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

O Tomescu, SJ Xia, D Strezlecki, JL Bennicelli… - Laboratory …, 2004 - nature.com
O Tomescu, SJ Xia, D Strezlecki, JL Bennicelli, J Ginsberg, B Pawel, FG Barr
Laboratory investigation, 2004nature.com
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 …
Abstract
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. Using these two sets of resources, we investigated several candidate PAX3-FKHR target genes. First, we demonstrated in both short-term and long-term systems that PAX3-FKHR upregulates expression of the gene encoding the chemokine receptor CXCR4. In addition, we found that expression of wild-type PAX3 is upregulated, whereas expression of wild-type PAX7 is downregulated by PAX3-FKHR. In the presence of cycloheximide, CXCR4 and PAX3 are still inducible, supporting the hypothesis that these genes are direct transcriptional targets of PAX3-FKHR. Finally, studies of ARMS tumors revealed CXCR4, PAX3, and PAX7 expression levels consistent with our cell culture results. These findings of genes regulated by PAX3-FKHR will direct future biological and clinical investigation to important pathways contributing to ARMS tumorigenesis and progression.
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