Distinct Roles Of Mesenchymal Stem Cells In Initial And Progressive Stage Of Hepatocellular Carcinoma

Background and AimsThe tumor microenvironment plays an important role on liver cancer genesis and development.It is noted that tumors are more than insular masses of proliferating cancer cells.Instead,they are complex tissues composed of multiple distinct cell types that participate in heterotypic interactions with one another.Cancer cells can recruit normal cells,which form tumor-associated stroma,constituting the tumor microenvironment.The plasticity of tumor microenvironment is also a significant characteristic of the pathogenesis of liver cancer.Mesenchymal stem cells(MSCs),a pivotal part of tumor stroma,are recruited and enriched in liver tumors.However,the exact impact of MSCs on liver cancer remains elusive,as a variety of effects of these cells that have been reported included a plethora of tumor-promoting effects and anti-oncogenic properties.In this study,we will discus the roles and mechanisms of MSCs regulating genesis and development of hepatocellular carcinoma in different stages,and may provide powerful evidences for using MSCs to treat liver cancer or even premalignant liver diseases safely and effectively.Methods and Results Part1: MSCs regulated genesis and development of hepatocellular carcinoma in different stages.At first,we established the rat model of hepatocellular carcinoma induced by diethyl nitrosamine(DEN),and divided the initial stage(Is)and progressive stage(Ps)of liver cancer through continuous observation of liver cancer tumorigenesis and development in different induced time(0,4,8,12,16 weeks).In addition,we injected the bone marrow-derived mesenchymal stem cells(MSCs)to rats in initial and progressive stage separately.Finally,we analysed the survival,incidence of tumor,largest size of tumor and numbers of tumors occurred in aboved rats.Results: Firstly,with observation of the various points such as liver structure,texture and H&E staining,we divided initial stage from 0 week to 9 weeks,whereas 9 weeks to 17 weeks can be classified as tumor progressive stage.Secondly,compared with group DEN,we found group DEN+MSCs(Is)had lower incidence of tumor,smaller size of largest tumor,less numbers of tumors and significant prolongation of survival;Whereas in group DEN+MSCs(Ps),the incidence of tumor,size of largest tumor,numbers of tumors were significantly increased and the survival was shortened.Part2: The mechanisms of MSCs regulating genesis and development of hepatocellular carcinoma in different stages.To investigate the mechanism of MSCs inhibiting tumorigenesis in initial stage,we detected liver function(ALT and AST)and liver cells apoptosis at 8 weeks.The results showed that ALT and AST in DEN+MSCs(Is)were lower than DEN,and liver cells apoptosis was reduced significantly.Meanwhile,we detected the accumulation of ROS and DNA damage,which were decreased significantly in DEN+MSCs(Is).Additionslly,compared with DEN,we found that DEN+MSCs(Is)had less perivascular infiltration lymphocytes and secretion of inflammation factors in liver tissue.Further study had been done,there were lower liver tissue fibrosis and inactivation of hepatic stellate cells in DEN+MSCs(Is).To discuss the machenisms of MSCs promoting development of tumor in progressive stage,we detected cells apoptosis and proliferation in liver cancer tissues at 14 weeks,finding that apoptosis cells of DEN+MSCs(Ps)and DEN had no significant difference,but DEN+MSCs(Ps)had more proliferative cells in cancer tissue.Besides,we found that DEN+MSCs(Ps)had a higher expression of tumor stem cell markers(EpCAM and AFP)and EMT activated markers in cancerous tissue.To further confirm the effect of MSCs,we treated CBRH-7919 with MSC-CM in vitro experiments,and found that MSC-CM had no significant effect to promote cancer cells proliferation,activate cancer stem cells and EMT.Interestingly,the CM from MSCs with TNF-?/IFN-? treatment can significantly promote cancer cells proliferation,activate cancer stem cells and EMT.ConclusionIn summary,combined the results of two parts,we can draw the following conclusions: Firstly,MSCs played different roles in different stages of hepatocellular carcinoma.MSCs can inhibit tumorigenesis significantly in initial statge,whereas promote development of tumor in progressive stage.Secondly,in iniatial stage,MSCs can probably inhibit ROS and DNA damage,further to reduce inflammation effect and inhibit liver fibrosis,so as to inhibit liver carcinogenesis.In progressive stage,inflammatory factors in microenvironment such as TNF-?/IFN-? can stimulate MSCs to promote cancer cells proliferation,activate cancer stem cells and EMT,increasing the malignant degree of liver cancer in the end.