Molecular mechanisms underlying postoperative peritoneal tumor dissemination may differ between a laparotomy and carbon dioxide pneumoperitoneum: a syngeneic mouse model with controlled respiratory support

The mechanisms promoting postoperative peritoneal tumor dissemination are unclear. This study aimed to investigate postoperative tumor dissemination over time on both tissue and molecular levels.For this study, C57BL6 mice were randomized into four groups: anesthesia alone (control), carbon dioxide (CO(2)) pneumoperitoneum at low (2 mmHg) or high (8 mmHg) intraperitoneal pressure (IPP), and laparotomy. A mouse ovarian cancer cell line (ID8) was injected intraperitoneally just before surgery. The groups were further subdivided into three groups, and a laparotomy was performed to evaluate tumor dissemination on postoperative day (POD) 7, 14, or 42.The incidence of cancer cell invasion into the muscle layers of the abdominal wall was significantly higher in the laparotomy and high-IPP groups than in the low-IPP and control groups on PODs 7 and 42. Expression levels of beta 1 integrin, cMet, urokinase-type plasminogen activator (uPA), urokinase-type plasminogen activator receptor (uPAR), and type-1 plasminogen activator inhibitor (PAI-1) mRNA in the disseminated nodules were not significantly different among the four groups on POD 7. However, the expression levels of all these genes in the disseminated nodules in the laparotomy group were significantly higher on POD 14 than on POD 7. They then returned to control levels on POD 42. There were no significant differences in the expression levels of any of these genes among the groups on POD 42.The current study suggests that the molecular mechanisms underlying postoperative peritoneal tumor dissemination may differ between a laparotomy and CO(2) pneumoperitoneum. Therefore, strategies targeting postoperative tumor dissemination likely will need to account for the surgical environment.