Pergamon 0955-2235(95)00002-X BIOCHEMICAL AND MITOGENIC PROPERTIES OF THE HEPARIN-BINDING GROWTH FACTOR HARP Khalid Laaroubi, Francis Vacherot, Jean Delbk, Daniile Caruelle, Denis Barritault* and JosC Courty Laboratoire de Recherche sur la Croissance Cellulaire, la Reparation et la RegCnCration Tissulaires (C.R.R.E.T.). LJRA-CNRS No. 1813, MERS EA No. 415, affilit INSERM, UniversitC Paris Val de Marne. Avenue du G&&al de Gaulle, 94010 CrCteil, France Hepurin @in regulatory peptide (HARP), also called Pleiotrophin (PTNj. is u poi_vpeptide thut displays a high affinity for heparin und thut shores upproximute1.v 50% sequence homology with Midkine (MK). According to this structurul homolog),. these two molecules constitute u new ftimily of heparin-binding proteins. The biologi- cal properties of HARP and MK remain largely a sttbj’ect of’ debate. Both proteins have been described us neurite outgrowth promoting agents whereus until recently the mitogenic activity has been controversial. The aim of this review is to summurix the infbrmation on HARP with special f&us on the recent data reluting to its mito,penic properties. Keywords: Growth factor, heparin affin regulatory peptide, pleiotrophin, heparin- binding growth associated molecule, mitogenic, heparin. INTRODUCTION Growth factors and cytokines play important functions in the regulation of growth and in the differentiation of the cells. Recently, a novel molecule called HARP (Heparin Affin Regulatory Peptide) [ 1] displaying cellular growth and differ- entiation activities has been reported by several laboratories. HARP, which was also described by other authors under the names of pl8 [2], HB-GAM (Heparin- binding Growth Associated Molecule) [3, 41, PTN (Pleiotrophin) [5, 61, HBNF (Heparin-binding Neurotrophic Factor) [7] and, OSF-1 (Osteoblast Specific Factor) *Correspondence: D. Barritault, Laboratoire de Recherche sur la Croissance Cellulaire. la Rtparation et la Regtneration Tissulaires (C.R.R.E.T), Universite Paris Val de Marne, Avenue du GCntral de Gaulle, 94010 CrCteil, France; Tel. +33 1 45 17 18 15. Fax +33 1 45 17 18 16. Acknolvk~dgemenrs-This work was supported by the CNRS and the MRES, BIOMED (PL 931168). grants from “ Association pour la Recherche sur le Cancer” (No. 6595). the “Ligue National contre le Cancer” and Naturalia et Biologa. V.F. is recipient of “ Association pour la recherche sur les Tumeurs de Prostate” . 25