Nucleic acid combinations: A new frontier for cancer treatment

Is it Time for Multi-Drug Therapy with Combination of Therapeutic Nucleic Acids?

Therapeutic nucleic acids (TNAs) are a new class of drugs that exhibit different properties and mechanisms of action from those of small molecules or biological drugs. Over twenty oligonucleotide drugs and several COVID-19 vaccines have received regulatory approval for clinical use. A characteristic feature of these TNAs is that they are directed against one specific biological target and one specific RNA or DNA sequence. Consequently, TNAs currently used are administered as monotherapy. Due to the known advantages of multidrug therapy with low molecular weight drugs, it may be time to intensify work on such a treatment protocol, also in the case of TNAs.

Lysosomal-mediated drug release and activation for cancer therapy and immunotherapy

The development of carrier systems that are able to transport and release therapeutics to target cells is an emergent strategy to treat cancer; however, they following endocytosis are usually trapped in the endo/lysosomal compartments. The efficacy of drug conjugates and nanotherapeutics relies critically on their intracellular drug release ability, for which advanced systems responding to the unique lysosomal environment such as acidic pH and abundant enzymes (e.g. cathepsin B, sulfatase and β-glucuronidase) or equipped with photochemical internalization property have been energetically pursued. In this review, we highlight the recent designs of smart systems that promote efficient lysosomal release and/or escape of anticancer agents including chemotherapeutics (e.g. doxorubicin, platinum, chloroquine and hydrochloroquine) and biotherapeutics (e.g. proteins, siRNA, miRNA, mRNA and pDNA) to cancer cells or immunotherapeutic agents (e.g. antigens, mRNA and immunoadjuvants) to antigen-presenting cells (APCs), thereby boosting cancer therapy and immunotherapy. Lysosomal-mediated drug release presents an appealing approach to develop innovative cancer therapeutics and immunotherapeutics.

Lipoplexes for effective in vitro delivery of microRNAs to adult human cardiac fibroblasts for perspective direct cardiac cell reprogramming

Design of nanocarriers for efficient miRNA delivery can significantly improve miRNA-based therapies. Lipoplexes based on helper lipid, dioleoyl phosphatidylethanolamine (DOPE) and cationic lipid [2-(2,3-didodecyloxypropyl)-hydroxyethyl] ammonium bromide (DE) were formulated to efficiently deliver miR-1 or a combination of four microRNAs (miRcombo) to adult human cardiac fibroblasts (AHCFs). Lipoplexes with amino-to-phosphate groups ratio of 3 (N/P 3) showed nanometric hydrodynamic size (372 nm), positive Z-potential (40 mV) and high stability under storage conditions. Compared to commercial DharmaFECT1 (DF), DE-DOPE/miRNA lipoplexes showed superior miRNA loading efficiency (99 % vs. 64 %), and faster miRNA release (99 % vs. 82 % at 48 h). DE-DOPE/miR-1 lipoplexes showed superior viability (80-100 % vs. 50 %) in AHCFs, a 2-fold higher miR-1 expression and Twinfilin-1 (TWF-1) mRNA downregulation. DE-DOPE/miRcombo lipoplexes significantly enhanced AHCFs reprogramming into induced cardiomyocytes (iCMs), as shown by increased expression of CM markers compared to DF/miRcombo.

Combination Cancer Immunotherapy with Dendritic Cell Vaccine and Nanoparticles Loaded with Interleukin-15 and Anti-beta-catenin siRNA Significantly Inhibits Cancer Growth and Induces Anti-Tumor Immune Response

PURPOSE

The invention and application of new immunotherapeutic methods can compensate for the inefficiency of conventional cancer treatment approaches, partly due to the inhibitory microenvironment of the tumor. In this study, we tried to inhibit the growth of cancer cells and induce anti-tumor immune responses by silencing the expression of the β-catenin in the tumor microenvironment and transmitting interleukin (IL)-15 cytokine to provide optimal conditions for the dendritic cell (DC) vaccine.

