| Objective Gr-1+CD11b+ myeloid-derived suppressor cells(MDSCs) are a subset of bone marrow-derived immune cells which preferentially infiltrates the primary tumor and actively promotes cancer cell dissemination.The kind of tumor-infiltrating MDSC strikingly accumulate and expand in the tumor-bearing mice, combined with tumor progression. The expression level of CD40 was observed to significantly correlate with MDSCs’ accumulation and CD40-induced MDSC apoptosis partly is potential attender. However, whether CD40 is a mediator of MDSCs’ migration has not yet been thoroughly investigated. The present study aimed to analyze the differences of chemokine expression between CD40+MDSC and CD40-MDSC, in order to preliminarily demonstrate that CD40 mediate the expression level of CXCR5 on MDSC which play a pivotal role in the pathophysiological events of MDSCs’ migration,recruiting and accumulation.Methods The purified CD40+MDSCs and CD40-MDSCs were analyzed on the flow cytometry in order to measure the expression level of CXCR5 on them. In vitro assay purified MDSCs showed that CXCR5-CXCL13 chemokine receptor-ligand pair signaling pathway is used to compare the migrated capacity of CD40+MDSC with CD40-MDSC. WT and CD40-/- knockout mices were injected subcutaneously with MFC to build tumor-bearing mice models. The expression levels of tumor-infiltrating MDSC and CD40 expressed on MDSC were detected dynamically by flow cytometry. The test of mouse tumorigenicity was used to observate the growth trend of gastric tumor in WT and KO mice, validating the migrated ability for tumor formation. of CD40+MDSC and CD40-MDSC.Results( 1) Our flow cytometry indicated that CXCR5 expressed on purified CD40+MDSCs is specially increased(77.33±3.29%) comparing with CD40-MDSCs(1.62±0.85%).( 2) In vitro transwell assays showed that CD40+MDSCs were significantly attracted to the mixed solution of MFC containing CXCL13 recombinant relative to without that(104.2±17.9 vs 50.2±7.2,p<0.01). CXCL13 respectively in concentration( 125,250,500 ng/m L) statistically was elevated, the migrated rate of MDSC significantly increased(119.4 ± 11.8, 125.2 ± 25.3, 149.8 ± 18.8; p<0.05).The mount of CD40-MDSC migrating to the mixed solution was increased comparing with the control group(61.2±17.3 vs 41.7±3.8,p<0.05),but the number of migration had no difference between grounps containing CXCL13 recombinant(75.4±9.5,78.2±15.6,76.2±14.8).( 3) MDSCs in tumor tissue of WT mice were significantly more overproduced than that of KO mice(8.97±0.81% vs 2.96±0.92%;p<0.01),and the expressed percentage of CD40+MDSCs in tumor-infitating MDSC was apparently higher than CD40-MDSC(68.58±7.35% vs 31.52±7.18%,p<0.01);there is no difference between CXCR5 expressed on CD40+MDSCs of tumor tissue and bone marrow(72.93±2.05 % vs 77.33±3.29%).( 4) It was found that tumor formation occurred at different time-point.The tumor of WT mice form at the 5th day after MFC inoculated and that of KO mice form at the 7th day.As for the tumorous morphology, the tumors in WT mice were more bigger and irregular.Conclusion( 1) CD40 as critical molecules controls the expression level of CXCR5 on MDSC.Downregulation of CD40 expression can reduce its ability of migration,involved in regulating accumulated mechanism of MDSC.( 2) Under the pathological condition of gastric carcinoma,CXCR5-CXCL13 axis played an important role in inducing the migration of CD40+MDSC.( 3) CD40 improves MDSCs’ chemotactic migrated ability to promote tumor progression by regulating the expression level of CXCR5 on them. |
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