IMMU-03. IDENTIFICATION OF GENETIC BIOMARKERS TO PREDICT RESPONSE TO HSV-1 G207 AND POLIO:RHINOVIRUS IMMUNOTHERAPY

BACKGROUND: The polio:rhinovirus chimera, PVSRIPO, and the herpes simplex virus, G207, are viral immunotherapies with promising results in Phase I trials of pediatric high-grade glioma (pHGG) and medulloblastoma. While some patients have durable responses, others have no benefit. The purpose of this study is to identify genes that putatively confer resistance to viral immunotherapy. METHODS: A panel of medulloblastoma and pHGG cell lines were treated with either PVSRIPO or G207 and categorized into “sensitive” and “resistant” groups based viability. Flow cytometry was used to quantify cell receptor expression (CD111 for G207, CD155 for PVSRIPO). RNA sequencing was completed on treated resistant and sensitive cells. RESULTS: D341 and D556 medulloblastoma had < 50% viability at 72h (G207) and 24h (PVSRIPO) and were categorized as sensitive; D283 and D324 were categorized as resistant. There was a correlation between CD111 expression and cell viability (Spearman r=0.71) but no correlation between CD155 and viability. The number of significantly differentially expressed (DE) genes (adjusted p≤0.05) was significantly higher in sensitive compared to resistant medulloblastoma, both for enriched (mean 666.4±614 vs. 454.6±377.4, P=0.0422) and depleted (826.9±645.5 vs. 449±367.8, P=0.0167) genes after treatment. There were few shared DE genes between cells treated with PVSRIPO and G207: GCLM, LANCL2, and RBM3 were enriched while ADAMTS1 and VEGFA were depleted. Likewise, there were few shared DE genes enriched between medulloblastoma and pHGG cell lines treated with G207: GPSM2, CHECK2, SEPTIN2, EIF4G2, GCLM, GDAP1, LANCL2, and PWP1. CONCLUSIONS: Genetic analysis demonstrates minimal overlap in DE genes between the two viral immunotherapies. PVRIPO and G207 infection resulted in significantly more DE gene expression in sensitive vs. resistant cells. GCLM and LANCL2 are enriched by both PVSRIPO and G207 and in medulloblastoma and pHGG. These genes may serve as potential biomarkers in predicting response to viral immunotherapy.