Tumor interstitial fluid and gastric cancer metastasis: An experimental study to verify the hypothesis of “tumor-phlegm microenvironment”

Objective:To extract tumor interstitial fluid(TIF) from MKN-45 gastric cancer which is similar to "muddy phlegm" in Chinese medicine and observe influences of MKN-45 tumor interstitial fluid(MKN-45 TIF) intervention on metastasis of gastric cancer and on the expressions of vascular endothelial growth factor(VEGF), kinase insert domain containing receptor(KDR),epithelial-cadherin(E-cad),cyclooxygenase-2(COX-2),intercellular adhesion molecule-1(ICAM-1) and telomerase genes and proteins in primary tumor tissue.Methods:An MKN-45 tumor-bearing model was established in 50 nude mice.The modeled animals were equally randomized to 5 groups: the simple tumor-bearing group(model group),the normal saline(NS) via tail vein injection(i.v.) group(NS i.v. group),MKN-45 TIF i.v.group(TIF i.v.group),NS intraperitoneal injection(i.p.) group(NS i.p.group),and MKN-45 TIF i.p.group(TIF i.p.group).The TIF and NS intervention groups received injection(i.p.or i.v.) of MKN-45 TIF or NS twice a week,0.2 mL at a time.After 8 weeks,the primary tumors were removed,weighed and HE stained to observe tumor metastasis.The primary tumor tissues were analyzed by immunohistochemistry and real-time quantitative PCR to detect expressions of VEGF,KDR,E-cad,COX-2,ICAM-1,and telomerase genes and proteins in different groups.Results:There were significant differences in tumor weight between TIF intervention groups and the model and NS intervention groups.Tumor metastasis was observed in all 5 groups,but the tumor metastasis rate in TIF intervention groups was significantly higher than those in the model and NS intervention groups.The gene and protein expressions of gastric cancer-related factors VEGF,KDR,COX-2,ICAM-1 and telomerase were unregulated while the gene and protein expressions of E-cad were downregulated in TIF intervention groups. Conclusions:TIF promotes tumor growth,invasion and metastasis of gastric cancer.These findings provide preliminary experimental clues for verifying the hypothesis of "tumor-phlegm microenvironment".