RNAi mediated silencing of STAT3/PD-L1 in tumor-associated immune cells induces robust anti-tumor effects in immunotherapy resistant tumors.

Malignant tumors are often associated with an immunosuppressive tumor microenvironment (TME), rendering most of them resistant to standard-of-care immune checkpoint inhibitors (CPIs). Signal transducer and activator of transcription 3 (STAT3), a ubiquitously expressed transcription factor, has well-defined immunosuppressive functions in several leukocyte populations within the TME. Since the STAT3 protein has been challenging to target using conventional pharmaceutical modalities, we investigated the feasibility of applying systemically delivered RNA interference (RNAi) agents to silence its mRNA directly in tumor-associated immune cells. In preclinical rodent tumor models, chemically stabilized acylated small interfering RNAs (siRNAs) selectively silenced Stat3 mRNA in multiple relevant cell types, reduced STAT3 protein levels, and increased cytotoxic T cell infiltration. In a murine model of CPI-resistant pancreatic cancer, RNAi-mediated Stat3 silencing resulted in tumor growth inhibition, which was further enhanced in combination with CPIs. To further exemplify the utility of RNAi for cancer immunotherapy, this technology was used to silence Cd274, the gene encoding the immune checkpoint protein programmed death-ligand 1 (PD-L1). Interestingly, silencing of Cd274 was effective in tumor models that are resistant to PD-L1 antibody therapy. These data represent the first demonstration of systemic delivery of RNAi agents to the TME and suggest applying this technology for immuno-oncology applications.

First-in-human randomized study of RNAi therapeutic RG6346 for chronic hepatitis B virus infection.

BACKGROUND & AIMS: RG6346 is an N-acetyl-D-galactosamine (GalNAc)-conjugated, double-stranded RNA interference agent targeting the HBV genome S-region. We investigated the safety, tolerability, pharmacokinetics, and pharmacodynamics of RG6346 in healthy volunteers and patients with chronic HBV infection (CHB). METHODS: This first-in-human, adaptive, randomized, double-blinded, phase I study recruited three groups of participants: Group A, 30 healthy volunteers received single-dose RG6346 at 0.1, 1.5, 3.0, 6.0, or 12.0 mg/kg, or placebo; Group B, nucleos(t)ide analogue-naïve participants with CHB received single-dose RG6346 at 3.0 mg/kg (n = 6) or placebo (n = 3); Group C, participants with nucleos(t)ide-suppressed CHB received four doses (every 28 days) of RG6346 at 1.5, 3.0, or 6.0 mg/kg (n = 4 in each cohort) or placebo (n = 6). RESULTS: RG6346 treatment for up to 4 months was safe and well tolerated. The most common adverse event was a mild injection site reaction. Several nucleos(t)ide-naïve participants exhibited self-resolving transaminase elevations with preserved liver function. By the end of RG6346 treatment in Group C (Day 112), the mean reduction from baseline in hepatitis B surface antigen (HBsAg) was 1.39, 1.80, and 1.64 log10 IU/ml in the 1.5, 3.0, and 6.0 mg/kg cohorts, respectively. Of the 12 participants in Group C, 11 (91.7%) achieved a ≥1 log10 IU/ml reduction in HBsAg (3 of 11 [27.3%] had the response sustained at conditional follow-up Day 448). No dose-response relationship was apparent between RG6346 and serum HBsAg levels. The RG6346-induced HBsAg response was independent of hepatitis B e antigen status. Moderate-to-marked sustained reductions of hepatitis B core-related antigen, HBV RNA, HBV DNA (in nucleos[t]ide analogue-naïve participants), and hepatitis B e antigen levels were observed. CONCLUSIONS: These favorable safety and pharmacodynamic data support the clinical development of RG6346 as the backbone of a finite antiviral treatment regimen, with the goal of sustained HBsAg loss (functional cure) in patients with CHB. CLINICAL TRIAL NUMBER: ClinicalTrials.gov NCT03772249. IMPACT AND IMPLICATIONS: Currently available therapies for chronic HBV infection are associated with low rates of functional cure and new, more efficacious treatments are needed. This first-in-human study of RG6346, an RNA interference therapy, showed a favorable safety profile as well as marked and durable reductions in hepatitis B surface antigen levels. These results support the continued development of RG6346 as the backbone of a finite treatment regimen targeting high functional cure rates and are important for HBV researchers and physicians.

