Inhibition Of CXCR4/SDF1-α Signaling With CXCR4 Antagonist Overcomes Resistance In Acute Myeloid Leukemia

Acute myeloid leukemia(AML)is a group of heterogeneous leukemias,which originates from the clonal expansion of malignant hematopoietic precursor cells,is prone to relapse and drug resistance,and the five-year survival rate is 20%-25%.Recent studies have shown that CXCR4/SDF1-α signaling pathway plays an important role in the progress and development of AML;clinical evidence also suggested that the cell surface expression level of CXCR4 is closely related to the prognosis of AML patients.In this study,we first investigated whether POL(a new type of CXCR4 antagonist)can inhibit the activity of CXCR4/SDF1-α signaling pathway in AML cells.The results showed that the cell surface expression level of CXCR4 on the AML cells was significantly reduced by POL treatment,therefore their migrantion to stromal cells and high concentrations of SDF1-α were significantly inhibited.In addition,we also found that phosphorylation of CXCR4 in AML cells was effectively inhibited,as well as the the phosphorylation of the key signaling pathway proteins ERK and AKT downstream of CXCR4 that contributes to the survival of leukemia cells.To evaluate the mobilization effect of POL on leukemia cells in vivo,a Ba/F3-ITD leukemia mouse model was employed.POL was injected subcutaneously into the mice on the 10 th day after cell transplantation,and peripheral blood was collected 1 hour before and 1 hour after injection to calculate the number of circulating AML cells.The results proved that POL administation can mobilize AML cells to the peripheral blood circulation in mice.Furthermore,using the above-mentioned leukemia model,we administered POL treatment one hour before each treatment with the chemotherapy drug Ara-C.The results showed that the combined treatement can significantly reduce the leukemia burden in the mice compared to Ara-C treatment alone,and the survival rate of mice was prolonged by about 35%.Next,we further investigated the mechanisms of CXCR4/SDF1-α signaling pathway and AML resistance.Our results showed that the activation of CXCR4 signal promotes autophagy in AML cells and inhibits Ara-C-induced apoptosis.SIRT1 plays an important role in CXCR4/SDF1-α signaling and autophagy: the activation of CXCR4 signaling upregulates the expression of SIRT1,and the interaction of SIRT1 with autophagy-related proteins ATG5 and LC3 up-regulates the level of autophagy.Correspondingly,the combined use of autophagy inhibitors and Ara-C significantly increases the sensitivity of AML cells to Ara-C both in vitro and in vivo.In addition,we also confirmed that the expression level of CXCR4 on the cell surface in primary AML samples is positively correlated with the expression levels of SIRT1 and other autophagy-related proteins.In summary,the activation of the CXCR4/SDF1-α signaling pathway in AML cells can up-regulate the level of autophagy and reduce apoptosis induced by chemical drugs,which helps them survive under selective pressures such as Ara-C.The combined use of CXCR4 antagonists,autophagy inhibitors and chemotherapeutic drugs may help improve the efficacy of AML.The above results will provide a reference and theoretical basis for the development of new clinical AML treatment programs.