title: Effect of CD44 binding peptide conjugated to an engineered inert matrix on maintenance of breast cancer stem cells and tumorsphere formation.
abstract: BACKGROUND
  As cancer cells are affected by many factors in their microenvironment, a major challenge is to isolate the effect of a specific factor on cancer stem cells (CSCs) while keeping other factors unchanged. We have developed a synthetic inert 3D polyethylene glycol diacrylate (PEGDA) gel culture system as a unique tool to study the effect of microenvironmental factors on CSCs response. We have reported that CSCs formed in the inert PEGDA gel by encapsulation of breast cancer cells maintain their stemness within a certain range of gel stiffness. The objective was to investigate the effect of CD44 binding peptide (CD44BP) conjugated to the gel on the maintenance of breast CSCs.
  
  
  METHODS
  4T1 or MCF7 breast cancer cells were encapsulated in PEGDA gel with CD44BP conjugation. Control groups included dissolved CD44BP and the gel with mutant CD44BP conjugation. Tumorsphere size and density, and expression of CSC markers were determined after 9 days. For in vivo, cell encapsulated gels were inoculated in syngeneic Balb/C mice and tumor formation was determined after 4 weeks. Effect of CD44BP conjugation on breast CSC maintenance was compared with integrin binding RGD peptide (IBP) and fibronectin-derived heparin binding peptide (FHBP).
  
  
  RESULTS
  Conjugation of CD44BP to the gel inhibited breast tumorsphere formation in vitro and in vivo. The ability of the encapsulated cells to form tumorspheres in the peptide-conjugated gels correlated with the expression of CSC markers. Tumorsphere formation in vitro was enhanced by FHBP while it was abolished by IBP.
  
  
  CONCLUSIONS
  CD44BP and IBP conjugated to the gel abolished tumorsphere formation by encapsulated 4T1 cells while FHBP enhanced tumorsphere formation compared to cells in the gel without peptide. The PEGDA hydrogel culture system provides a novel tool to investigate the individual effect of factors in the microenvironment on CSC maintenance without interference of other factors.
authors.affiliation: Biomimetic Materials and Tissue Engineering Laboratory, Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina, United States of America.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Yang
authors.forename: Samaneh K
authors.initials: SK
authors.lastname: Sarvestani
authors.forename: Seyedsina
authors.initials: S
authors.lastname: Moeinzadeh
authors.forename: Xuezhong
authors.initials: X
authors.lastname: He
authors.forename: Esmaiel
authors.initials: E
authors.lastname: Jabbari
mesh_terms: D015415:Biomarkers; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival; D005260:Female; D005353:Fibronectins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D018960:Hyaluronan Receptors / Q000737:chemistry / Q000378:metabolism*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry; D014411:Neoplastic Stem Cells / Q000378:metabolism*; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D018874:Spheroids, Cellular; D014407:Tumor Cells, Cultured
chemical_list: D015415:Biomarkers; D005353:Fibronectins; D018960:Hyaluronan Receptors; D009842:Oligopeptides; D010455:Peptides; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; C047981:arginyl-glycyl-aspartic acid