Therapeutic RNA interference: A novel approach to the treatment of primary hyperoxaluria.

RNA interference (RNAi) is a natural biological pathway that inhibits gene expression by targeted degradation or translational inhibition of cytoplasmic mRNA by the RNA induced silencing complex. RNAi has long been exploited in laboratory research to study the biological consequences of the reduced expression of a gene of interest. More recently RNAi has been demonstrated as a therapeutic avenue for rare metabolic diseases. This review presents an overview of the cellular RNAi machinery as well as therapeutic RNAi design and delivery. As a clinical example we present primary hyperoxaluria, an ultrarare inherited disease of increased hepatic oxalate production which leads to recurrent calcium oxalate kidney stones. In the most common form of the disease (Type 1), end-stage kidney disease occurs in childhood or young adulthood, often necessitating combined kidney and liver transplantation. In this context we discuss nedosiran (Dicerna Pharmaceuticals, Inc.) and lumasiran (Alnylam Pharmaceuticals), which are both novel RNAi therapies for primary hyperoxaluria that selectively reduce hepatic expression of lactate dehydrogenase and glycolate oxidase respectively, reducing hepatic oxalate production and urinary oxalate levels. Finally, we consider future optimizations advances in RNAi therapies.

RNAi-Mediated ß-Catenin Inhibition Promotes T Cell Infiltration and Antitumor Activity in Combination with Immune Checkpoint Blockade.

Wnt/ß-catenin signaling mediates cancer immune evasion and resistance to immune checkpoint therapy, in part by blocking cytokines that trigger immune cell recruitment. Inhibition of ß-catenin may be an effective strategy for increasing the low response rate to these effective medicines in numerous cancer populations. DCR-BCAT is a nanoparticle drug product containing a chemically optimized RNAi trigger targeting CTNNB1, the gene that encodes ß-catenin. In syngeneic mouse tumor models, ß-catenin inhibition with DCR-BCAT significantly increased T cell infiltration and potentiated the sensitivity of the tumors to checkpoint inhibition. The combination of DCR-BCAT and immunotherapy yielded significantly greater tumor growth inhibition (TGI) compared to monotherapy in B16F10 melanoma, 4T1 mammary carcinoma, Neuro2A neuroblastoma, and Renca renal adenocarcinoma. Response to the RNAi-containing combination therapy was not dependent on Wnt activation status of the tumor. Importantly, this drug combination was associated with elevated levels of biomarkers of T cell-mediated cytotoxicity. Finally, when CTLA-4 and PD-1 antibodies were combined with DCR-BCAT in MMTV-Wnt1 transgenic mice, a genetic model of spontaneous Wnt-driven tumors, complete regressions were achieved in the majority of treated subjects. These data support RNAi-mediated ß-catenin inhibition as an effective strategy to increase response rates to cancer immunotherapy.

Specific Inhibition of Hepatic Lactate Dehydrogenase Reduces Oxalate Production in Mouse Models of Primary Hyperoxaluria.

