Importantly, BCL-2 selective inhibitor ABT-199 improved cell death in irradiated STS117 and STS109, despite their low levels of BCL-2 and the upregulation of expression of BCL-XL (Figure 3A,B) suggesting that BCL-2 may be a central mediator of STS apoptosis resistance to RT. This evidence concerns the gene BCL2 and telomere syndrome.