64Cu-Labeled Aptamers for Tumor-Targeted Radionuclide Delivery

Aptamer-Based Immunotheranostic Strategies

The escape from immune surveillance is a hallmark of cancer progression. The classic immune checkpoint molecules PD-1, PD-L1, CTLA-4, LAG-3, TIM-3 novel ones are part of a sophisticated system of up- and downmodulation of the immune system, which is unregulated in cancer. In recent years, there have been remarkable advances in the development of targeting strategies, focused principally on immunotherapies aiming at blocking those molecules involved in the evasion of the immune system. However, there are still challenges to predicting their efficacy due to the wide heterogeneity of clinical responses. Thus, there is a need to develop new strategies, and theranostics has much to contribute in this field. Besides that, aptamers have emerged as promising molecules with the potential to generate a huge impact in the immunotheranostic field. They are single-stranded oligonucleotides with a unique self-folding tridimensional structure, with high affinity and specificity for the target. In particular, their small size and physicochemical characteristics make them a versatile tool for designing theranostic strategies. Here, we review the progress in theranostic strategies based on aptamers against immune checkpoints, and highlight the potential of those approaches.

RNA Interference and Nanotechnology: A Promising Alliance for Next Generation Cancer Therapeutics

Cancer is a significant health hazard of the 21st century, and GLOBOCAN predicts increasing cancer incidence in the coming decades. Though several conventional treatment modalities exist, most of them end up causing off-target and debilitating effects, and drug resistance acquisition. Advances in our understanding of tumor molecular biology offer alternative strategies for precise, robust, and potentially less toxic treatment paradigms for circumventing the disease at the cellular and molecular level. Several deregulated molecules associated with tumorigenesis have been developed as targets in RNA interference (RNAi) based cancer therapeutics. RNAi, a post-transcriptional gene regulation mechanism, has significantly gained attention because of its precise multi-targeted gene silencing. Although the RNAi approach is favorable, the direct administration of small oligonucleotides has not been fruitful because of their inherent lower half-lives and instability in the biological systems. Moreover, the lack of an appropriate delivery system to the primary site of the tumor that helps determine the potency of the drug and its reach, has limited the effective medical utilization of these bio-drugs. Nanotechnology, with its unique characteristics of enhanced permeation and better tumor-targeting efficiency, offers promising solutions owing to the various possibilities and amenability for modifications of the nanoparticles to augment cancer therapeutics. Nanoparticles could be made multimodal, by designing and synthesizing multiple desired functionalities, often resulting in unique and potentially applicable biological structures. A small number of Phase I clinical trials with systemically administered siRNA molecules conjugated with nanoparticles have been completed and the results are promising, indicating that, these new combinatorial therapies can successfully and safely be used to inhibit target genes in cancer patients to alleviate some of the disease burden. In this review, we highlight different types of nano-based delivery strategies for engineering Nano-RNAi-based bio drugs. Furthermore, we have highlighted the insights gained from current research that are entering the preclinical evaluation and information about initial clinical developments, shaping the future for next generation cancer therapeutics.

Sgc8-c Aptamer as a Potential Theranostic Agent for Hemato-Oncological Malignancies

Background: Aptamers represent an emerging class of oligonucleotides that have the ability to bind ligands with high affinity. Sgc8-c aptamer recognizes PTK7, a member of the catalytically defective receptor protein tyrosine kinase family that is upregulated in various cancers, including hemato-oncological malignancies. Herein, an Sgc8-c-NOTA-radiolabeled probe was prepared for theranostic purpose. Materials and Methods: In this work, an Sgc8-c-radiolabeled probe against PTK7 was prepared, and biological evaluations-pharmacokinetic studies, biodistribution analysis, and in vivo molecular imaging-were performed. To obtain the radiolabeled probe, a modified 5'-amino-derivative of the Sgc8-c aptamer was bound to the metal chelator NOTA, and subsequently labeled with ⁶⁷Ga with high yield and radiochemical purity. The precursor, Sgc8-c-NOTA, the radio probe Sgc8-c-NOTA-⁶⁷Ga, and its nonradioactive complex, Sgc8-c-NOTA-^69/71Ga, were purified by reverse-phase high-performance liquid chromatography and characterized by electrospray ionization mass spectrometry. The binding ability of Sgc8-c-NOTA-⁶⁷Ga was studied in vitro against purified PTK7 receptor. In addition, the binding was also evidenced against the hemato-oncological A20 cell line, derived from B lymphocytes, and the corresponding A20-green fluorescent protein (GFP)-transfected cells. The proof of concept was performed on A20-GFP tumor-bearing mice, in which the biodistribution of the radiolabeled probe was evaluated through imaging, using X-ray, fluorescence, and γ modalities. The specific uptake of the probe was confirmed by blocking with the Sgc8-c aptamer in an in vivo competition assay. Results: The biodistribution results showed considerable uptake in tumor since 2 h, with highest at 48 h postinjection. However, the blood and muscle ID/g (injected dose per gram of tissue) activities were decreasing with time and tumor/no-target ratios increasing to 20 at 24 h postinjection. These results are consistent with the in vivo images. Conclusions: This study supports the utility of Sgc8-c-NOTA radiolabeled as a theranostic agent.