Publications by Year: 2020

MicroRNAs (miRNAs), small non-coding RNAs that repress target genes, are a promising new focus of targeted therapeutics for cancer. miR-155 is a well-studied miRNA involved in inflammation that acts oncogenically in many hematological malignancies. Like other miRNAs, its role in these diseases is complex and nuanced, which gives particular power to its inhibition in diseased cells. This, together with increasing understanding of its key targets in cancer and the use of powerful mouse models of miR-155 in cancer, makes miR-155 an ideal target for therapeutic inhibition. Here, we review the role of miRNAs, and particularly miR-155, in cancers, and discuss progress on therapeutically targeting it, including the ongoing clinical trial of anti-miR-155 molecule Cobomarsen (MRG-106).

MicroRNAs (miRNAs) have increasingly been shown to be involved in human cancer, and interest has grown about the potential use of miRNAs for cancer therapy. miRNA levels are known to be altered in cancer cells, including in non-small cell lung cancer (NSCLC), a subtype of lung cancer that is the most prevalent form of cancer worldwide and that lacks effective therapies. The let-7 miRNA is involved in the regulation of oncogene expression in cells and directly represses cancer growth in the lung. let-7 is therefore a potential molecular target for tumor therapy. However, applications of RNA interference for cancer research have been limited by a lack of simple and efficient methods to deliver oligonucleotides (ONs) to cancer cells. In this study, we have used in vitro and in vivo approaches to show that HCC827 cells internalize hydrophobically modified let-7b miRNAs (hmiRNAs) added directly to the culture medium without the need for lipid formulation. We identified functional let-7b hmiRNAs targeting the HMGA2 mRNA, one of the let-7 target genes upregulated in NSCLC, and show that direct uptake in HCC827 cells induced potent and specific gene silencing in vitro and in vivo. Thus, hmiRNAs constitute a novel class of ONs that enable functional studies of genes involved in cancer biology and are potentially therapeutic molecules.

Gastric cancer (GC) is the fifth most common cancer worldwide. In approximately 10% of GC cases, cancer cells show ubiquitous and monoclonal Epstein-Barr virus (EBV) infection. A significant feature of EBV-associated GC (EBVaGC) is high lymphocytic infiltration and high expression of immune checkpoint proteins, including programmed death-ligand 1 (PD-L1). This highlights EBVaGC as a strong candidate for immune checkpoint blockade therapy. Indeed, several recent studies have shown that EBV positivity in GC correlates with positive response to programmed cell death protein 1 (PD-1)/PD-L1 blockade therapy. Understanding the mechanisms that control PD-L1 expression in EBVaGC can indicate new predictive biomarkers for immunotherapy, as well as therapeutic targets for combination therapy. Various mechanisms have been implicated in PD-L1 expression regulation, including structural variations, post-transcriptional control, oncogenic activation of intrinsic signaling pathways, and increased sensitivity to extrinsic signals. This review provides the most recent updates on the multilayered control of PD-L1 expression in EBVaGC.

Adenosine deaminases acting on RNA (ADARs) convert adenosine to inosine in double-stranded RNA. A-to-I editing of RNA is a widespread posttranscriptional process that has recently emerged as an important mechanism in cancer biology. A-to-I editing levels are high in several human cancers, including thyroid cancer, but ADAR1 editase-dependent mechanisms governing thyroid cancer progression are unexplored. To address the importance of RNA A-to-I editing in thyroid cancer, we examined the role of ADAR1. Loss-of-function analysis showed that ADAR1 suppression profoundly repressed proliferation, invasion, and migration in thyroid tumor cell models. These observations were validated in an in vivo xenograft model, which showed that ADAR1-silenced cells had a diminished ability to form tumors. RNA editing of miRNAs has the potential to markedly alter target recognition. According to TCGA data, the tumor suppressor miR-200b is overedited in thyroid tumors, and its levels of editing correlate with a worse progression-free survival and disease stage. We confirmed miR-200b overediting in thyroid tumors and we showed that edited miR-200b has weakened activity against its target gene ZEB1 in thyroid cancer cells, likely explaining the reduced aggressiveness of ADAR1-silenced cells. We also found that RAS, but not BRAF, modulates ADAR1 levels, an effect mediated predominantly by PI3K and in part by MAPK. Lastly, pharmacological inhibition of ADAR1 activity with the editing inhibitor 8-azaadenosine reduced cancer cell aggressiveness. Overall, our data implicate ADAR1-mediated A-to-I editing as an important pathway in thyroid cancer progression, and highlight RNA editing as a potential therapeutic target in thyroid cancer.

