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The O-glycosyltransferase C1GALT1 promotes EWSR1::FLI1 expression and is a therapeutic target for Ewing sarcoma

ABSTRACT: Ewing sarcoma (ES) is an aggressive bone cancer driven by the oncogenic fusion-protein EWSR1::FLI1, which is not present in normal cells and is therefore an attractive therapeutic target. However, as a transcription factor, EWSR1::FLI1 is considered undruggable. Factors that promote EWSR1::FLI1 expression, and thus whose inhibition would reduce EWSR1::FLI1 protein levels and function, are potential drug targets. Here, using genome-scale CRISPR/Cas9 knockout screening, we identify C1GALT1, a galactosyltransferase required for the biosynthesis of many O-glycoproteins, as a factor that promotes EWSR1::FLI1 expression. We show that C1GALT1 acts by O-glycosylating the pivotal Hedgehog (Hh) signaling component Smoothened (SMO), thereby stabilizing SMO and stimulating the Hh pathway, which we find directly activates EWSR1::FLI1 transcription. Itraconazole, an FDA-approved anti-fungal agent that is known to inhibit C1GALT1, reduces EWSR1::FLI1 levels in ES cell lines and suppresses growth of ES xenografts in mice. Our study reveals a therapeutically targetable mechanism that promotes EWSR1::FLI1 expression and ES tumor growth.

ORGANISM(S): Homo sapiens

PROVIDER: GSE287721 | GEO | 2025/01/22

REPOSITORIES: GEO

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Project description:Endometrial cancer (EC) is the most common cancer of female reproductive organs. Because some low-grade ECs might also experience tumor recurrence after surgery and a worse prognosis, the study of alterations related to EC pathogenesis of the disease might help to get insights into underlying mechanisms involved in EC development and metastasis and identify novel markers associated to the disease. Here, low C1GALT1 protein expression levels were associated to a more aggressive phenotype of EC. Then, we aimed at investigating the role of C1GALT1 in EC progression by quantitative proteomics. ECC-1 cells were used as endometrioid EC model, and the effect of C1GALT1 depletion was analyzed using C1GALT1 specific short hairpin RNAs (shRNA) in comparison to SCRAMBLE shRNA. SILAC and mass spectrometry analysis were performed to identify and quantify dysregulated proteins associated with C1GALT1 depletion in the cell extract and secretome proteome of shC1GALT1 and SCRAMBLE ECC-1 cells. Out of 5208 proteins identified and quantified by LC-MS/MS, 76 and 143 proteins showed dysregulation (fold-change ≥1.5 or ≤0.67) in shC1GALT1 ECC-1 cells’ extracts and secretome, respectively. Nine dysregulated proteins were selected for validation by orthogonal techniques, confirming their dysregulation upon C1GALT1 depletion. Bioinformatics analyses pointed out to an increase in pathways and dysregulated proteins that associated with more aggressive phenotype. This finding was corroborated by loss-of-function cell-based assays. A higher proliferation, invasion, migration, colony formation and angiogenesis capacity of C1GALT1 depleted cells was observed. Finally, the negative protein expression correlation found by proteomics between C1GALT1 and LGALS3 was confirmed by IHC in actual EC samples, suggesting C1GALT1 stably depleted ECC-1 cells mimic the aggressive phenotype of EC cells and might be useful for the identification and validation of potential markers in aggressive ECs.

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The O-glycosyltransferase C1GALT1 promotes EWSR1::FLI1 expression and is a therapeutic target for Ewing sarcoma

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