Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan.
Magn Reson Med Sci. 2011;10(3):155-8. doi: 10.2463/mrms.10.155.
Manganese-enhanced magnetic resonance imaging (MEMRI), used to trace neuronal connections and visualize brain activity, has recently been suggested useful for tumor detection, but the mechanism of tumor enhancement by manganese (Mn) is poorly understood. Our recent report of preferential enhancement of human mesothelioma cells with higher levels of manganese-superoxide dismutase (Mn-SOD) expression may suggest a correlation between Mn-SOD expression and enhancement. We investigate this possibility further using engineered human ovarian cancer cells overexpressing Mn-SOD.
We subcutaneously implanted SK-OV-3 human ovarian cancer cells stably overexpressing Mn-SOD (SK-Mn-SOD) into athymic nude mice and SK-OV-3 cells with plasmid DNAs carrying neomycin-resistant genes (SK-neo) into the same mice for controls. We conducted MEMRI in the tumor-bearing mice and compared enhancement between the 2 tumors.
Subcutaneous SK-Mn-SOD tumors were preferentially enhanced in MEMRI compared to SK-neo tumors. After Mn enhancement, the T(1)-relaxation rate (R(1)=1/T(1)) increased significantly for SK-Mn-SOD but not SK-neo tumors.
In some tumors, high expression of Mn-SOD may be a biological factor responsible for enhanced signal in MEMRI.
锰增强磁共振成像（MEMRI）用于追踪神经元连接和可视化大脑活动，最近被认为对肿瘤检测有用，但锰（Mn）增强肿瘤的机制尚不清楚。我们最近的报告表明，具有更高水平锰-超氧化物歧化酶（Mn-SOD）表达的人间皮瘤细胞优先增强，这可能表明 Mn-SOD 表达与增强之间存在相关性。我们使用过表达 Mn-SOD 的工程化人卵巢癌细胞进一步研究了这种可能性。
我们将稳定过表达 Mn-SOD 的 SK-OV-3 人卵巢癌细胞（SK-Mn-SOD）皮下植入裸鼠，将携带新霉素抗性基因的质粒 DNA 的 SK-OV-3 细胞（SK-neo）植入同一裸鼠作为对照。我们在荷瘤小鼠中进行了 MEMRI，并比较了两种肿瘤的增强情况。
与 SK-neo 肿瘤相比，皮下 SK-Mn-SOD 肿瘤在 MEMRI 中优先增强。Mn 增强后，SK-Mn-SOD 肿瘤的 T1 弛豫率（R1=1/T1）显著增加，但 SK-neo 肿瘤没有增加。
在某些肿瘤中，Mn-SOD 的高表达可能是 MEMRI 中信号增强的一个生物学因素。