Primary hyperoxalurias (PHs) are autosomal recessive disorders caused by the overproduction of oxalate leading to calcium oxalate precipitation in the kidney and eventually to end-stage renal disease. One promising strategy to treat PHs is to reduce the hepatic production of oxalate through substrate reduction therapy by inhibiting liver-specific glycolate oxidase (GO), which controls the conversion of glycolate to glyoxylate, the proposed main precursor to oxalate. Alternatively, diminishing the amount of hepatic lactate dehydrogenase (LDH) expression, the proposed key enzyme responsible for converting glyoxylate to oxalate, should directly prevent the accumulation of oxalate in PH patients. Using RNAi, we provide the first in vivo evidence in mammals to support LDH as the key enzyme responsible for converting glyoxylate to oxalate. In addition, we demonstrate that reduction of hepatic LDH achieves efficient oxalate reduction and prevents calcium oxalate crystal deposition in genetically engineered mouse models of PH types 1 (PH1) and 2 (PH2), as well as in chemically induced PH mouse models. Repression of hepatic LDH in mice did not cause any acute elevation of circulating liver enzymes, lactate acidosis, or exertional myopathy, suggesting further evaluation of liver-specific inhibition of LDH as a potential approach for treating PH1 and PH2 is warranted.

Inhibition of Glycogen Synthase II with RNAi Prevents Liver Injury in Mouse Models of Glycogen Storage Diseases.

Glycogen storage diseases (GSDs) of the liver are devastating disorders presenting with fasting hypoglycemia as well as hepatic glycogen and lipid accumulation, which could lead to long-term liver damage. Diet control is frequently utilized to manage the potentially dangerous hypoglycemia, but there is currently no effective pharmacological treatment for preventing hepatomegaly and concurrent liver metabolic abnormalities, which could lead to fibrosis, cirrhosis, and hepatocellular adenoma or carcinoma. In this study, we demonstrate that inhibition of glycogen synthesis using an RNAi approach to silence hepatic Gys2 expression effectively prevents glycogen synthesis, glycogen accumulation, hepatomegaly, fibrosis, and nodule development in a mouse model of GSD III. Mechanistically, reduction of accumulated abnormally structured glycogen prevents proliferation of hepatocytes and activation of myofibroblasts as well as infiltration of mononuclear cells. Additionally, we show that silencing Gys2 expression reduces hepatic steatosis in a mouse model of GSD type Ia, where we hypothesize that the reduction of glycogen also reduces the production of excess glucose-6-phosphate and its subsequent diversion to lipid synthesis. Our results support therapeutic silencing of GYS2 expression to prevent glycogen and lipid accumulation, which mediate initial signals that subsequently trigger cascades of long-term liver injury in GSDs.

Inhibition of Glycolate Oxidase With Dicer-substrate siRNA Reduces Calcium Oxalate Deposition in a Mouse Model of Primary Hyperoxaluria Type 1.

Primary hyperoxaluria type 1 (PH1) is an autosomal recessive, metabolic disorder caused by mutations of alanine-glyoxylate aminotransferase (AGT), a key hepatic enzyme in the detoxification of glyoxylate arising from multiple normal metabolic pathways to glycine. Accumulation of glyoxylate, a precursor of oxalate, leads to the overproduction of oxalate in the liver, which accumulates to high levels in kidneys and urine. Crystalization of calcium oxalate (CaOx) in the kidney ultimately results in renal failure. Currently, the only treatment effective in reduction of oxalate production in patients who do not respond to high-dose vitamin B6 therapy is a combined liver/kidney transplant. We explored an alternative approach to prevent glyoxylate production using Dicer-substrate small interfering RNAs (DsiRNAs) targeting hydroxyacid oxidase 1 (HAO1) mRNA which encodes glycolate oxidase (GO), to reduce the hepatic conversion of glycolate to glyoxylate. This approach efficiently reduces GO mRNA and protein in the livers of mice and nonhuman primates. Reduction of hepatic GO leads to normalization of urine oxalate levels and reduces CaOx deposition in a preclinical mouse model of PH1. Our results support the use of DsiRNA to reduce liver GO levels as a potential therapeutic approach to treat PH1.

Knockdown of ß-catenin with dicer-substrate siRNAs reduces liver tumor burden in vivo.

