Abstract
Background: It has been reported that cancer stem cells (CSCs) play an important role in the progression of carcinoma and have a high potential for survival in various stress environments such as starvation and hypoxia. However, the mechanisms responsible for the capacity of CSCs to survive under stresses have been unclear. The aim of this study was to clarify the significance of the autophagy systems of CSCs under stress environments.Methods: Four human gastric cancer cell line, OCUM-12, OCUM-2MD3, MKN-45 and MKN-74 were used. Side population (SP) cells were sorted from the parent OCUM-12 and OCUM-2MD3, as CSC rich cells. The expression of stem cell markers was examined by RT-PCR. The viability of cancer cells under starvation and hypoxia (1%O2) was evaluated by MTT assay with or without the autophagy inhibitor, chloroquine. The expression level of the autophagy molecule LC3-II was examined by western blot. The numbers of autophagosomes and autolysosomes were counted by electron microscope.Results: SP cells of OCUM-12 showed a higher expression of stem cell markers and higher viability in starvation and hypoxia. Western blot and electron microscope examinations indicated that the autophagy was more induced in SP cells than in parent cells. The autophagy inhibitor significantly decreased the viability and the proportion of SP cells under the stress environments.Conclusions: Cancer stem cells of gastric cancer might maintain their viability under stress environments of starvation and hypoxia via the autophagy system. Autophagy inhibitors might be a promising therapeutic agent for gastric cancer.
Lack of correlation of stem cell markers in breast cancer stem cells
