MKI67 and neoplasm: In addition, the treatment effect of eMSCs could not be further enhanced by increasing the dosing frequency, as weekly dosing of eMSCs from 2 to 4 w p.i. of 4T1 cells induced similar tumor growth reduction and Ki67 proliferation index increase as a single dose at 2 w p.i., also without negatively affecting animal welfare (Figures 1B-G).