The Discovery of RNA Aptamers that Selectively Bind Glioblastoma Stem Cells

Abstract

Glioblastoma (GBM) is the most aggressive primary brain tumor in adults. Despite progress in surgical and medical neuro-oncology, prognosis for GBM patients remains dismal, with a median survival of only 14-15 months. The modest benefit of conventional therapies is due to the presence of GBM stem cells (GSCs) that cause tumor relapse and chemoresistance and, therefore, that play a key role in GBM aggressiveness and recurrence. So far, strategies to identify and target GSCs have been unsuccessful. Thus, the development of an approach for GSC detection and targeting would be fundamental for improving the survival of GBM patients. Here, using the cell-systematic evolution of ligand by exponential (SELEX) methodology on human primary GSCs, we generated and characterized RNA aptamers that selectively bind GSCs versus undifferentiated GBM cells. We found that the shortened version of the aptamer 40L, which we have called A40s, costained with CD133-labeled cells in human GBM tissue, suggestive of an ability to specifically recognize GSCs in fixed human tissues. Of note, both 40L and A40s were rapidly internalized by cells, allowing for the delivery of the microRNA miR-34c and the anti-microRNA anti-miR-10b, demonstrating that these aptamers can serve as selective vehicles for therapeutics. In conclusion, the aptamers 40L and A40s can selectively target GSCs. Given the crucial role of GSCs in GBM recurrence and therapy resistance, these aptamers represent innovative drug delivery candidates with a great potential in the treatment of GBM.

The Role of RNA and DNA Aptamers in Glioblastoma Diagnosis and Therapy: A Systematic Review of the Literature

“…Some years later, Affinito et al, in 2019, similarly selected the GBM-specific 2′-F-RNA aptamer A40s, using an RNA library on primary human GSCs. The authors demonstrated A40s-mediated detection in GBM cells and in human GSCs tissue sections [ 19 ]. Here too, the aptamer proved to have a high affinity for target cells in a low nanomolar range (Kd of 41.92 nM).…”

“…40L and A40s recognize not only primary GSCs but also human GBM tissues positive for the GBM stemness marker CD133. Interestingly, A40s binds primary GSCs in the nanomolar range (about 42 nM), and the authors demonstrate that A40s can be used to deliver secondary molecules, for example, microRNAs [ 19 ]. The same authors in 2020 published a second paper in which A40s is fully characterized in vitro for its therapeutic effect thanks to the discovery of the aptamer’s target, EphA2.…”

Aptamers: Novel Therapeutics and Potential Role in Neuro-Oncology

“…Recently, using differential cell-SELEX, Affinito et al identified A40s, a novel aptamer that can internalize in GBM stem cells and specifically deliver miR-34c and anti-miR10b to the stem cell population. The researchers demonstrated that A40s can cross the BBB to reach the tumor site and selectively bind the EphA2 receptor, thus inhibiting tumor growth and reducing tumor relapse [ 83 , 91 ].…”

Potential and Challenges of Aptamers as Specific Carriers of Therapeutic Oligonucleotides for Precision Medicine in Cancer

“…More recently, the same groups used a GL21.T-miR-137 chimera to specifically deliver miR-137 to both glioblastoma stem cells (GSCs), reducing GSC number and migration [53] and NSCLC, inhibiting tumor growth in vitro and in vivo [54]. Moreover, Affinito et al, designed two new conjugates based on A40s aptamer able to recognize specifically GBM stem cells and miR-34c and anti-miR-10b, as a new therapeutic approach to treat GBM [55].…”