METHODS

For this purpose, we used folic acid (FA)-conjugated SPION-carboxymethyl dextran (CMD) chitosan (C) nanoparticles (NPs) to deliver anti-β-catenin siRNA and IL-15 to cancer cells.

RESULTS

The results showed that the codelivery of β-catenin siRNA and IL-15 significantly reduced the growth of cancer cells and increased the immune response. The treatment also considerably stimulated the performance of the DC vaccine in triggering anti-tumor immunity, which inhibited tumor development and increased survival in mice in two different cancer models.

CONCLUSIONS

These findings suggest that the use of new nanocarriers such as SPION-C-CMD-FA could be an effective way to use as a novel combination therapy consisting of β-catenin siRNA, IL-15, and DC vaccine to treat cancer.

Drug delivery, biodistribution and anti-EGFR activity: theragnostic nanoparticles for simultaneous in vivo delivery of tyrosine kinase inhibitors and kinase activity biosensors

In vivo delivery of small molecule therapeutics to cancer cells, assessment of the selectivity of administration, and measuring the efficacity of the drug in question at the molecule level, are important ongoing challenges in developing new classes of cancer chemotherapeutics. One approach that has the potential to provide targeted delivery, tracking of biodistribution and readout of efficacy, is to use multimodal theragnostic nanoparticles to deliver the small molecule therapeutic. In this paper, we report the development of targeted theragnostic lipid/peptide/DNA lipopolyplexes. These simultaneously deliver an inhibitor of the EGFR tyrosine kinase, and plasmid DNA coding for a Crk-based biosensor, Picchu-X, which when expressed in the target cells can be used to quantify the inhibition of EGFR in vivo in a mouse colorectal cancer xenograft model. Reversible bioconjugation of a known analogue of the tyrosine kinase inhibitor Mo-IPQA to a cationic peptide, and co-formulation with peptides containing both EGFR-binding and cationic sequences, allowed for good levels of inhibitor encapsulation with targeted delivery to LIM1215 colon cancer cells. Furthermore, high levels of expression of the Picchu-X biosensor in the LIM1215 cells in vivo allowed us to demonstrate, using fluorescence lifetime microscopy (FLIM)-based biosensing, that EGFR activity can be successfully suppressed by the tyrosine kinase inhibitor, released from the lipopolyplexes. Finally, we measured the biodistribution of lipopolyplexes containing 125I-labelled inhibitors and were able to demonstrate that the lipopolyplexes gave significantly higher drug delivery to the tumors compared with free drug.

DNAzymes, Novel Therapeutic Agents in Cancer Therapy: A Review of Concepts to Applications

The past few decades have witnessed a rapid evolution in cancer drug research which is aimed at developing active biological interventions to regulate cancer-specific molecular targets. Nucleic acid-based therapeutics, including ribozymes, antisense oligonucleotides, small interference RNA (siRNA), aptamer, and DNAzymes, have emerged as promising candidates regulating cancer-specific genes at either the transcriptional or posttranscriptional level. Gene-specific catalytic DNA molecules, or DNAzymes, have shown promise as a therapeutic intervention against cancer in various in vitro and in vivo models, expediting towards clinical applications. DNAzymes are single-stranded catalytic DNA that has not been observed in nature, and they are synthesized through in vitro selection processes from a large pool of random DNA libraries. The intrinsic properties of DNAzymes like small molecular weight, higher stability, excellent programmability, diversity, and low cost have brought them to the forefront of the nucleic acid-based therapeutic arsenal available for cancers. In recent years, considerable efforts have been undertaken to assess a variety of DNAzymes against different cancers. However, their therapeutic application is constrained by the low delivery efficiency, cellular uptake, and target detection within the tumour microenvironment. Thus, there is a pursuit to identify efficient delivery methods in vivo before the full potential of DNAzymes in cancer therapy is realized. In this light, a review of the recent advances in the use of DNAzymes against cancers in preclinical and clinical settings is valuable to understand its potential as effective cancer therapy. We have thus sought to firstly provide a brief overview of construction and recent improvements in the design of DNAzymes. Secondly, this review stipulates the efficacy, safety, and tolerability of DNAzymes developed against major hallmarks of cancers tested in preclinical and clinical settings. Lastly, the recent advances in DNAzyme delivery systems along with the challenges and prospects for the clinical application of DNAzymes as cancer therapy are also discussed.

