ALDH1A1 and rhabdomyosarcoma: Supporting our model, gene expression profiles of the refractory chemoresistant rhabdomyosarcoma PDXs strikingly corresponds with the stemness-associated gene expression signature identified in our study, including significant upregulation of ALDH6A1, SOX4, CDH15, and MYOD1 expression as well as downregulation of ALDH1A1 and ALDH1A3 (Figure 7).