Abstract 3485: PELP1 is a novel mediator of medulloblastoma progression

Abstract

Abstract Background: Medulloblastoma (MB) is the most common and deadliest primary brain tumor in children that accounts for 15-20% of all pediatric brain tumors. Despite recent advances in multimodal treatment, the 5-year overall survival of MB patients is approximately 60-70%. Unfortunately, improved outcome have been associated with significant long-term toxicities. Identifying novel targets that drive MB progression is urgently needed. Proline-, glutamic acid-, and leucine-rich protein 1 (PELP1) is a scaffolding protein that functions as a coregulator of several nuclear receptors. Oncogenic PELP1 signaling is implicated in the progression of several cancers including breast, ovarian, prostate, lung, pancreas and colon. However, its role in the progression of medulloblastoma remains unknown. Here, we examined the role of proto-oncogene PELP1 in the progression of MB. Methods: The expression of PELP1 in tumor micro arrays was analyzed using validated PELP1 antibodies for immunohistochemistry. PELP1 expression was determined in vitro by western blotting. PELP1 knockdown cells were generated using PELP1 shRNA lentiviral particles or PELP1 siRNA. The effect of PELP1 knockdown or overexpression was studied using cell proliferation, colony formation and migration using established in vitro assays. Mechanistic studies were conducted using RNA-seq, RT-qPCR, immunohistochemistry, reporter gene assays and signaling analysis. Interaction of PELP1 with NF-κB was examined by immunoprecipitation. Mouse orthotopic xenografts models were used for preclinical evaluation of PELP1 knock down. Results: Immunohistochemical analysis of MB tissue microarrays revealed that PELP1 is overexpressed in MB specimens compared to normal brain specimens. Knockdown of PELP1 using PELP1 specific siRNA or shRNA significantly reduced cell proliferation, cell survival, and cell migration of MB cell lines. RNA-seq analysis revealed that PELP1 knockdown significantly downregulated the pathways related to inflammation, angiogenesis and extracellular matrix. Further, gene set enrichment analysis (GSEA) confirmed that the PELP1-regualted genes were negatively correlated with NF-κB, extracellular matrix and angiogenesis. Mechanistic studies showed that PELP1 knockdown reduced the expression of NF-κB reporter gene activity and its target genes. Additionally, knockdown of PELP1 significantly reduced in vivo MB tumor progression in orthotopic models, and improved overall mice survival. IHC analysis demonstrated that the proliferation marker Ki67 and NF- κB targets were significantly downregulated in PELP1 knockdown tumors compared to controls. Conclusions: Taken together, these results provide the evidence that PELP1 could be a potential therapeutic target for therapeutic intervention in medulloblastoma. Citation Format: Yiliao Luo, Gangadhara Reddy Sareddy, Uday P. Pratap, Mengxing Li, Junhao Liu, Prabhakar Pitta-Venkata, Suryavathi Viswanadhapalli, Xiaonan Li, Manjeet Rao, Rajeshwar Rao Tekmal, Ratna K. Vadlamudi. PELP1 is a novel mediator of medulloblastoma progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3485.