A Potential Mechanism of Tumor Progression during Systemic Infections Via the Hepatocyte Growth Factor (HGF)/c-Met Signaling Pathway.

Increasing evidence has demonstrated that postoperative infectious complications (PICs) after digestive surgery are significantly associated with negative long-term outcomes; however, precise mechanisms of how PICs affect the poor long-term survival remain unclear. Here, we focused on the hepatocyte growth factor (HGF)/c-Met signaling pathway as one of those mechanisms. In the clinical setting, serum HGF levels were measured in the patients with sepsis and those with PICs after undergoing esophagectomy. Using a liver metastasis mouse model with cecal ligation and puncture (CLP), expressions of HGF and the roles of the HGF/c-Met pathway in the progression of tumor cells were examined. Serum HGF levels were very high in the patients with intra-abdominal infection on postoperative days (PODs) 1, 3, and 5; similarly, compared to the patients without PICs, those with PICs had significantly higher serum HGF levels on 1, 3, and 5 days after esophagectomy. The patients with PICs showed poorer overall survival than those without PICs, and the patients with high serum HGF levels on POD 3 showed poorer prognosis than those with low HGF levels. Similarly, at 24 and 72 h after operation, serum levels of HGF in CLP mice were significantly higher than those in sham-operated mice. Intraperitoneal injection of mouse recombinant HGF significantly promoted liver metastases in sham-operated mice on 14 days after surgery. Knocking down c-Met expression on NL17 tumor cells by RNAi technology significantly inhibited the promotion of CLP-induced liver metastases. Infections after surgery increased serum HGF levels in the clinical as well as experimental settings. Induction of high serum HGF levels by CLP promoted liver metastases in a murine liver metastasis model, suggesting the involvement of the HGF/c-Met signaling pathway in tumor promotion mechanisms. Thus, targeting the HGF/c-Met signaling pathway may be a promising approach for malignant tumors, particularly in the patients with PICs.