The Effects And Mechanism Of Lipopolysacchride On The Process Of Hepatic Metastasis Of Colorectal Carcinoma

Colorectal cancer(CRC) is one of the most commonly diagnosed cancers in the digestive tract.In China, the incidence of CRC has been increasing year by year, and it ranks the third leading cause of cancer-related death. Liver metastases occur in more than 50% of patients with CRC synchronously or metachronously, which imply the poor clinical therapeutic effect and become the primary cause of mortality of CRC.The seed and soil theory has been put forward to explain the probablemechanism of tumor metastasis for more than one hundred years. In recent years, increasing researches produce more and more proof to support this theory that the occurrence of distant metastasis attributes to not only the characteristics of cancer cells, but the microenvironment of distinct target organs and the interaction between them. Therefore, we hypothesize that this theory could also account for the hepatic metastasis of CRC.The endotoxemia is a common feature of CRC due to the obstruction of digestive tract which lead to the bacterial overgrowth、flora disequilibrium、the increased production and absorption of LPS. Emerging studies suggest that LPS could not only activate the immune system, but also play an important role in the tumor local progression and metastasis. In this study, we will explore whether LPS promotes the development of hepatic metastases of CRC.Stromal cell derived factor(SDF-1)/CXCR4 axis was initially described to regulate the homing of lymphocytes in inflammatory tissues. However, Recent studies have highlighted the importance of SDF-1/CXCR4 axis in the local progression and metastasis of various cancers including lung, pancreatic and breast cancers, as well as the CRC. The targeted organ produce and excrete SDF-1, attracting the migration of tumor cells which express the CXCR4 along the concentration gradient. In this study, we will explore whether LPS could activate the SDF-1/CXCR4 axis by inducing the produce of SDF-1 in liver and augmenting the expression of CXCR4 in tumor cells.Epithelial-mesenchymal transition(EMT) is a key process that is necessary during embryonic development. Recent studies suggest that EMT is associated with caner local invasion and distant metastasis by which cancer cells could acquire stronger invasive ability and stem cell properties. We hypothesize that EMT may be one of themechanisms involved in the development of hepatic metastasis promoted by LPS.Based on the above analyses, the study consists of three parts: first, the effect of LPS on the liver injury and the development of hepatic metastasis of CRC; secondly, the activation of SDF-1/CXCR4 and EMT is the potential mechanism underlying enhanced invasive capacities of CRC cells induced by LPS; finally, the statistic correlation between the expression of CXCR4 of CRC patients and the Clinic prognosis.Part I The effect of LPS on the development of hepatic metastasis of CRC in vivo.We first used mouse colon cancer cell line C26 and mouse splenic vein metastasis assay to research the role of LPS in the liver metastasis. The results demonstrated that LPS treating the C26 cells and mouse liver simultaneously promote the most occurrence of liver metastases, indicating that LPS could affect on both tumor cells and liver tissue. Next, we manufacture the survival curve of the experimental animals, which indicated that LPS could worsen the prognosis of the Laboratory models. Furthermore, ELISA and Western-blot analyses results suggest that LPS could induce the produce of SDF-1 of liver cells, indicating SDF-1/CXCR4 axis endowed LPS with the effect on hepatic metastasis.Part II The activation of SDF-1/CXCR4 and EMT is the potential mechanism underlying enhanced invasive capacities of CRC cells induced by LPS.Wound healing and Transwell assay were performed to detected the alteration of the invasive capacities of tumor cells treated by LPS. Next, RT-PCR、Western-blot analysis and immunofluorescence were employed to measure the CXCR4 gene expression, the results showed that LPS could promote the expression of CXCR4 on tumor cells. AT last, the expression of EMT-related genes were detected showing that the tumor cells managed by LPS undergone EMT.Part III The statistic correlation between the expression of CXCR4 of CRC patients and the Clinic prognosis.We obtained the primary CRC tissue samples from 80 patientsundergoing surgical resection of primary CRC at the Department of Surgery, Eastern Hepatobiliary Surgery Hospital of the Second Military Medical University since 2000 and all of the specimens were subjected to Immunohistochemistry for staining of CXCR4. According to the positive CXCR4 expression, all patients were divided into two groups: the high expression group(n=44) and low expressiongroup(n=36). The higher expression of CXCR4 of CRC was significantly correlated with lymphatic metastasis and hepatic metastasis. The survival curve also showed that there is a more poor prognosis in the patients with higher expression of CXCR4.Above all, the following conclusion could be drawn:1、LPS promote the development of hepatic metastasis of CRC.2、SDF-1/CXCR4 axis and EMT are involved in hepatic metastasis of CRC promoted by LPS.3、The high expression of CXCR4 worsen the prognosis of CRC patients.