Modifying peptide/lipid-associated nucleic acids (PLANAs) for CRISPR/Cas9 ribonucleoprotein delivery

With the first reports on the possibility of genome editing by Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR-associated protein (Cas)9 surfacing in 2005, the enthusiasm for protein silencing via nucleic acid delivery experienced a resurgence following a period of diminished enthusiasm due to challenges in delivering small interfering RNAs (siRNA), especially in vivo. However, delivering the components necessary for this approach into the nucleus is challenging, maybe even more than the cytoplasmic delivery of siRNA. We previously reported the birth of peptide/lipid-associated nucleic acids (PLANAs) for siRNA delivery. This project was designed to investigate the efficiency of these nanoparticles for in vitro delivery of CRISPR/Cas9 ribonucleoproteins. Our initial experiments indicated higher toxicity for PLANAs with the more efficient reverse transfection method. Therefore, polyethylene glycol (PEG) was added to the composition for PEGylation of the nanoparticles by partially replacing two of the lipid components with the PEG-conjugated counterparts. The results indicated a more significant reduction in the toxicity of the nanoparticle, less compromise in encapsulation efficiency and more PEGylation of the surface of the nanoparticles using DOPE-PEG2000 at 50 % replacement of the naïve lipid. The cell internalization and transfection efficiency showed a comparable efficiency for the PEGylated and non-PEGylated PLANAs and the commercially available Lipofectamine™ CRISPRMAX™. Next Generation Sequencing of the cloned cells showed a variety of indels in the transfected cell population. Overall, our results indicate the efficiency and safety of PEGylated PLANAs for in vitro transfection with CRISPR/Cas9 ribonucleoproteins. PEGylation has been studied extensively for in vivo delivery, and PEGylated PLANAs will be candidates for future in vivo studies.

Targeting Breast Cancer: The Familiar, the Emerging, and the Uncharted Territories

Breast cancer became the most diagnosed cancer in the world in 2020. Chemotherapy is still the leading clinical strategy in breast cancer treatment, followed by hormone therapy (mostly used in hormone receptor-positive types). However, with our ever-expanding knowledge of signaling pathways in cancer biology, new molecular targets are identified for potential novel molecularly targeted drugs in breast cancer treatment. While this has resulted in the approval of a few molecularly targeted drugs by the FDA (including drugs targeting immune checkpoints), a wide array of signaling pathways seem to be still underexplored. Also, while combinatorial treatments have become common practice in clinics, the majority of these approaches seem to combine molecularly targeted drugs with chemotherapeutic agents. In this manuscript, we start by analyzing the list of FDA-approved molecularly targeted drugs for breast cancer to evaluate where molecular targeting stands in breast cancer treatment today. We will then provide an overview of other options currently under clinical trial or being investigated in pre-clinical studies.

Development and validation of a UPLC-MS/MS method to investigate the plasma pharmacokinetics of a KCa 2.2/KCa 2.3 positive allosteric modulator in mice

RATIONALE

There is currently no treatment for spinocerebellar ataxias (SCAs), which are a group of genetic disorders that often cause a lack of coordination, difficulty walking, slurred speech, tremors, and eventually death. Activation of K_Ca 2.2/K_Ca 2.3 channels reportedly exerts beneficial effects in SCAs. Here, we report the development and validation of an analytical method for quantitating a recently-developed positive allosteric modulator of K_Ca 2.2/K_Ca 2.3 channels (compound 2q) in mouse plasma.

METHODS

Mouse plasma samples (10 μL) containing various concentrations of 2q were subjected to protein precipitation in the presence of a structurally similar internal standard (IS). Subsequently, the analytes were separated on a C₁₈ UPLC column and detected by a tandem mass spectrometer. The method was validated using FDA guidelines. Finally, the validated assay was applied to the measurement of the plasma concentrations of 2q in plasma samples taken from mice after single intravenous doses of 2 mg/kg of 2q, and the pharmacokinetic parameters of 2q were determined.

RESULTS

The calibration standards were linear (r² ≥ 0.99) in the range of 1.56 - 200 nM of 2q with intra- and inter-run accuracy and precision values within the FDA guidelines. The lower limit of quantitation of the assay was 1.56 nM (0.258 pg on the column). The recoveries of 2q and IS from plasma were > 94%, with no appreciable matrix effect. The assay showed no significant carryover, and the plasma samples stored at -80^o C or the processed samples stored in the autosampler at 10^o C were stable for at least three weeks and 36 h, respectively. After intravenous injection, 2q showed a bi-exponential decline pattern in the mouse plasma, with a clearance of 30 mL/min/kg, a terminal volume of distribution of 1.93 mL/kg, and a terminal half-life of 45 min.

CONCLUSIONS

The developed assay is suitable for preclinical pharmacokinetic-pharmacodynamic studies of 2q as a potential drug candidate for ataxias.

Redox-Responsive Disulfide Cyclic Peptides: A New Strategy for siRNA Delivery

RNA interference (RNAi) is a powerful tool capable of targeting virtually any protein without time-consuming and expensive drug development studies. However, due to obstacles facing efficient and safe delivery, RNAi-based therapeutic approach remains a challenge. Herein, we have designed and synthesized a number of disulfide-constraining cyclic and hybrid peptides using tryptophan and arginine residues. Our hypothesis was that peptide structures would undergo reduction by intracellular glutathione (more abundant in cancer cells) and unpack the small interfering RNA (siRNA) from the peptide/siRNA complexes. A subset of newly developed peptides (specifically, C4 and H4) exhibited effective cellular internalization of siRNA (∼70% of the cell population; monitored by flow cytometry and confocal microscopy), the capability of protecting siRNA against early degradation by nucleases (monitored by gel electrophoresis), minimal cytotoxicity in selected cell lines (studied by cell viability and LC₅₀ calculations), and efficient protein silencing by 70-75% reduction in the expression of targeting signal transducer and activator of transcription 3 (STAT3) in human triple-negative breast cancer (TNBC) MDA-MB-231 cells, analyzed using the Western blot technique. Our results indicate the birth of a promising new family of siRNA delivery systems that are capable of safe and efficient delivery, even in the presence of nucleases.

[(WR)8WKβA]-Doxorubicin Conjugate: A Delivery System to Overcome Multi-Drug Resistance against Doxorubicin

Doxorubicin (Dox) is an anthracycline chemotherapeutic agent used to treat breast, leukemia, and lymphoma malignancies. However, cardiotoxicity and inherent acquired resistance are major drawbacks, limiting its clinical application. We have previously shown that cyclic peptide [WR]₉ containing alternate tryptophan (W) and arginine (R) residues acts as an efficient molecular transporter. An amphiphilic cyclic peptide containing a lysine (K) residue and alternative W and R was conjugated through a free side chain amino group with Dox via a glutarate linker to afford [(WR)₈WKβA]-Dox conjugate. Antiproliferative assays were performed in different cancer cell lines using the conjugate and the corresponding physical mixture of the peptide and Dox to evaluate the effectiveness of synthesized conjugate compared to the parent drug alone. [(WR)₈WKβA]-Dox conjugate showed higher antiproliferative activity at 10 µM and 5 µM than Dox alone at 5 μM. The conjugate inhibited the cell viability of ovarian adenocarcinoma (SK-OV-3) by 59% and the triple-negative breast cancer cells MDA-MB-231 and MCF-7 by 71% and 77%, respectively, at a concentration of 5 μM after 72 h of incubation. In contrast, Dox inhibited the proliferation of SK-OV-3, MDA-MB-231, and MCF-7 by 35%, 63%, and 57%, respectively. Furthermore, [(WR)₈WKβA]-Dox conjugate (5 µM) inhibited the cell viability of Dox-resistant cells (MES-SA/MX2) by 92%, while the viability of cells incubated with free Dox was only 15% at 5 μM. Confocal microscopy images confirmed the ability of both Dox conjugate and the physical mixture of the peptide with the drug to deliver Dox through an endocytosis-independent pathway, as the uptake was not inhibited in the presence of endocytosis inhibitors. The stability of Dox conjugate was observed at different time intervals using analytical HPLC when the conjugate was incubated with 25% human serum. Half-life (t_1/2) for [(WR)₈WKβA]-Dox conjugate was (∼6 h), and more than 80% of the conjugate was degraded at 12 h. The release of free Dox was assessed intracellularly using the CCRF-CEM cell line. The experiment demonstrated that approximately 100% of free Dox was released from the conjugate intracellularly within 72 h. These data confirm the ability of the cyclic cell-penetrating peptide containing tryptophan and arginine residues as an efficient tool for delivery of Dox and for overcoming resistance to it.

