光学分子活体成像监测评价MUC1-DC疫苗治疗乳腺癌MCF-7细胞裸鼠移植瘤的效果

Treatment efficacy of MUC1-DC vaccine in breast cancer MCF-7 cell xenografts in nude mice evaluated by monitoring tumor growth with optical molecular imaging

目的:评价黏蛋白1(mucin 1,MUC1)基因转染的DC疫苗治疗乳腺癌MCF-7细胞裸鼠移植瘤的效果及其可能的机制。方法:采用GFP慢病毒转染MCF-7细胞获得GFP-MCF-7细胞,皮下种植于BALB/c裸鼠,成瘤后随机分为3组。各组裸鼠首先尾静脉注射体外活化的CIK细胞(1×108个/只),治疗组于皮下注射MUC1基因转染的MUC1-DC(MUC1-DC组)或DC(DC组)(0.2 ml,1×107个/只),对照组(Control组)注射等体积生理盐水,每天治疗1次,连续5 d;采用小动物活体光学成像系统在开始治疗前及治疗后第35天观察移植瘤荧光成像,分析荧光强度和荧光面积;并采用免疫组化法检测瘤组织中Caspase 3的表达、TUNEL法检测细胞凋亡率。结果:GFP-MCF-7接种后7 d,成瘤率100%;光学分子成像法监测结果显示,治疗前MUC1-DC组、DC组和Control组之间体内移植瘤荧光信号强度无明显差异(P>0.05);第35天,MUC1-DC组的荧光信号强度明显低于Control组(P<0.05);DC与Control、MUC1-DC与DC组间均无显著性差异(均为P>0.05),但MUC1-DC比DC组荧光信号更低;治疗前MUC1-DC组、DC组和Control组之间体内移植瘤荧光信号分布面积无显著差异(P>0.05);第35天,Control组荧光信号呈多处散在分布,MUC1-DC组和DC组的荧光信号面积均明显低于Control组(均为P<0.01),MUC1-DC组的荧光信号面积低于DC组,但无显著差异(P>0.05);Control组Caspase 3表达最少,DC组次之,MUC1-DC组呈高表达Caspase 3,3组间差异均有统计学意义(均为P<0.05);3组细胞凋亡率分别为:Control组(4.11±2.61)%、DC组(9.63±2.27)%、MUC1-DC组(25.30±8.24)%,3组间差异均有统计学意义(均P<0.05)。结论:MUC1-DC疫苗比单纯DC免疫治疗人乳腺癌荷瘤小鼠能够更有效地抑制肿瘤的生长和扩散,发挥了更好的促进肿瘤细胞凋亡的作用。

Objective: To evaluate the treatment efficacy of mucin 1(MUC1) gene transfected dendritic cell(MUC1-DC) vaccine on breast cancer MCF-7 cell xenografts in nude mice and its possible mechanism. Methods: GFP lentivirus were transfected into human breast cancer MCF-7 cells to obtain the GFP-MCF-7 cells which were subcutaneously implanted into BALB/c nude mice. After tumorigenesis, the mice were randomly divided into three groups. First, CIK cells activated in vitro(1×108 cells/mouse) were injected into the mice of each group via tail vein. In the treatment groups, MUC1-DC(MUC1-DC group) or DC(DC group) were injected subcutaneously(0.2 ml, 1×107 cells/mouse). In the control group, normal saline of the same volume was injected. The treatment frequency was once per day for 5 consecutive days. The fluorescence imaging of transplanted tumor was observed before and 35 days after the treatment with optical imaging system, and fluorescence intensity and area were analyzed. The expression of Caspase 3 in xenograft tissues was detected by immunohistochemistry, and the cell apoptosis was detected by TUNEL assay. Results: The tumor formation rate of nude mice was 100% at 7 days after GFP-MCF-7 implantation. The results of optical molecular imaging showed that there was no significant difference in fluorescence signal intensity among MUC1-DC group, DC group and Control group before treatment(P>0.05). At day 35 after treatment, the fluorescence signal intensity of MUC1-DC group and DC group was significantly lower than that of Control group(P<0.05). There was no significant difference between DC and Control group, as well as between MUC1-DC and DC group(all P>0.05), but the fluorescence signal of MUC1-DC group was lower than that of DC group. There was no significant difference in the distribution area of fluorescence signal among MUC1-DC group, DC group and Control group before treatment(P>0.05). At day 35, the fluorescence signal in Control group was scattered in multiple areas, and the area of fluorescence signal in MUC1-DC group and DC group was significantly smaller than that in Control group(all P<0.01), but there was no significant difference between MUC1-DC group and DC group(P>0.05). Caspase 3 expression was the highest in MUC1-DC group, followed by DC group, and the least in Control group, and the differences among the three groups were significant(all P<0.05). TUNEL results showed that the apoptosis rate of Control group, DC group and MUC1-DC group was(4.11±2.61)%,(9.63±2.27)%, and(25.30±8.24)%, respectively(all P<0.05). Conclusion: Compared with mere DC immunotherapy, MUC1-DC vaccine can more effectively inhibit tumor growth and metastasis in nude mice bearing human breast cancer cell xenografts, exerting a better effect in promoting tumor cell apoptosis.