锰增强MRI检测结直肠癌转移潜能的可行性研究

Manganese-enhanced MRI for detection of metastatic potential in colorectal cancer

目的：探讨锰增强MRI（MEMRI）检测结直肠癌（CRC）转移潜能的可行性，研究CRC细胞株锰超氧化物歧化酶（MnSOD）表达与转移潜能的关系。方法选用高转移潜能人结直肠癌细胞株SW620、HCT116、LoVo，低转移潜能细胞株SW480、DLD-1、HCT15、Caco-2和正常人结肠黏膜上皮细胞株CCD841 CoN，进行培养、传代。采用蛋白免疫印迹杂交定量方法分析细胞株MnSOD表达，共测量3次。在HCT15、DLD-1、LoVo与SW620细胞株行体外摄锰检测及裸鼠皮下移植后行MEMRI检查，采用MnCl2· 4H2O溶液配制锰对比剂，测量计算细胞的T1缩短值。采用单因素方差分析比较不同细胞株间MnSOD表达水平、体外细胞摄锰及移植瘤T1缩短值的差异。结果不同细胞株间MnSOD表达水平的差异有统计学意义（P＜0.05）。除Caco-2表达低于正常细胞外，其余瘤细胞株表达均高于正常细胞。MnSOD表达水平较高的均为低转移潜能瘤细胞株（DLD-1、HCT15）；MnSOD表达水平较低者既包括低转移潜能细胞株SW480，也包括高转移潜能细胞株LoVo、SW620与HCT116。细胞株体外摄锰MEMRI，高转移潜能细胞株SW620与LoVo T1值缩短大[分别为（289.33±0.57）、（268.45±6.87）ms]，低转移潜能细胞株DLD-1与HCT15次之，正常细胞株CCD841 CoN T1缩短最小[（65.12±0.12）ms]，差异有统计学意义（P＜0.05）。体内种植共形成29个移植瘤，增强扫描肿瘤最大径5 mm组及10 mm组高转移潜能细胞株SW620与LoVo T1缩短值大，低转移潜能细胞株DLD-1与HCT15缩短小，差异均有统计学意义（P＜0.05），其中高、低转移潜能移植瘤间的T1缩短值差异有统计学意义（P＜0.05），同种转移潜能移植瘤间的T1缩短值差异无统计学意义（P＞0.05）。结论 MEMRI可区分不同转移潜能的结直肠癌，高转移潜能者强化明显。结直肠癌细胞株MnSOD表达水平与转移潜能不对应。

Objective To study manganese superoxide dismutase （MnSOD） expression in colorectal cancer （CRC） cells and observe its relation to metastatic potential. To investigate the diagnostic performance of manganese-enhanced magnetic resonance imaging （MEMRI） for detecting metastatic potential of CRC. Methods High and low metastatic potential CRC cell lines SW620, HCT116, LoVo and SW480, DLD-1, HCT15, Caco-2, as well as normal colon mucosal cell CCD841 CoN were cultured. MnSOD expression level in cells was detected by western blot and the measurement was repeated for three times. HCT15, DLD-1, LoVo and SW620 cells were selected to perform in vitro MEMRI and subcutaneous xenografts were developed for subsequent in vivo MEMRI. MnCl2· 4H2O solution was utilized as the contrast agent and T1 shortening was calculated. The differences of MnSOD expression level in cells, average T1 value shortening of cells and xenografts were separately compared by one-way ANOVA.Results The difference of MnSOD expression level in CRC cells were significant （P〈0.05）. All CRC cells have shown higher level of MnSOD expression than normal cell, except for Caco-2. The highest expression were shown in low metastatic potential cells （HCT15 and DLD-1）. Whereas relatively low MnSOD expression was found both in high and low metastatic potential cells （LoVo, SW620, HCT116 and SW480）. In vitro MEMRI demonstrated that the average T1 value shortening was greatest in high metastatic potential cells SW620 and LoVo [（289.33±0.57） and （268.45 ± 6.87） ms）], was significantly lower in low metastatic potential cells DLD-1 and HCT15, was lowest in CCD841 CoN [（65.12 ± 0.12）ms] （P〈0.05）. Twenty nine xenografts were successfully developed, high metastatic potential SW620 and LoVo tumors of 5 and 10 mm group showed greater T1 shortening, low metastatic potential DLD-1 and HCT15 tumors showed significantly less T1 shortening （P〈0.05）. However no significant difference was found in similar metastatic potential tumors （P〉0.05）. Conclusions MEMRI has the potential to noninvasively distinguish different metastatic potential CRC by revealing greater T 1 value shortening in more aggressive one. However the MnSOD expression in CRC cells is not corresponding to malignant potential.