Molecular Mechanism And Efficacy Of ¹²⁵I Radioactive Seeds Implantation In The Treatment Of Recurrent Nasopharyngeal Carcinoma

Background:Nasopharyngeal carcinoma is a common head and neck malignant tumor in China.Radiotherapy based comprehensive treatment has achieved over 80%5-year survival rate.But after the first course of treatment,there is still a recurrence rate of up to 20%.Recurrent nasopharyngeal carcinoma is currently lack of effective treatment.125I radioactive seed implantation has shown good curative effect in the treatment of some malignant tumors.It has the advantages of safe,effective,minimally invasive and so on.And 125I seed implantation can still be used for cases of failure or recurrence of radiotherapy.However,there are few reports about the clinical application of 125I radioactive seeds in the treatment of recurrent nasopharyngeal carcinoma.We carried out this project to systematically study the molecular mechanism of 125I radioactive seeds in the treatment of nasopharyngeal carcinoma,the killing effect on nude mice bearing tumor and the efficacy and safety of clinical application.Part 1 Regulation of 125I seeds on the biological behavior of nasopharyngeal carcinoma cellsObjective:The changes of proliferation,apoptosis were observed by irradiation with different doses of 125I seeds.The expression of apoptosis-related proteins was also investigated.The aim of this study was to elucidate the expression of 125I seeds anti-tumor mechanism and to provide theoretical and experimental basis.Methods:The cells were randomly divided into four groups,control group:cells without any treatment,conventional culture;0.2 mCi group:0.2 mCi 125I seeds were irradiated at close range;0.5 mCi group:0.5 mCi 125I seeds were irradiated at close range;1.0 mCi group:1.0 mCi 125I seeds were irradiated at close range.MTT assay was used to detect the proliferative activity of the cells.Flow cytometry was used to detect the apoptotic rate and membrane potential.Cell viability was measured by Transwell chamber method.Cell migration ability was measured by cell scratches.The expressions of Caspase-3,Caspase-9,Bcl-2 and Bax in the above-mentioned groups were detected by western blot.Results:Compared with that of control group,the proliferation inhibition rate of each 125I seed dose group was significantly higher(P<0.05);the proliferation inhibition rate of CNE-1 cells increased apparently;the apoptotic rate of each 125I seed dose group was significantly higher(P<0.05).the membrane potential of each CNE-1 cell was signiflcantly decreased(P<0.05);the number of invasive cells in each 125I seed dose group was significantly lower(P<0.05);the cell migration rate of each 125I seed dose group was significantly lower(P<0.05);the expression of Caspase-3,Caspase-9 and Bax protein in CNE-1 cells was significantly higher(P<0.05),and the expression level of Bcl-2 protein was significantly higher than that of control group(P<0.05).Followed by the increase of 125I dose,the tendency of above changes increased gradually.Conclusion:125I seed can inhibit the proliferation,invasion and migration of nasopharyngeal carcinoma cells,decrease the level of membrane potential and promote cell apoptosis in a dose-dependent manner.Part 2 125I seeds implantation killing effect on human nasopharyngeal nude mice xenograftsObjective:The aim of this study was to investigate the inhibitory effect of 125I radioactive seeds implantation on tumor in nude mice by establishing the model of CNE-1 tumor in nude mice as a target.The aim of this study was to further clarify that 125I radioactive seeds were implanted in inhibiting tumor growth and to lay a theoretical and experimental basis for its better application in the treatment of clinical nasopharyngeal carcinoma.Methods:The model of transplanted tumor of nasopharyngeal carcinoma in nude mice was established by the method of inoculation of human nasopharyngeal carcinoma CNE-1 cells.60 tumor-bearing nude mice were randomly divided into 3 groups,20 mice in each group.Blank control group:"cold particles"(visual activity 0)implanted in nude mice transplanted tumor tissue;model group:Tumor-bearing nude mice without treatment;observation group:percutaneous 125I(0.4 mci/tablets)radioactive seed implantation under direct vision.The length(L)and width(W)of the nude mice were measured every 3 days after the corresponding treatment.The tumor volume was calculated and the growth curve of the transplanted tumor was drawn.Nude mice were sacrificed on the 15th day after treatment.The tumor tissue was completely separated and the tumor weight was weighed.Tumor tissues were taken for pathological section HE staining to compare tumor regression.Results:The tumor volume of the nude mice in the control group was significantly higher than that of the observation group(P<0.05).Compared with the control group,the weight of the transplanted tumor of the nude mice in the observation group was significantly decreased(P<0.05).The tumor regression in the observation group was more obvious than that in the control group.Conclusion:125I seed implantation can significantly inhibit the growth of human nasopharyngeal nude mice xenografts.Part 3 Clinical study of CT-guided 125I seeds implantation for unresectable recurrent nasopharyngeal carcinomaObjective:This study was to investigate the efficacy of CT-guided 125I radioactive seeds implantation in the treatment of unresectable recurrent nasopharyngeal carcinoma.Methods:30 cases of unresectable recurrent nasopharyngeal carcinoma patients were chosen and treated by using CT-guided 125I radioactive seeds implantation.The local control rate,survival time,survival rate of 1-,2-and 3-years were analyzed,and the influences of initial treatment,tumor size,type and stage on survival time were analyzed.And the complications were observed.Results:The local control rates of 3 months after the procedure of 125I seeds implantation was 92.1%(35/38).The overall 1-,2-,and 3-years survival rates were 80.0%(24/30),30.0%(9/30),and 6.7%(2/30),respectively;with a median survival period of 17.6± 8.6 months.The survival periods of patients with the primary radiotherapy with or without chemotherapy were 15.8±7.9 and 24.3±7.9 months.Kaplan-Meier survival analysis demonstrated that X2(log rank)was 7.555,with very significant difference(p<0.01).The survival periods of patients with tumor diameter ≤2 cm and 2cm were 10.1±2,9 and 11.3±3.6months,respectively(P<0.05).The survival periods of patients with differentiated nasopharyngeal carcinoma and undifferentiated nasopharyngeal carcinoma were 16.9±8.4 and 24.1±8.1 months,respectively(P<0.05).The survival period of the patients with I,II,III and IV stages was 25.4±8.7 months,19.8±9.4 months,16.1±4.5 months and 12.8±7.8 months respectively.The difference was statistically significant(p<0.05).There were no serious complications during and after the operation.Conclusion:CT-guided 125I seeds implantation is effective in recurrent nasopharyngeal carcinoma.Tumor staging is an important prognostic factor.The implantation of 125I seeds may be an effective method for the treatment of recurrent nasopharyngeal carcinoma.125I seeds can still be implanted in the recurrent cases after radiotherapy.The operation is safe and no serious complications are found.