Despite progress in identifying molecular drivers of cancer, it has been difficult to translate this knowledge into new therapies, because many of the causal proteins cannot be inhibited by conventional small molecule therapeutics. RNA interference (RNAi), which uses small RNAs to inhibit gene expression, provides a promising alternative to reach traditionally undruggable protein targets by shutting off their expression at the messenger RNA (mRNA) level. Challenges for realizing the potential of RNAi have included identifying the appropriate genes to target and achieving sufficient knockdown in tumors. We have developed high-potency Dicer-substrate short-interfering RNAs (DsiRNAs) targeting ß-catenin and delivered these in vivo using lipid nanoparticles, resulting in significant reduction of ß-catenin expression in liver cancer models. Reduction of ß-catenin strongly reduced tumor burden, alone or in combination with sorafenib and as effectively as DsiRNAs that target mitotic genes such as PLK1 and KIF11. ß-catenin knockdown also strongly reduced the expression of ß-catenin-regulated genes, including MYC, providing a potential mechanism for tumor inhibition. These results validate ß-catenin as a target for liver cancer therapy and demonstrate the promise of RNAi in general and DsiRNAs in particular for reaching traditionally undruggable cancer targets.

Glutathione and Bcl-2 targeting facilitates elimination by chemoradiotherapy of human A375 melanoma xenografts overexpressing bcl-xl, bcl-2, and mcl-1.

BACKGROUND: Bcl-2 is believed to contribute to melanoma chemoresistance. However, expression of Bcl-2 proteins may be different among melanomas. Thus correlations among expression of Bcl-2-related proteins and in vivo melanoma progression, and resistance to combination therapies, was investigated. METHODS: Human A375 melanoma was injected s.c. into immunodeficient nude mice. Protein expression was studied in tumor samples obtained by laser microdisection. Transfection of siRNA or ectopic overexpression were applied to manipulate proteins which are up- or down-regulated, preferentially, during melanoma progression. Anti-bcl-2 antisense oligonucleotides and chemoradiotherapy (glutathione-depleting agents, paclitaxel protein-binding particles, daunorubicin, X rays) were administered in combination. RESULTS: In vivo A375 cells down-regulated pro-apoptotic bax expression; and up-regulated anti-apoptotic bcl-2, bcl-xl, and mcl-1, however only Bcl-2 appeared critical for long-term tumor cell survival and progression in vivo. Reduction of Bcl-2, combined with partial therapies, decreased melanoma growth. But only Bcl-2 targeting plus the full combination of chemoradiotherapy eradicated A375 melanoma, and led to long-term survival (> 120 days) without recurrence in 80% of mice. Tumor regression was not due to immune stimulation. Hematology and clinical chemistry data were within accepted clinical toxicities. CONCLUSION: Strategies to target Bcl-2, may increase the effectiveness of antitumor therapies against melanomas overexpressing Bcl-2 and likely other Bcl-2-related antiapoptotic proteins.

Hepatic Lactate Dehydrogenase A: An RNA Interference Target for the Treatment of All Known Types of Primary Hyperoxaluria.

INTRODUCTION: Primary hyperoxaluria (PH) is a family of 3 rare genetic disorders of hepatic glyoxylate metabolism that lead to overproduction and increased renal excretion of oxalate resulting in progressive renal damage. LDHA inhibition of glyoxylate-to-oxalate conversion by RNA interference (RNAi) has emerged as a potential therapeutic option for all types of PH. LDHA is mainly expressed in the liver and muscles. METHODS: Nonclinical data in mice and nonhuman primates show that LDHA inhibition by RNAi reduces urinary oxalate excretion and that its effects are liver-specific without an impact on off-target tissues, such as the muscles. To confirm the lack of unintended effects in humans, we analyzed data from the phase I randomized controlled trial of single-dose nedosiran, an RNAi therapy targeting hepatic LDHA. We conducted a review of the literature on LDHA deficiency in humans, which we used as a baseline to assess the effect of hepatic LDHA inhibition. RESULTS: Based on a literature review of human LDHA deficiency, we defined the phenotype as mainly muscle-related with no liver manifestations. Healthy volunteers treated with nedosiran experienced no drug-related musculoskeletal adverse events. There were no significant alterations in plasma lactate, pyruvate, or creatine kinase levels in the nedosiran group compared with the placebo group, signaling the uninterrupted interconversion of lactate and pyruvate and normal muscle function. CONCLUSION: Phase I clinical data on nedosiran and published nonclinical data together provide substantial evidence that LDHA inhibition is a safe therapeutic mechanism for the treatment of all known types of PH.

