To identify the CTC in blood circulation in GBM bearing mice, we utilized a commercially available CELLTRACKS kit system24 that immunomagnetically separates the CTC from the remainder of the blood cells and subsequently captures cells positive for CD146, a high molecular weight tumor-associated antigen, and fluorescently stains for CD105 and CD45 thereby enumerating the CD105+/CD45− populations within the CD146 expressing cells25,26. The gene discussed is ENG; the disease is glioblastoma.