[(WR)8WKβA]-Doxorubicin Conjugate: A Delivery System to Overcome Multi-Drug Resistance against Doxorubicin

Doxorubicin (Dox) is an anthracycline chemotherapeutic agent used to treat breast, leukemia, and lymphoma malignancies. However, cardiotoxicity and inherent acquired resistance are major drawbacks, limiting its clinical application. We have previously shown that cyclic peptide [WR]9 containing alternate tryptophan (W) and arginine (R) residues acts as an efficient molecular transporter. An amphiphilic cyclic peptide containing a lysine (K) residue and alternative W and R was conjugated through a free side chain amino group with Dox via a glutarate linker to afford [(WR)8WKβA]-Dox conjugate. Antiproliferative assays were performed in different cancer cell lines using the conjugate and the corresponding physical mixture of the peptide and Dox to evaluate the effectiveness of synthesized conjugate compared to the parent drug alone. [(WR)8WKβA]-Dox conjugate showed higher antiproliferative activity at 10 µM and 5 µM than Dox alone at 5 μM. The conjugate inhibited the cell viability of ovarian adenocarcinoma (SK-OV-3) by 59% and the triple-negative breast cancer cells MDA-MB-231 and MCF-7 by 71% and 77%, respectively, at a concentration of 5 μM after 72 h of incubation. In contrast, Dox inhibited the proliferation of SK-OV-3, MDA-MB-231, and MCF-7 by 35%, 63%, and 57%, respectively. Furthermore, [(WR)8WKβA]-Dox conjugate (5 µM) inhibited the cell viability of Dox-resistant cells (MES-SA/MX2) by 92%, while the viability of cells incubated with free Dox was only 15% at 5 μM. Confocal microscopy images confirmed the ability of both Dox conjugate and the physical mixture of the peptide with the drug to deliver Dox through an endocytosis-independent pathway, as the uptake was not inhibited in the presence of endocytosis inhibitors. The stability of Dox conjugate was observed at different time intervals using analytical HPLC when the conjugate was incubated with 25% human serum. Half-life (t1/2) for [(WR)8WKβA]-Dox conjugate was (∼6 h), and more than 80% of the conjugate was degraded at 12 h. The release of free Dox was assessed intracellularly using the CCRF-CEM cell line. The experiment demonstrated that approximately 100% of free Dox was released from the conjugate intracellularly within 72 h. These data confirm the ability of the cyclic cell-penetrating peptide containing tryptophan and arginine residues as an efficient tool for delivery of Dox and for overcoming resistance to it.

Design and application of hybrid cyclic-linear peptide-doxorubicin conjugates as a strategy to overcome doxorubicin resistance and toxicity

Doxorubicin (Dox) is used for breast cancer, leukemia, and lymphoma treatment as an effective chemotherapeutic agent. However, Dox use is restricted due to inherent and acquired resistance and an 8-fold increase in the risk of potentially fatal cardiotoxicity. Hybrid cyclic-linear peptide [R₅K]W₇A and linear peptide R₅KW₇A were conjugated with Dox through a glutarate linker to afford [R₅K]W₇A-Dox and R₅KW₇A-Dox conjugates to generate Dox derivatives. Alternatively, [R₅K]W₇C was conjugated with Dox via a disulfide linker to generate [R₅K]W₇C-S-S-Dox conjugate, where S-S is a disulfide bond. Comparative antiproliferative assays between conjugates [R₅K]W₇A-Dox, [R₅K]W₇C-S-S-Dox, linear R₅KW₇A-Dox, the corresponding physical mixtures of the peptides, and Dox were performed in normal and cancer cells. [R₅K]W₇A-Dox conjugate was 2-fold more efficient than R₅KW₇A-Dox, and [R₅K]W₇C-S-S-Dox conjugates in inhibiting the cell proliferation of human leukemia cells (CCRF-CEM). Therefore, hybrid cyclic-linear [R₅K]W₇A-Dox conjugate was selected for further studies and inhibited the cell viability of CCRF-CEM (84%), ovarian adenocarcinoma (SK-OV-3, 39%), and gastric carcinoma (AGS, 73%) at a concentration of 5 μM after 72 h of incubation, which was comparable to Dox (5 μM) efficacy (CCRF-CEM (85%), SK-OV-3 (33%), and AGS (87%)). While [R₅K]W₇A-Dox had a significant effect on the viability of cancer cells, it exhibited minimal cytotoxicity to normal kidney (LLC-PK1, 5-7%) and heart cells (H9C2, <9%) at concentrations of 5-10 μM (compared to free Dox at 5 μM that reduced the viability of kidney and heart cells by 85% and 44%, respectively). The fluorescence microscopy images were consistent with the cytotoxicity studies, indicating minimal uptake of the cyclic-linear [R₅K]W₇A-Dox (5 μM) in H9C2 cells. In comparison, Dox (5 μM) showed significant uptake, reduced cell viability, and changed the morphology of the cells after 24 h. [R₅K]W₇A-Dox showed 16-fold and 9.5-fold higher activity against Dox-resistant cells MDA231R and MES-SA/MX2 (lethal dose for 50% cell death or LC₅₀ of 2.3 and 4.3 μM, respectively) compared to free Dox (LC₅₀ of 36-41 μM, respectively). These data, along with the results obtained from the cell viability tests, indicate comparable efficiency of [R₅K]W₇A-Dox to free Dox in leukemia, ovarian, and gastric cancer cells, significantly reduced toxicity in normal kidney LLC-PK1 and heart H9C2 cells, and significantly higher efficiency in Dox-resistant cells. A number of endocytosis inhibitors did not affect the cellular uptake of [R₅K]W₇A-Dox.

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.

Peptide/Lipid-Associated Nucleic Acids (PLANAs) as a Multicomponent siRNA Delivery System

RNAi is a biological process that utilizes small interfering RNA (siRNA) to prevent the translation of mRNA to protein. This mechanism could be beneficial in preventing the overexpression of proteins in cancer. However, the cellular delivery of siRNA has proven to be challenging due to its inherent negative charge and relative instability. Here, we designed a multicomponent delivery system composed of a specifically designed peptide (linear or cyclic fatty acyl peptide conjugates and hybrid cyclic/linear peptides) and several lipids (DOTAP, DOPE, cholesterol, and phosphatidylcholine) to form a nanoparticle, which we have termed as peptide lipid-associated nucleic acids (PLANAs). Five formulations were prepared (a formulation with no peptide, which was named lipid-associated nucleic acid or LANA, and PLANA formulations A-D) using a mini extruder to form uniform nanoparticles around 100 nm in size with a slightly positive charge (less than +10 mv). Formulations were evaluated for peptide incorporation, siRNA encapsulation efficiency, release profile, toxicity, cellular uptake, and protein silencing. Our experiments showed effective encapsulation of siRNA (>95%), a controlled release profile, and negligible toxicity in formulations that did not contain a positively charged lipid. The results also revealed that PLANAs C and D exhibited optimum cellular uptake (with 80-90% siRNA-positive cells for most of the formulations). PLANA D formulation was selected to silence two model proteins (Src and RPS6KA5) in the triple-negative human breast cancer cell line MDA-MB-231, with promising silencing efficiency, which diminished the expression of RPS6KA5 and Src to approximately 29 and 38% compared to naïve cells, respectively. Many approaches have been investigated for safe and efficient delivery of nucleic acids in the last 20 years; however, many have failed due to the multifaceted challenges to overcome. Our results show a promising potential for a multicomponent design that incorporates different components for a variety of delivery tasks, which warrants further investigation of PLANAs in vivo.

