Expression And Function Of Stromal Cell-derived Factor1Receptor CXCR7in Human Acute Leukemia

Background and objective：The rapid proliferation, adhesion, migration and drug resistance of leukemia cells areimportant biological characteristics of acute leukemia. They are also the momentousreasons of the clinical treatment failure in malignant hematologic diseases. The presentresearches indicate that stromal cell-derived factor-1(SDF-1) secreted by bone marrowstromal cells can regulate the bone marrow microenvironment via stimulating CXCR4(CXCchemokine receptor4) receptor. SDF-1/CXCR4axis has a wide range of effects onregarding to tumor process, but the primary role of SDF-1/CXCR4appears to be the therecruitment of hematopoietic cells, establishment of tumor cells within the tumormicroenvironment, proliferation, adhesion or infiltration of tumor cell, and theneoangiogenesis or formation of tumor vasculature.CXCR7(CXC chemokine receptor7, CXCR7) is a recently appraised receptor for thechemokines CXCL12and CXCL11(I-TAC). It is a seven-transmembrane receptor coupledto G proteins and composed by three hundred and sixty two amino acid sequences. TheCXCR7gene maps are located in mouse chromosome1and human chromosome2, inwhich the genes encoding CXCR1, CXCR2, and CXCR4are located. Recent study in solidtumor has found that CXCR7is highly expressed in many tumor cell lines and mediatesproliferation or apoptosis of these cells. SDF-1/CXCR7reinforces adhesion and infestationof tumor cells by regulating cell adhesion molecule(CAM). Overexpressed CXCR7regulates the neoangiogenesis and formation of tumor vasculature by up-regulating theexpression of angiogenesis factors such as IL-8(interleukin-8) and VEGF(vascularendothelial growth factor). Some small molecular inhibitors, siRNA, or blocking antibodieshave already been used in experimental models in vitro and in vivo. They can significantlyinhibit the tumor growth and metastasis in mammary adenocarcinoma, lung cancer, andprostatic cancer. Thus, SDF-1/CXCR7axis can be used as a new therapeutic target for thetreatment of malignant tumor. The expression and function of CXCR7in malignant hematologic neoplasms have notbeen reported on domestic and overseas yet. This experiment aims to investigate theexpression of CXCR7in acute leukemia bone marrow cells and acute leukemia cell lines. Weobserved the proliferation and adhesion of THP-1cells which were co-cultured with bonemarrow stromal cells after inhibiting SDF-1/CXCR7by using anti-CXCR7monoclonalantibody11G8so as to investigate the relationship between the expression of CXCR7andacute leukemia, find out the changes of biological characteristics of leukemic cells afterblocking SDF-1/CXCR7. We wish to provide some reliable experimental evidence for theexploration of a new method in the clinical treatment of acute leukemia.Methods:1. The expression of CXCR7in acute leukemia bone marrow cells.The bone marrow biopsy specimen were obtained from25patients with acutelymphocytic leukemia(ALL),19patients with acute myeloid leukemia (AML) and17normal people.(1)The expression of CXCR7in bone marrow cells were observed by Flow cytometryanalysis.(2)The expression of CXCR7in bone marrow cells were observed by Western-blotmethod.2. The expression of CXCR7in acute leukemia cell lines.(1)Human acute monocytic leukemia cell line THP-1, Human acute promyelocyticleukemia cell line HL-60and human acute T lymphocytic leukemia cell line Jurkat werecultured.(2)The expression of CXCR7in these cell lines were observed by Flow cytometryanalysis.3. The relationship between the change of proliferation and adhesion rate of THP-1cells and the inhibition of CXCR7by using11G8.(1)Human acute monocytic leukemia cell line THP-1were cultured. The bone marrowbiopsy specimen were obtained from10normal people.(2)Cultivate bone marrow stromal cells.(3)THP-1cells were co-cultured with bone marrow stromal cells(4)The proliferation rate of THP-1cells was observed by CCK-8method. (5)The adhesion rate of THP-1cells was observed by CCK-8method.Results:1. The expression of CXCR7in acute leukemia bone marrow cells.(1)The expression level of CXCR7in AML group was19.03±3.84%, in ALL groupwas3.34±1.71%and in normal group was2.40±1.27%.(2)The expression level of CXCR7had significant difference between AML group and normal group(p<0.01).(3)Theexpression of CXCR7in AML group was higher than ALL group (p<0.01).(4)In addition,there was no notable distinction between ALL group and normal group (p>0.05).2. The expression of CXCR7in acute leukemia cell lines.(1)The expression level of CXCR7in THP-1cells was69.05±3.04%, in HL-60cellswas20.17±1.53%and in Jurkat cells was3.41±2.46%.(2)The expression level of CXCR7was significantly higher in THP-1cells, as compared with HL-60cells and Jurkatcells(p<0.01), besides, the expression level of CXCR7in Jurkat cells was dramaticlly lowerthan in HL-60cells(p<0.01).3. The relationship between the change of proliferation and adhesion rate of THP-1cells and the inhibition of CXCR7by using11G8.(1)The bone marrow stromal cells and THP-1cells grew well in the co-culture system.(2)The changes of growth curve in each THP-1group were similar, the proliferation wasnot obvious in initial48hours and cells entered the logarithmic growth phase after48hours.Compared with two THP-1groups, the rise of growth curve in control group wassignificantly higher than experimental group,which indicated that proliferation rate could benotablely decreased by11G8(p<0.05).(3)The adhesion rate of THP-1cells was(39.16±5.33)%in control group after co-culturing for24hours and was (14.24±3.70)%inexperimental group. The adhesion rate in experimental group was dramaticlly lower thancontrol group(p<0.05).Conclusion:1. The experssion level of CXCR7in AML group was dramaticlly higher than ALLgroup and normal group. It meant that CXCR7might be connected with the generation anddevelopment of AML.2. The experssion level of CXCR7in THP-1cells and HL-60cells were both higher thanJurkat cells. 3The proliferation of THP-1cells was significantly descend, and the adhesion ofTHP-1cells to bone marrow stromal cells was obviously decreased after inhibitingSDF-1/CXCR7by using anti-CXCR7monoclonal antibody11G8, which indicated thatCXCR7might play an important role in proliferation and adhesion of leukemia cells.