title: A6 peptide activates CD44 adhesive activity, induces FAK and MEK phosphorylation, and inhibits the migration and metastasis of CD44-expressing cells.
abstract: The A6 peptide (acetyl-KPSSPPEE-amino) has antitumor activity in the absence of significant adverse events in murine tumor models and clinical trials. A6 shares sequence homology with CD44, an adhesion receptor involved in metastasis that is also a marker of cancer stem cells and drug-resistant phenotypes. We investigated the mechanism of action of A6 by examining its effects on CD44 activity, cell migration, and metastasis. A6 inhibited the migration of a subset of ovarian and breast cancer cell lines, exhibiting IC(50) values of 5 to 110 nmol/L. The ability of A6 to inhibit migration in vitro correlated with CD44 expression. Immunopreciptation studies showed that CD44 binds A6 and that biotin-tagged A6 can be cross-linked to CD44. The binding of A6 altered the structure of CD44 such that it was no longer recognized by a monoclonal antibody to a specific epitope. Importantly, A6 potentiated the CD44-dependent adhesion of cancer cells to hyaluronic acid and activated CD44-mediated signaling, as evidenced by focal adhesion kinase and MAP/ERK kinase phosphorylation. In vivo, A6 (100 mg/kg delivered s.c. twice daily) reduced the number of lung foci generated by the i.v. injection of B16-F10 melanoma cells by 50% (P = 0.029 in an unpaired t test). We conclude that A6 potently blocks the migration of CD44-positive cells in vitro through an interaction with CD44 that alters its structure and activates CD44 to enhance ligand binding and downstream signaling. The concurrent ability of A6 to agonize the CD44 receptor suggests that CD44 activation may represent a novel strategy for inhibiting metastatic disease.
authors: Bio-Quant, Inc., San Diego, USA. rspiotrowicz@san.rr.com
authors: Randolph S
authors: RS
authors: Piotrowicz
authors: Bassam B
authors: BB
authors: Damaj
authors: Mohamed
authors: M
authors: Hachicha
authors: Francesca
authors: F
authors: Incardona
authors: Stephen B
authors: SB
authors: Howell
authors: Malcolm
authors: M
authors: Finlayson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000378:metabolism; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D002448:Cell Adhesion / Q000187:drug effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects*; D002633:Chemotaxis / Q000187:drug effects; D005260:Female; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D006801:Humans; D018960:Hyaluronan Receptors / Q000276:immunology / Q000378:metabolism*; D006820:Hyaluronic Acid / Q000737:chemistry / Q000494:pharmacology; D008546:Melanoma, Experimental / Q000188:drug therapy; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D041681:NIH 3T3 Cells; D009362:Neoplasm Metastasis / Q000188:drug therapy*; D010051:Ovarian Neoplasms / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D014568:Urokinase-Type Plasminogen Activator / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D018960:Hyaluronan Receptors; D010446:Peptide Fragments; D006820:Hyaluronic Acid; D051416:Focal Adhesion Protein-Tyrosine Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D014568:Urokinase-Type Plasminogen Activator; C489333:acetyl-lysyl-prolyl-seryl-seryl-prolyl-prolyl-glutamyl-glutamic acid amide