Bcl-2 and glutathione depletion sensitizes B16 melanoma to combination therapy and eliminates metastatic disease.

PURPOSE: Advanced melanoma resists all current therapies, and metastases in the liver are particularly problematic. Prevalent resistance factors include elevated glutathione (GSH) and increased expression of bcl-2 in melanoma cells. GSH has pleiotropic effects promoting cell growth and broad resistance to therapy, whereas Bcl-2 inhibits the activation of apoptosis and contributes to elevation of GSH. This study determined the in vivo efficacy of combination therapies administered while GSH and Bcl-2 were individually and simultaneously decreased in metastatic melanoma lesions. EXPERIMENTAL DESIGN: Highly metastatic murine B16 melanoma (B16M-F10) cells have elevated levels of both GSH and Bcl-2. B16M-F10 cells were injected i.v. to establish metastatic lesions in vivo. GSH was decreased using an L-glutamine--enriched diet and administration of verapamil and acivicin, whereas Bcl-2 was reduced using oligodeoxynucleotide G3139. Paclitaxel, X-rays, tumor necrosis factor-alpha, and IFN-gamma were administered as a combination therapy. RESULTS: Metastatic cells were isolated from liver to confirm the depletion of GSH and Bcl-2 in vivo. Reduction of Bcl-2 and GSH, combined with partial therapies, decreased the number and volume of invasive B16M-F10 foci in liver by up to 99% (P<0.01). The full combination of paclitaxel, X-rays, and cytokines eliminated B16M-F10 cells from liver and all other systemic disease, leading to long-term survival (>120 days) without recurrence in 90% of mice receiving the full therapy. Toxicity was manageable; the mice recovered quickly, and hematology and clinical chemistry data were representative of accepted clinical toxicities. CONCLUSIONS: Our results suggest a new strategy to induce regression of late-stage metastatic melanoma.

Knock-down of Bcl-2 by antisense oligodeoxynucleotides induces radiosensitization and inhibition of angiogenesis in human PC-3 prostate tumor xenografts.

Expression of the proto-oncogene Bcl-2 is associated with tumor progression. Bcl-2's broad expression in tumors, coupled with its role in resistance to chemotherapy and radiation therapy-induced apoptosis, makes it a rational target for anticancer therapy. Antisense Bcl-2 oligodeoxynucleotide (ODN) reagents have been shown to be effective in reducing Bcl-2 expression in a number of systems. We investigated whether treating human prostate cancer cells with antisense Bcl-2 ODN (G3139, oblimersen sodium, Genasense) before irradiation would render them more susceptible to radiation effects. Two prostate cancer cell lines expressing Bcl-2 at different levels (PC-3-Bcl-2 and PC-3-Neo) were subjected to antisense Bcl-2 ODN, reverse control (CTL), or mock treatment. Antisense Bcl-2 ODN alone produced no cytotoxic effects and was associated with G(1) cell cycle arrest. The combination of antisense Bcl-2 ODN with irradiation sensitized both cell lines to the killing effects of radiation. Both PC-3-Bcl-2 and PC-3-Neo xenografts in mice treated with the combination of antisense Bcl-2 ODN and irradiation were more than three times smaller by volume compared with xenografts in mice treated with reverse CTL alone, antisense Bcl-2 ODN alone, irradiation alone, or reverse CTL plus radiotherapy (P = 0.0001). Specifically, PC-3-Bcl-2 xenograft tumors treated with antisense Bcl-2 ODN and irradiation had increased rates of apoptosis and decreased rates of angiogenesis and proliferation. PC-3-Neo xenograft tumors had decreased proliferation only. This is the first study which shows that therapy directed at Bcl-2 affects tumor vasculature. Together, these findings warrant further study of this novel combination of Bcl-2 reduction and radiation therapy, as well as Bcl-2 reduction and angiogenic therapy.

