MKI67 and neoplasm: The same CAF-triggered mitogenic effects were observed in MDA-MB-231 cells as the percentage of Ki67-positive tumor cells was higher (85%, p<0.001) compared to that of either MDA-MB-231 cell cultures or MDA-MB-231 cell/NF mixed nodules (61.7% and 60.3%, respectively) (Figure 4A and 4B).