Abstract 4880: MAGE gene family expression in pediatric medulloblastoma: frequency and possible therapeutic target

Abstract

Abstract Background: The melanoma antigen gene family (MAGE) is a group of related genes that were first discovered in malignant melanoma. Among the approximately 40 MAGE genes in the human genome, two thirds are classified as Type I (MAGE-A, MAGE-B, and MAGE-C), referred to also as cancer testis antigens (CTAs), proteins that are restricted to testis but often aberrantly expressed in many adult cancers. Despite their common expression in adult cancers and their oncogenic potential, little is known about their expression and role in pediatric cancers. To determine the frequency of MAGE expression in pediatric medulloblastoma, we measured expression levels of Type I MAGEs in patient tumors. In addition, we examined how MAGE expression in medulloblastoma cells affects their growth and oncogenic potential. Methods: We searched the Children’s Health pathology database for pediatric medulloblastoma between 2008 - 2015 and were able to recover an adequate amount of RNA from formalin-fixed paraffin-embedded tissue samples of 34 patients. The RNA was converted to cDNA using reverse transcriptase, and the relative expression of 23 Type I MAGE genes was measured by qRT-PCR. To determine if MAGE expression is critical for medulloblastoma cell survival we knocked down several MAGEs using siRNAs in two MAGE-expressing medulloblastoma cell lines (D283 and DAOY) and evaluated the effect by cell viability (Alamar Blue and Cell titer Glo), apoptosis assays (Annexin V), and colony formation in soft agar. Results: In 34 medulloblastoma patient samples we found that 10 (29.4%) expressed at least one MAGE gene, and one case had high levels of expression of 10 of the 23 Type I MAGEs. MAGE expression was associated with the non-WNT/SHH (G3/G4) molecular subgroup of tumors in our study. There was no correlation between MAGE expression and histologic subtype. Furthermore, using MAGE-A/-B2 positive medulloblastoma cell lines, we showed that siRNA knock down of multiple MAGE-As and -B2 decreased cell viability by 15 - 80%, increased apoptosis (-B2), and decreased growth of cells in soft agar. Conclusion: Type I MAGE genes are expressed in 30% of pediatric medulloblastoma in our study. In MAGE positive medulloblastoma cells, MAGE genes are important for cell survival and clonogenic growth. The decreased cell survival after MAGE knockdown appears to be related, at least in part, to increased apoptosis. Our results indicate that targeting of MAGEs in medulloblastoma may be a potential therapeutic option. Citation Format: Rebecca R. Collins, Klementina Fon Tacer, Dinesh Rakheja, Patrick Ryan Potts. MAGE gene family expression in pediatric medulloblastoma: frequency and possible therapeutic target [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4880. doi:10.1158/1538-7445.AM2017-4880