人脐带间充质干细胞运载呼肠孤病毒对人慢性髓系白血病K562细胞溶瘤作用的研究OA北大核心CSTPCD

AIM:To investigate the oncolytic effect of human umbilical cord mesenchymal stem cells(hUMSCs)delivering reovirus type 3(Reo3)on chronic myeloid leukemia(CML)K562 cells.METHODS:The expression of junc-tional adhesion molecule-A(JAM-A),a receptor susceptible to Reo3,on the surface of hUMSCs and K562 cells was as-sessed by flow cytometry.Intracellular viral inclusion body distribution 72 h after Reo3 infection in hUMSCs was observed by electron microscopy.The hUMSCs were infected with various multiplicities of infection(MOI)of Reo3(MOI=0,1,2 and 3)for 24,48,72,96 and 120 h,and the most suitable MOI was identified by CCK-8 assay.Subsequently,hUMSCs were infected with the optimal titer of Reo3 for the same durations,and supernatants were collected.The titer of Reo3 in the supernatant from each group was measured using mouse fibroblast L929 cells combined with median tissue culture in-fectious dose(TCID50)method,determining the optimal infection time.The K562 cells were divided into 4 groups:con-trol group,hUMSCs group,Reo3 group,and hUMSCs-Reo3 group.Ratios of hUMSCs to K562 cells in hUMSCs group and hUMSCs-Reo3 group were set at low,medium and high(5∶1,10∶1 and 20∶1).The changes of K562 cell viability af-ter co-cultured with hUMSCs-Reo3 for 24,48 and 72 h were analyzed by CCK-8 assay.The apoptosis of K562 cells was evaluated by flow cytometry.The half maximal effective concentration(EC50)of anti-Reo3 monoclonal antibody was deter-mined using L929 cells.The oncolytic effect of hUMSCs-Reo3 on K562 cells with antibody present in vitro was verified.Western blot analysis was used to detect the protein levels of Bcl-2,Bax,survivin and cleaved caspase-3 in K562 cells af-ter treatment.A BALB/c nude mouse subcutaneous tumor model was constructed with K562 cells(n=6)to analyze the in vivo anti-tumor effect of hUMSCs-Reo3.RESULTS:The expression levels of JAM-A on the surfaces of hUMSCs and K562 cells were found to be 11.0%and 99.0%,respectively.Electron microscopy revealed a significant presence of viral inclusion bodies within hUMSCs 72 h following infection with Reo3.Within 120 h,no statistically significant difference was observed in the viability of hUMSCs between Reo3(MOI=1)group and uninfected group,establishing the optimal MOI.The TCID50 results indicated that the highest virus titer in the lysate of hUMSCs in Reo3(MOI=1)group occurred 48 h after infection,determining 48 h as the optimal infection time.The K562 cells co-cultured with hUMSCs-Reo3 for 24,48 and 72 h showed a dose-and time-dependent inhibition of cell viability.The EC50 of the anti-Reo3 monoclonal antibody was found to be 1∶34.Even in the presence of antibodies at various concentrations(1∶34,1∶300 and 1∶600),hUMSCs were capable of transporting Reo3 to inhibit K562 cell viability and induce apoptosis in vitro.Compared with control group,significant down-regulation of Bcl-2 and survivin expression levels in K562 cells was noted after 48 h of co-culture with hUMSCs-Reo3(P<0.05),while Bax and cleaved caspase-3 expression levels were significantly up-regulated(P<0.05 or P<0.01).In the BALB/c nude mouse tumor-bearing model,determination of tumor volume changes,pathological examination of tumor tissue and major organs,and assessment of cathepsin B/L activity using a small animal live imaging system confirmed the oncolytic effect of hUMSCs-Reo3 on K562 cells in vivo without adverse effects on normal tissues.CONCLUSION:The hUMSCs are effective in transporting Reo3,and this delivery system is capable of releasing suffi-cient quantities of Reo3 in both in vivo and in vitro settings to inhibit the malignant proliferation of K562 cells and promote apoptosis,thereby exerting an oncolytic effect.