| Objective:This study established the patient-derived xenograft mouse model of gastric cancer,analyzed the factors affecting the establishment of the model,and explored the observation method of tumor growth in the mouse model,so as to optimize the technical process of model establishment,so as to improve the success rate of PDX model.To provide an effective preclinical model for the research of gastric cancer and the screening of accurate treatment schemes for patients with gastric cancer.Methods:A total of 33 patients with gastric cancer from Department of Oncology,Lanzhou University Second Hospital from October 2019 to January 2021 were included in the study.Among the tumor tissues of these patients,6 were obtained from gastroscopic biopsy,25 from laparoscopic radical gastrectomy,and 2 from gastroscopic biopsy and laparoscopic surgery.The fresh tumor tissues（F0）of these patients were transplanted into the unilateral or bilateral renal capsule,groin,axillary,muscle and greater omentum of NOD/SCID mice at different times within 24 hours after in vitro with the size of 1×1×1～3×3×3mm~3 to establish the PDX model of gastric cancer.Meanwhile:（1）analyze the clinical characteristics of patients,including age,gender,Borrmann type,the number of Ki67 positive cells,TNM stage,blood biochemical level,Serum tumor marker level,coagulation factor level and the relationship with model construction.（2）The effects of tumor tissue sampling method,transplantation site,histopathological type,degree of tissue differentiation,transplantation time and tumor size on the establishment of the model were analyzed.（3）After the PDX model was established,nuclear magnetic resonance imaging（MRI）was used to observe the tumor growth at each transplantation site of the PDX model every 7～10 days,and draw the tumor growth curve.When the tumor tissue increased to 300-500m~3,the tumor was removed（recorded as F1 generation）.（4）A portion of tumor tissue was used for passage（F2,F3...）.In the other part,pathological HE staining and immunohistochemical staining（Ki67）were performed,and the whole exome sequencing was performed to determine the consistency between the tumor of PDX model and the patient’s primary tumor.The remaining tumor were stored in tissue preservation solution at low temperature for resuscitation.Results:A total of 82 PDX models were constructed from the tumor tissues of 33patients with gastric cancer,of which 9 died due to postoperative infection before observation,with a mortality of 10.9%.Of the 73 PDX models observed,28 were successfully established,with a success rate of 38.4%（28/73）,and the average tumor growth time was 38.6 days.（1）Compared with the failure group,the level of ALB（P=0.007）and FVII（P=0.009）in the successful modeling group was significantly higher,and the level of NLR was lower（P=0.022）;The levels of absolute lymphocyte count（ALC）（P=0.023）in the successful modeling group were also higher than those in the failed group.There was no significant difference in age,sex,Borrmann type,number of Ki67 positive cells,TNM stage,absolute neutrophil count（ANC）,HGB,PLT,CEA,CA125,CA199,APTT,FIB,PT,D-dimer,F VIII and F X between the successful modeling group and the failed group（P>0.05）.（2）The successful establishment of the model was related to the sampling method（P=0.007）,It was related to the site of transplantation（P=0.000）,the pathological type of tumor（P=0.033）,the degree of tumor differentiation（P=0.028）,the time of tumor tissue transplantation（P=0.003）,and the size of the transplanted tumor（P=0.033）.The success rate of surgical sampling was48.1%（25/52）higher than that of biopsy 14.3%（3/21）（P<0.01）.The success rate of renal capsule was 28.3%（34/120）,which was higher than that of groin 3.1%（2/66）,axillary 0%（0/20）,greater omentum 0%（0/16）and muscle 0%（0/18）（P<0.01）.The success rate of neuroendocrine tumors was 100%（3/3）,which was higher than that of adenocarcinoma 37.9%（25/66）（P>0.05）and squamous cell carcinoma 0%（0/4）（P<0.05）.The success rate of poor differentiation was 51.2%（21/41）,which was higher than that of moderately and well differentiation 21.9%（7/32）（P<0.05）.The success rate of transplantation within 2 hours was 55.6%（20/36）,which was higher than 21.6%（8/37）at 2 hours later（P<0.01）.The tumor formation rate at 2×2×2mm~3 was 57.1%（16/28）,which was higher than 27.6%（8/29）at 1×1×1 mm~3 and 25%（4/16）at 3×3×3mm~3（P<0.05）.（3）The PDX model with tumor growth in MRI observation was measured.It was found that the tumor growth curve of PDX model with successful modeling showed that the tumor volume decreased in the first 25 days after modeling,and the tumor volume gradually began to increase after 25 days,while the tumor growth curve of PDX model with failed modeling showed that the tumor volume continued to decrease after modeling,and the tumor disappeared in 32 days.（4）The results of HE staining of transplanted tumor and patient tumor tissue in PDX model suggest that both F1 generation PDX model and patient tumor tissue（F0）are poorly differentiated gastric adenocarcinoma,and F2 and F3 generation PDX model is moderately and well differentiated gastric adenocarcinoma.Immunohistochemical staining showed that the number of Ki67 positive cells（%）was similar in F0-F3generation,which were 21%,17%,23%and 25%respectively.The whole exome sequencing results showed that the tumor of patients and PDX model microsatellite instability was microsatellite instability-high,and the pathogenic mutation of mismatch repair gene was not detected.c.C892T mutation of PTEN gene,c.T665C mutation of FGFR1 gene and wild-type TP53 gene were detected in patients’tumors,which were consistent with the detection results of PDX model.Conclusion:（1）The poorly differentiated tumor tissues from patients with laparoscopic gastrectomy were cut into 2×2×2mm~3 within 2h and transplanted under the renal capsule of NOD/SCID mice,which had a higher success rate of transplantation.（2）The success rate of gastric cancer PDX model transplantation may be related to the levels of patient’s serum ALB,ALC,NLR,FVII and tumor histopathological type.（3）MRI can be used as a noninvasive and continuous means to evaluate the success of PDX model of gastric cancer.（4）The PDX model of gastric cancer has good fidelity. |
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