DNA Methylation Profiling Separates SDH-Deficient GISTs From KIT-PDGFRA-Driven GISTs and Identifies Predictive...

Area of Science:

• Oncology
• Molecular Pathology
• Genetics

Background:

• Succinate dehydrogenase (SDH) deficiency causes a subset of gastrointestinal stromal tumors (GISTs), known as SDH-deficient GISTs.
• These tumors exhibit unique clinicopathological features, including predilection for females and young adults, and lack common GIST oncogenic drivers like KIT or PDGFRA mutations.

Purpose of the Study:

• To evaluate the utility of a sarcoma DNA methylation classifier for SDH-deficient GISTs.
• To identify potential predictive biomarkers for targeted therapy in SDH-deficient GISTs.

Main Methods:

• DNA methylation profiling of 30 SDH-deficient GISTs using a sarcoma DNA methylation classifier.
• Analysis of MGMT promoter methylation and MDM4 copy number alterations (gain/low-level amplification).

Main Results:

• SDH-deficient GISTs formed a distinct methylation cluster, separate from other GISTs and leiomyosarcomas.
• MGMT promoter methylation was detected in 6 primary and 5 metastatic tumors.
• MDM4 gain/low-level amplification was observed in 3 primary and 4 metastatic tumors, suggesting MDM4-p53 axis activation.

Conclusions:

• The sarcoma DNA methylation classifier can identify SDH-deficient GISTs as a unique molecular entity.
• MGMT promoter methylation and MDM4 gain/low-level amplification are potential predictive biomarkers for targeted therapies in SDH-deficient GISTs.