Abstract B01: Simultaneous targeting of mTOR and mLST8 in human breast cancer cells

Despite our continually increasing knowledge of cancer biology and intracellular mechanisms, identifying targets for cancer treatment remains a challenge. Cancer cells are heterogeneous and plastic, which are involved in innate and acquired resistance to molecularly targeted anticancer drugs, respectively. This project focuses on the PI3K/Akt cell signaling pathway, specifically mammalian target of rapamycin (mTOR) and GβL (mLST8), to halt cell proliferation. The breast cancer cell lines MDA-MB-231, MDA-MB-468, and AU565 were exposed to small interfering RNAs (siRNAs) targeting mTOR or mLST8, as well as a combination of both. The cell protein expression profile was studied to investigate the efficiency of protein silencing, and potential synergistic effect on downstream effectors of the pathway. Due to poor cellular internalization of siRNA, we also investigated the efficiency of small cell-penetrating peptides specifically designed as siRNA carriers. Three cyclic peptides (WR5, [R5K]W5 and [R6K]W6) incorporating ring-forming arginines (as a cationic moiety for inter-ionic interaction with nucleic acids), tryptophan (as a hydrophobic chain to enhance interaction with cell membrane, and lysine as the conjugation site for tryptophan chain were studied for in vitro siRNA delivery. The siRNA complexes formed with these amphiphilic peptides were delivered to the same breast cancer cell lines, and the efficiency of cellular internalization and mTOR and mLST8 silencing was investigated. Our findings confirm the efficiency of siRNAs in interrupting formation of mTOR complexes, and the activation of downstream proteins. Further studies are required to confirm these findings in patient cells and to evaluate the efficacy of this approach in vivo.

Citation Format: Melissa Coyle, Romina Nabiee, Robert Lamboy, Parvin Mahdipoor, Keykavous Parang, Hamidreza Montazeri Aliabadi. Simultaneous targeting of mTOR and mLST8 in human breast cancer cells [abstract]. In: Proceedings of the AACR Special Conference on Targeting PI3K/mTOR Signaling; 2018 Nov 30-Dec 8; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(10_Suppl):Abstract nr B01.

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.

A systematic comparison of lipopolymers for siRNA delivery to multiple breast cancer cell lines: In vitro studies

Small interfering RNA (siRNA) therapy is a promising approach for treatment of a wide range of cancers, including breast cancers that display variable phenotypic features. To explore the general utility of siRNA therapy to control aberrant expression of genes in breast cancer, we conducted a detailed analysis of siRNA delivery and silencing response in vitro in 6 separate breast cancer cell models (MDA-MB-231, MDA-MB-231-KRas-CRM, MCF-7, AU565, MDA-MB-435 and MDA-MB-468 cells). Using lipopolymers for siRNA complexation and delivery, we found a large variation in siRNA delivery efficiency depending on the specific lipopolymer used for siRNA complexation and delivery. Some lipopolymers were effective in all cell types used in this study, indicating the possibility of universal carriers for siRNA therapy. The delivery efficiency for effective lipopolymers was not correlated with dextran uptake in the cells tested, which indicated a receptor-mediated internalization for siRNA complexes with lipopolymers, unlike fluid-phase transfer associated with dextran uptake. Consistent with this, specific inhibitors involved in clathrin- and caveolin-mediated endocytosis significantly (>50%) reduced the internalization of siRNA complexes in all cell types. Using JAK2 and STAT3 silencing in MDA-MB-231 and MDA-MB-468 cells, a general correlation between the uptake and silencing efficiency at the mRNA level was evident, but it appeared that the choice of the target rather than the cell type was more critical for consistent silencing. We conclude that siRNA therapy with lipopolymers can be undertaken in multiple breast cancer cell phenotypes with similar efficiency, indicating the general applicability of non-viral RNAi in clinical management of molecularly heterogeneous breast cancers. STATEMENT OF SIGNIFICANCE: The manuscript investigated the efficacy of siRNA carriers across multiple breast cancer cell lines. The lipopolymeric carriers were capable of delivering effective dose of siRNA to a range of breast cancer cells. Despite some differences in uptake efficiency among cell types, the mechanism of delivery was similar, with CME and CvME significantly involved in the internalization of polyplexes, while fluid-phase endocytosis was not significant. Specific target silencing was correlated to delivery efficiency, but we did notice the presence of lipopolymers that achieved high silencing with minimal siRNA delivery. Silencing specific targets in different cell types were more uniformly achieved as compared to targeting different targets in the same cells. Our studies enhance the feasibility of delivering siRNA to different types of breast cancer cells.

Heterogeneity and Plasticity of Human Breast Cancer Cells in Response to Molecularly-Targeted Drugs

Non-responsive subpopulation of tumor cells, and acquired resistance in initially responsive cells are major challenges for cancer therapy with molecularly-targeted drugs. While point mutations are considered the major contributing factor to acquired resistance, in this study we explored the role of heterogeneity and plasticity of selected human breast cancer cell lines (MDA-MB-231, MDA-MB-468, and AU565) in their initial and adjusted response, respectively, to ruxolitinib, everolimus, and erlotinib. After determination of lethal concentration for 50% cell death (LC50), cells were exposed to selected drugs using three different approaches: single exposure to 4 × LC50 and collection of surviving cells, multiple exposures to 1.5 × LC50 and monitoring the surviving population, and exposure to gradually increasing concentrations of selected drugs (range of concentrations equivalent to 10% of LC50 to 1.5 × LC50). Surviving cells were studied for adjustments in expression level of selected proteins using quantitative PCR and Western Blot. Our data indicated overexpression of a variety of proteins in resistant populations, which included cell membrane receptors EGFR and HER2, anti-apoptotic proteins Bcl-2 and BIRC8, and other proteins involved in cell signaling (e.g., Akt1, MAPK7, and RPS6KA5). Silencing the identified alternative proteins via siRNA resulted in significant drop in the LC50 of the selected molecularly-targeted drugs cells resistant to ruxolitinib (via targeting Akt), everolimus (via targeting EGFR, MAPK7, RPS6KA5, and HER2), and erlotinib (via silencing Bcl2 and BIRC8). Our data indicates that targeting well-selected alternative proteins could potentially sensitize the resistant cells to the effect of the molecularly-targeted treatment.

Amphiphilic Peptides for Efficient siRNA Delivery

A number of amphiphilic cyclic peptides—[FR]₄, [WR]₅, and [WK]₅—containing hydrophobic and positively-charged amino acids were synthesized by Fmoc/tBu solid-phase peptide methods and evaluated for their efficiency in intracellular delivery of siRNA to triple-negative breast cancer cell lines, MDA-MB-231 and MDA-MB-468, in the presence and absence of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). Among the peptides, [WR]₅, which contains alternate tryptophan (W) and arginine (R) residues, was found to be the most efficient in the delivery of siRNA by improving the delivery by more than 3-fold when compared to other synthesized cyclic peptides that were not efficient. The data also showed that co-formulation of [WR]₅ with lipid DOPE significantly enhanced the efficiency of siRNA delivery by up to ~2-fold compared to peptide alone. Based on the data indicating the efficiency of [WR]₅ in siRNA delivery, peptides containing arginine residues on the ring and tryptophan residues on the side chain, [R₆K]W₆ and [R₅K]W₅, were also evaluated, and demonstrated improved delivery of siRNA. The presence of DOPE again enhanced the siRNA delivery in most cases. [WR]₅, [R₅K]W₅, and [R₆K]W₆ did not show any significant toxicity in MDA-MB-231, MDA-MB-468, and AU565 WT cells at N/P ratios of 20:1 or less, in the presence and absence of DOPE. Silencing of kinesin spindle protein (KSP) and Janus kinase 2 (JAK2) was evaluated in MDA-MB-231 cells in the presence of the peptides. The addition of DOPE significantly enhanced the silencing efficiency for all selected peptides. In conclusion, peptides containing tryptophan and arginine residues were found to enhance siRNA delivery and to generate silencing of targeted proteins in the presence of DOPE.