Suppression of Human Coronavirus 229E Infection in Lung Fibroblast Cells via RNA Interference

Despite extensive efforts to repurpose approved drugs, discover new small molecules, and develop vaccines, COVID-19 pandemic is still claiming victims around the world. The current arsenal of antiviral compounds did not perform well in the past viral infections (e.g., SARS), which casts a shadow of doubt for use against the new SARS-CoV-2. Vaccines should offer the ultimate protection; however, there is limited information about the longevity of the generated immunity and the protection against possible mutations. This study uses Human Coronavirus 229E as a model coronavirus to test the hypothesis that effective delivery of virus-specific siRNAs to infected cells will result in lower viral load and reduced cell death. Two different categories of nucleic acid delivery systems, Peptide/Lipid-Associated Nucleic Acids (PLANAs) and lipophilic polymers, were investigated for their toxicity in human lung fibroblast cells and their ability to deliver specific siRNAs targeting Spike and Envelope proteins in order to prevent cell death in infected cells. Selected siRNAs were effectively delivered to human lung fibroblast cells with negligible toxicity. Cell death due to viral infection was significantly reduced with individual and combinatorial silencing of selected viral proteins. The combinatorial silencing of Spike and Envelope proteins restored the cell viability completely and eliminated plaques in the investigated system. Our cell culture data indicate promising results for the RNAi based approach as an alternative antiviral treatment.

How can molecular dynamics simulations assist with gene medicines?

Molecular Dynamics (MD) simulations can provide a glimpse of complex atomistic and molecular events at the interface of biomaterials and biosystems. Gene therapy efforts that deploy biomaterial mediated delivery of nucleic acids could benefit immensely from such MD simulations. These efforts most commonly employ supramolecular assembly whose structure is highly dynamic and influential in the final outcomes. By careful analysis of the behavior of constituting elements, one can visualize the assembly as it makes its way though biosystems. We highlight the beneficial information to be gained from MD studies in this short perspective and outline a vision for future activity in the field.

RNA Interference Nanotherapeutics for Treatment of Glioblastoma Multiforme

Nucleic acid therapeutics for RNA interference (RNAi) are gaining attention in the treatment and management of several kinds of the so-called "undruggable" tumors via targeting specific molecular pathways or oncogenes. Synthetic ribonucleic acid (RNAs) oligonucleotides like siRNA, miRNA, shRNA, and lncRNA have shown potential as novel therapeutics. However, the delivery of such oligonucleotides is significantly hampered by their physiochemical (such as hydrophilicity, negative charge, and instability) and biopharmaceutical features (in vivo serum stability, fast renal clearance, interaction with extracellular proteins, and hindrance in cellular internalization) that markedly reduce their biological activity. Recently, several nanocarriers have evolved as suitable non-viral vectors for oligonucleotide delivery, which are known to either complex or conjugate with these oligonucleotides efficiently and also overcome the extracellular and intracellular barriers, thereby allowing access to the tumoral micro-environment for the better and desired outcome in glioblastoma multiforme (GBM). This Review focuses on the up-to-date advancements in the field of RNAi nanotherapeutics utilized for GBM treatment.

