Effect Of CO₂ Pneumoperitoneum On Expressions Of MMP2 And CD34 In Rabbit Liver VX2 Tumor

Objective: To detect the expressions of MMP2 and CD34 proteins in rabbit liver VX2 tumor during CO₂ environment, so as to explore the effect of CO₂ on invasion, growth and metastasis in malignant tumor, and infer its mechanism from our findings.METHODS:Healthy male New Zealand rabbits weighing 2.5³.5kg were employed to establish models. After feeding one week under the same condition, thirty rabbits which were successfully implanted VX2 into liver were divided into 3 groups: Group A(Pneumoperitoneum group, n=10), Group B(MMPi group, n=10), Group C(Pneumoperitoneum-free group, n=10).Group A and Group B received laparoscopic operation under condition that CO₂ pressure was 7.5mmHg, CO₂ flow was 0.4L/min. A Trocar was put into abdominal cavity at right lower quadrant. Five millilitres normal saline were administrated through intraperitoneal injection in Group A when the operation began, while 1,10-Phenanthroline (25mg/kg) were administrated through intraperitoneal injection in Group B. Pneumoperitoneum lasted for 3 hours. Group C did not establish pneumo- peritoneum instead of suspending rabbits'abdominal wall, the other treatments were the same as Group A. All animals were killed by euthanasia after raising 14 days under the same condition. We observed the tumor growth, measured tumor maximum diameters, tumor volume, tumor weight, and detected MMP2 and CD34 expressions both in tumor tissue and paratumor tissue by immunohistochemistry stain. Then,we analyzed the mean optical density of MMP2 and CD34 proteins by IPP system (Image-pro-plus 5.0.2).RESULTS: (1).No metastases or ascites were observed. (2).Tumor maximum diameter was (3.15±0.21)cm in Group A,(2.43±0.32)cm in Group B and (2.16±0.29) cm in Group C(P=0.000). Tumor volume was (2.97±0.57) cm3 in Group A,(2.00±0.68) cm3 in Group B,and (1.33±0.27) in Group C(P=0.000). Tumor weight was (4.39±0.40)g in Group A,(3.78±0.65)g in Group B and (3.36±0.41)g in Group C(P=0.000). (3). Expressions of MMP2 protein: In Group A, B, C, respectively, the mean optical density was 0.2052±0.0167,0.1980±0.0332,0.1711±0.0284 (P=0.022) in tumor tissue and 0.2081±0.0199, 0.1726±0.0073, 0.1396±0.0079 (P=0.000) in paratumor tissue. (4). Expressions of CD34 protein: In Group A, B, C, respectively, the mean optical density was 0.2310±0.0226, 0.2219±0.0154, 0.1886±0.0180 (P=0.000) in tumor tissue and 0.2198±0.0505, 0.1761±0.0237, 0.1108±0.0046 (P=0.000) in paratumor tissue. CONCLUSION: 1.CO₂ gas promotes the growth of VX2 tumor in rabbit liver. MMP2 stimulates tumor angiogenesis. 2. Matrix metallo- proteinase inhibitor can partially inhibit the growth of VX2 tumor in rabbit liver. 3. The change of expressions of MMP2 may play an important role in malignant tumor growth and metastasis after laparoscopic surgery.