In vitro and ex-vivo evaluation of topical formulations designed to minimize transdermal absorption of Vitamin K1

Topical application of Vitamin K1 has been demonstrated to effectively treat papulopustular skin rash, a serious and frequently encountered side effect of Epidermal Growth Factor Inhibitors (EGFRIs). Systemic absorption of vitamin K1 from skin and the resultant consequence of antagonizing EGFRIs anticancer effects jeopardizes the clinical acceptability of this rather effective treatment. The purpose of the present study was to rationally formulate and evaluate the release rate and transdermal absorption of a wide range of Vitamin K1 dermal preparations with a variety of physiochemical properties. A library of 33 formulations with were compounded and tested for Vitamin K1 permeation using hydrophobic membranes and porcine skin mounted in a Fran diffusion cells. Our results demonstrate the lowest diffusion for water-in-oil emulsions, which also demonstrated a negligible transdermal absorption. The statistical analysis showed a significant correlation between in vitro and ex vivo results. While viscosity did not have a significant impact on the diffusion or absorption of vitamin K1, an increase in the lipid content was correlated with an increase in transmembrane diffusion (not with transdermal absorption). Overall, formulation design significantly impacts the release rate and transdermal absorption of vitamin K1, and confirms the possibility of minimal systemic distribution of this vitamin for this specific purpose.

"Do We Know Jack" About JAK? A Closer Look at JAK/STAT Signaling Pathway

Janus tyrosine kinase (JAK) family of proteins have been identified as crucial proteins in signal transduction initiated by a wide range of membrane receptors. Among the proteins in this family JAK2 has been associated with important downstream proteins, including signal transducers and activators of transcription (STATs), which in turn regulate the expression of a variety of proteins involved in induction or prevention of apoptosis. Therefore, the JAK/STAT signaling axis plays a major role in the proliferation and survival of different cancer cells, and may even be involved in resistance mechanisms against molecularly targeted drugs. Despite extensive research focused on the protein structure and mechanisms of activation of JAKs, and signal transduction through these proteins, their importance in cancer initiation and progression seem to be underestimated. This manuscript is an attempt to highlight the role of JAK proteins in cancer biology, the most recent developments in targeting JAKs, and the central role they play in intracellular cross-talks with other signaling cascades.

Synthesis, characterization, and in vitro cytotoxicity of fatty acyl-CGKRK-chitosan oligosaccharides conjugates for siRNA delivery

In this studies, three fatty acyl derivatives of CGKRK homing peptides were coupled successfully to chitosan oligosaccharides (COS) using sulfosuccinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate sodium salt (sulfo-SMCC). The COS-SMCC was prepared by direct coupling between COS and sulfo-SMCC in PBS (pH7.5) at RT for 48h. The structure of COS-SMCC and the three fatty acyl-CGKRK-SMCC-COS conjugates were characterized by FT-IR, ¹³C NMR, and SEM. The ability of three conjugates to condense siRNA into nanosized polyplexes and their efficacy in protecting siRNA from serum nucleases degradation were investigated. Among the investigated derivatives, S-CGKRK-COS showed higher siRNA binding affinity as compared to the P-CGKRK-COS and O-CGKRK-COS, respectively. At a ratio of 10:1, complete protection for siRNA from early enzymatic degradation was achieved. The polymers and the polymer/siRNA polyplexes showed negligible cytotoxicity on human breast cancer cell line MDA-MB-231 at all investigated ratios. However, the polyplexes prepared with palmitoyl and oleoyl derivatives at polymer concentration 10μg/mL reduced the cell viability by 21.5% and 35%, respectively. The results of this study revealed the potential use of fatty acyl-CGKRK-COS as a siRNA carrier and confirmed the importance of incorporating a hydrophobic moiety into chitosan to improve its capacity in complexing with siRNA and protection from degradation.

Abstract B087: A systematic approach to JAK/STAT pathway shut-down

Janus Kinase Protein (JAK) plays a crucial role in a variety of intracellular mechanisms, and has been extensively studied for its role in proliferation and survival of cancer cells. One of the unique characteristics of this kinase is the variety of cell membrane receptors with which it is associated, and can trigger JAK activation process. Family of Signal Transducer and Activators of Transcription (STATs) are the direct downstream proteins that further transfer JAK signaling to the nucleus, which results in modification of expression level of a wide range of proteins. Triple-negative breast cancer (TNBC) represents one of the most aggressive and challenging subtypes of human breast cancer, due to lack of estrogen, progesterone, and human epidermal growth factor receptor 2 (HER2) receptors, which renders the cells nonresponsive to hormone therapy. Several studies have confirmed that IL-6/gp130/JAK2/STAT3 signaling pathway is one of the crucial pathways that is implicated in TNBC development. However, monotherapies targeting JAK2 or STAT3 with molecularly targeted drugs have faced several challenges, including inherent and acquired resistance. Therefore, we aimed to determine feasibility and efficacy of therapy of TNBC using combinatorial silencing of different components in gp130/JAK2/STAT3 pathway. The downregulatory effects of siRNA targeting gp130, JAK2, STAT3, Importin α-3 alone or in combination were evaluated in human TNBC cells MDA 231 and MDA 468, and their effect on downstream targets involved in cell apoptosis and cell cycle were determined by real-time PCR and Western blot. The effect of individual and combinatorial silencing of the pathway components on cell proliferation and cell migration were also examined using CCK assay and Scratch assay, respectively. The siRNA treatment effectively reduced gene expression of gp130/JAK2/STAT pathway components at the mRNA level. Simultaneous inhibition of selected components significantly decreased TNBC cell proliferation rate. Moreover, combinatorial siRNA silencing inhibited the migration of TNBC cells. In conclusion, simultaneous inhibition of well-selected components of JAK/STAT pathway could represent an effective therapy for human TNBC. This warrants further in vivo study in animal models.

Citation Format: Hamidreza Montazeri Aliabadi, Emira Bousoik, Parvin Mahdipoor. A systematic approach to JAK/STAT pathway shut-down [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B087.

Alzheimer's Disease: Dawn of a New Era?

Alzheimer's disease (AD) is an irreversible neurodegenerative disease characterized by a progressive decline in cognition and memory, leading to significant impairment in daily activities and ultimately death. It is the most common cause of dementia, the prevalence of which increases with age; however, age is not the only predisposing factor. The pathology of this cognitive impairing disease is still not completely understood, which has limited the development of valid therapeutic options. Recent years have witnessed a wide range of novel approaches to combat this disease, so that they greatly increased our understanding of the disease and of the unique drug development issues associated with this disease. In this paper, we provide a brief overview of the history, the clinical presentation and diagnosis, and we undertake a comprehensive review of the various approaches that have been brought to clinical trials in recent years, including immunotherapeutic approaches, tau-targeted strategies, neurotransmitter-based therapies, neurotropic and hematopoietic growth factors, and antioxidant therapies, trying to highlight the lessons learned from these approaches. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Difatty Acyl-Conjugated Linear and Cyclic Peptides for siRNA Delivery

A number of amphiphilic difatty acyl linear and cyclic R₅K₂ peptide conjugates were synthesized by solid-phase peptide methods to enhance the interaction with the hydrophobic cellular phospholipid bilayer and to improve siRNA delivery and silencing. Binding to siRNA molecules was significantly less for the cyclic peptide conjugates. A gradual decrease was observed in the particle size of the complexes with increasing peptide/siRNA ratio for most of the synthesized peptides, suggesting the complex formation. Most of the complexes showed a particle size of less than 200 nm, which is considered an appropriate size for in vitro siRNA delivery. A number of fatty acyl-conjugated peptides, such as LP-C16 and LP-C18, displayed near complete protection against serum degradation. Flow cytometry studies demonstrated significantly higher internalization of fluorescence-labeled siRNA (FAM-siRNA) in the presence of LP-C16, LP-C18, and CP-C16 with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) addition. Confocal microscopy confirmed the cellular internalization of fluorescence-labeled siRNA in the presence of LP-C16 and LP-C18 with DOPE when compared with cells exposed to DOPE/FAM-siRNA. While C16- and C18-conjugated peptides (especially linear peptides) showed silencing against kinesin spindle protein (KSP) and janus kinase 2 (JAK2) proteins, the addition of DOPE enhanced the silencing efficiency significantly for all selected peptides, except for CP-C16. In conclusion, C16 and C18 difatty acyl peptide conjugates were found to enhance siRNA delivery and generate silencing of targeted proteins in the presence of DOPE. This study provides insights for the design and potential application of optimized difatty acyl peptide/lipid nanoparticles for effective siRNA delivery.