ß-Catenin mRNA Silencing and MEK Inhibition Display Synergistic Efficacy in Preclinical Tumor Models.

Colorectal carcinomas harbor well-defined genetic abnormalities, including aberrant activation of Wnt/ß-catenin and MAPK pathways, often simultaneously. Although the MAPK pathway can be targeted using potent small-molecule drugs, including BRAF and MEK inhibitors, ß-catenin inhibition has been historically challenging. RNAi approaches have advanced to the stage of clinical viability and are especially well suited for transcriptional modulators, such as ß-catenin. In this study, we report therapeutic effects of combined targeting of these pathways with pharmacologic agents. Using a recently described tumor-selective nanoparticle containing a ß-catenin-targeting RNAi trigger, in combination with the FDA-approved MEK inhibitor (MEKi) trametinib, we demonstrate synergistic tumor growth inhibition in in vivo models of colorectal cancer, melanoma, and hepatocellular carcinoma. At dose levels that were insufficient to significantly impact tumor growth as monotherapies, combination regimens resulted in synergistic efficacy and complete tumor growth inhibition. Importantly, dual MEKi/RNAi therapy dramatically improved survival of mice bearing colorectal cancer liver metastases. In addition, pharmacologic silencing of ß-catenin mRNA was effective against tumors that are inherently resistant or that acquire drug-induced resistance to trametinib. These results provide a strong rationale for clinical evaluation of this dual-targeting approach for cancers harboring Wnt/ß-catenin and MAPK pathway mutations. Mol Cancer Ther; 17(2); 544-53. ©2017 AACR.

Irradiation of human prostate cancer cells increases uptake of antisense oligodeoxynucleotide.

PURPOSE: To investigate whether irradiation before antisense Bcl-2 oligodeoxynucleotide (ODN) administration enhances tissue uptake, and whether periodic dosing enhances cellular uptake of fluorescently labeled ODN relative to constant dosing. METHODS AND MATERIALS: PC-3-Bcl-2 cells (prostate cancer cell line engineered to overexpress Bcl-2) were subjected to increasing doses of irradiation (0-10 Gy) with or without increasing concentrations of fluorescently labeled antisense Bcl-2 ODN (G4243). The fluorescent signal intensity was quantified as the total grain area with commercial software. In addition, PC-3-Bcl-2 subcutaneous xenograft tumors were treated with or without irradiation in combination with various dosing schemas of G4243. The uptake of fluorescent G4243 in tumors was quantitated. RESULTS: The uptake of G4243 was increased in prostate cancer cells exposed to low doses of irradiation both in vitro and in vivo. Irradiation before G4243 treatment resulted in increased fluorescent signal intensity in xenograft tumors compared with those irradiated after G4243 treatment. A single weekly dose of G4243 produced higher G4243 uptake in xenograft tumors than daily dosing, even when the total dose administered per week was held constant. CONCLUSIONS: These findings suggest that ionizing radiation increases the uptake of therapeutic ODN in target tissues and, thus, has potential to increase the efficacy of ODN in clinical applications.

Bcl-2 protein in 518A2 melanoma cells in vivo and in vitro.