Histidine-Based Reduction-Sensitive Star-Polymer Inclusion Complex as a Potential DNA Carrier: Biophysical Studies Using Time-Resolved Fluorescence as an Important Tool

An ideal DNA carrier is one that is capable of effectively condensing DNA into complexes of optimum size and shape, preventing premature decomplexation in the bloodstream and efficiently releasing the DNA into affected cells. In this context, we have developed a novel β-cyclodextrin (β-CD)-based four-arm star-shaped polymer inclusion complex (IC) with arms made of a poly(l-histidine)-based cationic polymer. The polymer was well characterized by gel permeation chromatography, NMR, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. We have also investigated its DNA complexation and release properties. Bisadamantane containing a disulfide bond was synthesized that linked two such poly(l-histidine)-containing β-CD units via guest-host interactions to prepare the presented IC. Besides using the conventional steady-state fluorescence spectroscopy, the ability of this IC to condense DNA to form polyplexes and their release behavior have been established by using the time-resolved fluorescence spectroscopy technique. Thiazole orange (TO) was used for the first time as a DNA-intercalating dye in the time-resolved fluorescence spectroscopic study. The superior DNA-condensing ability of the IC as compared to that of the precursor two-arm β-CD and linear poly(l-histidine) of a comparable molecular weight, as confirmed by dynamic light scattering, zeta potential, atomic force microscopy, and gel electrophoresis studies, could be attributed to a higher charge density. The IC-DNA polyplexes were found to be stable in a medium similar to an extracellular fluid but could efficiently release DNA in the presence of 10 mM glutathione, a concentration prevalent in the intracellular fluid of cancer cells. Hence, here, we have successfully demonstrated the synthesis of a novel biocompatible star-shaped IC with the potential to carry and release DNA in cancer cells and also established the feasibility of using the time-resolved fluorescence spectroscopic technique to study the complexation behavior of the polycation and DNA using TO as a DNA-intercalating dye.

Prospects for RNAi Therapy of COVID-19

COVID-19 caused by the SARS-CoV-2 virus is a fast emerging disease with deadly consequences. The pulmonary system and lungs in particular are most prone to damage caused by the SARS-CoV-2 infection, which leaves a destructive footprint in the lung tissue, making it incapable of conducting its respiratory functions and resulting in severe acute respiratory disease and loss of life. There were no drug treatments or vaccines approved for SARS-CoV-2 at the onset of pandemic, necessitating an urgent need to develop effective therapeutics. To this end, the innate RNA interference (RNAi) mechanism can be employed to develop front line therapies against the virus. This approach allows specific binding and silencing of therapeutic targets by using short interfering RNA (siRNA) and short hairpin RNA (shRNA) molecules. In this review, we lay out the prospect of the RNAi technology for combatting the COVID-19. We first summarize current understanding of SARS-CoV-2 virology and the host response to viral entry and duplication, with the purpose of revealing effective RNAi targets. We then summarize the past experience with nucleic acid silencers for SARS-CoV, the predecessor for current SARS-CoV-2. Efforts targeting specific protein-coding regions within the viral genome and intragenomic targets are summarized. Emphasizing non-viral delivery approaches, molecular underpinnings of design of RNAi agents are summarized with comparative analysis of various systems used in the past. Promising viral targets as well as host factors are summarized, and the possibility of modulating the immune system are presented for more effective therapies. We place special emphasis on the limitations of past studies to propel the field faster by focusing on most relevant models to translate the promising agents to a clinical setting. Given the urgency to address lung failure in COVID-19, we summarize the feasibility of delivering promising therapies by the inhalational route, with the expectation that this route will provide the most effective intervention to halt viral spread. We conclude with the authors' perspectives on the future of RNAi therapeutics for combatting SARS-CoV-2. Since time is of the essence, a strong perspective for the path to most effective therapeutic approaches are clearly articulated by the authors.