Application of iChip to Grow "Uncultivable" Microorganisms and its Impact on Antibiotic Discovery

PURPOSE

Antibiotics have revolutionized modern medicine, allowing significant progress in healthcare and improvement in life expectancy. Development of antibiotic resistance by pathogenic bacteria is a natural phenomenon; however, the rate of antibiotic resistance emergence is increasing at an alarming rate, due to indiscriminate use of antibiotics in healthcare, agriculture and even everyday products. Traditionally, antibiotic discovery has been conducted by screening extracts of microorganisms for antimicrobial activity. However, this conventional source has been over-used to such an extent that it poses the risk of "running out" of new antibiotics. Aiming to increase access to a greater diversity of microorganisms, a new cultivation method with an in situ approach called iChip has been designed. The iChip has already isolated many novel organisms, as well as Teixobactin, a novel antibiotic with significant potency against gram-positive bacteria.

Multiple siRNA delivery against cell cycle and anti-apoptosis proteins using lipid-substituted polyethylenimine in triple-negative breast cancer and nonmalignant cells

Conventional breast cancer therapies have significant limitations that warrant a search for alternative therapies. Short-interfering RNA (siRNA), delivered by polymeric biomaterials and capable of silencing specific genes critical for growth of cancer cells, holds great promise as an effective, and more specific therapy. Here, we employed amphiphilic polymers and silenced the expression of two cell cycle proteins, TTK and CDC20, and the anti-apoptosis protein survivin to determine the efficacy of polymer-mediated siRNA treatment in breast cancer cells as well as side effects in nonmalignant cells in vitro. We first identified effective siRNA carriers by screening a library of lipid-substituted polyethylenimines (PEI), and PEI substituted with linoleic acid (LA) emerged as the most effective carrier for selected siRNAs. Combinations of TTK/CDC20 and CDC20/Survivin siRNAs decreased the growth of MDA-MB-231 cells significantly, while only TTK/CDC20 combination inhibited MCF7 cell growth. The effects of combinational siRNA therapy was higher when complexes were formulated at lower siRNA:polymer ratio (1:2) compared to higher ratio (1:8) in nonmalignant cells. The lead polymer (1.2PEI-LA6) showed differential transfection efficiency based on the cell-type transfected. We conclude that the lipid-substituted polymers could serve as a viable platform for delivery of multiple siRNAs against critical targets in breast cancer therapy. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 3031-3044, 2016.

Abstract B15: In vivo analysis of repeated siRNA silencing on protein expression levels

An ever increasing number of anticancer drugs are under investigation, and enter the clinical setting targeting different tumor survival and/or growth mechanisms; however, development of resistance against the mechanism of action of even the most promising drugs seems to be inevitable and remains a major concern. RNA interference (RNAi) have shown considerable promise in silencing proteins involved in tumor vascularization, as well as intracellular pathways involved in cell proliferation and/or survival. Despite the apparent efficacy of this powerful tool (especially in vitro), our information about the factors affecting siRNA efficiency and the possibility of resistance development against the silencing effect are limited at best. This study focused on determining the possibility of resistance development against siRNA treatment as a result of repeated exposure to siRNA in vivo. Our preliminary experiments in vitro revealed an unaffected siRNA cellular internalization and reproducible silencing efficiency of selected targets. The expression level of other mediators involved in breast cancer cell survival and proliferation (notably survivin, JUN, JAK2, NFkB and STAT3) were, however, altered in siRNA treated cells. In vivo experiments in a xenograft model demonstrated a similar silencing efficiency at the mRNA level after each repeated dose, with little, if any, apparent resistance development to the siRNA therapy. We conclude that cells would respond to repeated siRNA treatments in a similar fashion after a temporary initial alteration.

Citation Format: Hamidreza Montazeri Aliabadi, Parvin Mahdipoor, Hasan Uludag. In vivo analysis of repeated siRNA silencing on protein expression levels. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Angiogenesis and Vascular Normalization: Bench to Bedside to Biomarkers; Mar 5-8, 2015; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl):Abstract nr B15.

Targeting Cell Cycle Proteins in Breast Cancer Cells with siRNA by Using Lipid-Substituted Polyethylenimines

The cell cycle proteins are key regulators of cell cycle progression whose deregulation is one of the causes of breast cancer. RNA interference (RNAi) is an endogenous mechanism to regulate gene expression and it could serve as the basis of regulating aberrant proteins including cell cycle proteins. Since the delivery of small interfering RNA (siRNA) is a main barrier for implementation of RNAi therapy, we explored the potential of a non-viral delivery system, 2.0 kDa polyethylenimines substituted with linoleic acid and caprylic acid, for this purpose. Using a library of siRNAs against cell cycle proteins, we identified cell division cycle protein 20 (CDC20), a recombinase RAD51, and serine–threonine protein kinase CHEK1 as effective targets for breast cancer therapy, and demonstrated their therapeutic potential in breast cancer MDA-MB-435, MDA-MB-231, and MCF7 cells with respect to another well-studied cell cycle protein, kinesin spindle protein. We also explored the efficacy of dicer-substrate siRNA (DsiRNA) against CDC20, RAD51, and CHEK1, where a particular DsiRNA against CDC20 showed an exceptionally high inhibition of cell growth in vitro. There was no apparent effect of silencing selected cell cycle proteins on the potency of the chemotherapy drug doxorubicin. The efficacy of DsiRNA against CDC20 was subsequently assessed in a xenograft model, which indicated a reduced tumor growth as a result of CDC20 DsiRNA therapy. The presented study highlighted specific cell cycle protein targets critical for breast cancer therapy, and provided a polymeric delivery system for their effective down-regulation.

Abstract A57: Effects of pre-exposure to siRNA on silencing response: Do cells become resistant to siRNA silencing?

Development of resistance against cytotoxic effect of different generations of anticancer drugs is considered inevitable and remains a major concern for cancer therapy. An alternative therapeutic approach based on protein silencing via RNA interference (RNAi) have shown considerable promise; however, our information about the factors affecting siRNA efficiency and the limitations to their efficacy are limited. This study focused on determining the possibility of development of resistance against siRNA treatment as a result of repeated exposure to siRNA that could affect cellular internalization of the particles, silencing efficiency at mRNA level, and ultimately, the observed cellular response. Two approaches to siRNA exposure were undertaken: one involving a single high concentration exposure to eradicate siRNA-responsive cells, and one involving multiple exposures with a gradually increasing siRNA concentration to study the potential intracellular adaptations. Our results demonstrated a temporary decrease in silencing efficiency at mRNA level without significant alteration in siRNA cellular uptake. We conclude that cells would respond to repeated siRNA exposure in a similar fashion after a temporary initial alteration; however, we could not rule out the possibility of a change in phenotypical response (e.g., number of viable cells) as a result of adjustments in (or selection of cells reliant on) alternative pathways.

Citation Format: Hamidreza Montazeri Aliabadi, Parvin Mahdipoor, Cezary Kucharsky, Nicole Chan, Hasan Uludag. Effects of pre-exposure to siRNA on silencing response: Do cells become resistant to siRNA silencing? [abstract]. In: Proceedings of the AACR Precision Medicine Series: Drug Sensitivity and Resistance: Improving Cancer Therapy; Jun 18-21, 2014; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(4 Suppl): Abstract nr A57.

