Abstract 60: Heparan sulfate proteoglycans can mediate cancer cell oriented migration through integrin independent Rac 1 activation
Authors: Bracci Luisa , Depau Lorenzo , Brunetti Jlenia , Riolo Giulia , Mandarini Elisabetta , Zanchi Marta , Zevolini Fabrizia , Pini Alessandro , Falciani Chiara 
Published: August 2019

Cancer cell membranes and tumor associated extracellular matrix are characterized by a predominant presence of highly sulfated Heparan Sulfate Proteoglycans (HSPGs), which have already been identified as potential tumor markers in different cancers.

We previously reported on stable tetra-branched peptides named NT4, which selectively bind different human cancer tissues and cells, thanks to their high affinity binding to sulfated glycosaminoglycans (GAGs). Using drug-conjugated NT4 peptides as selective tumor targeting agents, we obtained a significant reduction in tumor growth, compared with animals treated with the unconjugated drug under identical conditions. Drug-conjugated NT4 can also by-pass drug resistance mediated by membrane transporters (1-8).

Besides being potential tumor markers, HSPG are also interesting potential drug targets since they appear to take part in many crucial events of cancer progression, such as epithelial mesenchymal transition, migration and invasion.

We identified a putative sulfated oligosaccharide motif allowing high-affinity binding of NT4 to sulfated GAGs. NT4 was then used as a specific tool to analyze the role of sulfated GAGs in signaling events regulating oriented cancer cell migration.

NT4 binding exerts different effects on adhesion and migration in different cancer cells. In PANC-1 human pancreatic adenocarcinoma cells, NT4 binding to sulfated GAGs abolishes cell adhesion and dramatically affects directional migration, inducing disorganization of actin filaments and stress fibers and increasing the number filopodia. This occurs without any effect on activation of beta1 integrins or focal adhesion kinase, but with a clear reduction in Rac1 activity. Otherwise, in TE-671 human rhabdomyosarcoma cells, binding of NT4 to sulfated GAGs has little effect on cell adhesion and cell migration. Untreated TE671 have a slow and scarcely oriented migration and a general morphology which recalls that assumed by PANC-1 upon treatment with NT4, with many filopodia and scarcely organized stress fibers. Interestingly, activated Rac1 is not detectable in untreated migrating TE671 cells. PANC-1 and TE671 have a very different expression of syndecans, particularly syndecan 2 and syndecan 4.

Our results suggest that HSPGs can work as primary players in directional cell migration and actin filaments assembly, by regulating Rac1 activity through an integrin-independent signaling pathway, which seems to require the expression of syndecan 4.

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Note: This abstract was not presented at the meeting.

Citation Format: Luisa Bracci, Lorenzo Depau, Jlenia Brunetti, Giulia Riolo, Elisabetta Mandarini, Marta Zanchi, Fabrizia Zevolini, Alessandro Pini, Chiara Falciani. Heparan sulfate proteoglycans can mediate cancer cell oriented migration through integrin independent Rac 1 activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 60.