MRP1-CD28 bi-specific oligonucleotide aptamers: target costimulation to drug-resistant melanoma cancer stem cells.

Mario Martínez Soldevilla,Susana Inoges,Helena Villanueva,Fernando Pastor,Ascensión López-Díaz De Cerio,Maurizio Bendandi,Noelia Casares,Juan Jose Lasarte

doi:10.18632/oncotarget.8095

Abstract

In this work we show a clinically feasible strategy to convert in situ the own tumor into an endogenous vaccine by coating the melanoma cancerous cells with CD28 costimulatory ligands. This therapeutic approach is aimed at targeting T-cell costimulation to chemotherapy-resistant tumors which are refractory and been considered as untreatable cancers. These tumors are usually defined by an enrichment of cancer stem cells and characterized by the higher expression of chemotherapy-resistant proteins. In this work we develop the first aptamer that targets chemotherapy-resistant tumors expressing MRP1 through a novel combinatorial peptide-cell SELEX. With the use of the MRP1 aptamer we engineer a MRP1-CD28 bivalent aptamer that is able to bind MRP1-expressing tumors and deliver the CD28 costimulatory signal to tumor-infiltrating lymphocytes. The bi-specific aptamer is able to enhance costimulation in chemotherapy-resistant tumors. Melanoma-bearing mice systemically treated with MRP1-CD28 bivalent aptamer show reduced growth, thus proving an improved mice survival.Besides, we have designed a technically feasible and translational whole-cell vaccine (Aptvax). Disaggregated cells from tumors can be directly decorated with costimulatory ligand aptamers to generate the vaccine Aptvax. CD28Aptvax made of irradiated tumor cells coated with the CD28-agonistic aptamer attached to MRP1 elicits a strong tumor- cell immune response against melanoma tumors reducing tumor growth.

Highlights

Aptamers are defined as single-stranded oligonucleotide ligands that are selected through a complex combinatorial technique known as Systematic Evolution of Ligands by Exponential Enrichment (SELEX)
We evaluated whether the aptamer would be able to reverse chemotherapy resistance to doxorubicin and etoposide in H69AR by MTT, but it did not have any inhibition (Supplementary Figure 1), indicating that the aptamer binds to regions of Multidrug Resistant-associated Protein 1 (MRP1) proteins that might not be important for the expulsion of chemotherapy drugs
Based on the premise that lack of costimulation at the tumor site might hamper the ability of tumorspecific T cells to eliminate the tumor cells, we developed a bi-specific aptamer that is aimed at targeting CD28 costimulation to chemotherapy-resistant MRP1 cancer cells

Summary

Introduction

Aptamers are defined as single-stranded oligonucleotide ligands that are selected through a complex combinatorial technique known as Systematic Evolution of Ligands by Exponential Enrichment (SELEX). Aptamers display high affinity and specificity for their targets, and represent a new therapeutic platform in life science. There are several aptamers in clinical trials; one of them (Macugen anti VEGF aptamer) has already been approved by the FDA for the treatment of macular degeneration [1]. Aptamers can be chemically synthesized, they are less immunogenic compounds than protein-based products, and they show higher plasticity. Considering all these advantages, it is easy to envision that in the near future aptamers will gain a significant niche in the clinic [2]. Lack of therapeutic approaches to tackle residual chemotherapyresistant tumor cells puts those patients at high risk of disease recurrence

Methods

Results

Conclusion