Reprogrammed glucose metabolism as a result of increased glycolysis and glucose uptake is a hallmark of cancer. Here we show that cancer cells can suppress glucose uptake by non-tumour cells in the pre-metastatic niche, by secreting vesicles that carry high levels of the miR-122 microRNA. High miR-122 levels in the circulation have been associated with metastasis in breast cancer patients and we show that cancer-cell-secreted miR-122 facilitates metastasis by increasing nutrient availability in the pre-metastatic niche. Mechanistically cancer-cell-derived miR-122 suppresses glucose uptake by niche cells in vitro and in vivo by downregulating the glycolytic enzyme pyruvate kinase (PKM). In vivo inhibition of miR-122 restores glucose uptake in distant organs, including brain and lungs, and decreases the incidence of metastasis. These results demonstrate that by modifying glucose utilization by recipient pre-metastatic niche cells, cancer-derived extracellular miR-122 is able to reprogram systemic energy metabolism to facilitate disease progression.

Efficient delivery of siRNA to specific cell populations in vivo remains a formidable challenge to its successful therapeutic application. We describe a novel siRNA-based approach – synthetically linking siRNA to an oligonucleotide TLR9 agonist – that targets and silences genes in TLR9+ myeloid cells and B cells, both of which are key components of the tumor microenvironment. Because Stat3 in tumor-associated immune cells suppresses antitumor immune responses and hinders TLR9-induced immune stimulation, we tested CpG-Stat3siRNA conjugates for anti-tumor effects. When injected locally at the tumor site or systemically through an intravenous route, the CpG-Stat3siRNA conjugates access tumor-associated dendritic cells, macrophages and B cells, inhibit Stat3 expression, leading to activation of tumor-associated immune cells, and ultimately potent anti-tumor immune responses. Our findings demonstrate the potential of TLR agonist-siRNA conjugates for targeted gene silencing coupled with TLR stimulation and immune activation in the tumor microenvironment.

MicroRNAs (miRNAs) are critical regulators of gene expression, and exert extensive impacts on development, physiology, and disease of eukaryotes. A high degree of parallelism is found in the molecular basis of miRNA biogenesis and action in plants and animals. Recent studies interestingly suggest a potential cross-kingdom action of plant-derived miRNAs, through dietary intake, in regulating mammalian gene expression. Although the source and scope of plant miRNAs detected in mammalian specimens remain controversial, these initial studies inspired us to determine whether plant miRNAs can be detected in Western human sera and whether these plant miRNAs are able to influence gene expression and cellular processes related to human diseases such as cancer. Here we found that Western donor sera contained the plant miRNA miR159, whose abundance in the serum was inversely correlated with breast cancer incidence and progression in patients. In human sera, miR159 was predominantly detected in the extracellular vesicles, and was resistant to sodium periodate oxidation suggesting the plant-originated 2'-O-methylation on the 3′ terminal ribose. In breast cancer cells but not non-cancerous mammary epithelial cells, a synthetic mimic of miR159 was capable of inhibiting proliferation by targeting TCF7 that encodes a Wnt signaling transcription factor, leading to a decrease in MYC protein levels. Oral administration of miR159 mimic significantly suppressed the growth of xenograft breast tumors in mice. These results demonstrate for the first time that a plant miRNA can inhibit cancer growth in mammals.

The envelope glycoprotein of human immunodeficiency virus (HIV) consists of an exterior glycoprotein (gp120) and a trans-membrane domain (gp41) and has an important role in viral entry into cells. HIV-1 entry has been validated as a clinically relevant anti-viral strategy for drug discovery. In the present work, several 2′-F substituted RNA aptamers that bind to the HIV-1BaL gp120 protein with nanomole affinity were isolated from a RNA library by the SELEX (Systematic Evolution of Ligands by EXponential enrichment) procedure. From two of these aptamers we created a series of new dual inhibitory function anti-gp120 aptamer–siRNA chimeras. The aptamers and aptamer–siRNA chimeras specifically bind to and are internalized into cells expressing HIV gp160. The Dicer-substrate siRNA delivered by the aptamers is functionally processed by Dicer, resulting in specific inhibition of HIV-1 replication and infectivity in cultured CEM T-cells and primary blood mononuclear cells (PBMCs). Moreover, we have introduced a ‘sticky’ sequence onto a chemically synthesized aptamer which facilitates attachment of the Dicer substrate siRNAs for potential multiplexing. Our results provide a set of novel inhibitory agents for blocking HIV replication and further validate the use of aptamers for delivery of Dicer substrate siRNAs.

Therapeutic strategies designed to treat HIV infection with combinations of antiviral drugs have proven to be the best approach for slowing the progression to AIDS. Despite this progress, there are problems with viral drug resistance and toxicity, necessitating new approaches to combating HIV-1 infection. We have therefore developed a different combination approach for the treatment of HIV infection in which an RNA aptamer, with high binding affinity to the HIV-1 envelope (gp120) protein and virus neutralization properties, is attached to and delivers a small interfering RNA (siRNA) that triggers sequence-specific degradation of HIV RNAs. We have tested the antiviral activities of these chimeric RNAs in a humanized Rag2−/−γc−/− (RAG-hu) mouse model with multilineage human hematopoiesis. In this animal model, HIV-1 replication and CD4+ T cell depletion mimic the situation seen in human HIV-infected patients. Our results show that treatment with either the anti-gp120 aptamer or the aptamer-siRNA chimera suppressed HIV-1 replication by several orders of magnitude and prevented the viral-induced helper CD4+ T cell decline. In comparison to the aptamer alone, the aptamer-siRNA combination provided more extensive inhibition, resulting in a significantly longer antiviral effect that extended several weeks beyond the last injected dose. The aptamer thus acts as a broad-spectrum HIV-neutralizing agent and an siRNA delivery vehicle. The combined aptamer-siRNA agent provides an attractive, nontoxic therapeutic approach for treatment of HIV infection.