TRAIL therapy and prospective developments for cancer treatment

Tumor Necrosis Factor (TNF) Related Apoptosis-Inducing Ligand (TRAIL), an immune cytokine of TNF-family, has received much attention in late 1990s as a potential cancer therapeutics due to its selective ability to induce apoptosis in cancer cells. TRAIL binds to cell surface death receptors, TRAIL-R1 (DR4) and TRAIL-R2 (DR5) and facilitates formation of death-inducing signaling complex (DISC), eventually activating the p53-independent apoptotic cascade. This unique mechanism makes the TRAIL a potential anticancer therapeutic especially for p53-mutated tumors. However, recombinant human TRAIL protein (rhTRAIL) and TRAIL-R agonist monoclonal antibodies (mAb) failed to exert robust anticancer activities due to inherent and/or acquired resistance, poor pharmacokinetics and weak potencies for apoptosis induction. To get TRAIL back on track as a cancer therapeutic, multiple strategies including protein modification, combinatorial approach and TRAIL gene therapy are being extensively explored. These strategies aim to enhance the half-life and bioavailability of TRAIL and synergize with TRAIL action ultimately sensitizing the resistant and non-responsive cells. We summarize emerging strategies for enhanced TRAIL therapy in this review and cover a wide range of recent technologies that will provide impetus to rejuvenate the TRAIL therapeutics in the clinical realm.

Enabling Combinatorial siRNA Delivery against Apoptosis-Related Proteins with Linoleic Acid and α-Linoleic Acid Substituted Low Molecular Weight Polyethylenimines

PURPOSE

Short interfering RNA (siRNA) therapy promises a new era in treatment of breast cancers but effective delivery systems are needed for clinical use. Since silencing complementary targets may offer improved efficacy, this study was undertaken to identify non-viral carriers for combinatorial siRNA delivery for more effective therapy.

METHODS

A library of lipid-substituted polymers from low molecular weight polyethyleneimine (PEI), linoleic acid (LA) and α-linoleic acid (αLA) with amide or thioester linkages was prepared and investigated for delivering Mcl-1, survivin and STAT5A siRNAs in breast cancer cells.

RESULTS

The effective polymers formed 80-190 nm particles with similar zeta-potentials, but the serum stability was greater for complexes formed with amide-linked lipid conjugates. The LA and αLA substitutions, with the low molecular weight PEI (1.2 kDa and 2.0 kDa) were able to deliver siRNA effectively to cells and retarded the growth of breast cancer cells. The amide-linked lipid substituents showed higher cellular delivery of siRNA as compared to thioester linkages. Upon combinational delivery of siRNAs, growth of MCF-7 cells was inhibited to a greater extent with 2.0PEI-LA9 mediated delivery of Mcl-1 combined survivin siRNAs as compared to individual siRNAs. The qRT-PCR analysis confirmed the decrease in mRNA levels of target genes with specific siRNAs and 2.0PEI-LA9 was the most effective polymer for delivering siRNAs (either single or in combination).

CONCLUSIONS

This study yielded effective siRNA carriers for combinational delivery of siRNAs. Careful choice of siRNA combinations will be critical since targeting individual genes might alter the expression of other critical mediators.

Acid-activated nonviral peptide vector for gene delivery

Nonviral vector-based gene therapy is a promising strategy for treating a myriad of diseases. Cell-penetrating peptides are gaining increasing attention as vectors for nucleic acid delivery. However, most studies have focused more on the transfection efficiency of these vectors than on their specificity and toxicity. To obtain ideal vectors with high efficiency and safety, we constructed the vector stearyl-TH by attaching a stearyl moiety to the N-terminus of the acid-activated cell penetrating peptide TH in this study. Under acidic conditions, stearyl-TH could bind to and condense plasmids into nanoparticle complexes, which displayed significantly enhanced cellular uptake and transfection efficiencies. In contrast, stearyl-TH lost the capacities of DNA binding and transfection at physiological pH. More importantly, stearyl-TH and the complexes formed by stearyl-TH and plasmids displayed no obvious toxicity at physiological pH. Consequently, the high transfection efficiency under acidic conditions and low toxicity make stearyl-TH a potential nucleic acid delivery vector for gene therapy.

