ATR and colorectal carcinoma: The human CRC line DLD1 engineered to homozygously harbor this mutation (termed ATRs/s cells) [14, 22–24] thus represents an ideally-suited model system for our question, as subtotal ATR protein depletion likely mimics the incomplete inhibition of ATR achievable through pharmacological means more closely than the complete and in most instances lethal ATR gene knockout [33].