The impact of zymosan-induced acute inflammation on progression and metastasis in pancreatic cancer animal model

Abstract

Introduction Although clinically, acute inflammation is thought to influence the growth of cancer, there have been no preclinical studies on the relationship between acute inflammation and cancer progression. The aim of this study was to evaluate the impact of acute inflammation on cancer progression in an animal model concerning morphological change as well as molecular features reflecting the epithelial-to-mesencymal transition (EMT) and circulating tumor cells (CTC). Method and materials Murine pancreas ductal adenocarcinoma cell line (Panc-02) and zymosan were used for the induction of cancer and acute inflammation respectively, in C57/BL6 mice. In the control group (n=10, C group), 2x107 Panc02 cells were injected into the tail of the pancreas and the mice were sacrificed after 4 weeks. In the second group (n=10, Z1 group), Panc02 cell injection was performed and 1 week later, 3mg of zymosan was injected intraperitoneally. The mice were sacrificed 4 weeks after tumor cell injection. In the third group (n=10, Z2 group), after Panc02 cell injection, intraperitoneal injection of zymosan was performed at 1 and 2 weeks after tumor injection respectively, and the mice were sacrificed 4 weeks after tumor cell injection. Histopathological analysis of tumor progression and inflammatory cell infiltration in the three groups was done. Expressions of EpCAM,muc1, E-Cadherin, Snail1, NLRP3 and miR-155 in the tissues were analyzed by confocal microscopy. Additionally, expression of E-Cadherin, Snail1 and Vimentin in the liver tissues were analyzed by reverse transcription polymerase chain reaction (RT-PCR) and western blot. Results Among the 30experimental mice, seven were excluded four died before autopsy and three displayed no tumors. Autopsies were performed in the remaining 23 mice. Histopathological analysis showed that the tumor volume of the Z2 group was larger than that of the C group (P=0.021) and the presence of liver metastasis was significantly more common in the Z2 group than in the C and Z1 groups (P=0.025). The degree of inflammation was also more severe in the Z2 group than in the other two groups. Confocal microscopy analysis revealed significantly more expression of EpCAM, muc1,NLRP3 and miR-155 in the liver and pancreas in the Z2 group than in the other two groups. EpCAM and muc1 was detected in blood samples in the Z2group by confocal microscopy and flow cytometry, but not in the other two groups. On RT-PCR and western blot analysis, expression of Snail1 and Vimentin1 in the Z2 group were stronger in the liver compared to the C group. On the contrary, E-Cadherin expression in the Z2 group was weaker compared to the C group. Conclusion Our results showed that acute inflammation accompanied with cancer promotes cancer progression.