(EN) The invention can be summarized as follows. A method of modulating glycosylation of proteins, in a cell, preferably where the cell is in an animal where the method comprises administering an effective amount of a substance having 16K activity, to an animal in need thereof. The invention relates to a method of modulating tumor-related glycosylation of cell surface receptors and may be used to suppress the invasive growth, migration, or metastasis of tumor cells.