Downregulation of STAT3, β-Catenin, and Notch-1 by Single and Combinations of siRNA Treatment Enhance Chemosensitivity of Wild Type and Doxorubicin Resistant MCF7 Breast Cancer Cells to Doxorubicin

Combinatorial therapeutic strategies using siRNA and small molecules to eradicate tumors are emerging. Targeting multiple signaling pathways decreases the chances of cancer cells switching and adapting new signaling processes that may occur when using a single therapeutic modality. Aberrant functioning of Notch-1, Wnt/β-catenin, and STAT3 proteins and their crosstalk signaling pathways have been found to be involved in tumor survival, drug resistance, and relapse. In the current study, we describe a therapeutic potential of single and combinations of siRNA designed for silencing Notch-1, Wnt/β-catenin, and STAT3 in MCF7_DoxS (wild type) and MCF7_DoxR (doxorubicin resistant) breast cancer cells. The MCF7_DoxR cells were developed through treatment with a gradual increase in doxorubicin concentration, the expression of targeted genes was investigated, and the expression profiling of CD44/CD24 of the MCF7_DoxS and MCF7_DoxR cells were detected by flow cytometry. Both MCF7_DoxS and MCF7_DoxR breast cancer cells were treated with single and combinations of siRNA to investigate synergism and were analyzed for their effect on cell proliferation with and without doxorubicin treatment. The finding of this study showed the overexpression of targeted genes and the enrichment of the CD44⁻/CD24⁺ phenotype in MCF7_DoxR cells when compared to MCF7_DoxS cells. In both cell lines, the gene silencing efficacy showed a synergistic effect when combining STAT3/Notch-1 and STAT3/Notch-1/β-catenin siRNA. Interestingly, the chemosensitivity of MCF7_DoxS and MCF7_DoxR cells to doxorubicin was increased when combined with siRNA treatment. Our study shows the possibility of using single and combinations of siRNA to enhance the chemosensitivity of cancer cells to conventional antitumor chemotherapy.

At the Intersection of Biomaterials and Gene Therapy: Progress in Non-viral Delivery of Nucleic Acids

Biomaterials play a critical role in technologies intended to deliver therapeutic agents in clinical settings. Recent explosion of our understanding of how cells utilize nucleic acids has garnered excitement to develop a range of older (e.g., antisense oligonucleotides, plasmid DNA and transposons) and emerging (e.g., short interfering RNA, messenger RNA and non-coding RNAs) nucleic acid agents for therapy of a wide range of diseases. This review will summarize biomaterials-centered advances to undertake effective utilization of nucleic acids for therapeutic purposes. We first review various types of nucleic acids and their unique abilities to deliver a range of clinical outcomes. Using recent advances in T-cell based therapy as a case in point, we summarize various possibilities for utilizing biomaterials to make an impact in this exciting therapeutic intervention technology, with the belief that this modality will serve as a therapeutic paradigm for other types of cellular therapies in the near future. We subsequently focus on contributions of biomaterials in emerging nucleic acid technologies, specifically focusing on the design of intelligent nanoparticles, deployment of mRNA as an alternative to plasmid DNA, long-acting (integrating) expression systems, and in vitro/in vivo expansion of engineered T-cells. We articulate the role of biomaterials in these emerging nucleic acid technologies in order to enhance the clinical impact of nucleic acids in the near future.

Light-Controlled in Vitro Gene Delivery Using Polymer-Tethered Spiropyran as a Photoswitchable Photosensitizer

A gene delivery system using spiropyran as a photoswitchable photosensitizer for the controlled photochemical internalization effect was developed by engineering the outer coating of a polyethylenimine/DNA complex with a small amount of spiropyran-containing cationic copolymers. The successful binding of cationic polymers by the polyethylenimine coating was detected by the distance-sensitive fluorescence resonance energy-transfer technique that evidenced the occurrence of energy transfer between fluorescein-labeled cationic copolymers and polyethylenimine-condensed rhodamine-labeled DNA. The ternary polyplexes feature reversible controllability of singlet oxygen generation based on the dual effect of spiropyrans in photochromism and aggregation-induced enhanced photosensitization, allowing significant light-induced amplification of bPEI-mediated in vitro transgene efficiency (from original 15% to final 91%) at a low DNA dose, with the integrity of supercoiled DNA structure unaffected. The use of spiropyran without the need of other photosensitizers circumvents the issue of uncontrolled long-lasting photocytotoxicity in gene delivery.

