RESUMEN
AIM:To explore the synergistic sensitization effect of human umbilical cord mesenchymal stem cell culture supernatant(hUMSC-CM)combined with temozolomide(TMZ)on various glioma cell lines,and to elucidate the underlying mechanisms.METHODS:The hUMSC-CM was harvested using two different serum deprivation tech-niques at 24 and 48 h,and was converted into freeze-dried powder,which was then given to rat malignant glioma cell line RG-2,human astrocytoma cell line U251 and human glioblastoma cell line LN-428 at 5 concentrations(0,1,3,6 and 9 g/L).The effectiveness and sensitivity of hUMSC-CM for inhibiting growth of glioma cells at 24,48 and 72 h were as-sessed using CCK-8 assay.Hematoxylin-eosin(HE)staining combined with CCK-8 assay was employed to evaluate the chemotherapy sensitivity of glioma cells after 48 h of treatment with TMZ at 6 concentrations(0,25,50,100,200 and 400 μmol/L).Two concentrations(3 and 9 g/L)of hUMSC-CM and 3 concentrations(50,100 and 200 μmol/L)of TMZ were chosen for concurrent treatment of glioma cells to assess the proliferation and pathological alterations.TUNEL staining was utilized to detect apoptosis.Flow cytometry was utilized to analyze cell cycle modifications.The expression alterations of apoptosis-inducing proteins,cleaved caspase-3,cleaved caspase-8 and cleaved PARP1,as well as autophagy-inducing proteins beclin-1 and LC3,were examined using Western blot to investigate the synergistic sensitization mechanism of hUMSC-CM combined with TMZ in vitro.RESULTS:The susceptibility of glioma cell lines to hUMSC-CM and TMZ varied,with RG-2 showing the highest sensitivity,followed by U251,and then LN-428.The inhibitory effect of hUMSC-CM(3 and 9 g/L)and TMZ(50,100 and 200 μmol/L)combined treatment on glioma cells was significantly greater than that that of single-agent treatments(P＜0.05),demonstrating a dose-and concentration-dependent enhancement.Notably,the combination of 9 g/L hUMSC-CM(C9)with 50 μmol/L TMZ(T50)effectively suppressed glioma cell growth.CCK-8 as-say indicated a significant reduction of cell viability in C9+T50 group compared with either C9 or T50 alone(P＜0.05).HE staining and TUNEL staining revealed pronounced morphological changes and significant apoptotic features in glioma cells treated with C9+T50.Flow cytometric analysis confirmed that C9+T50 induced cell cycle arrest in glioma cells.Fur-thermore,compared with control group,the levels of cleaved caspase-3,cleaved caspase-8,cleaved PARP1,beclin-1,and LC3-Ⅱ/LC3-Ⅰ were significantly elevated in the C9+T50-treated glioma cells(P＜0.01).CONCLUSION:(1)The concomitant administration of hUMSC-CM and TMZ exerts a broad inhibitory effect on glioma cells,with a synergistic sen-sitization observed across different cell lines.(2)The enhancement of glioma cell sensitivity to TMZ by hUMSC-CM may be attributed to the modulation of caspase-8/caspase-3/PARP1 signaling pathway and the induction of both apoptosis and autophagy in glioma cells.