Figure 6.

(A and B) Formation of tumors in nude mice after injection of SK-N-BE(2) cells precultured for 72 h at 1% or 21% O₂. The animals were killed when the tumors reached a diameter of 15 mm. (A) Mean time until tumor take (open bars) and termination (filled bars). Data are given as mean of two separate experiments with five mice in each group. In one experiment, one mouse in each group did not develop a tumor within 3 weeks. (B) Weights of the recovered tumors (P = 0.068). (C) Schematic representation of changes in gene expression in N-myc-amplified NB cells exposed to hypoxia. In hypoxic cells, neuronal marker genes chromogranin, dHAND, GAP-43, HASH-1, N-myc, and NPY (solid line) are down-regulated, whereas hypoxia-driven genes GAPDH, IGF-2, TH, and VEGF (dots) and neural-crest marker genes c-kit, HES-1, Id2, and Notch-1 (dashed line) are induced.