Background Interactions of tumor cells with the microenvironment were deemed to promote the tumor invasion and metastasis. CXC chemokine receptor 4 （CXCR4） and extracellular matrix metalloproteinase inducer （EMMPRIN） had reported to participate in this process. However the roles of bone marrow microenvironment in leukemic infiltration were not well investigated. Methods A co-culture system between SHI-1 cells and bone marrow stromal cells （BMSCs） is used to simulate the interactions of leukemic cells with their microenvironment. The trans-matrigel invasion was used to detect the capability of SHI-1 cells invasion. The BMSCs and SHI-1 cells were mixed in a ratio of 1：10 and added to the millicell chamber coated with matrigel. Either the co-culture supernatant or the functional blocking peptide of CXCR4 and EMMPRIN were added to the trans-matrigel invasion system. The expressions of EMMPRIN in SHI-1 cells and BMSCs were detected by RT-PCR. The changes of the expression of matrix metalloproteinase-2, 9 （MMP-2, MMP-9）, tissue inhibitor of metalloproteinase 2 （TIMP-2）, and CXCR4 mRNA in SHI-1 cells were determined by real-time PCR. The concentration of stromal cell derived factor 1 （SDF-1） in serum free supernatant was measured by ELISA. Results Both SHI-1 cells and BMSCs express EMMPRIN. SHI-1 cells could hardly invade the matrigel membrane; the co- culture supernatant did not induce the invasion of SHI-1 cells. When contacting directly with BMSCs, SHI-1 cells invaded to the lower chamber of millicell were significantly increased. The functional blocking peptide of CXCR4 and EMMPRIN could significantly inhibit the invasion triggered by BMSCs. When co-culturing with BMSCs, the expression of CXCR4, MMP-2, MMP-9 and TIMP-2 mRNA in SHI-1 cells were significantly elevated in company with a significantly higher level of SDF-1 in the co-cultured serum-free supernatant. Conclusion The interactions of leukemic cells and BMSCs play important roles in leukemic cell infiltration.
LI Zhen-jiangCHEN Zi-xingCEN Jian-nongHE JunQIU Qiao-cheng
