KRAS and neoplasm: As Table 1 demonstrates, allografts with dual-positive cells develop significantly higher number of tumors in both Rag1−/− (7 tumors out of 10 transplants) and NOD/SCID (8 tumors out of 9 transplants) mice compared with Kras-mutant type II cells that do not express type I markers (2 tumors out of 10 transplants in Rag1−/− and 0 tumor out of 8 transplants in NOD/SCID) suggesting that the dual-positive (type I/II+) cells preferentially propagate tumors in vivo.