FOXO3 and neuroblastoma: However, the activation of FOXO3 did not fully eradicate proliferating tumor cells, but promoted heterogeneity of the residual tumor tissue with some FOXO3-negative tumor cells and NB cells with high, nuclear FOXO3 levels that apparently persisted during 4OHT-induced FOXO3 activation (Figure 5C and Supplementary Figure S4).