Nucleolin antagonist triggers autophagic cell death in human glioblastoma primary cells and decreased in vivo tumor growth in orthotopic brain tumor model.

Elisabetta Benedetti,Loredana Cristiano,Alessia Fidoamore,Andrea Antonosante,Benedetta Cinque,Tiziana Marilena Florio,José Courty,Anne Chloé Dhez,Michele D’Angelo,Antonio Giordano,Carlo Astarita,Annamaria Cimini,Damien Destouches,Floriana Rosati,Renato Galzio,Rodolfo Ippoliti,Maria Grazia Cifone

doi:10.18632/oncotarget.5990

Abstract

Nucleolin (NCL) is highly expressed in several types of cancer and represents an interesting therapeutic target. It is expressed at the plasma membrane of tumor cells, a property which is being used as a marker for several human cancer including glioblastoma. In this study we investigated targeting NCL as a new therapeutic strategy for the treatment of this pathology. To explore this possibility, we studied the effect of an antagonist of NCL, the multivalent pseudopeptide N6L using primary culture of human glioblastoma cells. In this system, N6L inhibits cell growth with different sensitivity depending to NCL localization. Cell cycle analysis indicated that N6L-induced growth reduction was due to a block of the G1/S transition with down-regulation of the expression of cyclin D1 and B2. By monitoring autophagy markers such as p62 and LC3II, we demonstrate that autophagy is enhanced after N6L treatment. In addition, N6L-treatment of mice bearing tumor decreased in vivo tumor growth in orthotopic brain tumor model and increase mice survival. The results obtained indicated an anti-proliferative and pro-autophagic effect of N6L and point towards its possible use as adjuvant agent to the standard therapeutic protocols presently utilized for glioblastoma.

Highlights

Nucleolin is a ribonucleoprotein over-expressed in highly proliferative cells such as cancer cells [1]
We studied the effect of an antagonist of NCL, the multivalent pseudopeptide N6L using primary culture of human glioblastoma cells
Nucleolin is abundantly expressed in the cytoplasm and membrane of the more N6L responsive cultures (Figure 1C), while it is less abundant in cells which are less sensitive to N6L (Figure 1D)

Summary

Introduction

Nucleolin is a ribonucleoprotein over-expressed in highly proliferative cells such as cancer cells [1]. NCL is expressed at the plasma membrane of tumor cells, a property which is being used as a marker of several human cancer, including glioblastoma [4]. Various ligands targeting cell-surface nucleolin have been used to block tumor growth and angiogenesis, including endostatin [8] aptamer AS1411 [9], F3 tumor-homing peptide [10] and the multivalent pseudopeptide N6L [11]. N6L targets cancer cells, exhibiting anti-tumor activity in various human tumor cell lines derived from mammary, colorectal carcinoma, melanoma and glioblastoma (GB) [12]. This therapeutic peptide is currently in phase I/IIa clinical trials (NCT01711398)

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Results

Conclusion