Cytotoxic effects of aptamer-doxorubicin conjugates in an ovarian cancer cell line.

Despite medical advances in treatment strategies over the past 30-years, epithelial ovarian cancer (EOC) continues to be defined by poor patient survival rates and aggressive, drug resistant relapse. Traditional approaches to cancer chemotherapy are typically limited by severe off-target effects on healthy tissue and aggressive drug-resistant recurrence. Recent shifts towards targeted therapies offer the possibility of circumventing the obstacles experienced by these treatments. While antibodies are the pioneering agents in such targeted therapies, several intrinsic characteristics of antibodies limits their clinical translation and efficacy. In contrast, oligonucleotide chemical antibodies, known as aptamers, are ideal for this application given their small size and lack of immunogenicity. This study explored the efficacy of a DNA aptamer, designed to target a well-established cancer biomarker, EpCAM, to deliver a chemotherapeutic drug. The results from this study support evidence that EpCAM aptamers can bind to epithelial ovarian cancer; and offers a valid alternative as a targeting ligand with tuneable specificity and sensitivity. It also supports the growing body of evidence that aptamers show great potential for application-specific, post-SELEX engineering through rational modifications. Through in vitro assays, these aptamers demonstrated cytotoxicity in both monolayer and tumoursphere assays, as well as in tumourigenic enriching assays. Further experimentation based on the results achieved in this project might aid in the development of novel cancer therapeutics and guide the novel designs of drugs for targeted drug delivery.

The Work Experience of Newly Recruited Male Nurses during COVID-19: A Qualitative Study.

PURPOSE: This study was to investigate the work experience of newly recruited male nurses during the COVID-19 pandemic. METHODS: With a phenomenological approach, this qualitative study was adopted semistructured interviews by phone or video calls. A total of 9 male nurses newly recruited for the COVID-19 wards in Chinese hospitals were interviewed for this study. And Colaizzi's method was applied for evaluation in the data analysis. RESULTS: Based on our findings, three themes were extracted. First, the newly recruited male nurses showed negative emotions at the beginning of COVID-19 epidemic, which was caused by changes in working conditions and content, but also prompted the nurses to change the way of coping with the crisis. Second, they gradually mastered the working skills and psychological training to cope with COVID-19 and developed a positive attitude toward life and a high sense of professional responsibility. Finally, we learned about their needs to respond to public health emergencies such as the COVID-19 pandemic. CONCLUSION: COVID-19 is a disaster for all of humanity. The newly recruited male nurses are an important force in emergency rescue. Although they suffered from short-term negative emotions, they quickly adapted to the crisis. In order to better prepare for future emergencies, the disaster response capacity of newly recruited male nurses needs to be further improved. In addition, newly recruited male nurses have a strong demand for timely and personalized career development guidance.

Ru(II) Complexes Bearing O, O-Chelated Ligands Induced Apoptosis in A549 Cells through the Mitochondrial Apoptotic Pathway.

Two new Ru(II) complexes containing O, O-chelated ligands, Ru(dip)2(SA) (Ru-1) and Ru(dmp)2(SA) (Ru-2) (dip = 4,7-diphenyl-1,10-phenanthroline; dmp = 2,9-dimethyl-1,10-phenanthroline; SA = salicylate) were synthesized to evaluate their cytotoxicity in vitro. These complexes were found to exhibit moderate antitumor activity to different types of human cancers, including A549 (human lung carcinoma), MCF-7 (breast cancer), HeLa (human cervical cancer), and HepG2 (human hepatocellular carcinoma) cell lines, but displayed low toxicity to human normal cell lines BEAS-2B (immortalized human bronchial epithelial cells) when compared with that of cisplatin. Further studies revealed that these complexes could induce apoptosis in A549 cells, including activating caspase family proteins and poly (ADP-ribose) polymerase (PARP), reducing Bcl-2/Bax and Bcl-xl/Bad ratio, enhancing cellular reactive oxygen species (ROS) accumulation, triggering DNA damage, decreasing mitochondrial membrane potential (MMP), and leading cytochrome c release from mitochondria. Notably, complex Ru-1 showed low toxicity to developing zebrafish embryos. The obtained results suggest that these new synthetic complexes have the potential to be developed as low-toxicity agents for lung cancer treatment.

Bifunctional Aptamer-Doxorubicin Conjugate Crosses the Blood-Brain Barrier and Selectively Delivers Its Payload to EpCAM-Positive Tumor Cells.

The prognosis for breast cancer patients diagnosed with brain metastases is poor, with survival time measured merely in months. This can largely be attributed to the limited treatment options capable of reaching the tumor as a result of the highly restrictive blood-brain barrier (BBB). While methods of overcoming this barrier have been developed and employed with current treatment options, the majority are highly invasive and nonspecific, leading to severe neurotoxic side effects. A novel approach to address these issues is the development of therapeutics targeting receptor-mediated transport mechanisms on the BBB endothelial cell membranes. Using this approach, we intercalated doxorubicin (DOX) into a bifunctional aptamer targeting the transferrin receptor on the BBB and epithelial cell adhesion molecule (EpCAM) on metastatic cancer cells. The ability of the DOX-loaded aptamer to transcytose the BBB and selectively deliver the payload to EpCAM-positive tumors was evaluated in an in vitro model and confirmed for the first time in vivo using the MDA-MB-231 breast cancer metastasis model (MDA-MB-231Br). We show that colocalized aptamer and DOX are clearly detectable within the brain lesions 75 min postadministration. Collectively, results from this study demonstrate that through intercalation of a cytotoxic drug into the bifunctional aptamer, a therapeutic delivery vehicle can be developed for specific targeting of EpCAM-positive brain metastases.

