Additive effects of a small molecular PCNA inhibitor PCNA-I1Sand DNA damaging agents on growth inhibition and DNA damagein prostate and lung cancer cells.

Shan Lu,Zhongyun Dong,Robert W Sobol

doi:10.1371/journal.pone.0223894

Shan Lu, Zhongyun Dong + Show 1 more

Open Access

https://doi.org/10.1371/journal.pone.0223894

Copy DOI

Journal: PloS one	Publication Date: Oct 10, 2019
Citations: 13	License type: CC BY 4.0

Affiliation: University of Cincinnati Medical Center

Abstract

Proliferating cell nuclear antigen (PCNA) is essential for DNA replication and repair, and cell growth and survival. Previously, we identified a novel class of small molecules that bind directly to PCNA, stabilize PCNA trimer structure, reduce chromatin-associated PCNA, selectively inhibit tumor cell growth, and induce apoptosis. The purpose of this study was to investigate the combinatorial effects of lead compound PCNA-I1S with DNA damaging agents on cell growth, DNA damage, and DNA repair in four lines of human prostate and lung cancer cells. The DNA damage agents used in the study include ionizing radiation source cesium-137 (Cs-137), chemotherapy drug cisplatin (cisPt), ultraviolet-C (UV-C), and oxidative compound H2O2. DNA damage was assessed using immunofluorescent staining of γH2AX and the Comet assay. The homologous recombination repair (HRR) was determined using a plasmid-based HRR reporter assay and the nucleotide excision repair (NER) was indirectly examined by the removal of UV-induced cyclobutane pyrimidine dimers (CPD). We found that PCNA-I1S inhibited cell growth in a dose-dependent manner and significantly enhanced the cell growth inhibition induced by pretreatment with DNA damaging agents Cs-137 irradiation, UV-C, and cisPt. However, the additive growth inhibitory effects were not observed in cells pre-treated with PCNA-I1S, followed by treatment with cisPt. H2O2 enhanced the level of chromatin-bound PCNA in quiescent cells, which was attenuated by PCNA-I1S. DNA damage was induced in cells treated with either PCNA-I1S or cisPt alone and was significantly elevated in cells exposed to the combination of PCNA-I1S and cisPt. Finally, PCNA-I1S attenuated repair of DNA double strand breaks (DSBs) by HRR and the removal of CPD by NER. These data suggest that targeting PCNA with PCNA-I1S may provide a novel approach for enhancing the efficacy of chemotherapy and radiation therapy in treatment of human prostate and lung cancer.

Highlights

Proliferating cell nuclear antigen (PCNA) is an evolutionally very well conserved multifunctional protein [1, 2] and a non-oncogenic protein essential for tumor cell growth and survival
We found that treatment with the lead compound PCNA-I1 induces DNA damage and apoptosis, and suppresses tumor growth in mice [31]
Through the structure-activity relationship analysis and functional validation, we identified another lead compound PCNA-I1S that is more potent than PCNA-I1 in suppressing cell growth and stabilizing PCNA trimer structure [30]

Summary

Introduction

Proliferating cell nuclear antigen (PCNA) is an evolutionally very well conserved multifunctional protein [1, 2] and a non-oncogenic protein essential for tumor cell growth and survival. It is overexpressed in all tumors [2]. Given that tumor cells are more active in replication and contain much higher levels of damaged DNA [9, 10] than normal cells, they are more vulnerable to the stress of downregulation or inhibition of PCNA function. PCNA interacts with some cell signaling proteins, such as PI3K proteins, and regulates cell signaling processes [19]. PCNA interacts with its partner proteins containing PIP (PCNA interaction protein)-box, KA-box, APIM (AlkB homologue 2 PCNAinteracting motif), and other motifs [2, 16, 19]

Objectives

Methods

Results

Conclusion