WNT1 and neoplasm: These AAV-K–induced tumors in MMTV-Wnt1 mice exhibited high histological similarities to spontaneous tumors arising in noninjected MMTV-Wnt1 transgenic mice, while Lenti-KrasG12D–induced tumors did not, suggesting that precision editing mimics natural tumor evolution—which often involves spontaneous activating mutations of Hras in this transgenic Wnt1 model (31)—more closely than virus-introduced ectopic expression of oncogenes.