Optimization of Short RNA Aptamers for TNBC Cell Targeting

Recent Advancements of Aptamers in Cancer Therapy

Aptamers are chemical antibodies possessing the capability of overcoming the limitations posed by conventional antibodies, particularly for diagnostic, therapeutic, and theranostic applications in cancer. The ease of chemical modifications or functionalization, including conjugations with nucleic acids, drug molecules, and nanoparticles, has made these aptamers to gain priorities in research. In this Mini-review, various reports on therapeutics with aptamer-functionalized nanomaterials for controlled or multistep drug release, targeted delivery, stimuli-responsive drug release, etc. are discussed. In the case of nucleic-acid-conjugated aptamers, DNA nanotrains and DNA beacons are discussed in terms of the possibility of multidrug loading for chemotherapy and gene therapy. Developments with electrochemical aptasensors and signal-enhanced immune aptasensors are also discussed. Further, the future scope of aptamer technology in cancer theranostics and the prevailing limitations are discussed.

Aptamer-Based Strategies to Boost Immunotherapy in TNBC

The immune system (IS) may play a crucial role in preventing tumor development and progression, leading, over the last years, to the development of effective cancer immunotherapies. Nevertheless, immune evasion, the capability of tumors to circumvent destructive host immunity, remains one of the main obstacles to overcome for maximizing treatment success. In this context, promising strategies aimed at reshaping the tumor immune microenvironment and promoting antitumor immunity are rapidly emerging. Triple-negative breast cancer (TNBC), an aggressive breast cancer subtype with poor outcomes, is highly immunogenic, suggesting immunotherapy is a viable strategy. As evidence of this, already, two immunotherapies have recently become the standard of care for patients with PD-L1 expressing tumors, which, however, represent a low percentage of patients, making more active immunotherapeutic approaches necessary. Aptamers are short, highly structured, single-stranded oligonucleotides that bind to their protein targets at high affinity and specificity. They are used for therapeutic purposes in the same way as monoclonal antibodies; thus, various aptamer-based strategies are being actively explored to stimulate the IS’s response against cancer cells. The aim of this review is to discuss the potential of the recently reported aptamer-based approaches to boost the IS to fight TNBC.

Application of aptamer-drug delivery system in the therapy of breast cancer

Despite significant treatment advances, breast cancer remains the leading cause of cancer death in women. From the current treatment situation, in addition to developing chemoresistant tumours, distant organ metastasis, and recurrences, patients with breast cancer often have a poor prognosis. Aptamers as "chemical antibodies" may be a way to resolve this dilemma. Aptamers are single-stranded, non-coding oligonucleotides (DNA or RNA), resulting their many advantages, including stability for long-term storage, simplicity of synthesis and function, and low immunogenicity, a high degree of specificity and antidote. Aptamers have gained popularity as a method for diagnosing and treating specific tumors in recent years. This article introduces the application of ten different aptamer delivery systems in the treatment and diagnosis of breast cancer, and systematically reviews their latest research progress in breast cancer treatment and diagnosis. It provides a new direction for the clinical treatment of breast cancer.

Breast Cancer: From Pathophysiology to Novel Therapeutic Approaches 2.0

Breast cancer (BC) is the most common malignancy in women worldwide [...].

Aptamer-Functionalized Nanoparticles Mediate PD-L1 siRNA Delivery for Effective Gene Silencing in Triple-Negative Breast Cancer Cells

Small interfering RNA (siRNA) therapies require effective delivery vehicles capable of carrying the siRNA cargo into target cells. To achieve tumor-targeting, a drug delivery system would have to incorporate ligands that specifically bind to receptors expressed on cancer cells to function as portals via receptor-mediated endocytosis. Cell-targeting and internalizing aptamers are the most suitable ligands for functionalization of drug-loaded nanocarriers. Here, we designed a novel aptamer-based platform for the active delivery of siRNA targeting programmed cell death-ligand 1 (PD-L1) to triple-negative breast cancer (TNBC) cells. The generated nanovectors consist of PLGA-based polymeric nanoparticles, which were loaded with PD-L1 siRNA and conjugated on their surface with a new RNA aptamer, specific for TNBC and resistant to nucleases. In vitro results demonstrated that these aptamer-conjugated nanoparticles promote siRNA uptake specifically into TNBC MDA-MB-231 and BT-549 target cells, along with its endosomal release, without recognizing non-TNBC BT-474 breast cancer cells. Their efficiency resulted in an almost complete suppression of PD-L1 expression as early as 90 min of cell treatment. This research provides a rational strategy for optimizing siRNA delivery systems for TNBC treatments.

Selection of RNA aptamers targeting hypoxia in cancer

Hypoxia plays a crucial role in tumorigenesis and drug resistance, and it is recognised as a major factor affecting patient clinical outcome. Therefore, the detection of hypoxic areas within the tumour micro-environment represents a useful way to monitor tumour growth and patients’ responses to treatments, properly guiding the choice of the most suitable therapy. To date, non-invasive hypoxia imaging probes have been identified, but their applicability in vivo is strongly limited due to an inadequate resistance to the low oxygen concentration and the acidic pH of the tumour micro-environment. In this regard, nucleic acid aptamers represent very powerful tools thanks to their peculiar features, including high stability to harsh conditions and a small size, resulting in easy and efficient tumour penetration. Here, we describe a modified cell-SELEX (Systematic Evolution of Ligands by EXponential enrichment) approach that allows the isolation of specific RNA aptamers for the detection of the hypoxic phenotype in breast cancer (BC) cells. We demonstrated the effectiveness of the proposed method in isolating highly stable aptamers with an improved and specific binding to hypoxic cells. To our knowledge, this is the first example of a cell-SELEX approach properly designed and modified to select RNA aptamers against hypoxia-related epitopes expressed on tumour cell surfaces. The selected aptamers may provide new effective tools for targeting hypoxic areas within the tumour with great clinical potential.