Effective down-regulation of signal transducer and activator of transcription 3 (STAT3) by polyplexes of siRNA and lipid-substituted polyethyleneimine for sensitization of breast tumor cells to conventional chemotherapy

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that plays a major role in the development of resistance to conventional anti-cancer drugs in many types of cancer, when constitutively activated. Inhibition of STAT3 is considered as a promising strategy for inhibition of tumor growth and overcoming the drug resistance manifested. In this study, the capability of STAT3 knockdown by lipid substituted low molecular weight (2 kDa) polyethyleneimine (PEI2) complexes of STAT3-siRNA was assessed. The efficiency of PEI/STAT3-siRNA polyplexes in the induction of STAT3 associated cell death in wild type and drug-resistant MDA-MB-435 breast cancer cells as monotherapy and upon combination with chemotherapeutic agents, doxorubicin and paclitaxel, was also investigated. Our results identified linoleic acid-substituted (PEI-LA) polymer as the most efficient carrier among different lipid substituted PEI2 for siRNA delivery, leading to most STAT3 associated loss of cell viability in MDA-MB-435 cells. STAT3-siRNA delivery by the PEI-LA polymer resulted in efficient down-regulation of STAT3 at both mRNA and protein levels. Furthermore, pre-treatment of cancer cells with STAT3-siRNA formulation increased the cytotoxic effect of doxorubicin and paclitaxel in both wild type and drug resistant MDA-MB-435 cells. The results of this study point to the potential of PEI-LA polyplexes of STAT3-siRNA as inhibitors of STAT3 expression in breast tumor cells. The results also demonstrate an improved efficacy for chemotherapeutic drugs in combination with lipid-substituted low molecular weight PEI-LA/STAT3-siRNA complexes in comparison to drug therapy alone.

Gelatin coating to stabilize the transfection ability of nucleic acid polyplexes

Amphiphilic polymers are effective in complexing and delivering therapeutic nucleic acids, such as plasmid DNA (pDNA) and short interfering RNA (siRNA). However, long-term stability of the complexes is not desirable, as it may have an impact on the transfection efficiency in vivo. To develop a method to preserve complex stability we first showed that pDNA complexes formed with the amphiphilic polymer linoleic acid-substituted polyethylenimine (PEI-LA) and incubated at 37°C lost ~90% of their transfection efficiency after only 24h of complex formation. Polyethyleneglycol modification of complexes to control the increase in complex size and incubation in scaffolds used for implantation did not preserve the transfection ability of the complexes. Among a variety of approaches explored, gelatin coating of complexes was found to be the best at maintaining the original transfection efficiency. Mechanistic studies suggested that improved complex uptake, not size stability, was responsible for retention of the transfection efficiency. Similarly to the results with pDNA, gelatin coating also prevented the decreases in uptake and silencing efficiency of siRNA complexes observed following incubation at 37°C. Gelatin-stabilized complexes were, furthermore, effective in vivo and led to subcutaneous transgene expression with a low pDNA dose that was otherwise ineffective. We conclude that a simple gelatin coating approach offers an efficient means to preserve the transfection efficiency of polyplexes.

Effective non-viral delivery of siRNA to acute myeloid leukemia cells with lipid-substituted polyethylenimines

Use of small interfering RNA (siRNA) is a promising approach for AML treatment as the siRNA molecule can be designed to specifically target proteins that contribute to aberrant cell proliferation in this disease. However, a clinical-relevant means of delivering siRNA molecules must be developed, as the cellular delivery of siRNA is problematic. Here, we report amphiphilic carriers combining a cationic polymer (2 kDa polyethyleneimine, PEI2) with lipophilic moieties to facilitate intracellular delivery of siRNA to AML cell lines. Complete binding of siRNA by the designed carriers was achieved at a polymer:siRNA ratio of ∼0.5 and led to siRNA/polymer complexes of ∼100 nm size. While the native PEI2 did not display cytotoxicity on AML cell lines THP-1, KG-1 and HL-60, lipid-modification on PEI2 slightly increased the cytotoxicity, which was consistent with increased interaction of polymers with cell membranes. Cellular delivery of siRNA was dependent on the nature of lipid substituent and the extent of lipid substitution, and varied among the three AML cell lines used. Linoleic acid-substituted polymers performed best among the prepared polymers and gave a siRNA delivery equivalent to better performing commercial reagents. Using THP-1 cells and a reporter (GFP) and an endogenous (CXCR4) target, effective silencing of the chosen targets was achieved with 25 to 50 nM of siRNA concentrations, and without adversely affecting subsequent cell growth. We conclude that lipid-substituted PEI2 can serve as an effective delivery of siRNA to leukemic cells and could be employed in molecular therapy of leukemia.

Abstract A65: Combinational siRNA silencing of MCL-1 and P-gp enhances the apoptotic response in Human Breast Cancer Cells

Multidrug resistance (MDR) remains is a major hurdle to overcome in cancer therapy. Enhanced cell proliferation and survival of cancerous cells in solid tumor environment along with survival of stem cells to repopulate the tumor and metastasis complicate the matter even more. Therefore, retardation of cell growth and/or induction of apoptosis by posttranscriptional silencing based on short interfering RNA (siRNA) is promising, but remains challenging due to inability of anionic siRNA to cross cell membrane. We previously reported the safety and efficiency of lipid substitution on small molecular weight, non-toxic polyethylenimine (PEI) as promising approach for siRNA delivery. In this study, we report silencing of myeloid cell leukemia 1 (MCL-1) both as an individual target to induce apoptosis and incorporated in multiple silencing in wild type (WT) MDA-MB-435 human breast cancer cells, as well as cells rendered resistant as a result of exposure to an anticancer agent and MDR version of the same cells. Down-regulation of P-glycoprotein (P-gp), survivin, and MCL-1 with respective siRNAs were studied individually and in combinations. While silencing MCL-1 caused almost 90% cell death in the WT cells, the effect was less significant in the MDR cells. Silencing both MCL-1 and P-gp in the MDR cells showed a synergistic effect. Resistance induction, as confirmed by both IC50 experiments and doxorubicin (DOX) uptake, caused an up-regulation in the expression of not only P-gp, but also BCRP, survivin, and MCL-1. Our double silencing experiments in resistance-induced cells showed a similar pattern to MDR cells; however, in the later stages of resistance induction, prolonged exposure to higher DOX concentrations caused a cell dependency on MCL-1 and a cross-link between MCL-1 and P-gp. MCL-1 silencing was proven to be more efficient in causing cell death in resistance-induced cells compared to MDR cells. A re-sensitization to cytotoxic effect of DOX was observed in resistance-induced cells after silencing of MCL-1. In addition to confirming MCL-1 as a viable target for siRNA silencing, this study indicates that anti-apoptotic proteins such as survivin and MCL-1 may have a role in resistance that could be closely related to efflux proteins.

Abstract B32: Impact of Lipid-Substitution on Assembly and Delivery of siRNA by Cationic Polymers

Downregulation of target protein expression by small interfering RNA (siRNA) has been one of the most promising strategies in medicinal therapy since the discovery of this revolutionary process in late 1990s. Many obstacles, however, have to be overcome to achieve safe and efficient siRNA delivery to target cells. Short in vivo half-life of siRNA and safety concerns involved with viral vectors used for DNA transfection are among the main reasons for the necessity of a better delivery system to take full advantage of this strategy. Polycationic polymers have been studied extensively for this purpose and high molecular weight polyethylenimines (PEIs) have led to promising results; however, unacceptable toxicity profile of these polymers has been a hurdle for their clinical application. In this study, we report characterization of a library of polymers synthesized by hydrophobic modification of a low molecular weight (2 kDa) PEI (PEI2) with a wide range of different fatty acids, engineered to enhance their ability to protect and deliver their nucleotide cargo to the cells, while still being water soluble. A general increase in lipid substitution was observed as the lipid:PEI ratio was increased during the synthesis. Among the polymers derived from lipid:PEI ratio of 0.066, caprylic acid-substituted polymer showed a lower binding affinity, while all other polymers performed similarly. Complete siRNA binding was typically achieved at polymer:siRNA ratio of &lt; 0.5. The BC50 (polymer:siRNA ratio needed for 50% binding) was generally increased with the extent of lipid substitution, indicating an adverse effect of lipid substitution on siRNA complexation. Particle size analysis showed a range of 300 to 600 nm for all of the polymer/siRNA complexes, and for all lipid-substituted polymers, a continuous increase in the ζ-potential was observed with increasing polymer:siRNA weight ratio, and all polymers showed positive ζ-potential at the ratio of 10:1. The ζ-potentials of complexes formed with lipid-modified polymers were higher than complexes of PEI2 at all ratios. With the polymer:siRNA ratio of 1:1, all lipid-substituted polymers showed complete protection against degradation, while naked siRNA was readily degraded (&lt;5% intact siRNA remaining) and only ∼68% of siRNA bound with PEI2 remained intact under the experimental conditions. The cytotoxicity of the synthesized polymers was slightly higher than PEI2, but significantly lower than larger MW PEI. Polymer/siRNA complexes formed with lipid-modified polymers increased the cellular uptake of siRNA significantly. Down-regulation of two different target proteins was also evaluated using the modified polymers: a housekeeping enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and an efflux protein involved in multi-drug resistance (MDR), P-glycoprotein (P-gp). Optimum silencing for the target proteins was achieved by using polymer:siRNA ratio of 4:1 for GAPDH and 8:1 for P-gp. A maximum of 66% and 67% downregulation was observed for GAPDH and P-gp, respectively. Our results indicate that hydrophobic modification of low molecular PEI could render this otherwise ineffective polymer to a safe effective delivery system for intracellular siRNA delivery and silencing of protein expression.

