Figure 2

Cell 'accounting' procedure for quantifying in vivo cell survival and metastatic efficiency. Inert plastic fluorescent microspheres (approximately 10 μm) are included in a cell suspension, in a known cell : microsphere ratio. The suspension is injected intravenously to target an organ (eg mesenteric vein to target liver). The microspheres remain indefinitely where they arrest in the microcirculation, providing a reference marker for the number of cells that originally reached that volume of tissue. Based on cell:microsphere ratios at later times, the percentages of surviving cells can be calculated (see example provided).