Tumor-suppressive activities of SA1/STAG2 and effects of PARP impairment during brain development

Area of Science:

• Cellular Biology
• Genetics
• Oncology

Background:

• The cohesin complex regulates chromatin organization and DNA repair.
• Somatic variants in cohesin genes, including STAG2, are implicated in various cancers.
• The role of cohesin gene variants in brain tumorigenesis remains largely undefined.

Purpose of the Study:

• To investigate the presence of STAG2 variants in glioblastoma and medulloblastoma.
• To determine the functional impact of STAG2 loss in human cells and its homolog SA1 in Drosophila.
• To explore the therapeutic potential of combining PARP inhibitors with cohesin-targeting strategies in brain tumors.

Main Methods:

• Analysis of STAG2 variants in patient-derived glioblastoma and medulloblastoma samples.
• Functional studies involving STAG2 depletion in human cell lines.
• In vivo studies using Drosophila melanogaster models with reduced SA1 expression.
• Assessment of apoptosis induction by Poly ADP-ribose polymerase (PARP) inhibitors in combination with STAG2/SA1 depletion.

Main Results:

• STAG2 variants were identified in glioblastoma and medulloblastoma patients.
• Loss of SA1 in Drosophila brain development impaired neural stem cell differentiation and promoted tumorigenesis.
• Combined treatment with PARP inhibitors and STAG2/SA1 depletion induced significant apoptosis in vitro and in vivo.
• Reduced PARP activity in flies ameliorated tumor phenotypes in SA1-deficient tissues.

Conclusions:

• Impaired cohesin activity due to STAG2 variants contributes to brain tumorigenesis.
• Pharmacological inhibition of PARP can compensate for reduced cohesin function.
• This suggests a potential therapeutic vulnerability for exploiting cohesin dysfunction in brain tumors.