Elucidating the cancer-specific genetic alteration spectrum of glioblastoma derived cell lines from whole exome and RNA sequencing

Cell lines derived from tumor tissues have been used as a valuable system tostudy gene regulation and cancer development. Comprehensive characterization ofthe genetic background of cell lines could provide clues on novel genes responsiblefor carcinogenesis and help in choosing cell lines for particular studies. Here, we havecarried out whole exome and RNA sequencing of commonly used glioblastoma (GBM)cell lines (U87, T98G, LN229, U343, U373 and LN18) to unearth single nucleotidevariations (SNVs), indels, differential gene expression, gene fusions and RNA editingevents. We obtained an average of 41,071 SNVs out of which 1,594 (3.88%) werepotentially cancer-specific. The cell lines showed frequent SNVs and indels in someof the genes that are known to be altered in GBM- EGFR, TP53, PTEN, SPTA1 andNF1. Chromatin modifying genes- ATRX, MLL3, MLL4, SETD2 and SRCAP also showedalterations. While no cell line carried IDH1 mutations, five cell lines showed hTERTpromoter activating mutations with a concomitant increase in hTERT transcript levels.Five significant gene fusions were found of which NUP93-CYB5B was validated. Anaverage of 18,949 RNA editing events was also obtained. Thus we have generated acomprehensive catalogue of genetic alterations for six GBM cell lines.

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Patil V, Pal J, Somasundaram K