Role Of β2 Adrenergic Receptor In Breast Cancer Metastasis And Regulating Chemokine Receptor CXCR4

Objective:To investigate the role ofβ2 adrenergic receptor(β2-AR.) in breast cancer invasion and metastasis.To study the effect ofβ2-AR on chemokine receptor CXCR4.Methods:The expression ofβ2-AR in human breast cancer cell lines was determined using reverse transcription-polymerase chain reaction(RT-PCR) and immunocytochemistry (ICC).The cell cycle and cell proliferation of breast cancer cells MDA-MB-231 cultured withβ2-AR agonists were observed using flow cytometry and alive cell count agents CCK-8 respectively.The invasion capability of MDA-MB-231 cells induced byβ2-AR agonists was detected using transwell invasion assay.After stable transfection with the vector containing human entire coding sequence ofβ2-AR,the transfected cells MDA-MB-435_β2-AR were identified by RT-PCR and ICC,and the cell cycle and cell proliferation were observed using flow cytometry and growth curve.The effect ofβ2-AR-transfection on cell invasion was defined by transwell.The expression ofβ2-AR in 90 female primary breast cancer samples and 23 normal or benign breast diseases tissues was determined using immunohistochemistry(IHC),and then analyzed their relationship with clinical feature, furthermore,followed up the breast cancer patients.Human breast cancer cells(MDA-MB -231,MDA-MB-435) were injected orthotopically into BALB/c female nude mice,and then stimulatedβ2-AR by immobilizing the mice in cages or administratingβ2-AR agents carried within mini osmotic pumps.The effect ofβ2-AR on chemokine receptor CXCR4 was investigated using functional gene microarray,Real-time PCR,Western Blot and transwell.Results:.Although absent in breast cancer cell lines MDA-MB-435,MDA-MB -435HM,MCF-7 and T47D,β2-AR was present in normal human breast epithelial cell HBL-100 and breast cancer cell lines BT-549,HCC1937 and BCaP-37.Furthermore,β2-AR was highly expressed in MDA-MB-231,MDA-MB-231HM and MDA-MB-468 cells.β2-AR agonists not only enhanced the G₂/M proportion and cell proliferation of MDA-MB-231 cells,but also induced MDA-MB-231 cells invasion.β2-AR-overexpression can enable MDA-MB-435 cells to be attracted byβ2-AR agonists.In contrast to the non-enhanced expression in all the 23 normal or benign breast diseases tissues,β2-AR was intensely expressed in 21%(19/90) primary breast cancer samples.Strong expression is very positively correlated with lymph node metastasis(P=0.011 ).However,there still were 20%samples withoutβ2-AR presence.β2-AR agonists can down regulate the expression and function of chemokine receptor CXCR4 viaβ2-AR.Conclusions:β2 adrenergic receptor may play an important role in breast cancer metastasis.