A sample preparation method was developed to simulate the process of intracellular metabolites metabonomics analysis of Escherichia coli. The Escherichia coli cell was firstly quenched with cold sodium chloride solution ( 0. 85 %，precooled at -80℃ for 15 min).The quenched bacterial cell was treated by using the technique of vacuum freeze-drying and liquid nitrogen freezing combined with ultrasonic processing to increase cell membrane penetrability. Finally，a cold aqueous solution of methanol (MeOH:H2O, 1:1，V/ V, 4 ℃) was used as extraction solvent to extract metabolites. In the present research，flow cytometry and OD value recovery were performed to evaluate the degree of cell damage caused by quenching at single cell level and at integral level respectively. The tested results indicated that the degree of damage to cells caused by cold sodium chloride solution was less than 5%. The peak quantity and the total ion intensity detected by LC-TOF in low collision energy were used to evaluate extraction effects. Three different cell membrane penetrability modes and 4 kinds of extraction solvents were investigated and compared.The results showed that the technique of liquid nitrogen freezing combined with ultrasonic processing for cell membrane penetrability and a cold aqueous solution of methanol (MeOH/H2O，1:1，V/V, 4℃) for extraction of metabolites had the best extraction effect(peak quantity was greater than or equal to 105，and total ion intensity was in the range of 106-107).Therefore，in this work，the freeze drying，grinding with liquid nitrogen and ultrasonic extraction were combined to extract metabolites. In this way，it effectively promoted cell lysis and improved the efficiency of extraction. The result of synthetic analysis showed that the method proposed here could meet the requirements of the metabonomics analysis of Escherachaa coli.

[摘 要] 目的：探究错配修复蛋白2（MSH2）在胃癌中表达和其与患者临床特征的关系及其对胃癌细胞恶性生物学行为的作用及机制。方法：收集2020年5月至2022年7月期间在邢台市人民医院收治的40例胃癌患者的癌组织和配对癌旁组织及患者的一般临床资料。常规培养正常人胃黏膜上皮细胞GES-1和胃癌细胞AGS、MKN45和BGC-823，用转染试剂分别将sh-NC、shMSH2-1和shMSH2-2慢病毒载体转染至AGS和MKN45细胞中，实验分为sh-NC、shMSH2-1和shMSH2-2组。CCK-8法、克隆形成实验、EdU染色、Transwell小室实验分别检测各组AGS和MKN45细胞的增殖、迁移和侵袭能力。构建裸鼠MKN45细胞移植瘤模型，观察敲减MSH2对移植瘤生长的影响。WB法检测各组细胞中及移植瘤组织中 MSH2、PI3K/AKT/mTOR通路、上皮间质转化相关蛋白的表达。结果：MSH2在胃癌组织和细胞中呈高表达且与淋巴结转移、T分期进展及组织学分化不良均有关联（均P < 0.001）；在AGS和MKN45细胞中成功地敲减了MSH2的表达（P < 0.001）；敲减 MSH2均能显著抑制AGS和MKN45细胞的活力、EdU染色阳性率、克隆形成能力、迁移及侵袭能力和移植瘤的生长（均P < 0.001）；均能显著抑制AGS和MKN45细胞和MKN45移植瘤组织中MSH2蛋白、PI3K/AKT/mTOR通路相关蛋白、N-cadherin蛋白的表达（均P < 0.001），促进E-cadherin蛋白的表达（P < 0.001）。结论：MSH2在胃癌组织和细胞中呈高表达且与淋巴结转移、T分期进展及组织学分化不良有关联，敲减MSH2表达通过抑制PI3K/AKT/mTOR通路调控AGS和MKN45细胞的恶性生物学行为，MSH2可能是胃癌治疗的潜在靶点。