3/FOXO1 in alveolar rhabdomyosarcoma (aRMS).
- Targeting these fusion proteins is crucial, but direct small-molecule inhibition has been challenging.
- Existing drugs may offer therapeutic potential for these specific pediatric tumors.
Purpose of the Study:
- To screen a small-molecule library for compounds that modulate the transcriptional activity of the PAX3/FOXO1 fusion protein.
- To identify existing drugs, particularly FDA-approved ones, as potential treatments for aRMS.
- To evaluate the efficacy of identified compounds in preclinical models of translocation-positive rhabdomyosarcoma.
Main Methods:
- Development of a reporter cell line using the PAX3/FOXO1 target gene AP2ß.
- Screening of an FDA-approved drug library using luciferase activity and cell viability assays.
- Assessment of fenretinide's effects on PAX3/FOXO1 expression, target genes, apoptosis markers, and in vivo tumor growth.
Main Results:
- Fenretinide emerged as the most effective inhibitor, down-regulating PAX3/FOXO1 mRNA and protein levels.
- Fenretinide reduced the expression of PAX3/FOXO1 target genes and induced apoptosis via caspase 9 and PARP cleavage.
- Significant anti-tumor effects were observed in vivo, with fenretinide demonstrating similar efficacy to its use in neuroblastoma and Ewing sarcoma.
Conclusions:
- Fenretinide effectively modulates the PAX3/FOXO1 oncogenic driver in alveolar rhabdomyosarcoma.
- Fenretinide shows potential as a novel therapeutic agent for translocation-positive rhabdomyosarcoma.
- The findings support further investigation of fenretinide for pediatric sarcomas with specific chromosomal translocations.