Overexpression of Merlin in B16F10 mouse melanoma cells reduces their metastatic activity: role of the cell surface heparan sulfate glycosaminoglycans.

Merlin, the protein product of the neurofibromatosis type 2 gene (NF2) acts as a tumor suppressor in mice and humans. In this study, melanoma B16F10 cells were engineered to overexpress the NF2 gene by establishing stable transductants. A cell line overexpressing Merlin (B16F10-M) was generated. When compared to the parental cells, the B16F10-M cells demonstrated differences in their cell surface organization. The overexpressing strain changed its ability to grow in soft agar as well as its cell motility properties. B16F10-M cells were then examined in the in vivo mouse melanoma tumor growth and tumor metastasis models. While tumor growth was marginally affected, the presence of increased Merlin severely reduced the metastastatic ability of the cells. When isolated using specific enzymes with distinct substrate specificity, the cell surface heparan sulfate glycosaminoglycans (HSGAGs) from the overexpressing B16F10-M cells, inhibited the metastatic properties of the parental B16F10 cells. The results obtained provide a causal link between the reorganization/changes to the cell surface HSGAGs by the overexpression of Merlin and the inhibition of the metastatic activity of the mouse melanoma B16F10 cells in vivo.