Classically, the alveolar subtype is characterized by a chromosomal translocation t(2;13)(q35;q14) or t(1;13)(p36;q14) fusing the PAX3 or PAX7 gene, respectively, to the FOXO1 gene, although fusion-negative cases of alveolar rhabdomyosarcoma (ARMS) occur; these share considerably more with the genomic profiles and biological behavior of embryonal rhabdomyosarcoma than with fusion-positive ARMS.
Whereas ARMS tumors typically contain translocations generating PAX3-FOXO1 or PAX7-FOXO1 fusions that block terminal myogenic differentiation, no functionally comparable genetic event has been found in ERMS tumors.
These results indicate that the PAX3-NCOA2 fusion gene has a dual role in the tumorigenesis of RMS: promotion of the proliferation and inhibition of the myogenic differentiation of RMS cells.
We found disagreement in only three samples: one ES/pPNET and one embryonal rhabdomyosarcoma harbor a PAX3-FOXO1 translocation (for ARMS), and one neuroepithelioma harboring a EWS-WT1 (for DSRCT).
In this study, cytogenetic and/or molecular characterization to include FISH, reverse transcription polymerase chain reaction (RT-PCR), and sequencing analyses of five rhabdomyosarcomas [four ARMS and one embryonal rhabdomyosarcoma (ERMS)] with novel, recurrent t(2;2)(p23;q35) or t(2;8)(q35;q13) revealed that these noncanonical translocations fuse PAX3 to NCOA1 or NCOA2, respectively.
In this study, we analyzed the complex chromosomal translocation in one case with embryonal rhabdomyosarcoma by means of spectral karyotyping (SKY) and identified a novel translocation involving chromosome band 2q35, which is the locus of PAX3 gene.
Ectopic expression of the fusion gene characteristic of ARMS (paired box 3-forkhead homolog in rhabdomyosarcoma [PAX3-FKHR]) in ERMS cells was sufficient to convert them to an ARMS signaling phenotype and render ILK activity oncogenic.
Identification of PAX3-FKHR-regulated genes differentially expressed between alveolar and embryonal rhabdomyosarcoma: focus on MYCN as a biologically relevant target.
PAX3-FKHR fusion transcripts were positive in 3/7 and PAX 7-FKHR fusion transcripts were positive in 2/7 of ARMS patients, respectively, and were all negative in ERMS and Control tumors.
PAX3 methylation was analyzed in 15 embryonal rhabdomyosarcomas, 12 alveolar rhabdomyosarcomas, and in six normal skeletal muscle samples, using semi-quantitative PCR analysis of DNA digested with methyl-sensitive restriction enzymes.
PAX3 methylation was analyzed in 15 embryonal rhabdomyosarcomas, 12 alveolar rhabdomyosarcomas, and in six normal skeletal muscle samples, using semi-quantitative PCR analysis of DNA digested with methyl-sensitive restriction enzymes.
The majority, but not all, alveolar rhabdomyosarcoma carry the specific PAX3(7)/FKHR-translocation, whereas there is no consistent genetic abnormality recognized in embryonal rhabdomyosarcoma.
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.
A sample from a patient with a diagnosis of embryonal rhabdomyosarcoma on presentation and expression of PAX3-FKHR fusion transcript yielded a small focus of alveolar rhabdomyosarcoma and was reclassified as alveolar rhabdomyosarcoma.
With the use of Southern blot methodology, genomic rearrangements of PAX3 intron 7 were detected in 23 of 23 fusion-positive alveolar rhabdomyosarcomas and were not detected in 19 fusion-negative embryonal rhabdomyosarcomas.