Fig. 1

a Flow cytometry plots showing populations from human PC xenografts. PI⁺, mouse-CD31⁺mouse-lineage⁺, or mouse-H-2Kd⁺ cells are excluded in order to isolate only viable nonmouse-derived cells. ALDH activity was measured using ALDEFLUOR reagent (Aldefluor Kit, Stem Cell Technologies, Vancouver, BC, Canada) in the presence/absence of N,N-diethylaminobenzaldehyde (DEAB) . The CD44⁺CD24⁺ gate was created based on cells stained with ALDEFLUOR, and IgG2bk-APC (isotypic control) and IgG2ak-PE (isotypic control) antibodies. Percentage of ALDH⁺CD44⁺CD24⁺ cells is given in the text. b Line plots showing cell-viability dose–response curves of PC-CSCs exposed to seaweed polyphenols. PC-CSCs derived from xenografts established using MiaPACa-2, Panc-1, Panc-3.27, or BXPC-3 cells were exposed to increasing concentrations (10, 20, 50, or 100 μg/ml) of SA-EA, PT-EA, or HT-EA and examined for alterations in cell viability using the automated countess trypan blue exclusion assay. Treatment with seaweed polyphenols exhibited dose-dependent inhibition of PC-CSC cell viability with maximum inhibition at 100 μg/ml. The dose-dependent decrease in cell viability by SA-EA, HT-EA, and PT-EA remained consistent in all four PC-CSC clones investigated. ALDH aldehyde dehydrogenase, CSC cancer stem cell, HT-EA ethyl acetate polyphenol fraction of Hormophysa triquerta, PC pancreatic cancer, PT-EA ethyl acetate polyphenol fraction of Padina tetrastromatica, SA-EA ethyl acetate polyphenol fraction of Spatoglossum asperum