A novel human heparanase splice variant, T5, endowed with protumorigenic characteristics

Heparanaseis a mammalian endo-β-d-glucuronidase that can cleave heparan sulfateside chains, an activity strongly implicated in tumor cell dissemination. The current study aimed to identify and characterize heparanase splicevariants. LEADS, Compugen’s alternative splicingmodeling platform (Compugen, Tel Aviv, Israel), was used to search for splicevariants in silico; tumor-derived cell lines (i.e., CAG myeloma) and tumor biopsies were utilized to validate T5 expression in vivo; signaling (i.e., Src phosphorylation) was evaluated following T5 gene silencing or overexpression and correlated with cell proliferation, colony formation, and tumor xenograft development. A novel splicedform of human heparanase, termed T5, was identified. In this splicevariant, 144 bp of intron 5 are joined with exon 4, which results in a truncated, enzymatically inactive protein. T5 overexpression resulted in increased cell proliferation and larger colonies in soft agar, mediated by Src activation. Furthermore, T5 overexpression markedly enhanced tumor xenograft development. T5 expression is up-regulated in 75% of human renal cell carcinoma biopsies examined, which suggests that this splicevariant is clinically relevant. Controls included cells overexpressing wild-type heparanaseor an empty plasmid and normal-looking tissue adjacent the carcinoma lesion. T5 is a novel functional splicevariant of human heparanaseendowed with protumorigenic characteristics.—Barash, U., Cohen-Kaplan, V., Arvatz, G., Gingis-Velitski, S., Levy-Adam, F., Nativ, O., Shemesh, R., Ayalon-Sofer, M., Ilan, N., Vlodavsky, I. A novel human heparanase splicevariant, T5, endowed with protumorigenic characteristics.