PURPOSE: Bcl-2 is an apoptotic protein that is highly expressed in advanced melanoma. Several strategies have been employed to target the expression of this protein, including G3139, an 18-mer phosphorothioate oligodeoxyribonucleotide targeted to the initiation region of the Bcl-2 mRNA. This compound has recently completed phase III global clinical evaluation, but the function of Bcl-2 as a target in melanoma has not been completely clarified. To help resolve this question, we have permanently and stably down-regulated Bcl-2 protein and mRNA expression in 518A2 cells by two different technologies and evaluated the resulting clones both in vitro and in vivo. EXPERIMENTAL DESIGN: 518A2 melanoma cells were transfected with plasmids engineered to produce either a single-stranded antisense oligonucleotide targeted to the initiation codon region of the Bcl-2 mRNA or a short hairpin RNA also targeted to the Bcl-2 mRNA. In vitro growth, the apoptotic response to G3139, and the G3139-induced release of cytochrome c from isolated mitochondria were evaluated. Cells were then xenografted into severe combined immunodeficient mice and tumor growth was measured. RESULTS: In vitro, down-regulation of Bcl-2 expression by either method produced no change either in the rate of growth or in sensitivity to standard cytotoxic chemotherapeutic agents. Likewise, the induction of apoptosis by G3139 was entirely Bcl-2 independent. In addition, the G3139-induced release from isolated mitochondria was also relatively independent of Bcl-2 expression. However, when xenografted into severe combined immunodeficient mice, cells with silenced Bcl-2, using either technology, either failed to grow at all or grew to tumors of low volume and then completely regressed. In contrast, control cells with "normal" levels of Bcl-2 protein expression expanded to be large, necrotic tumors. CONCLUSIONS: The presence of Bcl-2 protein profoundly affects the ability of 518A2 melanoma cells to grow as human tumor xenografts in severe combined immunodeficient mice. The in vivo role of Bcl-2 in melanoma cells thus differs significantly from its in vitro role, and these experiments further suggest that Bcl-2 may be an important therapeutic target even in tumors that do not contain the t14:18 translocation.

Direct Pharmacological Inhibition of ß-Catenin by RNA Interference in Tumors of Diverse Origin.

The Wnt/ß-catenin pathway is among the most frequently altered signaling networks in human cancers. Despite decades of preclinical and clinical research, efficient therapeutic targeting of Wnt/ß-catenin has been elusive. RNA interference (RNAi) technology silences genes at the mRNA level and therefore can be applied to previously undruggable targets. Lipid nanoparticles (LNP) represent an elegant solution for the delivery of RNAi-triggering oligonucleotides to disease-relevant tissues, but have been mostly restricted to applications in the liver. In this study, we systematically tuned the composition of a prototype LNP to enable tumor-selective delivery of a Dicer-substrate siRNA (DsiRNA) targeting CTNNB1, the gene encoding ß-catenin. This formulation, termed EnCore-R, demonstrated pharmacodynamic activity in subcutaneous human tumor xenografts, orthotopic patient-derived xenograft (PDX) tumors, disseminated hematopoietic tumors, genetically induced primary liver tumors, metastatic colorectal tumors, and murine metastatic melanoma. DsiRNA delivery was homogeneous in tumor sections, selective over normal liver and independent of apolipoprotein-E binding. Significant tumor growth inhibition was achieved in Wnt-dependent colorectal and hepatocellular carcinoma models, but not in Wnt-independent tumors. Finally, no evidence of accelerated blood clearance or sustained liver transaminase elevation was observed after repeated dosing in nonhuman primates. These data support further investigation to gain mechanistic insight, optimize dose regimens, and identify efficacious combinations with standard-of-care therapeutics. Mol Cancer Ther; 15(9); 2143-54. ©2016 AACR.

Quantitative analysis of dicer substrate oligonucleotides in mouse liver by ultra-high-performance liquid chromatography-electrospray ionization tandem mass spectrometry.

A method using multi-mode solid-phase extraction and ultra-high-performance liquid chromatography (UHPLC)-electrospray mass spectrometry was developed to quantify Dicer-substrate small interfering RNA (DsiRNA) directed against the hypoxanthine phosphoribosyltransferase 1 (HPRT1) gene transcript in mouse liver tissue. The oligonucleotides were separated into sense and antisense strands using a UHPLC C(18) column with mobile phases containing 1,1,1,3,3,3-hexafluoro-2-propanol in both water (mobile phase A) and methanol (mobile phase B) with triethylamine as the ion pairing agent at a column temperature of 65°C. The lower limits of detection for the sense and antisense strands were ~1 ng/mg. The dynamic ranges for the sense and antisense strands were 5 ng/mg-1,000 ng/mg and 1 ng/mg-1,000 ng/mg, respectively. The lower limits of quantification for the sense and antisense strands were 5 ng/mg and 1 ng/mg, respectively, each with a relative standard deviation <15% over the range of calibration curve with sufficient precision and accuracy. Oligonucleotides were quantified at different time intervals after intravenous administration of living mice with lipid nanoparticle formulated HPRT1 DsiRNA and were detected as early as 15 min after administration, but not detected beyond the 24 h time point.

