Targeting oncogenic drivers in Ewing sarcoma using G-Quadruplex interacting drugs
Ewing sarcoma (ES) is the second most common bone cancer affecting children and young adults. ES is characterized genetically by a translocation involving chromosome 22 of which the most common is t(11;22) resulting in a gene fusion of EWS1R and FLI1. Overexpression of key oncogenic drivers such as MYC, BCL-2, and TERT is seen in ES cells, but these genes can be difficult to target. Recent research has brought forward a promising new approach to targeting these genes using G-Quadruplex Interacting Drugs (GQID), which bind specific G-Quadruplex DNA structures in the promoters of these genes and inhibit their transcription. Several methods were used to evaluate the activity of GQIDs against ES cells, including Drug Dose Response Assays (DDRs), western blot analysis and siRNA gene silencing. Four GQIDs that targeted MYC, BCL-2 or TERT were tested for their cytotoxic activity on a panel of six ES and two normal cell lines. DDR assays were used to determine the EC50 values of each cell line demonstrating its drug sensitivity. Our results indicated that the ES cells were more sensitive to GQIDs targeting MYC and TERT compared to normal cells. Western blot analysis was used to determine protein expression of gene products in the panel of ES cells and showed high expression of MYC and BCL-2 on five of six ES cell lines. Furthermore, gene silencing of MYC, BCL-2 and TERT in the TC-71 ES cell line using siRNA showed that the downregulation of these genes led to decreased cell growth. Our results indicate that the oncogenic drivers MYC, BCL-2 and TERT are viable targets in ES cells and that GQIDS to these targets are effective against ES cell growth. Moreover, these results support the development of GQIDs as potential therapeutics for the treatment of ES.