Fig. 4

Somatostatin treatment on HT29 and SW480 cells does not change the ALDH+ population size or self-renewal abilities but inhibition of somatostatin decreases the ALDH+ population size. HT29 and SW480 cells were serum starved and then treated with 500 nM somatostatin or cyclosomatostatin for 48 h. Cells were trypsinized and analyzed for changes in ALDH positive cells, cell numbers, and cell viability. Somatostatin treatment did not significantly change the percentage of ALDH positive cells in either cell line for the number of ALDH positive cells (a), cell number (b), or cell viability (c), as compared to the control untreated cells. Cyclosomatostatin decreased the percentage of ALDH positive cells in both cells lines and only the cell number in HT29 cells, as compared to the controls. Data points represent the mean average values of treated cells over the controls (N = 3) * p ≤ 0.05. HT29 and SW480 cells were plated in ultra low attachment 6-well plates for colonosphere assay comparing untreated cells to somatostatin and cyclosomatostatin treatments, After 10 days, the number of spheres per well were counted and average numbers per well were calculated. Data points represent the mean average values of treated cells over the controls (d). SST = Somatostatin and CycloSST = Cyclosomatostatin