gms | German Medical Science

Objective: CXCR4 is a chemokine receptor that increases tumor cell growth and invasiveness. AMD 3100 is a CXCR4 inhibitor, which is used in leukemia therapy. ADAM9 is a transmembrane protein with metalloproteinase activity. It is also expressed in different solid cancers and increases tumor invasiveness. We examined CXCR4 and ADAM9 expression in vestibular schwannomas (VS) from patients with and without neurofibromatosis type 2 (NF2) and correlated the levels with clinical characteristics. Furthermore, CXCR4 inhibition by AMD3100 was tested as potential therapeutic drug.

Methods: CXCR4 and ADAM9 mRNA and protein levels were determined in VS samples (n=60); of these, 30 samples were from patients with NF2. Healthy nerves from autopsies served as controls. CXCR4 and ADAM9 mRNA levels were measured by PCR, and protein levels by immunohistochemistry (IHC) and Western blotting (WB). Tumor extension and hearing loss were categorized according to the Hannover Classification as clinical parameters. In addition, primary 2D and 3D cell cultures of CXCR4 positive VS samples (n=3) were established. Cells were treated with 500 µM AMD 3100 to examine its effect on the cell’s morphology, proliferation and migration by immunofluorescence microscopy, MTT-assays and the xCELLigence.

Results: CXCR4 mRNA levels were 4.6-fold higher in VS versus control; the levels were 4.9-fold higher in NF2 patients and 4.2-fold higher in sporadic VS. IHC and WB showed heterogeneous protein expression, and CXCR4 was expressed mainly in S100-positive Schwann cells. There was a trend between higher expression levels and greater hearing loss. There was no inhibition of proliferation or migration by AMD3100 detectable. 2D cultures revealed a considerable alteration of the cell’s shape and in 3D cultures the tumor formation in the third dimension was inhibited. ADAM9 mRNA levels were 8.8-fold higher in VS versus control; the levels were 5.6-fold higher in NF2 patients and 12-fold higher in sporadic VS patients (p=0.03). WB showed different protein isoforms, and ADAM9 was expressed mainly in S100-positive Schwann cells, too. There was a strong correlation between higher expression levels and greater hearing loss (p=0.01).

Conclusion: CXCR4 and ADAM9 mRNA were overexpressed in VS relative to healthy vestibular nerves, and ADAM9 expression correlated with the hearing impairment. Thus, CXCR4 and ADAM9 may be a prognostic marker of VS and AMD3100 a potential systemic therapeutic option.