PECAM1 and neoplasm: More importantly, hUMSC-IL-18 injection to breast cancer 4T1 cell-bearing BALB/c mice supported noticeable abrogation in tumor cell growth in vivo by activating immunocytes and immune cytokines, and also constraining tumor angiogenesis, as evidenced by reduced CD31 expression in hUMSC-IL-18 group compared with the control group (73).