Modulation of the heparanase-inhibiting activity of heparin through selective desulfation, graded N-acetylation, and glycol splitting.
Heparanase is an endo-beta-glucuronidase that cleaves heparan sulfate (HS) chains of heparan sulfate proteoglycans on cell surfaces and in the extracellular matrix (ECM). Heparanase, overexpressed by most cancer cells, facilitates extravasation of blood-borne tumor cells and causes release of growth factors sequestered by HS chains, thus accelerating tumor growth and metastasis. Inhibition of heparanase with HS mimics is a promising target for a novel strategy in cancer therapy. In this study, in vitro inhibition of recombinant heparanase was determined for heparin derivatives differing in degrees of 2-O- and 6-O-sulfation, N-acetylation, and glycol splitting of nonsulfated uronic acid residues. The contemporaneous presence of sulfate groups at O-2 of IdoA and at O-6 of GlcN was found to be non-essential for effective inhibition of heparanase activity provided that one of the two positions retains a high degree of sulfation. N-Desulfation/ N-acetylation involved a marked decrease in the inhibitory activity for degrees of N-acetylation higher than 50%, suggesting that at least one NSO3 group per disaccharide unit is involved in interaction with the enzyme. On the other hand, glycol splitting of preexisting or of both preexisting and chemically generated nonsulfated uronic acids dramatically increased the heparanase-inhibiting activity irrespective of the degree of N-acetylation. Indeed N-acetylated heparins in their glycol-split forms inhibited heparanase as effectively as the corresponding N-sulfated derivatives. Whereas heparin and N-acetylheparins containing unmodified D-glucuronic acid residues inhibited heparanase by acting, at least in part, as substrates, their glycol-split derivatives were no more susceptible to cleavage by heparanase. Glycol-split N-acetylheparins did not release basic fibroblast growth factor from ECM and failed to stimulate its mitogenic activity. The combination of high inhibition of heparanase and low release/potentiation of ECM-bound growth factor indicates that N-acetylated, glycol-split heparins are potential antiangiogenic and antimetastatic agents that are more effective than their counterparts with unmodified backbones.
Naggi
Annamaria
A
G. Ronzoni Institute for Chemical and Biochemical Research, via G. Colombo, 81, 20133 Milan, Italy.
Casu
Benito
B
Perez
Marta
M
Torri
Giangiacomo
G
Cassinelli
Giuseppe
G
Penco
Sergio
S
Pisano
Claudio
C
Giannini
Giuseppe
G
Ishai-Michaeli
Rivka
R
Vlodavsky
Israel
I
D000107:Acetylation; D000818:Animals; D016466:CHO Cells; D002240:Carbohydrate Sequence; D002417:Cattle; D002478:Cells, Cultured; D003315:Cornea / Q000166:cytology; D006224:Cricetinae; D004187:Disaccharides / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D020723:Glucuronic Acid / Q000737:chemistry; D005966:Glucuronidase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D006018:Glycols / Q000737:chemistry*; D006493:Heparin / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D020128:Inhibitory Concentration 50; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D014574:Uronic Acids / Q000737:chemistry; D000099175:Heparanase
D004187:Disaccharides; D016222:Fibroblast Growth Factor 2; D020723:Glucuronic Acid; D005966:Glucuronidase; D006018:Glycols; D006493:Heparin; D011994:Recombinant Proteins; D014574:Uronic Acids; D000099175:Heparanase