PI3K/AKT signaling modulates transcriptional expression of EWS/FLI1 through specificity protein 1.
Ewing sarcoma (ES) is the second most frequent bone cancer in childhood and is characterized by the presence of the balanced translocation t(11;22)(q24;q12) in more than 85% of cases, generating a dysregulated transcription factor EWS/FLI1. This fusion protein is an essential oncogenic component of ES development which is necessary for tumor cell maintenance and represents an attractive therapeutic target. To search for modulators of EWS/FLI1 activity we screened a library of 153 targeted compounds and identified inhibitors of the PI3K pathway to directly modulate EWS/FLI1 transcription. Surprisingly, treatment of four different ES cell lines with BEZ235 resulted in down regulation of EWS/FLI1 mRNA and protein by ~50% with subsequent modulation of target gene expression. Analysis of the EWS/FLI1 promoter region (-2239/+67) using various deletion constructs identified two 14 bp minimal elements as being important for EWS/FLI1 transcription. We identified SP1 as modulator of EWS/FLI1 gene expression and demonstrated direct binding to one of these regions in the EWS/FLI1 promoter by EMSA and ChIP experiments. These results provide the first insights on the transcriptional regulation of EWS/FLI1, an area that has not been investigated so far, and offer an additional molecular explanation for the known sensitivity of ES cell lines to PI3K inhibition.
Department of Oncology and Children's Research Center, University Children's Hospital, 8032 Zurich, Switzerland.
Chiara
C
Giorgi
Department of Oncology and Children's Research Center, University Children's Hospital, 8032 Zurich, Switzerland.
Aleksandar
A
Boro
Department of Oncology and Children's Research Center, University Children's Hospital, 8032 Zurich, Switzerland.
Florian
F
Rechfeld
Department of Oncology and Children's Research Center, University Children's Hospital, 8032 Zurich, Switzerland.
Laura A
LA
Lopez-Garcia
Department of Oncology and Children's Research Center, University Children's Hospital, 8032 Zurich, Switzerland.
Maria E
ME
Gierisch
Department of Oncology and Children's Research Center, University Children's Hospital, 8032 Zurich, Switzerland.
Beat W
BW
Schäfer
Department of Oncology and Children's Research Center, University Children's Hospital, 8032 Zurich, Switzerland.
Felix K
FK
Niggli
D000970:Antineoplastic Agents / Q000494:pharmacology; D001665:Binding Sites; D001859:Bone Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D059447:Cell Cycle Checkpoints; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism*; D058539:Phosphatidylinositol 3-Kinase / Q000235:genetics / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051789:Proto-Oncogene Protein c-fli-1 / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011804:Quinolines / Q000494:pharmacology; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034802:RNA-Binding Protein EWS / Q000235:genetics / Q000378:metabolism*; D012512:Sarcoma, Ewing / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D015398:Signal Transduction / Q000187:drug effects; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
D000970:Antineoplastic Agents; C106031:EWS-FLI fusion protein; D007093:Imidazoles; D015514:Oncogene Proteins, Fusion; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D051789:Proto-Oncogene Protein c-fli-1; D011804:Quinolines; D012333:RNA, Messenger; D034802:RNA-Binding Protein EWS; D016329:Sp1 Transcription Factor; C108209:SP1 protein, human; D058539:Phosphatidylinositol 3-Kinase; D051057:Proto-Oncogene Proteins c-akt; C531198:dactolisib
EWS/FLI1; Ewing sarcoma; PI3K pathway; promoter analysis