BCR-Abl Silencing by siRNA: A Potent Approach to Sensitize Chronic Myeloid Leukemia Cells to Tyrosine Kinase Inhibitor Therapy

Nonviral gene therapy with specific short interfering RNAs (siRNAs) against BCR-Abl can be an alternative and/or supportive therapy of chronic myeloid leukemia (CML) with tyrosine kinase inhibitors (TKIs), given the often observed resistance to TKIs in clinical setting. In this study, we explored the feasibility of BCR-Abl siRNA therapy in CML K562 cells in vitro by employing a cationic polymer derived from cholesterol (Chol) grafted low-molecular weight polyethyleneimine (PEI). The first generation TKI imatinib upregulated the expression of BCR-Abl in K562 cells as expected. Delivery of BCR-Abl siRNA in both drug-sensitive and drug-resistant K562 cells significantly downregulated the mRNA levels in both cell types. Similarly, the BCR-Abl siRNA treatment arrested the growth of both drug-sensitive and drug-resistant K562 cells with no obvious differences despite a large difference in drug responsiveness. The BCR-Abl gene silencing in combination with TKI treatments exhibited significant synergism in drug-resistant K562 cells in generating substantial antileukemic activity, where the TKIs on their own were not effective. The effect of BCR-Abl siRNA and TKIs on non-CML cells (Jurkat and primary fibroblast) was negligible, indicating the specificity of the proposed therapy. This strategy can significantly overcome TKI resistance in CML cells, suggesting a feasible and effective treatment model for CML patients suffering from clinical resistances.

siRNA Library Screening to Identify Complementary Therapeutic Pairs in Triple-Negative Breast Cancer Cells

The existence of tightly integrated cross talk through multiple signaling and effector pathways has been appreciated in malignant cells. The realization of the plasticity of such networks is stimulating the development of combinational therapy to overcome the limitations of one-dimensional therapies. Synergistic pairs of siRNAs or siRNA and drug combinations are the new frontiers in identifying effective therapeutic combinations. To elucidate effective combinations, we developed a versatile protocol to screen siRNA libraries in triple-negative breast cancer cell models. This protocol outlines the steps to identify synergistic combinations of siRNA-siRNA or siRNA-drug combinations using siRNA libraries via a robotic screen. By focusing on smaller functional siRNA libraries, we present methodologies to identify synergistic siRNA pairings against cancerous cell growth and molecular targets to augment the activity of pro-apoptotic TRAIL protein. Here, we summarize the critical steps to undertake such combinational target identification, emphasizing critical factors that affect the outcome of the screens. Our experience suggests that siRNA library screening is an efficient protocol to identify complementary therapeutic pairs of new or already-existing drugs. This protocol is simple, robust and can be completed within a 1-week working period.

Additive Polyplexes to Undertake siRNA Therapy against CDC20 and Survivin in Breast Cancer Cells

Small interfering RNA (siRNA) delivered to silence overexpressed genes associated with malignancies is a promising targeted therapy to decrease the uncontrolled growth of malignant cells. To create potent delivery agents for siRNA, here we formulated additive polyplexes of siRNA using linoleic acid-substituted polyethylenimine and additive polymers (hyaluronic acid, poly(acrylic acid), dextran sulfate, and methyl cellulose) and characterized their physicochemical properties and effectiveness. Incorporating polyanionic polymer along with anionic siRNA in polyplexes was found to decrease the ζ-potential of polyplexes but enhance the cellular delivery of siRNA. The CDC20 and survivin siRNAs delivered by additive polyplexes showed promising efficacy in breast cancer MDA-MB-231, SUM149PT, MDA-MB-436, and MCF7 cells. However, the side effects of the siRNA delivery were observed in nonmalignant cells, and a careful formulation of siRNA/polymer polyplexes was needed to minimize side effects on normal cells. Because the efficacy of siRNA delivery by additive polyplexes was independent of breast cancer phenotypes used in this study, these polyplexes could be further developed to treat a wide range of breast cancers.