<i>In vivo</i> tumorigenicity of TC-1 and LLC cells in immunocompetent and immunodeficient mice.

<p>Confidence interval plot of limiting dilution analysis is shown with the y-axis displaying the estimated frequency of cancer initiating cells (CIC). (<b>A</b>) A limiting dilution of TC-1 cells (120,000, 80,000, 40,000, 10,000, 5,000, and 1,000) were injected subcutaneously into syngeneic C57BL/6 mice (n = 4 to 8). Sphere derived cells were found to be more tumorigenic than adherent cells; *P≤0.001; **P<0.02. Day 1 sphere-derived cells were more tumorigenic than day 7; ***P = 0.04. A limiting dilution (10,000, 1,000, and 500 cells) (n = 6 to 8) of the same three groups were injected into NSG mice and CIC frequency was found to be below 1/500 for all groups. (<b>B</b>) Analysis of LLC limiting dilution tumor experiment for syngeneic (80,000, 40,000, 20,000, and 10,000 cells) and immunocompromised (NSG) mice (80,000, 40,000, 10,000, and 1,000 cells) (n = 4 to 9). No significant differences noted; however, sphere-derived cells trended towards being more tumorigenic than HM or LM adherent cells in C57BL/6 mice. Lower numbers of implanted cells were needed to initiate tumors in immunocompromised animals than in syngeneic animals with the estimated CIC frequency below 1/1000 for all LLC groups.