Induction of apoptosis by survivin silencing through siRNA delivery in a human breast cancer cell line

Post-transcriptional silencing of antiapoptotic genes is a promising strategy for cancer therapy, but delivering short interfering RNA (siRNA) molecules against such targets is challenging due to inability of anionic siRNA to cross cellular membranes. Lipid substitution on small molecular weight, nontoxic polyethylenimine (PEI) has been investigated as a promising approach for effective siRNA delivery. In this study, we report on the ability of low molecular weight, lipid-substituted PEI to deliver siRNA against the antiapoptotic protein survivin. Toxicity of a library of lipid-substituted PEIs, as well as their siRNA delivery and survivin silencing efficiency, was evaluated in MDA-MB-231 human breast cancer cells. A significant increase in cellular delivery of siRNA was observed as a result of lipid substitution. Most significant downregulation of survivin was established by caprylic acid-substituted polymers, which resulted in significant levels of apoptosis induction and resultant loss of cell viability. Survivin downregulation prior to anticancer drug treatment decreased the IC(50) of several drugs by 50- to 120-fold. Our experiments indicated an effective downregulation of survivin, a cell protective protein upregulated in tumor cells, by delivering siRNA with hydrophobically modified PEI. This study introduces a promising delivery system for safe and effective siRNA delivery that will be suitable for further investigation in preclinical animal models.

Lipid substitution on low molecular weight (0.6-2.0 kDa) polyethylenimine leads to a higher zeta potential of plasmid DNA and enhances transgene expression

Cationic polymers are desirable gene carriers because of their better safety profiles than viral delivery systems. Low molecular weight (MW) polymers are particularly attractive, since they display little cytotoxicity, but they are also ineffective for gene delivery. To create effective carriers from low MW polymers palmitic acid (PA) was substituted on 0.6-2.0 kDa polyethylenimines (PEIs) and their efficiency for plasmid DNA (pDNA) delivery was evaluated. The extent of lipid substitution was dependent on the lipid/PEI feed ratio and the polymer MW. While the hydrodynamic size of the polymer/pDNA complexes (polyplexes) increased or decreased depending on the extent of lipid substitution, the ζ potential of the assembled complexes was consistently higher as a result of lipid substitution. Lipid substitution generally increased the in vitro toxicity of the PEIs, but it was significantly lower than that of the 25 kDa branched PEI. The in vitro transfection efficiency of the lipid-substituted polymers was higher than that of native PEIs, which were not at all effective. The delivery efficiency was proportional to the extent of lipid substitution as well as the polymer MW. This correlated with the increased uptake of lipid-substituted polyplexes, based on confocal microscopic investigations with FITC-labeled pDNA. The addition of chloroquine further increased the transfection efficiency of lipid-substituted PEIs, indicating that endosomal release was a limiting factor affecting the efficiency of these carriers. This study indicates that lipid substitution on low MW PEIs makes their assembly more effective, resulting in better delivery of pDNA into mammalian cells.

The immunosuppressive activity of polymeric micellar formulation of cyclosporine A: in vitro and in vivo studies

We have previously developed micelles of methoxy poly(ethylene oxide)-b-poly(ε-caprolactone) as vehicles for the solubilization and delivery of cyclosporine A (CsA). These micelles were able to reduce the renal uptake and nephrotoxicity of CsA. The purpose of the current study was to test the efficacy of polymeric micellar formulation of CsA (PM-CsA) in suppressing immune responses by either T cells or dendritic cells (DCs). The performance of PM-CsA was compared to that of the commercially available formulation of CsA (Sandimmune®). Our results demonstrate that PM-CsA could exert a potent immunosuppressive effect similar to that of Sandimmune® both in vitro and in vivo. Both formulations inhibited phenotypic maturation of DCs and impaired their allostimulatory capacity. Furthermore, both PM-CsA and Sandimmune® have shown similar dose-dependent inhibition of in vitro T cell proliferative responses. A similar pattern was observed in the in vivo study, where T cells isolated from both PM-CsA-treated and Sandimmune®-treated mice have shown impairment in their proliferative response and IFN-γ production at similar levels. These results highlight the potential of polymeric micelles to serve as efficient vehicles for the delivery of CsA.

Impact of lipid substitution on assembly and delivery of siRNA by cationic polymers

Characterization of a polymer library engineered to enhance their ability to protect and deliver their nucleotide cargo to the cells is reported. The ζ-potential continuously increased with higher polymer:siRNA weight ratio, and the ζ-potential of lipid-modified polymers:siRNA complexes were higher than PEI2 at all ratios. At polymer:siRNA ratio of 1:1, all lipid-substituted polymers showed complete protection against degradation. Lipid-modified polymers significantly increased the cellular uptake of siRNA complexes and down-regulation of GAPDH and P-gp (max. 66% and 67%, respectively). The results indicate that hydrophobic modification of low molecular PEI could render this otherwise ineffective polymer to a safe effective delivery system for intracellular siRNA delivery and protein silencing.

Disposition of drugs in block copolymer micelle delivery systems: from discovery to recovery

Since their discovery in the early 1980s, polymeric micelles have been the subject of several studies as delivery systems that can potentially improve the therapeutic performance and modify the toxicity profile of encapsulated drugs by changing their pharmacokinetic characteristics. The efforts in this area have led in recent years to the advancement of several polymeric micellar formulations to clinical trials, some of which have shown promise in changing the biodistribution of the incorporated drug after intravenous administration as a means of tumour-targeted drug delivery. Recently, the possible benefit of polymeric micellar delivery in enhancing the absorption and bioavailability of incorporated drugs from alternative routes of drug administration has attracted interest. This article provides an overview of the effect of polymeric micellar delivery on absorption, distribution, metabolism and excretion of incorporated therapeutic agents. It also aims to assess the current information on the performance of polymeric micellar delivery systems in modifying the pharmacokinetics/pharmacodynamics of the incorporated drugs in clinical trials, and to re-examine the important structural factors required for successful design of polymeric micellar delivery systems capable of inducing favourable changes in the pharmacokinetics of the encapsulated drug.

