Experimental Study On The Tropism Of Umbilical Cord Blood Mesenchymal Stem Cells For The Gastric Carcinoma Xenografts And Its Molecule Mechanism.

Objective:To study the tropism of human umbilical cord blood msenchymal stem cells for gastric carcinoma xenografts and the molecule mechanism involved in the process.Methods:1.Morphological observation of MSCs and fibroblasts in different organs of hairless mice in the animal experiment:SGC-7901gastric cancer cells were injected subcutaneous at one side of the inguinal groove in the hairless mice to establish the animal model.Then mesenchymal stem cells labeled with fluorescent dye SP-DiI were injected at the opposite side.Ten days later,sacrifice the mice and the gastric carcinoma xenografts,liver,spleen,lung and the tissue of injected point were obtained.C ryosections from frozen tissues were processed for fluorescent microscopy and the distribution of MSCs and fibroblasts in different organs were observed.Adjacent sections were stained with H&E.2.RT-PCR method was used to detect the expression of CXCR4 mRNA in SGC-7901,MGC80-3 gastric cancer cells and HT-29 colon carcinoma cells,as well as the expression of SDF-1 mRNA in msenchymal stem cells.Investigate the role played by CXCR4/ SDF-1 axis in the process of tropism between cancer cells and MSCs.3.Fluorescent quantitative PCR and immunohistochemistry method were performed to understand the function of CXCR4/SDF-1 axis in lymph node metastasis in gastric cancer:40 clinical specimens were obtained and the expression of CXCR4 mRNA in cancer and normal mucous membrane and SDF-1 mRNA in lymph node around the stomach were detected.Results:1.Human umbilical cord blood msenchymal stem cells were mainly distributed in gastric carcinoma xenografts,but were not found in other organs.While fibroblasts were mainly observed in the tissue of injected point,but found none in other organs.2. The Fluorescent quantitative RT-PCR results revealed that the expression index of CXCR4 mRNA in gastric cancer(1.624±1.380)was significantly higher than that in normal mucous membrane(1.072±0.524)(P＜0.05).Also the expression index of CXCR4 mRNA in gastric cancer with lymph node metastasis(0.823±0.551)was significantly higher than that without lymph node metastasis(0.392±0.338)(P＜0.05).Significance differences in the expression index of SDF-1 mRNA were found between lymph node with metastasis of gastric cancer(0.5432±0.4907) and normal lymph node(0.2640±0.2601).The positive expression of SDF-1 mRNA in lymph node with metastasis of gastric cancer was consistent with the positive expression of CXCR4 mRNA in gastric cancer(r=0.776,P＜0.01).3.The result of immunohistochemistry displayed that the positive rate of CXCR4 in gastric cancer(70.0%) was significantly higher than that in normal mucous membrane(27.5%)(P＜0.05).The expression levels of CXCR4 were closely correlated with differentiation level,lymph node metastasis,clinical stage and Borrmann type(P＜0.05),but have no relationship with patients' age,sex,the size and position of tumor(P＞0.05). Significance differences in the positive rate of SDF-1 between lymph node with metastasis of gastric cancer(75.0%) and normal lymph node(27.5%) were found(P＜0.05).Conclusion:1.Human umbilical cord blood msenchymal stem cells have the tendency of migrating to tumor sites in animal body,so it can be hopefully used in the diagnosis and treatment of gastric cancer.2.CXCR4 was expressed in cancer cells while SDF-1 was expressed in MSCs and lymphocytes,which is accord with the fact that SDF-1 and CXCR4 can be mutual attraction in the CXCR4/SDF-1 axis.3.The CXCR4/SDF-1 axis plays an important role in the course of lymph node metastasis in gastric cancer.The mutual attraction between SDF-land CXCR4 leads to the lymph node metastasis.This phenomenon provides indirect evidences for the molecule mechanism of tropism.