VCAM1 and neoplasm: We knocked out Vcam1 in stably expressing Cas9 4T1 cells, implanted them into the mammary fat pads of BALB/c mice, and allowed tumors to grow with CTCs detected as early as 9–16 days after implantation before immune recognition of luciferase and/or fluorescent protein labels lead to potential tumor rejection (Figure 5E).