Chronic myelogenous leukemia (CML) stem cells (LSCs) are responsible for initiating and maintaining clonal hematopoiesis. These cells persist in the bone marrow (BM) despite effective inhibition of BCR-ABL kinase activity by tyrosine kinase inhibitors (TKIs). Here, we show that although miR-126 supports the quiescence, self-renewal and engraftment capacity of CML LSCs, miR-126 levels are lower in CML LSCs as compared to normal long-term hematopoietic stem cells (LT-HSCs). Down-regulation of miR-126 levels in CML LSCs is due to phosphorylation of SPRED1 by BCR-ABL, leading to inhibition of the RAN/EXP-5/RCC1 complex that mediates miRNA maturation. Endothelial cells (ECs) in the BM supply miR-126 to CML LSCs to support quiescence and leukemia growth, as shown using CML mouse models with conditional miR-126 knock-out (KO) in ECs and/or LSCs. Inhibition of BCR-ABL by TKI treatment causes an undesired increase in endogenous miR-126 levels, thereby enhancing LSC quiescence and persistence. miR-126 KO in LSCs and/or ECs, or treatment with a CpG-miR-126 inhibitor targeting miR-126 in both LSCs and ECs, enhances the in vivo anti-leukemic effects of TKI treatment and strongly diminishes LSC leukemia-initiating capacity, providing a new strategy for the elimination of LSCs in CML.

While microRNAs (miRNAs) clearly regulate multiple pathways integral to disease development and progression, the lack of safe and reliable means for specific delivery of miRNAs to target tissues represents a major obstacle to their broad therapeutic application. Our objective was to explore the use of nucleic acid aptamers as carriers for cell-targeted delivery of a miRNA with tumor suppressor function, let-7g. Using an aptamer that binds to and antagonizes the oncogenic receptor tyrosine kinase Axl (GL21.T), here we describe the development of aptamer-miRNA conjugates as multifunctional molecules that inhibit the growth of Axl-expressing tumors. We conjugated the let-7g miRNA to GL21.T and demonstrate selective delivery to target cells, processing by the RNA interference machinery, and silencing of let-7g target genes. Importantly, the multifunctional conjugate reduced tumor growth in a xenograft model of lung adenocarcinoma. Therefore, our data establish aptamer-miRNA conjugates as a novel tool for targeted delivery of miRNAs with therapeutic potential.

• CpG(A)-siRNA oligonucleotides allow for targeting genes specifically in human TLR9 ϩ immune cells and blood cancer cells.• Tumoricidal and immunostimulatory properties of CpG(A)-STAT3 siRNA provide a novel therapeutic opportunity for hematologic malignancies.STAT3 operates in both cancer cells and tumor-associated immune cells to promote cancer progression. As a transcription factor, it is a highly desirable but difficult target for pharmacologic inhibition. We have recently shown that the TLR9 agonists CpG oligonucleotides can be used for targeted siRNA delivery to mouse immune cells. In the present study, we demonstrate that a similar strategy allows for targeted gene silencing in both normal and malignant human TLR9 ؉ hematopoietic cells in vivo. We have developed new human cell-specific CpG(A) - IntroductionThe proliferation and survival of the majority of hematologic cancers depends on constitutive activity of STAT transcription factors. 1,2 The first evidence linking STAT activity with human blood cancer was derived from studies on multiple myeloma (MM). Permanent activity of STAT3 observed in myeloma cells was critical for their survival because of up-regulation of antiapoptotic BCL-X L protein. 3 Later reports identified constitutive activation of STAT3 not only in myeloma but also in other hematologic malignancies, with the highest frequency in B-cell lymphoma (BCL) and acute myeloid leukemia (AML) patient blasts. 1,4,5 The presence of activated STAT3 in leukemic blasts was associated with decreased disease-free survival of AML patients. 4 As a point of convergence for downstream signaling from cytokine and growth factor receptors, STAT3 plays a critical role in mediating cross-talk within the tumor microenvironment, which promotes tumor immune tolerance, vascularization, and metastasis. 6 Because STAT3 operates in both cancer cells and nonmalignant tumorassociated cells, it represents a highly desirable target for cancer therapy. 6 These important findings instigated numerous attempts to develop STAT3 inhibitors; however, pharmacologic inhibition of a protein lacking enzymatic activity is challenging. 4,7 An additional complication is the close structural similarity between oncogenic STAT3 and functionally distinct STAT1, a transcriptional factor critical for generation of antitumor immunity by IFNs. 8,9 The tyrosine kinase inhibitors upstream from STAT3, such as JAK, SRC, c-KIT, and FLT3 in leukemia, gained attention as promising blood cancer therapeutics. 4 However, the effect of small-molecule drugs, including FLT3 inhibitors, in most clinical trials was short-lived. 10,11 Other conventional treatment regimens for hematologic malignancies are limited by the high toxicity to normal tissues, development of drug resistance, and low disease-free survival rates. For personal use only. on May 11, 2018. by guest www.bloodjournal.org FromThe emergence of therapeutic strategies based on RNA interference (RNAi) created a unique opportunity to silence any diseaserelated target gene. 13,14 The major obstacle ...