HPSE and neoplasm: Transfecting U87 cells with Spalax heparanase splice variants S7, S12, or S36 results in specific functional changes: S7 increases tumor growth despite lacking enzymatic activity [34]; S12, reported for the first time in this article, lacks enzymatic activity, and its effect on cell behavior is not fully characterized yet; and S36 reduces tumor growth by inhibiting heparan sulfate degradation [34].