Certain bone and soft tissue (BST) tumours harbour a chromosomal translocation [t(6;22)(p21;q12)], which fuses the Ewing's sarcoma (EWS) gene at 22q12 with the octamer‐binding transcription factor 4 (Oct‐4) gene at 6p21, resulting in the chimeric EWS‐Oct‐4 protein that possesses high transactivation ability. Although abnormal activation of signalling pathways can lead to human cancer development, the pathways underlying these processes in human BST tumours remain poorly explored. Here, we investigated the functional significance of fibroblast growth factor (FGF) signalling in human BST tumours. To identify the gene(s) involved in the FGF signalling pathway and potentially regulated by EWS‐Oct‐4 (also called EWS‐POU5F1), we performed RNA‐Seq analysis, electrophoretic mobility shift assays, chromatin immunoprecipitation assays, and xenograft assays. Treating GBS6 or ZHBTc4 cells‐expressing EWS‐Oct‐4 with the small molecule FGF receptor (FGFR) inhibitors PD173074, NVPBGJ398, ponatinib, and dovitinib suppressed cellular proliferation. Gene expression analysis revealed that, among 22 Fgf and four Fgfr family members, Fgf‐4 showed the highest upregulation (by 145‐fold) in ZHBTc4 cells‐expressing EWS‐Oct‐4. Computer‐assisted analysis identified a putative EWS‐Oct‐4‐binding site at +3017/+3024, suggesting that EWS‐Oct‐4 regulates Fgf‐4 expression in human BST tumours. Fgf‐4 enhancer constructs showed that EWS‐Oct‐4 transactivated the Fgf‐4 gene reporter in vitro, and that overexpression of EWS‐Oct‐4 stimulated endogenous Fgf‐4 gene expression in vivo. Finally, PD173074 significantly decreased tumour volume in mice. Taken together, these data suggest that FGF‐4 signalling is involved in EWS‐Oct‐4‐mediated tumorigenesis, and that its inhibition impairs tumour growth in vivo significantly.

Background Tropomyosin‐receptor kinase fused gene (TFG) functions as a regulator of intracellular protein packaging and trafficking at the endoplasmic reticulum exit sites. TFG has recently been proposed as a cause of multisystem proteinopathy. Objectives Here, we describe a Korean family presenting with Parkinson's disease or amyotrophic lateral sclerosis caused by a novel variant of TFG (c.1148 G > A, p.Arg383His). Methods We collected clinical, genetic, dopamine transporter imaging, nerve conduction, and electromyography data from the seven subjects. To verify the pathogenicity of the R383H variant, we studied cell viability and the abnormal aggregation of α‐synuclein and TAR DNA‐binding protein 43 (TDP‐43) in HeLa cells expressing R383H‐TFG. Results The clinical phenotypes of the R383H‐TFG mutation varied; of the five family members, one had Parkinson's disease, three had subclinical parkinsonism, and one (the proband) had amyotrophic lateral sclerosis. The individual with multiple system atrophy was the proband's paternal cousin, but the TFG genotype was not confirmed due to unavailability of samples. Our in vitro studies showed that R383H‐TFG overexpression impaired cell viability. In cells co‐expressing R383H‐TFG and α‐synuclein, insoluble α‐synuclein aggregates increased in concentration and were secreted from the cells and co‐localized with R383H‐TFG. The levels of cytoplasmic insoluble aggregates of TDP‐43 increased in HeLa cells expressing R383H‐TFG and co‐localized with R383H‐TFG. Conclusions Clinical and in vitro studies have supported the pathogenic role of the novel TFG mutation in α‐synucleinopathy and TDP‐43 proteinopathy. These findings expand the phenotypic spectrum of TFG and suggest a pivotal role of endoplasmic reticulum dysfunction during neurodegeneration. © 2021 International Parkinson and Movement Disorder Society