Figure 7. In vivo competition reveals enhancement of the CD133⁺ CC stem cell population after TCF blockade.

CC36 cells transduced with RFP⁺ (red) lentivectors, or CC36-dnTCF4^ERT2 transduced with GFP⁺ (green) lentivectors were mixed in similar amounts (FACS green to red ratio of 0.8) in vitro. Untransduced cells were also present (black cells in the FACS plots). This mixture was injected subcutaneously into immunocompromised mice. Their treatment with TAM (+TAM) or corn oil vehicle only (−TAM) once a day for 8 days resulted in a 3.5-fold increase in the green/red ratio in MACS sorted CD133⁺ cells in the tumours treated with TAM as compared with control tumours (−TAM). The increase of green over red cells in tumours without TAM maybe due to a slight leakiness of the system leading to a small amount of dnTCF4 activity in the absence of TAM. Nevertheless, +TAM tumours were greener than −TAM tumours, which were yellow due to near equivalent green and red cell populations as exemplified in the micrographs in the bottom panels. n = 2 per sample. Average ratios are shown inside the FACS plots. Scale bar = 4 mm.