Abstract:

Objective To screen the differentially expressed exosomal miRNAs derived from liver cancer stem cells (LCSCs) and its effect on the malignant biological characteristics of liver cancer cells. Methods miRNA expression profile chip was used to analyze the differentially expressed exosomal miRNA derived from LCSCs. The effects of miRNA on malignant phenotypes of LCSCs were identified. The cells were further treated with doxorubicin at different concentrations (0, 150, 300 μmol/L), and the expression level of miR-196a was detected by quantitative real-time PCR (qRT-PCR). The apoptosis of liver cancer cells cultured by exosomes derived from LCSCs (Exo-NC group) and exosomes derived from miR-196a inhibited LCSCs (Exo-Inhibitor group) and the activity of caspase3/7 under the action of exosomes from LCSCs were detected. Nude mice were randomly divided into Do-PBS group, Do-Exo-Inhibitor group and Do-Exo-NC group using random number table method, with 5 mice in each group, and the effect of miR-196a on nude mice xenograft tumor model with liver cancer cells was analyzed. Results In this study, exosomes were isolated and purified from CD133⁺ Huh7 stem cell culture supernatant. miR-7162-3p, miR-1910-5, miR-3613-3p, miR-196a and miR-155-5p were up-regulated, while miR-1246 and miR-3613-5p were down-regulated. miR-7162-3p, miR-196a and miR-155-5p in exosomes had important effects on the self-renewal ability of LCSCs. miR-1910-5p, miR-196a and miR-155-5p had important effects on the invasion ability of liver cancer stem cells, among which miR-196a had the most significant inhibitory effect. Treatment for 24 h, the miR-196a expression level of the 0, 150 and 300 μmol/L doxorubicin was 0.96±0.05, 1.23±0.05 and 2.33±0.03 respectively, with a statistically significant difference (F=996.90, P<0.001). Treatment for 48 h, the miR-196a expression level of the 0, 150 and 300 μmol/L doxorubicin were 1.02±0.07, 2.35±0.05 and 2.89±0.55 respectively, with a statistically significant difference (F=303.00, P<0.001). When the concentration of doxorubicin was 0 and 300 μmol/L, the apoptosis rates of the Exo-NC group were 9.37%±0.19% and 11.64%±0.27%, and those of the Exo-Inhibitor group were were 18.80%±1.91% and 22.79%±1.57%, with statistically significant differences (t=4.41, P=0.048; t=4.96, P=0.038). When doxorubicin was not used, the ratios of caspase3/7 in the Exo-NC group at 24 h and 48 h were 0.94±0.08 and 0.97±0.09, and those in the Exo-Inhibitor group were 1.56±0.01 and 1.58±0.01, with statistically significant differences (t=11.41, P=0.008; t=6.07, P=0.026). Under 300 μmol/L doxorubicin, the ratios of caspase3/7 in the Exo-NC group at 24 h and 48 h were 0.95±0.07 and 1.36±0.08, and those in the Exo-Inhibitor group were 2.84±0.08 and 3.20±0.14, with statistically significant differences (t=24.20, P=0.002; t=15.78, P=0.004). The results of xenograft tumor in nude mice showed that the tumor volumes of Do-PBS, Do-Exo-Inhibitor and Do-Exo-NC groups increased successively, which were (1 051.86±89.90) mm³, (1 310.91±86.66) mm³ and (2 185.14± 352.34) mm³ respectively, with a statistically significant difference (F=30.28, P<0.001). The weights of the transplanted tumors in the 3 groups increased successively, which were (0.36±0.10) g, (0.39±0.12) g and (0.76±0.16) g respectively, with a statistically significant difference (F=11.81, P=0.002). The expression of miR-196a in tumors was significantly decreased after miR-196a inhibitor transfection. The expression levels of the 3 groups were 1.05±0.16, 0.38±0.08 and 2.17±0.26, with a statistically significant difference (F=48.93, P<0.001). Conclusion The exosomal secreted by LCSCs can enhance the resistance of liver cancer cells to doxorubicin by miR-196a.

Key words: Liver neoplasms, Stem cells, Exosomes, miR-196a, Drug resistance