MicroRNA-34 (miR-34) is one of the major families of tumor suppressor miRNAs often lost in cancers. Delivery of miR-34a mimics to affected tumors as a therapeutic strategy has been tried in pre-clinical studies and in a phase I clinical trial. One approach to increase efficacy and reduce toxicity is to rationally identify drug combinations with small molecules that synergize with miR-34a. In this study we performed a high-throughput screen of a large panel of small molecules with known biological activity and identified ouabain as a candidate small molecule that synergized with miR-34a in killing lung cancer cells. We elucidated autophagy activation as a key mechanism by which miR-34a and ouabain causes increased cytotoxicity in cells. We posit that this combinatorial approach could reduce the active dose of miR-34a needed in vivo to observe tumor shrinkage and potentiate the development of miR-34a combination therapies in the future.

Spatially resolved gene expression patterns are emerging as a key component of medical studies, including companion diagnostics, but technologies for quantification and multiplexing are limited. We present a method to perform spatially resolved and multiplexed microRNA (miRNA) measurements from formalin-fixed, paraffin-embedded (FFPE) tissue. Using nanoliter well arrays to pixelate the tissue section and photopatterned hydrogels to quantify miRNA, we identified differentially expressed miRNAs in tumors from a genetically engineered mouse model for non-small cell lung cancer (K-rasLSL-G12D/+; p53fl/fl). This technology could be used to quantify heterogeneities in tissue samples and lead to informed, biomarker-based diagnostics.

Selective inhibition of microRNAs (miRNAs) offers a new avenue for cancer therapeutics. While most of the current anti-miRNA (antimiR) reagents target full length miRNAs, here we investigate novel nanoparticle-delivered short PNA probes containing cationic domains targeting the seed region of the miRNA for effective antimiR therapy. For proof of concept, we tested PNAs targeting miRNA-155 and employed poly(lactic-co-glycolic acid) (PLGA)-based nanoparticle formulation for delivery. A comprehensive evaluation of PLGA nanoparticles (NPs) containing short PNA probes showed significantly superior loading, release profile, and uniform size distribution, compared to conventional non-cationic PNA probes. Confocal microscopy and flow cytometry analyses showed efficient transfection efficiency and uniform distribution of PLGA NPs containing short PNA probes in the cytoplasm. Functional analysis also confirmed efficient miRNA-155 inhibition including an effect on its downstream target proteins. Further, reduced tumor growth was observed after systemic delivery of PLGA nanoparticles containing short PNA probes in vivo in a xenograft mouse model following inhibition of miR-155. There was no evidence of acute or chronic toxicity associated with systemic delivery of PLGA NPs containing short PNA probes in the mice. Overall, in this paper we present a novel antimiR strategy based on PLGA nanoparticle delivered short PNA probes for potential cancer therapy.

TRIM71 is an important RNA-binding protein in development and disease, yet its direct targets have not been investigated globally. Here we describe a number of disease and developmentally-relevant TRIM71 RNA targets such as the MBNL family, LIN28B, MDM2, and TCF7L2. We describe a new role for TRIM71 as capable of positive or negative RNA regulation depending on the RNA target. We found that TRIM71 co-precipitated with IMP1 which could explain its multiple mechanisms of RNA regulation, as IMP1 is typically thought to stabilize RNAs. Deletion of the NHL domain of TRIM71 impacted its ability to bind to RNA and RNAs bound by congenital hydrocephalus-associated point mutations in the RNA-binding NHL domain of TRIM71 clustered closely with RNAs bound by the NHL deletion mutant. Our work expands the possible mechanisms by which TRIM71 may regulate RNAs and elucidates further potential RNA targets.

Peptide nucleic acids (PNAs) have emerged as one of the most versatile tools with a wide range of biomedical applications including antisense, antimiR, antigene, as well as site-specific gene editing. The application and potential of PNAs has been limited due to low solubility and poor cellular uptake. Several strategies have been employed to overcome the aforementioned challenges like conjugation to cationic peptides or nanotechnology to achieve superior transfection efficiency ex vivo and in vivo. Here, we report a detailed procedure optimized in our lab for synthesis of short cationic PNA probes, which exhibit high purity and yield in comparison to full-length PNA oligomers. We also provide step-by-step details of encapsulating short cationic PNA probes in poly (lactic-co-glycolic acid) nanoparticles by double emulsion solvent evaporation technique. 1.Detailed procedure for synthesis of short cationic PNAs with or without fluorophore (dye) conjugation while ensuring high yield and purity.2.Step-by-step details for encapsulation of short cationic PNAs in PLGA nanoparticles via double emulsion solvent evaporation technique.