Polymeric Micellar Delivery Reduces Kidney Distribution and Nephrotoxic Effects of Cyclosporine A After Multiple Dosing

The aim of this study was to test the ability of poly(ethylene oxide)-b-poly (epsilon-caprolactone) (PEO-b-PCL) micelles to reduce the renal uptake and nephrotoxicity of Cyclosporine A (CyA) after multiple dose administration. Sprague-Dawley rats received CyA i.v. at a dose of 20 mg/kg/day delivered as the commercial formulation (Sandimmune) or polymeric micellar formulation (PM-CyA). Cremophor EL (the solubilizing agent in Sandimmune), unloaded PEO-b-PCL micelles, or normal saline were also administered i.v. to control rats. After 7 days, kidney function was assessed through measurement of creatinine (CLcr) and urea clearances, as well as electrolyte concentrations in plasma. Blood and kidney were collected and assayed for CyA. Sandimmune administration led to decreased CLcr, and increased urea and potassium levels in plasma. In contrast, functional nephrotoxicity with the PM-CyA was not apparent, as the CLcr did not change significantly. The rate of increase in body weight in control rats was 3.1-3.4% per day. Weight gains (1.8% per day) were also noted in the rats given PM-CyA, although the body weight of animals receiving Sandimmune remained constant. Compared to Sandimmune, polymeric micelles reduced kidney uptake of CyA by 2.6-fold, and increased CyA levels in blood by 2.1-fold. The results show a potential for PEO-b-PCL micelles in restricting the nephrotoxicity of CyA.

Polymeric micelles for drug targeting

Polymeric micelles are nano-delivery systems formed through self-assembly of amphiphilic block copolymers in an aqueous environment. The nanoscopic dimension, stealth properties induced by the hydrophilic polymeric brush on the micellar surface, capacity for stabilized encapsulation of hydrophobic drugs offered by the hydrophobic and rigid micellar core, and finally a possibility for the chemical manipulation of the core/shell structure have made polymeric micelles one of the most promising carriers for drug targeting. To date, three generations of polymeric micellar delivery systems, i.e. polymeric micelles for passive, active and multifunctional drug targeting, have arisen from research efforts, with each subsequent generation displaying greater specificity for the diseased tissue and/or targeting efficiency. The present manuscript aims to review the research efforts made for the development of each generation and provide an assessment on the overall success of polymeric micellar delivery system in drug targeting. The emphasis is placed on the design and development of ligand modified, stimuli responsive and multifunctional polymeric micelles for drug targeting.

A novel use of an in vitro method to predict the in vivo stability of block copolymer based nano-containers

The purpose of this study was to design an in vitro experiment that can assess the stability of polymeric micellar formulations of hydrophobic drugs such as cyclosporine A (CyA) in blood, and predict the in vivo performance of the examined delivery system. Poly(ethylene oxide)-block-poly(epsilon-caprolactone) (PEO-b-PCL) copolymers were assembled to polymeric nano-containers for the physical encapsulation of CyA by a co-solvent evaporation method using different loading conditions. CyA-loaded micelles were prepared and compared to commercially available intravenous formulation of CyA (Sandimmune) for in vitro release, protein binding, and pharmacokinetic parameters in Sprague-Dawley rats. The unbound fraction (fu) of CyA was determined using an erythrocyte vs. plasma and buffer partitioning technique. Different polymeric micellar formulations of CyA did not show any significant difference in CyA release when dialyzed against bovine serum albumin. The fu experiments, however, revealed a significant decrease in the fu of the loaded drug with an increase in the drug/polymer loading ratio, while the fu of all micellar formulations were significantly lower than Sandimmune. The pharmacokinetic study showed that fu of CyA in each formulation correlated with its in vivo performance determined by pharmacokinetic parameters: the lower fu of the formulation, translated to a higher area under the concentration versus time curve (AUC), and a lower clearance (CL) and volume of distribution (Vd). In conclusion, determination of the unbound fraction of encapsulated drug can be used to predict the in vivo stability of polymeric micellar nano-containers. PEO-b-PCL micelles containing higher CyA-loaded levels are shown to be more stable changing the pharmacokinetics of the encapsulated CyA to a higher extent.

Insights into the effects of hyperlipoproteinemia on cyclosporine A biodistribution and relationship to renal function

The purpose of this study was to assess the effect of hyperlipoproteinemia on the biodistribution of cyclosporine A (CyA), an extensively lipoprotein bound immunosuppressant, in a rat model and to determine the potential toxicological significance of this effect. Normolipidemic and hyperlipoproteinemic rats were given a single 5 mg/kg dose of CyA as intravenous bolus and at selected times postdose, tissues, blood, and plasma were harvested and assayed for CyA content. Hyperlipoproteinemia was induced by intraperitoneal injection of 1 g/kg poloxamer 407. Compared with normolipidemic animals, hyperlipoproteinemic rats had higher plasma, blood, kidney, and liver CyA concentrations. In contrast, in heart and spleen the concentrations were decreased in hyperlipoproteinemia. The nephrotoxic effect of CyA was also evaluated in normolipidemic and hyperlipoproteinemic rats after 7 days of dosing with 20 mg/kg/day. In both groups of animals, repeated doses of CyA were associated with equivalent decreases in creatinine and urea clearances compared with matching control and predose baseline measures. The concentrations of drug in kidney were equivalent at the conclusion of the study. However, despite these similarities there was microscopic evidence of more severe changes in the kidneys in the hyperlipoproteinemic rats, which also experienced a significant decrease in body weight compared with the normolipedemic animals. In conclusion, the distribution of CyA to kidneys was enhanced in poloxamer 407-induced hyperlipoproteinemic rats after single doses, and with repeated doses there was an apparent greater adverse effect on these animals compared with normolipidemic animals.

Encapsulation of hydrophobic drugs in polymeric micelles through co-solvent evaporation: the effect of solvent composition on micellar properties and drug loading

This study was designed to develop an optimized co-solvent evaporation procedure for the efficient encapsulation of hydrophobic drugs in polymeric micelles of methoxy poly(ethylene oxide)-block-poly(epsilon-caprolactone) (MePEO-b-PCL). MePEO-b-PCL block copolymers having varied MePEO and PCL molecular weights were synthesized, assembled to polymeric micelles, and used for the encapsulation of cyclosporine A (CyA) by a co-solvent evaporation method. The co-solvent composition was varied by changing the type of organic co-solvent (using acetone, acetonitrile and tetrahydrofuran), the ratio of organic to aqueous phase, and their order of addition. Carrier size, morphology and encapsulated CyA levels were defined by dynamic light scattering (DLS), transmission electron microscopy (TEM) and HPLC, respectively, and the effect of co-solvent composition on micellar properties and loaded CyA levels was evaluated. Application of acetone and acetonitrile as the selective co-solvent for the core-forming block led to a decrease in the average diameter of self-assembled structures. When acetone was added to water, a decrease in the ratio of organic to aqueous phase led to an increase in the loading efficiency of CyA in MePEO-b-PCL micelles. A similar trend in CyA loading was observed for MePEO-b-PCL micelles of varied MePEO and PCL block lengths. The ratio of organic to aqueous phase did not affect CyA loading when water was added to acetone. Irrespective of the order of addition, the decrease in the organic to aqueous phase ratio caused a reduction in the average diameter of the empty and CyA loaded micelles. We conclude that the co-solvent evaporation method may be optimized to improve the efficiency of drug encapsulation in polymeric micelles. For CyA encapsulation in MePEO-b-PCL micelles, addition of acetone to water at lower organic to aqueous phase ratio is shown to be the optimum procedure leading to higher drug encapsulation and smaller average diameter for the self-assembled structures.

Polymeric micelles for drug delivery

Polymeric micelles have been the subject of many studies in the field of drug delivery for the past two decades. The interest has specifically been focused on the potential application of polymeric micelles in three major areas in drug delivery: drug solubilisation, controlled drug release and drug targeting. In this context, polymeric micelles consisting of poly(ethylene oxide)-b-poly(propylene oxide), poly(ethylene oxide)-b-poly(ester)s and poly(ethylene oxide)-b-poly(amino acid)s have shown a great promise and are in the front line of development for various applications. The purpose of this manuscript is to provide an update on the current status of polymeric micelles for each application and highlight important parameters that may lead to the development of successful polymeric micellar systems for individual delivery requirements.

Polymeric micelles for the solubilization and delivery of cyclosporine A: pharmacokinetics and biodistribution

The aim of this study was to assess the potential of polymeric micelles to modify the pharmacokinetics and tissue distribution of cyclosporine A (CsA). Drug-loaded methoxy poly(ethylene oxide)-b-poly(epsilon-caprolactone) (PEO-b-PCL) micellar solutions in isotonic medium were prepared and administered intravenously to healthy Sprague-Dawley rats. