High expression of the PAX3-FKHR oncoprotein is required to promote tumorigenesis of human myoblasts.

PAX3-FKHR is a fusion oncoprotein generated by the 2;13 chromosomal translocation in alveolar rhabdomyosarcoma (ARMS), a cancer associated with the skeletal muscle lineage. Previous studies determined that high-level PAX3-FKHR expression is a consistent feature in ARMS tumors. To investigate the relationship between expression and phenotype in human myogenic cells, PAX3-FKHR was introduced into immortalized human myoblasts to produce a low overall PAX3-FKHR expression level.

Identification of PAX3-FKHR-regulated genes differentially expressed between alveolar and embryonal rhabdomyosarcoma: focus on MYCN as a biologically relevant target.

Rhabdomyosarcoma is a family of myogenic soft tissue tumors subdivided into two main subtypes: alveolar (ARMS) and embryonal (ERMS). ARMS is characterized by a frequent 2;13 chromosomal translocation that creates a PAX3-FKHR fusion transcription factor. To identify downstream targets of PAX3-FKHR, we introduced an inducible form of PAX3-FKHR into human RD ERMS cells.

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

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.

Chromosome translocations in sarcomas and the emergence of oncogenic transcription factors.

A subset of sarcomas is characterised by recurrent chromosome translocations that generate novel fusion oncoproteins. One or both of the genes involved in these translocations often encode transcription factors, and the resulting fusion proteins have aberrant transcriptional function compared to their wild-type counterparts. These fusion transcription factors disrupt multiple biological pathways by altering expression of target genes, and thereby result in a variety of altered cellular properties that contribute to the tumourigenic process.

Co-expression of alternatively spliced forms of PAX3, PAX7, PAX3-FKHR and PAX7-FKHR with distinct DNA binding and transactivation properties in rhabdomyosarcoma.

PAX3 and PAX7 encode transcription factors implicated in the pathogenesis of rhabdomyosarcoma (RMS), including alveolar RMS in which chromosomal translocations generate PAX3-FKHR and PAX7-FKHR fusions. Previous studies of wild-type PAX3 and PAX7 identified alternative splicing events that modify the paired box and generate 2 isoforms of PAX3 (Q+ and Q-) and 4 isoforms of PAX7 (Q+GL+, Q+GL-, Q-GL+, Q-GL-). In our study, we investigated alternative splicing of the wild-type and fusion forms of PAX3 and PAX7 in alveolar and embryonal RMS and assessed the functional implications.

Analysis of the transforming and growth suppressive activities of the PAX3-FKHR oncoprotein.

The 2;13 chromosomal translocation occurs in most cases of the cancer alveolar rhabdomyosarcoma (ARMS), and juxtaposes the genes encoding the PAX3 and FKHR transcription factors. The resulting chimeric protein PAX3-FKHR is a potent transcriptional activator, and is hypothesized to function as a dominant acting oncogene. To investigate its biological function, PAX3-FKHR was transduced into three immortalized murine cell lines in either a constitutive or inducible manner.

Inducible short-term and stable long-term cell culture systems reveal that the PAX3-FKHR fusion oncoprotein regulates CXCR4, PAX3, and PAX7 expression.

In the pediatric cancer alveolar rhabdomyosarcoma (ARMS), the 2;13 chromosomal translocation juxtaposes the PAX3 and FKHR genes to generate a chimeric transcription factor. To explore molecular pathways altered by this oncoprotein, we generated an inducible form by fusing PAX3-FKHR to a modified estrogen receptor ligand-binding domain and expressed this construct in the RD embryonal rhabdomyosarcoma cell line. This inducible system permits short-term evaluation of downstream expression targets of PAX3-FKHR and complements a panel of stable long-term RD subclones constitutively expressing PAX3-FKHR.

Molecular pathogenesis of rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) is a family of soft tissue tumors that are associated with the skeletal muscle lineage and generally occur in the pediatric population. Based on histopathologic features, two subtypes, embryonal (ERMS) and alveolar (ARMS), were identified and associated with distinct clinical characteristics and genetic alterations. ARMS is associated with 2;13 or 1;13 chromosomal translocations, which generate PAX3-FKHR and PAX7-FKHR fusion products, respectively.

Membrane association of glutathione S-transferase mGSTA4-4, an enzyme that metabolizes lipid peroxidation products.

Lipid peroxidation products have signaling functions and at higher concentrations are toxic and may trigger cell death. The compounds are metabolized predominantly by glutathione S-transferases exemplified by mGSTA4-4, an enzyme highly efficient in glutathione conjugation of 4-hydroxyalkenals, and possessing glutathione peroxidase activity toward phospholipid hydroperoxides. mGSTA4-4 belongs to the predominant group of "canonical" glutathione S-transferases that are soluble and generally localized in the cytoplasm.