Objective To investigate the application prospective of carboxyfullerene C_3 as a radioprotectant or assistant for tumor radiotherapy.Methods Different concentrations of C_3 were incubated with K562 and AHH-1 cell,CCK-8 assay and trypan blue rejection test were performed to examine the influence of C_3 on the cell viability.Annexin V/PI staining and flow cytometry assay were applied to assess the cell cycle and apoptosis after 7-ray irradiation.Results C_3 showed little toxicity to AHH-1 cell with the survival rate over 95% ,but 600 mg/L of C_3 markedly inhibited the growth of K562 cell (82%) .Pretreatment of 100 mg/L C_3 significantly increased the survival rate of AHH-1 cell after 4 Gy irradiation compared with the single radiation group(71.3% vs 90.3%) ,but decreased the apoptosis rate (26.3% vs 12.6%) ,while the survival rate of K562 cell was decreased and the apoptosis rate was elevated with the increase of C_3 concentration.Moreover,the cell cycle analysis revealed the G_2 phase block in AHH-1 cell after radiation exposure was mitigated by C_3 pretreatment,but that in K562 cell was aggravated.Conclusions C_3 has good radioprotective effects on AHH-1 cells.For K562 cell,C_3 could inhibit the cell proliferation,promote the radiation induced apoptosis and aggravate the G_2 phase block.

Objective To explore the effect and potential mechanisms of melatonin combined with gemcitabine on the chemosensitivity of human pancreatic cancer cell line PANC-1.Methods Human pancreatic cancer cell line PANC-1 was trea-ted with gemcitabine alone or in combination with melatonin.Cell viability was assessed using CCK-8.Effect of melatonin and gem-citabine alone or in combination on the clonogenic capacity of PANC-1 cells were observed through colony formation experiments.Scratch assays and transwell experiments were conducted to evaluate cell migration ability.Reactive oxygen species(ROS)and mitochondrial membrane point JC-1 assay kit were used to determine reactive oxygen species synthesis and membrane potential levels.Intracellular Fe2+level was measured using ferrous ion fluorescent probe.The protein expression levels of LC3,P62,GPX4 and SLC7A11 in different treatment groups were detected by immunofluorescence and Western blotting.Results CCK-8 results showed that the viability of PANC-1 cells was inhibited by gemcitabine alone after 48 h and 72 h of treatment in a time-and dose-dependent manner.The cell viability of gemcitabine combined with melatonin group was significantly lower than that of gemcitabine group,and the cell viability decreased with the increase of melatonin concentration.Scratch assays,transwell experiments,and plate colony formation assay results demonstrated that the proliferation and migration of cells in the gemcitabine combined with the me-latonin group were significantly inhibited compared with the gemcitabine group.The levels of reactive oxygen species and Fe2+in PANC-1 in gemcitabine combined with the melatonin group were higher than those in the gemcitabine group,and the mitochondri-al membrane potential was significantly decreased(P＜0.01).Western blotting and immunofluorescence results showed that the ra-tio of autophagy-related protein LC3-Ⅱ/LC3-Ⅰ in gemcitabine combined with the melatonin group was lower than that in the gem-citabine group,and the expression of P62 was up-regulated,and the expression of anti-iron death-related protein GPX4 and SLC7A11 was significantly inhibited(P＜0.05),suggesting that melatonin combined with gemcitabine can inhibit autophagy and promote ferroptosis in PANC-1 cells.Conclusion Melatonin enhances the chemosensitivity of pancreatic cancer cell PANC-1 to gemcitabine by inhibiting autophagy and promoting ferroptosis of tumor cells.