Human Umbilical Cord Mesenchymal Stem Cells Promote The Prostate Cancer Cell Line PC3 Proliferation

Background and purpose:The role that the stem cell plays in the tumorigenesis is currently one of the hot topics in the field of the cancer study. In this study, we isolated, cultured and identified mesenchymal stem cells from human umbilical cord to study the effect of the umbilical cord-mesenchymal stem cells(UC-MSCs) on the proliferation of the prostate cancer cell line PC3 and the mechanisms underlying the proliferation. Materials and methods:The umbilical cords used in the study were obtained with an informed consent from the second hospital of Jilin University. The umbilical cords were cut into pieces, attached to the bottom of cell culture flasks and cultured in an incubator. After 7 to 14 days, we collected the cells growing from the pieces, transferred them to a new flask and continue to culture in the incubator. The isolated stem cells were identified by the test of osteogenic differentiation and adipogenic differentiation. We first studied the effect of the UC-MSCs on the proliferation of 8 tumor cell lines. We cultured the 8 tumor cell lines in a conditioned medium of UC-MSCs(CM) and set a corresponding serum-free culture medium(DMEM/RAPI-1640) as a control. The PC3 cells were chosen for the entire study because the effect of the CM on the viability of PC3 cells was significant. We further confirmed that CM was able to promote the proliferation of the PC3 cells. According to the published papers, we hypothesized that osteoprotegerin(OPG) might be a key element in the CM mediated the proliferation of the PC3 cells. To confirm our hypothesis, we detected m RNA expression of OPG in the UC-MSCs, the PC3 cells and two other normal cell lines, tested the effect of OPG on the viability of the 8 tumor cell lines, studied the effect of CM that was neutralized with an anti-OPG antibody on the viability of the PC3 cells. Finally, we studied the effect of the CM on phosphorylation of the Erk in the PC3 cells and the effect of a MAPKK inhibitor on the viability of the PC3 cells. At last, we investigated whether MSCs would trip to PC3 cells in vitro by transwell experiment. The experimental techniques used in the study included flow cytometry, immunofluorescence, co-culture, RT-PCR, MTT and Western Blot. Results:We successfully isolated and identified the mesenchymal stem cells from the human umbilical cord. After screening eight different types of tumor cell lines with MTT experiment, we found that the viability of the PC3 cells cultured in the CM was increased 2.7 folds than those cultured in the control serum-free RAPI-1640 medium. The changes in the viability of the cells from other cell lines cultured in the CM are not statistically significant when comparing with the cells cultured in the control serum-free RAPI-1640 medium. We found that the expression level of OPG m RNA were about 1.7 folds higher in the umbilical cord-MSC than that in 3 other cell lines, and OPG was able to stimulate the proliferation of the PC3 cells and not to other cells from the 7 tumor cell lines. The proliferation of the PC3 cells was 1.3 folds higher in the OPG added group than that in the control group. When the CM was neutralized with anti-OPG antibody, the effect of OPG increasing in the viability of PC3 was eliminated indicating that OPG that produced by UC-MSCs was responsible for the effect. In the study, we also found that the CM was able to increase in the phosphorylation of the ERK, and MAPKK inhibitor was able to inhibit the increase in the viability of the PC3 cells cultured in the CM. More MSCs did the migration movement with the presence of PC3 cells. Conclusions:1. OPG produced in the human UC-MSCs could be a key molecule that mediated the effect of the CM-stimulated proliferation of the PC3 cells and the MAP kinase signaling pathway in the PC3 cells cultured with the CM may be activated2. MSCs move toward to PC3 cells in vitro.