The proliferation marker Ki67 was significantly decreased in breast cancer spheroids after co-culture with NPCs, both when comparing MDA-MB-231 and MCF7, and basal-like (MDA-MB-231, BT549, HS578T) combined, but not in the luminal-like cell comparison (MCF7, T47D, BT474). The gene discussed is MKI67; the disease is breast carcinoma.