NOTCH1 and neoplasm: As shown in Fig. 1d, FISH analysis of the various CAF strains, mostly at 2nd (CAF 11, 12, 13) or 3rd (CAF 8, 14, 15, 16) passage after tumor dissociation (except for CAF9 and 10 at passage 6), showed heterogeneous cell populations, with most cells harboring increased copies of the NOTCH1 gene (3–5), which were either separate from each other or juxtaposed on chromosome 9, as gene duplications (Fig. 1d).