Poster Presentation Melbourne Immunotherapy Spring Symposium 2025

Unveiling Immunotherapy Targets in Granulosa Cell Tumours Using Mass Spectrometry Based Immunopeptidomics (#116)

Terry Lim 1 2 3 , Amber Badvi 2 3 , Simon Chu 3 , Pouya Faridi 1 2 3
  1. Monash Proteomics and Metabolomics Platform, Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
  2. School of Clinical Sciences, Department of Medicine, Monash University, Clayton, VIC, Australia
  3. Hudson Institute of Medical Research, Clayton, VIC, Australia

Adult granulosa cell tumours (aGCT) are rare ovarian malignancies characterised by high recurrence rates and limited treatment options. A defining molecular feature of aGCT is the somatic FOXL2C134W mutation, present in over 95% of cases. This mutation plays a central role in tumour pathogenesis and represents a potential source of neoantigens for immunotherapy. Despite its prevalence, the immunogenicity and presentation of FOXL2C134W-derived peptides remain unexplored.

This study aimed to identify tumour-specific antigens in aGCT using advanced immunopeptidomic technologies. KGN cells, an aGCT-derived line harbouring the FOXL2C134W mutation, were treated with interferon-gamma (IFNγ) and Smac-mimetics - small molecules that antagonise inhibitor of apoptosis proteins (IAPs) and enhance immune recognition - to upregulate HLA class I surface expression. Peptides presented by HLA molecules were isolated and analysed using liquid chromatography-tandem mass spectrometry (LC-MS/MS), employing data-independent acquisition (DIA) approach to sensitively detect low-abundance tumour antigens.

Although FOXL2C134W-derived peptides were not detected, comprehensive profiling revealed a diverse repertoire of tumour-associated antigens. Notably, cancer antigens such as PRAME and MAGEC1 were identified, exhibiting tumour-specific expression and minimal presence in normal tissues. These antigens are known for their immunogenicity and restricted expression profiles, making them ideal candidates for targeted immunotherapy.

This study represents the first immunopeptidomic characterisation of an aGCT cell line and demonstrates the utility of combining cytokine stimulation, Smac-mimetic treatment, and DIA-based mass spectrometry for neoantigen discovery. The identification of tumour-specific antigens such as PRAME and MAGEC1 provides a foundation for the development of personalised immunotherapies for aGCT, addressing a critical unmet clinical need.