Abstract 1565: Identification of genetic and epigenetic biomarkers for prediction of chemoresistance in the treatment of high-risk advanced retinoblastoma
Authors: Song Wenping , Shao Rongguang , Li Liang 
Published: August 2018

Abstract
Background: Retinoblastoma (RB) is the most common pediatric retinal tumor initiated by biallelic inactivation of the retinoblastoma gene (RB1). Currently, chemotherapy with carboplatin, vincristine, and etoposide followed by optic enucleation is the most commonly used for retinoblastoma patients in China. The recurrence and metastasis of high-risk advanced RB is still a major obstacle for successful chemotherapy with very low survival rate only 26% in China, mainly due to chemotherapeutic resistance. The aim of the study is to identify genetic/epigenetic biomarkers with regarding to the prediction of outcome of chemotherapy for high-risk advanced RB, and to functionally characterize for mechanisms of candidate genes or potential biomarkers. Methods: Total of 41 pediatric patients with D- or E-stage retinoblastoma according to International Intraocular Retinoblastoma Classification (IIRC) staging standard were collected in the present study. Four complete remission (CR) and four recurrence patients due to their typical symptoms were selected to compare differences in profiles of whole-exome and genomic DNA methylation with high throughput next-generation sequencing technology by using their peripheral blood samples and to identify candidates in an integrative analysis of omics datasets. Subsequently, functional validation study was performed by using a human retinoblastoma Y79 cell line for those relevant candidate genes. Specifically, Y79 cells were knockdown or overexpressed with specific siRNA or expression vectors, respectively, followed by treatments with a diluted concentrations of carboplatin, vincristine, and etoposide in Cell Counting Kit (CCK-8) assay. Results: There were significantly different profiles of whole-exome and genomic DNA methylation in the integrative analysis. Total of 556 SNPs and 35 Indels were discriminated from whole-exome sequencing data, and 721 DNA methylation sites were detected with significant differences in RRBS assay between the datasets of those recurrence and CR patients. One variant (rs140693) in the exon 3 of MBD4 gene was identified in all those 4 recurrence patients and down-regulation of this gene by its specific siRNAs significantly altered the resistance of Y79 cells to all those above three drugs, as well as the cell growth rate, suggesting that the candidate variant/gene might be functional to impact on multiple drug resistances to carboplatin, vincristine and etoposide. Further functional studies would be required for characterization of its action mechanisms. Conclusion: Our study had identified novel genetic/epigenetic biomarkers to predict resistance against chemotherapeutics for high-risk advanced RB. It would be helpful as the first step toward precise medicine to explore intrinsic mechanism of chemoresistance and develop potential therapeutic targets for RB in future.
Citation Format: Wenping Song, Rongguang Shao, Liang Li. Identification of genetic and epigenetic biomarkers for prediction of chemoresistance in the treatment of high-risk advanced retinoblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1565.