Gene Expression Profiling of PDGFRA Mutant GIST Reveals Immune Signatures as a Specific Fingerprint of D842V Exon 18 Mutation

Platelet Derived Growth Factor Receptor Alpha (PDGFRA) mutations occur in only about 5-7% of gastrointestinal stromal tumors (GIST), notably with alterations on exons 12/14/18. The most frequent PDGFRA mutation is the exon 18 D842V, which is correlated to specific clinico-pathological features, such as primary imatinib resistance and higher indolence. Here, we present a gene expression profile (GEP) comparison of D842V vs. PDGFRA with mutations other than D842V (non-D842V). GEP was followed by in silico bioinformatic analysis aimed at evaluating differential expression, tumor microenvironment composition and pathway enrichment. We found a large set of oncogenes, transcription factors and nuclear receptors downregulated in the D842V mutant. Conversely, D842V showed a significant enrichment of immune- and interferon- related gene signatures. Differences in tumor microenvironment composition were also highlighted, including a higher abundance of CD8+ T-cells and an overexpression of the T cell-inflamed signature in the D842V mutant subgroup, which is predictive of immunotherapy response. PDGFRA D842V vs. non-D842V GIST display a different expression profile, with a prominent immunological signature, that could represent a proof of principle for testing immunotherapeutic strategies in this drug-orphan subset of GIST.