ATF3 and neoplasm: The effects of ATF3 overexpression on tumor growth were diminished by the overexpression of IFI6 or IFI27 (ATF3+IFI6 or ATF3+IFI27), which were further supported by staining of the cell proliferation marker Ki-67 (red arrows), which showed that the overexpression of ATF3 significantly suppressed the proliferation of tumor cells, and that suppression was blocked by the stable expression of IFI6 or IFI27 (Figs 6G, 6H and S13B).