Abstract
Abstract Gallbladder cancer (GBC) is a fatal malignancy with widespread geographical variations in incidence worldwide. There are limited studies on systematic molecular profiling of gallbladder cancer in literature. Previously, we carried out differential proteomic and methylome-based analysis in gallbladder tumors and adjacent non-tumors to identify differentially expressed proteins and global methylation status of genes involved in gallbladder cancer. Quantitative tissue proteomics analysis using Isobaric Tags for Relative and Absolute Quantitation (iTRAQ) based Liquid Chromatography-Mass Spectrometry (LC-MS/MS) showed that desmin protein was significantly downregulated (~3 folds) in tumors. Global methylation profiling using Illumina's Infinium Human Methylation 450 BeadChip array revealed hypermethylation in desmin in gallbladder tumors compared to non-tumor tissue. These findings lead us to further investigate the epigenetic regulation of desmin gene expression in gallbladder cancer. Real-time PCR analysis revealed significant downregulation of desmin (p=0.001) expression in tumors (n=12) as compared to the non-tumor tissue (n=12). Immunohistochemical analysis also showed significantly (p<0.0001) decreased level of desmin in 95% (26/27) of tumor cells in comparison to non-tumors 35.71% (5/14). This was again validated by Western blotting, showing downregulation of desmin (p=0.0081) at protein level in tumor tissues compared to the non-tumors. Methylation specific polymerase chain reaction analysis showed 86.67% methylation of desmin in corresponding gallbladder tumors compared to non-tumor tissue (p=0.004). Taken together, our observations showing decreased expression and hypermethylation of desmin gene suggest desmin as a potential epigenetically controlled biomarker for GBC. However, further studies are warranted to explore its role in tumorogenesis of gallbladder cancer. Citation Format: Shushruta Bhunia, Mustafa Ahmed Barbhuiya, Sanjiv Gupta, Braj Raj Shrivastava, Pramod Kumar Tiwari. Downregulation of desmin involves gene promoter hypermethylation in gallbladder cancer [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr A14.
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