| Objective:To investigate the biodistribution of 131I labeled Herceptin antibody (131I-Herceptin) against HER-2/neu in healthy Kunming mice and nude mice bearing human ovarian cancer xenografts, its imaging feature in nude mice bearing ovarian cancer xenografts and its biologic effectiveness on human ovarin cancer cell strain with high HER-2/neu expression in vitro, and to assess its feasibility of radioimmunotherapy in ovarian cancer.Method:1.Iodogen method was used for 131I labeling Herception, 131I-Herceptin was separated from excess 131I and Herception through a Sephadex G50 minicolumn. Labeling efficiency and radiochemical purity were estimated by paper chromatography method. 131I-Herceptin was immersed in the water and incubated with healthy human serum at 37οC, and radiochemical purity at different time points was demonstrated to know the stability of 131I-Herceptin. Immunocompetence of 131I-Herceptin was detected with cell conjugation assay. 2.The expression of HER-2/neu antigen in ovarian cancer cell line SKOV-3 and HO-8910 was detected by flow cytometer, and the expression of their HER-2/neu protein in xenograft tissues was observed by immunohistochemistry. 3.The inhibition effect of 131I-Herceptin on SKOV-3 and HO-8910 cell line was evaluated by MTT assay. The cell cycle changes and cell apoptotic rate of the intervention group and control group on SKOV-3 were evaluated by flow cytometer(FCM). 4.Animal models bearing SKOV-3 and HO-8910 xenografts were to be established by implanting corresponding cells in female athymic nude mice subcutaneously. After healthy Kunming mice and nude mice were injected with 131I-Herceptin antibody from tail veil, mice were sacrificed by cutting off carotid artery at different time points. The blood, organs and xenografts were harvested and weighted for calculating dose per gram of tissue (%ID/g) and tumor/non-tumor (T/NT) ratio. 5.Continuous imaging of the nude mice bearing xenografts was carried out at the different time point by SPECT after injection of 131I-Herceptin, meanwhile, it ought to be observed the imaging feature and to determine the optimal imaging time. Results:1.The labeling rate of 131I to Herceptin was 89.8%, the radiochemistry purity was 98.4%, and the specific activity was 27.5MBq/mg. The radiochemical purity still maintained above 90% and 80% after incubation in water bath at 37οC for 12h and 24h respectively. In 24h and 48h after incubation with healthy serum, the radiochemical purity still reached 80% and 65%, respectively. The immunobinding ratios were 65.8% and 8.6% for SKOV-3 cells and HO-8910 cells accordingly. 2.The positive ratios of HER-2/neu expression were 95.3% and 8.87% on SKOV-3 cells and HO-8910 cells, respectively. Immunohistochemistry showed that there were conspicuous distribution of positive cells in tissues of human SKOV-3 ovarian cancer, and brown particles were found in plasmalemma and cytoplasm of tumor cells, comparatively speaking, the above-mentioned was not found in tissues of human HO-8910 ovarian cancer. 3.By MTT assay, the inhibition effect of 131I-Herceptin on SKOV-3 cells was significantly higher than that of on HO-8910 cells, and was also significantly higher than that of 131I, Herceptin and 131I+Herceptin respectively. By flow cytometer assay, the apoptosis rate of 131I-Herceptin group was conspicuously higher than that of 131I group, Herceptin group and 131I+Herceptin group respectively. We also can see distinguished cell cycle blockage in all intervention groups, especially in 131I-Herceptin group. 4.After subcutaneous planted, all of athymic nude mice has formed xenografts, with a tumor forming rate of 100%. The metabolism of 131I-Herceptin mainly depended on reticuloendothelial system and kidney with rapid elimination in blood, and in vivo the distribution and elimination of 131I-Herceptin antibody were consistent with general McAb. 131I-Herceptin could concentrate on SKOV-3 xenografts selectedly for a long time. The %ID/g of xenografts was obviously higher than that of other organs and added up to 18.26% at peak amplitude at 24h post-injection. In another one, the high T/NT ratio could be attained and Tumor/brain ratio was 20.58 at 72h. 5.We could see the image of xenografts at 2h postinjection, as time ran off, the radioactivity of xenografts increased little by little, and the contradistinction compared to the background was by far conspicuous at 48h, Not until 120h could we still see transparent radioactivity aggregation in the region of xenografts, but in the control groups we didn't almost see xenografts imaging at every time point postinjection.Conclusion:1.131I-Herceptin has not only high labeling efficiency and radiochemical purity, but also has good stability both in vitro and in vivo, and keep good immunocompetence after being labeled with 131I. 2.131I-Herceptin can transparently inhibit and kill the human ovarian cancer cell SKOV-3 with high HER-2/neu expression. 3.131I-Herceptin accumulates mainly in xenografts sites and takes on remarkable targeting property to SKOV-3 xenografts, and with potential clinical value in radioimmunotherapy of varian cancer with high HER-2/neu expression.
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