High Boron-loaded DNA-Oligomers as Potential Boron Neutron Capture Therapy and Antisense Oligonucleotide Dual-Action Anticancer Agents.

Damian Kaniowski,Sławomir Janczak,Barbara Nawrot,Zbigniew Leśnikowski,Katarzyna Ebenryter-Olbińska,Milena Sobczak,Błażej Wojtczak

doi:10.3390/molecules22091393

Abstract

Boron cluster-modified therapeutic nucleic acids with improved properties are of interest in gene therapy and in cancer boron neutron capture therapy (BNCT). High metallacarborane-loaded antisense oligonucleotides (ASOs) targeting epidermal growth factor receptor (EGFR) were synthesized through post-synthetic Cu (I)-assisted “click” conjugation of alkyne-modified DNA-oligonucleotides with a boron cluster alkyl azide component. The obtained oligomers exhibited increased lipophilicity compared to their non-modified precursors, while their binding affinity to complementary DNA and RNA strands was slightly decreased. Multiple metallacarborane residues present in the oligonucleotide chain, each containing 18 B-H groups, enabled the use of IR spectroscopy as a convenient analytical method for these oligomers based on the diagnostic B-H signal at 2400–2650 cm−1. The silencing activity of boron cluster-modified ASOs used at higher concentrations was similar to that of unmodified oligonucleotides. The screened ASOs, when used in low concentrations (up to 50 μM), exhibited pro-oxidative properties by inducing ROS production and an increase in mitochondrial activities in HeLa cells. In contrast, when used at higher concentrations, the ASOs exhibited anti-oxidative properties by lowering ROS species levels. In the HeLa cells (tested in the MTT assay) treated (without lipofectamine) or transfected with the screened compounds, the mitochondrial activity remained equal to the control level or only slightly changed (±30%). These findings may be useful in the design of dual-action boron cluster-modified therapeutic nucleic acids with combined antisense and anti-oxidant properties.

Highlights

Boron neutron capture therapy (BNCT) is a therapeutic modality for the treatment of cancers based on the absorption of low-energy neutrons by nonradioactive boron-10 (10 B) atoms delivered to neoplastic cells in the form of a boron-carrying drug [1,2]
We describe the synthesis of high boron cluster-loaded antisense oligonucleotides (ASOs) targeting epidermal growth factor receptor (EGFR) and describe their physicochemical properties—lipophilicity, binding affinity to complementary DNA and RNA strands, circular dichroism (CD) and infrared (IR) spectroscopic features, as well as their biological potential-silencing, cytotoxic, and pro-and anti-oxidant activities
Synthesis of boron cluster-modified anti-EGFR antisense oligonucleotides 6 and 7 (Table 1) was performed in two steps (Scheme 1) according to a recently developed general approach allowing for the incorporation of various types of boron clusters into specific locations of oligonucleotide chains [9]

Summary

Introduction

Boron neutron capture therapy (BNCT) is a therapeutic modality for the treatment of cancers based on the absorption of low-energy neutrons by nonradioactive boron-10 (10 B) atoms delivered to neoplastic cells in the form of a boron-carrying drug [1,2]. The development of high boron-loaded, tumor-selective drugs will play an important role for BNCT to evolve into a clinically accepted cancer treatment. To date fission reactors have been used as a neutron source for BNCT [5]. We describe a new approach for designing boron carriers based on nucleic acid structures. Use of other methods such as targeted liposomal delivery systems may increase the selectivity of boronated oligonucleotides transport into cancer cells

Methods

Results

Conclusion