ATX-101, a Peptide Targeting PCNA, Has Antitumor Efficacy Alone or in Combination with Radiotherapy in Murine Models of Human Glioblastoma.

Giovanni Luca Gravina,Andrea Mancini,Francesco Marampon,Stefano Martellucci,Claudio Festuccia,Marit Otterlei,Leda Assunta Biordi,Vincenzo Mattei,Martina Di Franco,Alessandro Colapietro,Luca Ventura,Alessandra Rossetti

doi:10.3390/cancers14020289

Abstract

Simple SummaryPCNA is an interesting target for cancertreatment due to its essential activities in DNA replication and repair and its recently discovered regulatory roles in cellular signaling. Here, we demonstrate that ATX-101, a peptide targeting PCNA, has antitumor effects as a single agent and radiosensitizing properties in glioblastoma multiforme models.Cell proliferation requires the orchestrated actions of a myriad of proteins regulating DNA replication, DNA repair and damage tolerance, and cell cycle. Proliferating cell nuclear antigen (PCNA) is a master regulator which interacts with multiple proteins functioning in these processes, and this makes PCNA an attractive target in anticancer therapies. Here, we show that a cell-penetrating peptide containing the AlkB homolog 2 PCNA-interacting motif (APIM), ATX-101, has antitumor activity in a panel of human glioblastoma multiforme (GBM) cell lines and patient-derived glioma-initiating cells (GICs). Their sensitivity to ATX-101 was not related to cellular levels of PCNA, or p53, PTEN, or MGMT status. However, ATX-101 reduced Akt/mTOR and DNA-PKcs signaling, and a correlation between high Akt activation and sensitivity for ATX-101 was found. ATX-101 increased the levels of γH2AX, DNA fragmentation, and apoptosis when combined with radiotherapy (RT). In line with the in vitro results, ATX-101 strongly reduced tumor growth in two subcutaneous xenografts and two orthotopic GBM models, both as a single agent and in combination with RT. The ability of ATX-101 to sensitize cells to RT is promising for further development of this compound for use in GBM.

Highlights

Glioblastoma multiforme (GBM) is a very aggressive brain tumor [1] characterized by high inter- and intratumor heterogeneity [2] with high local invasiveness [3], extensive necrosis [4], and high vascularity [5]
We observed that glioblastoma multiforme (GBM) cell lines were responsive to ATX-101 with IC50 values between 4.3 (U87MG) and 12.0 μM (SNB19) (Figure 1A)
Representative inhibition curves with their IC50 determinations for seven cell lines, together with phase-contrast images showing altered morphology in U251 cells and inhibition of colony sphere formation of GSCs-5 (GIC), are shown in Supplementary Figure S1

Summary

Introduction

Glioblastoma multiforme (GBM) is a very aggressive brain tumor [1] characterized by high inter- and intratumor heterogeneity [2] with high local invasiveness [3], extensive necrosis [4], and high vascularity [5]. Greater knowledge of the molecular traits of GBM, i.e., altered cell signaling, can lead to more efficient targeted therapeutic approaches [7]. RT is an important treatment modality for GBM [9], alone or in association with temozolomide [4]. This therapy can induce various types of cell death [10], including apoptosis, necrosis, necroptosis, and autophagy, and RT may have both immunosuppressive and immunogenic effects. Recent approaches to improve the sensitivity of RT and chemotherapy have focused on targeting key proteins involved in DNA repair [17], DNA damage checkpoint activation [18], and hypoxia signaling [19,20]

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