A PCNA-derived cell permeable peptide selectively inhibits neuroblastoma cell growth.

Long Gu,Robert J Hickey,Shanna Smith,Walter H Lang,Jeremy M Stark,John A Sandoval,Caroline Li,Linda H Malkas,Gregg B Fields,Anja-Katrin Bielinsky

doi:10.1371/journal.pone.0094773

Abstract

Proliferating cell nuclear antigen (PCNA), through its interaction with various proteins involved in DNA synthesis, cell cycle regulation, and DNA repair, plays a central role in maintaining genome stability. We previously reported a novel cancer associated PCNA isoform (dubbed caPCNA), which was significantly expressed in a broad range of cancer cells and tumor tissues, but not in non-malignant cells. We found that the caPCNA-specific antigenic site lies between L126 and Y133, a region within the interconnector domain of PCNA that is known to be a major binding site for many of PCNA's interacting proteins. We hypothesized that therapeutic agents targeting protein-protein interactions mediated through this region may confer differential toxicity to normal and malignant cells. To test this hypothesis, we designed a cell permeable peptide containing the PCNA L126-Y133 sequence. Here, we report that this peptide selectively kills human neuroblastoma cells, especially those with MYCN gene amplification, with much less toxicity to non-malignant human cells. Mechanistically, the peptide is able to block PCNA interactions in cancer cells. It interferes with DNA synthesis and homologous recombination-mediated double-stranded DNA break repair, resulting in S-phase arrest, accumulation of DNA damage, and enhanced sensitivity to cisplatin. These results demonstrate conceptually the utility of this peptide for treating neuroblastomas, particularly, the unfavorable MYCN-amplified tumors.

Highlights

Neuroblastoma (NB) is one of the most common childhood neoplasms which originates from neural crest progenitor cells of the sympathetic nervous system and accounts for about 15% of all pediatric cancer deaths [1]
R9-caPep is able to selectively block Proliferating cell nuclear antigen (PCNA) interactions in cancer cells. It interferes with DNA synthesis and homologous recombination (HR) mediated doublestranded DNA break (DSB) repair, resulting in S-phase arrest, accumulation of DNA damage, and enhanced sensitivity to cisplatin. These results demonstrate that targeting protein-protein interactions involving the L126-Y133 region of PCNA may prove to be an effective approach to treating high-risk MYCN-amplified NB patients with reduced side effects
R9-caPep was well tolerated by non-malignant cells including human peripheral blood mononuclear cells (PBMC) and human neural crest stem cells (Fig 1c) with IC50 of 98 mM and more than 100 mM on these cells respectively, indicating that the R9-caPep selectively inhibits the growth of NB cancer cells

Summary

Introduction

Neuroblastoma (NB) is one of the most common childhood neoplasms which originates from neural crest progenitor cells of the sympathetic nervous system and accounts for about 15% of all pediatric cancer deaths [1]. Survival is excellent in low and intermediate risk groups and localized perinatal adrenal tumors often spontaneously regress [2]. Patients in the highrisk group have very aggressive disease and represents a significant clinical hurdle [3]. Modern treatment for high-risk NB consists of induction treatment (conventional chemotherapy and surgery with or without radiotherapy), high-dose chemotherapy and autologous stem cell transplantation (HDCT/autoSCT) as a consolidation treatment, and 13-cis-retinoid acid to reduce relapse from minimal residual disease. Approximately 50% of patients with advanced disease are refractory to treatment or relapse and the survival rate for high-risk NB patients is dismal [4,5]. There is a significant unmet medical need for new therapies to improve the treatment outcomes of this aggressive tumor phenotype

Methods

Results

Conclusion