Study On The Function And Mechanism Of FOXO3a In Liver Cancer Stem Cell Self-renewal

Liver cancer is a kind of worldwide malignant tumor with continued high incidence and mortality rate.It is also a common tumor in our country.The treatment means of liver cancer gradually increase,and the techniques are more and more mature in recent years.But the postoperative survival rate of liver cancer patients is still low due to extremely high transfer recurrence rate after treatment.A large number of studies show that is related to the liver cancer stem cells,which is in the tissue of the liver cancer,and has a strong differentiation potential.Therefore,the research and development targeting liver cancer stem cell therapy is becoming a hot spot of the treatment of liver cancer.FOXO3 a is an important member of the family of FOXO,its abnormal expression is closely related with the occurrence,development and prognosis of a wide variety of tumor.FOXO3 a considered to be an important tumor suppressor.Found in the related research of liver cancer,FOXO3 a is associated with the part of the biological behavior of hepatocellular carcinoma cells.Thus,further explore the connection of FOXO3 a and liver cancer stem cells have great significance.First,based on sorting system of Nanog promoter driving GFP expression,we get liver cancer stem cells by flow cytometry,and detect the expression of FOXO3 a in the cells.We find that the expression of FOXO3 a in liver cancer stem cells is lower than that in the liver cancer cells.On this basis,we construct two cell models that expression and interfere FOXO3 a.Then we detect the change of cell self-renewal ability through changing the expression of FOXO3 a,that is the change of cell clone formation efficiency and the sphere formation efficiency.Results show that the liver cancer stem cell self-renewal ability decreased after overexpressing FOXO3 a,and interfered the expression of FOXO3 a enhanced the ability of liver cancer cells transform to liver cancer stem cells.This suggests that FOXO3 a plays an important role in maintaining the ability of self-renewal in liver cancer stem cells.FOXO3 a can negatively regulate the liver cancer stem cells self-renewal ability.Further research shows,there is a certain correlation between FOXO3 a and proteasome system.FOXO3 a regulates liver cancer stem cells self-renewal ability through the positive regulation of the proteasome activity.Then we studied the upstream regulatory mechanism of FOXO3 a,and found that the IGF signaling also plays an important role in maintaining liver cancer stem cell self-renewal ability.IGF negatively regulate the expression of FOXO3 a.And,the change of expression of FOXO3 a can also affect the regulation of IGF on liver cancer stem cell self-renewal ability.Furthermore,after change the activity of IGF,the proteasome activity also changed.The activity of proteasome increased after inhibition of IGF signaling in liver cancer stem cells.On the contrary,the proteasome activity is reduced.That is shows that IGF also has a negative regulatory role in protease activity.And on this basis,when inhibit or activate the activation of IGF signaling,interference or raised FOXO3 a,respectively.The,we found that the regulation of IGF for proteasome activity is restrained.But,in turn,if the inhibition or activation of IGF signaling is on the basis of interference or overexpress FOXO3 a,the protease activity is not affected,and also the cells self-renewal ability has not changed.It fully shows that FOXO3 a not only takes part in the regulation of IGF for proteasome activity and liver cancer stem cells,but plays an important role in it.Therefore,synthesize the above results,shows that the FOXO3 a is negatively regulated by IGF signaling,maintaining low activity of proteasome,thereby to regulate liver cancer stem cell self-renewal ability.This study reasearch the role of FOXO3 a in liver cancer stem cell self-renewal,explore and verify the mechanism of its upstream and downstream signaling.It confirmed the regulation of IGF/ FOXO3a/ proteasome pathway for liver cancer stem cells self-renewal.The results can provide theoretical basis and lay the foundation of practice for research and development of the targeted therapy for hepatocellular carcinoma.