Regulation of Target Genes of PAX3-FOXO1 in Alveolar Rhabdomyosarcoma

Background: The majority of alveolar rhabdomyosarcoma (ARMS) are distinguished through the paired box 3-forkhead box protein O1 (PAX3-FOXO1) fusion oncoprotein, being generated by a 2;13 chromosomal translocation. This fusion-positive ARMS is the most clinically difficult type of rhabdomyosarcoma. The present study characterized four genes [gremlin 1 (GREM1), death-associated protein kinase-1 (DAPK1), myogenic differentiation-1 (MYOD1), and hairy/enhancer-of-split related with YRPW motif-1 (HEY1)] as targets of PAX3-FOXO1.

Materials And Methods: The expression of the four genes, PAX3-FOXO1, and v-myc myelocytomatosis viral-related oncogene, neuroblastoma-derived (avian) (MYCN) was determined in various ARMS cell models and primary tumors. The roles of PAX3-FOXO1 and MYCN expression were examined.

Results: Pulse-chase and cycloheximide experiments suggest that GREM1, DAPK1, and MYOD1 are directly regulated by PAX3-FOXO1. PAX3-FOXO1 appears to indirectly down-regulate HEY1 by up-regulating MYCN. Data reveal that the growth-suppressive activity of high PAX3-FOXO1 expression is closely-associated with up-regulation of the GREM1 and DAPK1 tumor-suppressor genes.

Conclusion: This study characterized four downstream targets of PAX3-FOXO1 that contribute to the biological activities of growth suppression and myogenic differentiation.