Development and Evaluation of Novel Aptamers Specific for Human PD1 Using Hybrid Systematic Evolution of Ligands by Exponential Enrichment Approach

Background: Programmed cell death protein 1 (PD1; also known as CD279) is an inhibitory receptor on T lymphocytes interacting with PD1-ligand 1 and PD1-ligand 2 in the synapse of T cells and antigen presenting cells (APC) resulting in the suppression of T cell activity. Systematic evolution of ligands by exponential enrichment (SELEX) is a method for generating aptamers which can bind specifically to the target of interest. PD-1 antagonistic aptamers could introduce an attractive alternative over the antibody-based treatments due to the distinguished advantages of aptamers including small size and efficient tissue penetration, low cost, lack of immunogenicity, and ease of manufacturing. Methods: Here, we developed single-stranded DNA aptamers which bind specifically to the human extracellular domain of PD-1. We performed hybrid SELEX, a combination of targeting of recombinant proteins and cell membrane expressed PD1 to select and identify specific aptamers and for the first time, homology of aptamer sequences selected from protein and cell SELEX pool have been evaluated in this study. Results: C42�aptamer, one of the selected aptamers, could specifically bind to human PD1 with dissociation constant in the nanomolar range. Although the developed aptamer inhibited binding of PD1 to PD-L1 but it was not able to restore the cell proliferation and cytokine production of the CD8+ CD279+ T cells. Conclusion: Further studies are required to assess the therapeutic potential of C42 aptamer and other aptamers developed in this study. The introduced PD1 specific aptamers can be used for specific detection of PD1 in diagnostic assay such as immunohistochemistry and targeted drug delivery to PD+ T cells. © 2020, © 2020 Taylor & Francis Group, LLC

Anticancer and apoptosis-inducing effects of quercetin in vitro and in vivo

The present study focused on the elucidation of the putative anticancer potential of quercetin. The anticancer activity of quercetin at 10, 20, 40, 80 and 120 μM was assessed in vitro by MMT assay in 9 tumor cell lines (colon carcinoma CT-26 cells, prostate adenocarcinoma LNCaP cells, human prostate PC3 cells, pheocromocytoma PC12 cells, estrogen receptor-positive breast cancer MCF-7 cells, acute lymphoblastic leukemia MOLT-4 T-cells, human myeloma U266B1 cells, human lymphoid Raji cells and ovarian cancer CHO cells). Quercetin was found to induce the apoptosis of all the tested cancer cell lines at the utilized concentrations. Moreover, quercetin significantly induced the apoptosis of the CT-26, LNCaP, MOLT-4 and Raji cell lines, as compared to control group (P<0.001), as demonstrated by Annexin V/PI staining. In in vivo experiments, mice bearing MCF-7 and CT-26 tumors exhibited a significant reduction in tumor volume in the quercetin-treated group as compared to the control group (P<0.001). Taken together, quercetin, a naturally occurring compound, exhibits anticancer properties both in vivo and in vitro