RESEARCH ARTICLE Open Access Creation of a novel peptide with enhanced nuclear localization in prostate and pancreatic cancer cell lines H Dan Lewis 1† , Ali Husain 1† , Robert J Donnelly 2 , Dimitrios Barlos 1 , Sheraz Riaz 1 , Kalyani Ginjupalli 1,5 , Adetola Shodeinde 3 , Beverly E Barton 1,4* Abstract Background: For improved uptake of oligonucleotide-based therapy, the oligonucleotides often are coupled to peptides that facilitate entry into cells. To this end, novel cell-penetrating peptides (CPPs) were designed for mediating intracellular uptake of oligonucleotide-based therapeutics. The novel peptides were based on taking advantage of the nuclear localization properties of transcription factors in combination with a peptide that would bind putatively to cell surfaces. It was observed that adding a glutamate peptide to the N-terminus of the nuclear localization signal (NLS) of the Oct6 transcription factor resulted in a novel CPP with better uptake and better nuclear colocalization than any other peptide tested. Results: Uptake of the novel peptide Glu-Oct6 by cancer cell lines was rapid (in less than 1 hr, more than 60% of DU-145 cells were positive for FITC), complete (by 4 hr, 99% of cells were positive for FITC), concentration- dependent, temperature-dependent, and inhibited by sodium azide (NaN 3 ). Substitution of Phe, Tyr, or Asn moieties for the glutamate portion of the novel peptide resulted in abrogation of novel CPP uptake; however none of the substituted peptides inhibited uptake of the novel CPP when coincubated with cells. Live-cell imaging and analysis by imaging flow cytometry revealed that the novel CPP accumulated in nuclei. Finally, the novel CPP was coupled to a carboxyfluorescein-labeled synthetic oligonucleotide, to see if the peptide could ferry a therapeutic payload into cells. Conclusions: These studies document the creation of a novel CPP consisting of a glutamate peptide coupled to the N-terminus of the Oct6 NLS; the novel CPP exhibited nuclear colocalization as well as uptake by prostate and pancreatic cancer cell lines. Background Experimental therapeutic approaches using oligonucleo- tides for prostate and pancreatic cancer are actively investigated in many laboratories, including ours [1,2]. Such inhibitors are attractive in theory but lack a practi- cal method for delivery in the clinical setting. One pos- sible approach to overcome this roadblock is to use peptide-mediated transport, thereby coupling a cell- penetrating peptide (CPP) to a therapeutic payload, such as a peptide nucleic acid (PNA). An inherent advantage of using CPPs is the ability to design cell specificity in the sequence, as well as target organelle specificity through inclusion of nuclear localization signals (NLS). CPP-mediated can be quite efficient, allowing for rapid and complete uptake and delivery of a PNA payload for the treatment of HIV [3]. CPPs for delivery of therapeutic oligonucleotides have gained attention in recent years; an excellent review describing the major categories of CPPs was published earlier this year [4]. CPPs for prostate cancer have been examined in conjunction with delivery of methotrexate- loaded liposomes [5,6], double-stranded decoys [7], and radioactive gadolinium complexes targeted to c-myc [8]. As for pancreatic cancer, the antennepedia protein Antp when coupled to the tumor suppressor p16 successfully * Correspondence: bartonbe@umdnj.edu † Contributed equally 1 Department of Surgery, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, 185 S. Orange Avenue, Newark, NJ 07103 USA Full list of author information is available at the end of the article Lewis et al. BMC Biotechnology 2010, 10:79 http://www.biomedcentral.com/1472-6750/10/79 © 2010 Lewis et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.