Analysis of genetic events that modulate the oncogenic and growth suppressive activities of the PAX3-FKHR fusion oncoprotein

• Published in: Laboratory investigation Vol. 87; no. 4; pp. 318 - 325
• Main Authors: Xia, Shujuan J, Rajput, Prerna, Strzelecki, Donna M, Barr, Frederic G
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.04.2007; Nature Publishing; Nature Publishing Group
• Subjects: alveolar rhabdomyosarcoma; Animals; Biological and medical sciences; Biotechnology; Cell Proliferation; Cell Transformation, Neoplastic; chromosomal translocation; Forkhead Box Protein O1; Forkhead Transcription Factors - genetics; Forkhead Transcription Factors - physiology; Fundamental and applied biological sciences. Psychology; gene fusion; growth suppression; Humans; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Mice; Mutation; NIH 3T3 Cells; Oncogene Proteins, Fusion - genetics; Oncogene Proteins, Fusion - physiology; Paired Box Transcription Factors - genetics; Paired Box Transcription Factors - physiology; PAX3 Transcription Factor; Rhabdomyosarcoma, Alveolar - genetics; transformation; Translocation, Genetic; growth suppression; transformation; alveolar rhabdomyosarcoma; gene fusion; chromosomal translocation; Chromosomal aberration; Biotechnology; Transformation; Sarcoma; Growth; Malignant tumor; Carcinogenesis; Biological activity; Carcinogen; Striated muscle disease; C-Onc gene; Clinical biology; Oncoprotein; Abnormal chromosome; Genetics; Onc gene; Transcription factor FOXO1; Hybrid gene; Alveolar rhabdomyosarcoma; Chromosome translocation
• ISSN: 0023-6837; 1530-0307
• DOI: 10.1038/labinvest.3700521

Alveolar rhabdomyosarcoma (ARMS) is associated with chromosomal translocations that generate PAX3-FKHR and PAX7-FKHR fusion oncoproteins. Based on studies demonstrating that high PAX3-FKHR expression causes growth suppression, the hypothesis is proposed that, during ARMS tumorigenesis, the translocations cause low oncoprotein expression and are followed by collaborating events that block growth suppression pathways and permit upregulation of oncoprotein expression. To investigate oncogenic function at low expression levels, PAX3-FKHR was introduced into NIH3T3 cells in the pBabe retroviral vector. Compared to high expression systems, PAX3-FKHR expression from pBabe was lower and did not suppress growth, but showed transforming activity in the soft agar assay. As a possible collaborating event, PAX3-FKHR paired box mutations were previously shown in high expression systems to reverse growth suppressive effects. In the low expression system, the paired box mutation enhanced transformation in soft agar and focus formation assays. Although these mutations are candidate collaborating events, sequencing of paired box regions in ARMS tumors did not identify mutations. Finally, genes from known genetic alterations in ARMS were introduced, alone or combined, into NIH3T3 cells with high PAX3-FKHR expression and did not rescue growth suppression. In summary, these studies provide a model for an event in ARMS tumorigenesis that enhances PAX3-FKHR oncogenicity and abrogates growth suppression, but do not demonstrate a known event occurring in ARMS tumors that fulfills these criteria.