活体荧光成像技术评价X射线对小鼠乳腺癌移植瘤的治疗效果

Evaluation of the radiotherapy effect on transplanted breast cancer in mice by in vivo fluorescence imaging technique

目的建立荧光素酶标记的小鼠乳腺癌细胞爪垫淋巴结转移模型，监测肿瘤早期淋巴结转移，并用荧光成像评价X射线局部治疗效果。方法将表达荧光素酶的小鼠乳腺癌细胞系4T1-Luc接种至裸鼠爪垫皮下，建立爪垫皮下淋巴结转移模型。通过裸鼠活体荧光成像系统连续观察肿瘤细胞在淋巴结中的转移情况，并将有早期淋巴转移的荷瘤裸鼠按随机数字表法分为对照组和治疗组，活体荧光成像系统观察治疗效果，HE染色观察评价病理形态学变化。结果成功建立了小鼠乳腺癌淋巴结转移模型，爪垫原发灶肿瘤体积与荧光光子数呈正相关性（r=0．958，P〈0．001），在肿瘤接种的第24天，治疗组爪垫肿瘤和胭窝处肿瘤部位的荧光光子数较对照组呈显著性降低（t=32．58，P〈0．05）；用荧光光子数计算抑瘤率高达85％以上。HE染色观察到治疗组较对照组移植瘤坏死明显。结论运用活体生物发光成像技术能够动态、客观、灵敏、可视化地评估X射线对小鼠乳腺癌肿瘤的抑瘤效应。

Objective To establish a mouse model of lymph node metastasis of breast cancer cells by luciferase imaging assay, to monitor early process of lymph node metastasis, and to evaluate the effect of X-ray radiation therapy on tumor. Methods The mouse mammary cancer cell line 4T1 -Luc expressing luciferase was inoculated subcutaneously into the paw pad of nude mice to establish a model of subcutaneous lymph node metastasis. The lymph node metastasis in nude mice was continuously observed by in vivo fluorescence imaging system, and the nude mice with early lymph node metastasis of breast cancer cells were divided into control group and treatment group randomly. The radiotherapy effect was observed by in vivo fluorescence imaging system and evaluated by the pathological changes of HE staining of tumor tissue. Results A mouse lymph node metastasis model of breast cancer cells was successfully established, and the volume of primary tumor in paw correlated with the fluorescence photon number positively （ r = 0. 958, P 〈 0. 001 ）. On the twenty-fourth day after inoculation, the fluorescence photon number in pad tumor and popliteal fossa tumor of treatment group were significantly decreased in comparison with the control group （ t = 32.58, P 〈 0.05 ） , and the inhibition ratio of radiotherapy on tumor growth approached to 85% . HE staining showed that the apoptosis and necrosis in irradiated tumor was obviously higher than that in control group. Conclusions Bioluminescence imaging technique can be used to evaluate the effect of X-ray on breast cancer suppression and lymph node metastasis in mice.