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bioRxiv · 10.1101/2024.05.14.594201

Melanoma antigens in pediatric medulloblastoma contribute to tumor heterogeneity and species-specificity of group 3 tumors

Collins, R. R. J.·Gee, R. R. F.·Sanchez, M. C. H.·Tozandehjani, S.·Bayat, T.·Breznik, B.·Lee, A. K.·Peters, S. T.·Connelly, J. P.·Pruett-Miller, S. M.·Roussel, M. F.·Rakheja, D.·Tillman, H. S.·Potts, P. R.·Fon Tacer, K.
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Abstract

BackgroundMedulloblastoma (MB) is the most malignant childhood brain cancer. Group 3 MB subtype accounts for about 25% of MB diagnoses and is associated with the most unfavorable outcomes. Herein, we report that more than half of group 3 MB tumors express melanoma antigens (MAGEs), which are potential prognostic and therapeutic markers. MAGEs are tumor antigens, expressed in several types of adult cancers and associated with poorer prognosis and therapy resistance; however, their expression in pediatric cancers is mostly unknown. The aim of this study was to determine whether MAGEs are activated in pediatric MB. MethodsTo determine MAGE frequency in pediatric MB, we obtained formalin-fixed paraffin-embedded tissue (FFPE) samples of 34 patients, collected between 2008 - 2015, from the Childrens Medical Center Dallas pathology archives and applied our validated reverse transcription quantitative PCR (RT-qPCR) assay to measure the relative expression of 23 MAGE cancer-testis antigen genes. To validate our data, we analyzed several published datasets from pediatric MB patients and patient-derived orthotopic xenografts, totaling 860 patients. We then examined how MAGE expression affects the growth and oncogenic potential of medulloblastoma cells by CRISPR-Cas9- and siRNA-mediated gene depletion. ResultsOur RT-qPCR analysis suggested that MAGEs were expressed in group 3/4 medulloblastoma. Further mining of bulk and single-cell RNA-sequencing datasets confirmed that 50-75% of group 3 tumors activate a subset of MAGE genes. Depletion of MAGEAs, B2, and Cs alter MB cell survival, viability, and clonogenic growth due to decreased proliferation and increased apoptosis. ConclusionsThese results indicate that targeting MAGEs in medulloblastoma may be a potential therapeutic option for group 3 medulloblastomas. Key PointsO_LISeveral Type I MAGE CTAs are expressed in >60% of group 3 MBs. C_LIO_LIType I MAGEs affect MB cell proliferation and apoptosis. C_LIO_LIMAGEs are potential biomarkers and therapeutic targets for group 3 MBs. C_LI Importance of the StudyThis study is the first comprehensive analysis of all Type I MAGE CTAs (MAGEA, -B, and -C subfamily members) in pediatric MBs. Our results show that more than 60% of group 3 MBs express MAGE genes, which are required for the viability and growth of cells in which they are expressed. Collectively, these data provide novel insights into the antigen landscape of pediatric MBs. The activation of MAGE genes in group 3 MBs presents potential stratifying and therapeutic options. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=175 SRC="FIGDIR/small/594201v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1ac274aorg.highwire.dtl.DTLVardef@1479944org.highwire.dtl.DTLVardef@19f5aaforg.highwire.dtl.DTLVardef@fad069_HPS_FORMAT_FIGEXP M_FIG C_FIG

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Collins, R. R. J., Gee, R. R. F., Sanchez, M. C. H., Tozandehjani, S., Bayat, T., Breznik, B., Lee, A. K., Peters, S. T., Connelly, J. P., Pruett-Miller, S. M., Roussel, M. F., Rakheja, D., Tillman, H. S., Potts, P. R., Fon Tacer, K.. 2024-05-17. Melanoma antigens in pediatric medulloblastoma contribute to tumor heterogeneity and species-specificity of group 3 tumors. https://doi.org/10.1101/2024.05.14.594201

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