瑞香素增强肺癌细胞放疗敏感性的机制研究OA

Objective To investigate the radiosensitizing mechanism of daphnetin on Lewis lung cancer(LLC)cell-induced xeno-grafts in mice.Methods A mouse xenograft model of LLC cells was established.When the average volume of xenografts reached approximately 80 mm³ with uniform size(designated as Day 0),24 mice were randomly divided into four groups:control group,daph-netin group,irradiation group,and daphnetin+irradiation group.At days 2-6,the mice in daphnetin group and daphnetin+irradiation group were intraperitoneally injected with daphnetin at 20 mg/kg once daily for five times,and the mice in control group and irradia-tion group received equal volumes of normal saline.At days 6,8,10,the mice in irradiation group and daphnetin+irradiation group underwent local radiotherapy at 4 Gy per session.No further treatments were administered from day 11 in all groups.Tumor volume was measured every other day from day 0.When the maximum tumor volume in control group reached 1 500 mm³(day 26),all mice were sacrificed by cervical dislocation.Tumor tissues were measured to calculate the tumor volume inhibition rate(TIR).Western blot was performed to detect the protein expression levels of p53,ribonucleotide reductase regulatory subunit M2(RRM2),and Cyclin D1 in tumor cells.Immunofluorescence was used to determine the fluorescence intensity of Cyclin D1.Results Compared with control group,tumor volumes were significantly reduced in daphnetin group,irradiation group,and daphnetin+irradiation group(P<0.01).Compared with daphnetin group and irradiation group,the mice in daphnetin+irradiation group showed a reduction in tumor volume and a increase of tumor volume inhibition rate(P<0.01).Compared with control group,p53 expression was significantly increased in daphnetin group and daphnetin+irradiation group(P<0.001),while the expressions of RRM2 and Cyclin D1 were decreased(P<0.05);and the expression of RRM2 and Cyclin D1 was increased in irradiation group(P<0.05).Compared with irradiation group,p53 expression significantly increased(P<0.001),and RRM2 and Cyclin D1 expressions significantly decreased in daphnetin+irradiation group(P<0.001).Immunofluorescence results showed that,compared with control group,Cyclin D1 fluorescence intensity decreased in daphnetin group and daphnetin+irradiation group(P<0.01),but increased in irradiation group(P<0.001).Cyclin D1 fluorescence intensity in daphnetin+irradiation group was also significantly lower than in irradiation group(P<0.001).Conclusion Daphnetin,at a radiosensitizing dose,can enhance the inhibitory effect of radiotherapy on the growth of LLC xenografts in mice,exerting a radiosen-sitizing effect.This mechanism may be related to the activation of p53,which in turn inhibits the formation of RRM2 and Cyclin D1,thereby hindering tumor cell repair.