Negative correlation of single-cell <i>PAX3:FOXO1</i> expression with tumorigenicity in rhabdomyosarcoma
Carla Regina, Ebrahem Hamed, Geoffroy Andrieux, Sina Angenendt, Michaela Schneider, Manching Ku, Marie Follo, Marco Wachtel, Eugene Ke, Ken Kikuchi, Anton G. Henssen, Beat W. Schäfer, Melanie Boerries, Amy J. Wagers, Charles Keller, Simone Hettmer
Abstract
Rhabdomyosarcomas (RMS) are phenotypically and functionally heterogeneous. Both primary human RMS cultures and low-passage Myf6Cre,Pax3:Foxo1,p53 mouse RMS cell lines, which express the fusion oncoprotein Pax3:Foxo1 and lack the tumor suppressor Tp53 ( Myf6Cre,Pax3:Foxo1,p53 ), exhibit marked heterogeneity in PAX3:FOXO1 ( P3F ) expression at the single cell level. In mouse RMS cells, P3F expression is directed by the Pax3 promoter and coupled to eYFP . YFP low /P3F low mouse RMS cells included 87% G0/G1 cells and reorganized their actin cytoskeleton to produce a cellular phenotype characterized by more efficient adhesion and migration. This translated into higher tumor-propagating cell frequencies of YFP low /P3F low compared with YFP high /P3F high cells. Both YFP low /P3F low and YFP high /P3F high cells gave rise to mixed clones in vitro, consistent with fluctuations in P3F expression over time. Exposure to the anti-tropomyosin compound TR100 disrupted the cytoskeleton and reversed enhanced migration and adhesion of YFP low /P3F low RMS cells. Heterogeneous expression of PAX3:FOXO1 at the single cell level may provide a critical advantage during tumor progression.