Dynamic equilibrium between cancer stem cells and non-stem cancer cells in human SW620 and MCF-7 cancer cell populations

Cancer stem cells (CSCs) paradigm suggests that CSCs might have important clinical implications in cancer therapy. Previously, we reported that accumulation efficiency of CSCs is different post low- and high-LET irradiation in 48 h. Cancer stem cells and non-stem cancer cells (NSCCs) were sorted and functionally identified through a variety of assays such as antigen profiles and sphere formation. Inter-conversion between CSCs and NSCCs were in situ visualised. Cancer stem cells proportions were assayed over multiple generations under normal and irradiation surroundings. Supplement and inhibition of TGF-β1, as well as immunofluorescence assay of E-cadherin and Vimentin, were performed. Surface antigen markers of CSCs and NSCCs exist in an intrinsic homoeostasis state with spontaneous and in situ visualisable inter-conversions, irrespective of prior radiations. Supplement with TGF-β1 accelerates the equilibrium, whereas inhibition of TGF-β signalling disturbs the equilibrium and significantly decreases CSC proportion. Epithelial mesenchymal transition (EMT) might be activated during the process. Our results indicate that the intrinsic inter-conversion and dynamic equilibrium between CSCs and NSCCs exist under normal and irradiation surroundings, and TGF-β might have important roles in the equilibrium through activating EMT.