Radiolabelled Aptamers for Theranostic Treatment of Cancer.

Cancer has a high incidence and mortality rate worldwide, which continues to grow as millions of people are diagnosed annually. Metastatic disease caused by cancer is largely responsible for the mortality rates, thus early detection of metastatic tumours can improve prognosis. However, a large number of patients will also present with micrometastasis tumours which are often missed, as conventional medical imaging modalities are unable to detect micrometastases due to the lack of specificity and sensitivity. Recent advances in radiochemistry and the development of nucleic acid based targeting molecules, have led to the development of novel agents for use in cancer diagnostics. Monoclonal antibodies may also be used, however, they have inherent issues, such as toxicity, cost, unspecified binding and their clinical use can be controversial. Aptamers are a class of single-stranded RNA or DNA ligands with high specificity, binding affinity and selectivity for a target, which makes them promising for molecular biomarker imaging. Aptamers are presented as being a superior choice over antibodies because of high binding affinity and pH stability, amongst other factors. A number of aptamers directed to cancer cell markers (breast, lung, colon, glioblastoma, melanoma) have been radiolabelled and characterised to date. Further work is ongoing to develop these for clinical applications.

EpCAM Immunotherapy versus Specific Targeted Delivery of Drugs.

The epithelial cell adhesion molecule (EpCAM), or CD326, was one of the first cancer associated biomarkers to be discovered. In the last forty years, this biomarker has been investigated for use in personalized cancer therapy, with the first monoclonal antibody, edrecolomab, being trialled in humans more than thirty years ago. Since then, several other monoclonal antibodies have been raised to EpCAM and tested in clinical trials. However, while monoclonal antibody therapy has been investigated against EpCAM for almost 40 years as primary or adjuvant therapy, it has not shown as much promise as initially heralded. In this review, we look at the reasons why and consider alternative targeting options, such as aptamers, to turn this almost ubiquitously expressed epithelial cancer biomarker into a viable target for future personalized therapy.

Aptamers as potential therapeutic agents for ovarian cancer.

Current therapy for ovarian cancer typically involves indiscriminate chemotherapies that can have severe off target effects on healthy tissue and are still plagued by aggressive recurrence. Recent shifts towards targeted therapies offer the possibility of circumventing the obstacles experienced by these traditional treatments. While antibodies are the pioneering agents in targeted therapies, clinical experience has demonstrated that their antitumor efficacy is limited due to their high immunogenicity, large molecular size, and costly and laborious production. In contrast, nucleic acid based chemical antibodies, also known as aptamers, are ideal for this application given their small size, lack of immunogenicity and in vitro production. As aptamers have begun to demonstrate their promise through targeting Epithelial Cell Adhesion Molecule (EpCAM), as well as a number of ovarian cancer biomarkers, in in vivo and in vitro models, their clinical applicability is slowly being realised. This review explores some of the current progress of aptamers targeting cancer biomarkers and their potential role as ovarian cancer therapeutics.

Development of a Bifunctional Aptamer Targeting the Transferrin Receptor and Epithelial Cell Adhesion Molecule (EpCAM) for the Treatment of Brain Cancer Metastases.

The treatment of brain disorders is greatly hindered by the presence of the blood-brain barrier, which restricts the overwhelming majority of small molecules from entering the brain. A novel approach by which to overcome this barrier is to target receptor mediated transport mechanisms present on the endothelial cell membranes. Therefore, we fused an aptamer that binds to epithelial cell adhesion molecule-expressing cancer cells to an aptamer targeting the transferrin receptor. This generated a proof of concept bifunctional aptamer that can overcome the blood-brain barrier and potentially specifically target brain disorders. The initial fusion of the two sequences enhanced the binding affinity of both aptamers while maintaining specificity. Additionally, mutations were introduced into both binding loops to determine their effect on aptamer specificity. The ability of the aptamer to transcytose the blood-brain barrier was then confirmed in vivo following a 1 nmol injection. This study has shown that through the fusion of two aptamer sequences, a bifunctional aptamer can be generated that has the potential to be developed for the specific treatment of brain disorders.

The Application of Aptamers for Immunohistochemistry.

Immunohistochemistry has helped to make surgical pathology the "gold" standard for tumor diagnosis. However, given the numerous problems associated with the use of antibodies for the staining of cellular markers in paraffin-embedded tissues, there is a requirement for novel agents that have the advantages of antibodies, but with few of the disadvantages. Aptamers, which are chemical antibodies, are highly specific and sensitive, like their protein counterparts, but display few of the disadvantages. These molecules represent a unique reagent that has the potential to revolutionize the field of histopathological diagnostics. In this study, we present a review of some of the aptamers that have been validated for use in diagnoses and suggest some of the advantages to using these molecules in the future.