MKI67 and neoplasm: While the data was variable and not statistically significant, there was indeed more Ki67 expression in the hNPC graft, particularly by two mice within the group, suggesting that the hNPCs might reveal a significantly greater tumor risk than the purified neurons if tested on a larger scale, i.e., if more animals were grafted, and with a higher number of cells per animal, and sacrificed after a greater duration post transplant.