Inhibition of BCL-2 in small cell lung cancer cell lines with oblimersen, an antisense BCL-2 oligodeoxynucleotide (ODN): in vitro and in vivo enhancement of radiation response.

BACKGROUND: Oblimersen, an ODN targeting BCL-2 RNA, has been shown to be effective in reducing BCL-2 expression in vitro and in in vivo models engineered to overexpress BCL-2. The present study evaluated the efficacy of combining BCL-2 ODN and radiation in small-cell lung cancers (SCLC) cell lines. MATERIALS AND METHODS: The in vitro effect was determined using short term (cell viability) and long term (clonogenic) assays. Apoptosis, BCL-2 expression and intratumoural uptake of the FAM-ODN with or without prior radiation treatment were also evaluated. Combination of ODN and RT was also assessed in vivo. RESULTS: Radiation was shown to increase intracellular and intratumoural penetration of oblimersen, confirming previous results obtained in prostate cancer xenograft models. Oblimersen decreased BCL-2 protein expression in vitro and in vivo. BCL-2 ODN sensitised H69 cells to radiation in vitro and in vivo. Oblimersen increased radiation-induced apoptosis and decreased in vivo tumoural vascularisation. CONCLUSION: Oblimersen was shown to increase in vitro and in vivo effect of RT on SCLC cell lines. Radiation increases intracellular and intratumoural penetration of ODN. This pre-clinical study argues in favour of clinical development in localised SCLC.

Downregulation of BCL-2 induces downregulation of carbonic anhydrase IX, vascular endothelial growth factor, and pAkt and induces radiation sensitization.

OBJECTIVES: Our group previously demonstrated that expression of the oncogene, Bcl-2, was associated with radiation resistance. The aim of the present study was to determine whether Bcl-2 expression in radiation-resistant tumors was associated with expression of carbonic anhydrase IX (CAIX), vascular endothelial growth factor (VEGF), and pAkt and whether downregulation of Bcl-2 could modulate the expression of CAIX, VEGF, and pAkt. METHODS: Two prostate cancer cell lines, PC-3-Bcl-2 and PC-3-Neo, were injected into the subcutaneous flanks of 192 athymic male nude mice; 96 received PC-3 Bcl-2 and 96 PC-3-Neo. The mice were then treated with antisense Bcl-2 oligodeoxynucleotide (ASODN), reverse control ODN, or vehicle only (mock treatment) with or without irradiation (4 Gy). The tumors were monitored for growth (ie, volume) over time, resected at various points, and processed and sectioned for protein analyses. RESULTS: Bcl-2 ASODN treatment was associated with downregulation of Bcl-2, VEGF, pAkt, and CAIX. PC-3-Bcl-2 and PC-3-Neo prostate tumor xenografts in mice treated with the combination of Bcl-2 ASODN and irradiation were significantly (ie, one third) smaller than those in mice treated with reverse control ODN alone, Bcl-2 ASODN alone, irradiation alone, or reverse control ODN plus irradiation (P = 0.0001). An increased tumor response to the combined therapy was associated with decreased expression of Bcl-2, VEGF, and pAkt proteins. CONCLUSIONS: These findings have demonstrated an intimate relationship among CAIX, VEGF, pAkt, and Bcl-2 in prostate tumors. Thus, CAIX might prove effective as a potential marker of tumor radiation resistance. Downregulation of CAIX might lead to radiation sensitization. Consequently, the combination of CAIX reduction and radiotherapy warrants further consideration as a new strategy for therapy.