Selective Killing of RAS-Malignant Tissues by Exploiting Oncogene-Induced DNA Damage

Abstract

Summary: Several oncogenes induce untimely entry into S phase and alter replication timing and progression, thereby generating replicative stress, a well-known source of genomic instability and a hallmark of cancer. Using an epithelial model in Drosophila, we show that the RAS oncogene, which triggers G1/S transition, induces DNA damage and, at the same time, silences the DNA damage response pathway. RAS compromises ATR-mediated phosphorylation of the histone variant H2Av and ATR-mediated cell-cycle arrest in G2 and blocks, through ERK, Dp53-dependent induction of cell death. We found that ERK is also activated in normal tissues by an exogenous source of damage and that this activation is necessary to dampen the pro-apoptotic role of Dp53. We exploit the pro-survival role of ERK activation upon endogenous and exogenous sources of DNA damage to present evidence that its genetic or chemical inhibition can be used as a therapeutic opportunity to selectively eliminate RAS-malignant tissues. : RAS oncoproteins are virtually “undruggable” cancer targets. Murcia et al. take advantage of the inherent induction of DNA damage and additional blockade of the DDR by the RAS oncogene to show that genetic or chemical inhibition of ERK coupled to radiation can selectively eliminate RAS-malignant tumors once they are formed. Keywords: Dp53, ERK, genomic instability, DNA damage, ATR, cancer, radiotherapy, cell death, malignancy