Metaherin Contributes To The Pathogenesis Of Chronic Lymohcytic Leukemia

Dysregulation of proliferation and apoptosis is associated the pathogenesis of CLL. More recently, Metadherin (MTDH) involved in aberrant proliferation, survival, and increased migration, invasiveness, and metastasis of tumor cells, has been demonstrated as a potential crucial mediator of various types of huamn malignancies. MTDH promotes tumor progression by modulating multiple oncogenic signaling pathways (NF-kB, PI3K/Akt and Wnt/beta-catenin). However, there is no report about the role of MTDH in CLL. Since Wnt signaling pathway had been proven to be unusual activated in CLL, the objective of this study was to investigate the role of MTDH in CLL and the relationship between MTDH and Wnt/beta-catenin signaling pathway.

Peripheral blood mononuclear cells (PBMCs) came from samples of 31 CLL patients. The characteristics of CLL patients were shown in Table 1. CD19+B cells were selected from peripheral blood of age-matched heathy donor, cord blood, bone marrow and tonsil of normal controls using CD19+ magnetic selection kits and detected the purity with anti-CD19-PE antibody by flow cytometry. Qantitative PCR and Western blot were used to detect the expression of mRNA and protein for MTDH, and the key functional components of Wnt/beta-catenin signaling pathway (beta-catenin and LEF-1). We also measured MTDH level in B cells by flow cytometry after intracellular staining. CLL cell line(MEC-1) were infected by lentivirus to interfer MTDH and the infection efficiencies were determined by fluorescence microscope and flow cytometry. Both primary CLL cells and MEC-1 were exposed to 10ug/ml goat F(ab`)₂ anti-human IgM for 48hours to mimic activation of BCR. The proliferation and apoptosis of these cells were evaluated by CCK-8 method and Annexin V kits.

mRNA of MTDH in PBMCs of 31 CLL patients were overexpression compared with CD19+ B cells coming from 15 age-matched healthy donors (Figure 1A). 27 out of 31 CLL samples were detected MTDH expression in protein level but none in normal controls (Figure 1B). The expression of MTDH was associated with Rai staging of CLL. There were no MTDH detection in CD19+ B cells collected from bone marrow, peripheral blood, tonsil and cord blood, which stand for precursor, mature, germinal center, and lineage B cells, respectively. The transfection efficiency of MEC-1 cells by interfering MTDH expression with Lentivirus was shown in Figure 1C. The level of MTDH knockdown was accompanied with LEF-1 downregulation (Figure 1D, 1E), as well as the downregulation of c-myc and cyclinD1 expression (Figure 1F). siRNA targeting MTDH treatment in MEC-1 decreased the proliferation and increased the apoptosis(Figure 2A, 2B). We further observed that the proliferation and MTDH expression both in CLL cells and MEC-1 were upregulation after stimulation of anti-human IgM (Figure 2C, 2D, 2E). This effect in the proliferation was blocked by MTDH inteference (Figure 2F).

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Our results demonstrated that MTDH is aberrant expression in B cells of CLL patients and correlated with clinical staging of CLL. MTDH was not expression in any subsets of normal B cells. MTDH may exert a preservative role through activation of Wnt signaling pathway. The CLL cell proliferation activation by BCR signaling pathway may be inhibited by MTDH interference. Our findings indicated that MTDH may be a potential therapeutic target of CLL.

No relevant conflicts of interest to declare.