MKI67 and neoplasm: Next, the above PS-BC cells were injected into the mice dorsal flanks to establish tumor-bearing mice models in vivo, and the results in Figure 3D showed that PR-BC-exo promoted tumorigenesis of MCF-7 cells by delivering ANXA6, which were supported by the Immunohistochemistry (IHC) assay results that ANXA6-positive PR-BC-exo also increased Ki67 protein levels in mouse tumor tissues (Figure 3E).