| Objective1. To establish the rabbit VX2 remnant breast tumor model with focused ultrasound ablation.2. To evaluate the pathological changes of the target tumor tissue and remnant tumor tissue immediately after focused ultrasound ablation.3. To observe the changes in proliferative capability of remnant breast tumor implanted in rabbits after focused ultrasound ablation.4. To study the effects of the remnant breast tumor on the body.Methods1. First,to establish rabbit VX2 implanted breast tumor model of using tissue mass embedding method;Then,FU was applied to the tumors and the remnant tumors were obtained by controlling temperature of the tumor tissue around the thermal sensor.2.The ablated and residual tumor tissue were both evaluated immediately after FU ablation by HE staining,electron microscopy and enzyme histochemistry staining (SDH and ACP) to confirm if the remnant tumor model has been established.3. The expression of PCNA and Ki-67 was determined by immunohistochemistry at different time points after FU ablation(immediately,3d,7d,14d,21d and 28d).4.The organ and lymph node metastases,and the natural survival time were observed after FU ablation.Results1. In the FU ablated tumor tissue immediately after FU ablation,the outline of cells remained,many vacuolat-like structures appeared in cells,and there were no significant changes in nucleus under light microscope;and electron microscopy showed that the outline of cells remained,but the continuity of cell membrane was lost,organelle structure was damaged or disappeared,nuclear membrane was ruptured,different sizes of vacuoles in cells,nuclear membrane ruptured,chromatin condensed and fragmented into massive structures;and the activity of SDH and ACP was completely inactivated;and the expression of PCNA and Ki-67 was negative.2. In the residual tumor tissue immediately after FU ablation,there was no significant change in cell morphology and nuclear morphology under light microscope;and electron microscopy showed the thermal injury performance that includes the edema of tumor cells and swelling structure of organelles;the activity of SDH and ACP was decreased;and the expression of PCNA and Ki-67 was significantly decreased.3. The expression of PCNA and Ki-67 in residual tumor cells were decreased after FU ablation for a short time,it was gradually recovered at day 14,and restored to the level before ablation at day 21,and without further significantly increase at day 28.4. In the remnant tumor group,the earliest metastasis time was at day 21 after ablation,and the total lymph node metastasis rate was 13.3% and total visceral metastasis rate was 6.7% on day 28 after ablation. In the control group,the earliest metastasis time was at day 7 after ablation,and the total lymph node metastasis rate was 50% and total visceral metastasis rate was 38.9% on day 28 after ablation.5. The mean natural survival time of rabbits in the remnant tumor group was 64.8d and certainly prolonged by 42%.Conclusion1. It is considered that the rabbit VX2 implanted breast tumor model was successfully built and the best time for FU ablation is when the tumor is 10mm～15mm in diameter.2. Although HE staining under light microscope can not determine the survival condition of VX2 tumor cells,however,the electron microscopy and enzyme histochemical staining both confirmed that the tumor cells are dead.3. By controlling the temperature of tumor tissue around thermal senser(the temperature was under 50℃and last less than 10s),the rabbit VX2 residual tumor model was successfully established.4. Though FU ablation was not completely eradicate tumor,the growth and metastasis of the rabbit VX2 residual breast tumors were effectively inhibitted for a short period time,and it can prolong the survival time of the subjects.
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