磁性纳米氧化铁颗粒在人肝癌Bel 7402细胞裸鼠模型中的定向浓集及其生物学效应

Investigation on the migration and biologic effects of nano FeOx powders under the exposure of extremely low frequency altering electric magnetic field in human heptoma-bearing nude mice in vivo

目的研究37nm左右磁性纳米氧化铁颗粒（MNPs）在外加极低频交变磁场（EMF）作用下对人肝癌细胞株Bel7402细胞抑制的效果及其机制。方法用共沉淀法制备粒径为37nm的MNPs，用尾静脉注射法注入Bel 7402细胞裸鼠模型，用静磁场定位MNPs于荷载肿瘤区，定位完成后用EMF照射病灶区，用磁共振检测静磁场定位MNPs的效果，用流式细胞仪检测肿瘤细胞凋亡及死亡情况，用Western blot方法检测细胞凋亡相关蛋白Bcl蛋白质组的表达。数据处理用单因素方差分析。结果磁性纳米粒子在肿瘤部位的含量达到98．9％。经EMF照射静磁场定位MNPs裸鼠模型存活时间延长至（27．4±0．7）d，肿瘤抑制率为37．5％±0．8％，此种条件下肿瘤细胞早期凋亡明显，凋亡率为18．1％±0．6％。EMF照射能导致肿瘤细胞凋亡相关Bcl蛋白质组表达明显，EMF照射MNPs静磁场定位细胞Bcl2／Bax的比值（0．07±0．01）与未进行静磁场定位的细胞（0．23±0．02）比较，差异有统计学意义（F=0．016，P〈0．05）。结论EMF照射静磁场MNPs定向浓集人肝癌Bel 7402细胞裸鼠模型能很好的抑制肿瘤增殖，并导致肿瘤细胞发生大量凋亡从而延长裸鼠肿瘤模型存活时间。

Objective To investigate the mechanism and biologic effects of 37 nm magnetic nano FeOx powders （MNPs） on human hepatoma-bearing nude mice. Methods 37 nm MNPs were prepared by coprecipitation methods and then injected into human hepatoma （Bel-7402） bearing-nude mice through the tail vein. After injection of MNPs, the mice were first exposed under static magnetic field and then treated under extremely low frequency altering-electric magnetic field directing to the tumor area. The migration and trafficking of MNPs were determined by MMR. Tumor growth was monitored with calipers every 5 days and tumor volume was calculated on the basis of three-dimensioned measurements. The apoptosis of tumor cells was analyzed by flow cytometry analysis. The expressions of apoptosis-associated proteins Bcl-2, Bax and HSP27 were determined using western-blot analysis. Results Static magnetic field could direct the migration and trafficking of MNPs to the tumor site with a higher ratio of 98.9%. Extremely Low Frequency Electric- Magnetic Field （EMF） treatment could inhibit the proliferation of tumor cells and prolong the survive time of tumor-bearing mice injected with MNPs. In addition, the survival time of tumor-bearing mice and percentages of prohibition on tumor cell growth were 27.4 ± 0.7 days and 37.5 ±0.8%（F = 0.005, P 〈 0.05）, respectively.The results of flow cytometry analyses showed that about 18.1 ± 0.6% （F= 0.030,P 〈 0.05） of tumor cells were induced into early apoptosis. Furthermore, expressions of apoptosis-associated proteins Bcl-2 and Bax were significantly induced by MNPs under EMF treatment. The ratio of Bcl/Bax in both MNPs and EMF treatment group was 0.07 ± 0.01, which was much lower than that of control group （0.23±0.02）（ F = 0.016, P 〈 0.05）. Heat shock protein-27 （Hsp-27） was not significantly induced in different treatment groups. Conclusion Injection of MNPs with EMF exposure on human hepatoma-bearing nude mice could significantly prolong the survival time, inhibit the tumor proliferation and growth, and induce tumor cells into apoptosis.