Increased metastases are associated with inflammation and matrix metalloproteinase-9 activity at incision sites in a murine model of peritoneal dissemination of colorectal cancer

Background: Pro-inflammatory processes associated with the early postoperative state are known to contribute to peritoneal metastases in patients with advanced diseases. This study aimed to determine whether the wound healing response after an abdominal incision leads to increased matrix metalloproteinase (MMP)-9 activity locally, contributing to peritoneal metastasis. Materials and methods: Metastatic tumors were initiated in C57bl/6J male mice (8 wk of age) using a peritoneal injection model with syngeneic MC38 murine colon cancer cells; appropriate control mice also were studied. Injections were performed into the peritoneum in the right lower quadrant. We then observed the occurrence and rate of peritoneal metastasis for each group. Results: By making an incision into the abdominal wall of mice, an inflammatory response was induced at the wound site. The inflammatory response initiated by the wound, in turn, increased the proliferation of mesothelial cells and increased inflammatory cell numbers locally, which contributed to an increase in parietal peritoneal metastases. In addition, the wound healing process increased the expression of pro-inflammatory cytokines and the number of inflammatory cells in the peritoneum. Moreover, MMP-9 in the modeled postoperative injury setting increased the number and severity of peritoneal metastases. Conclusions: Thus, we conclude that wound-associated inflammation enhances pro-MMP-9 expression, which plays a key role in the growth and progression of cancer cells associated with peritoneal metastases.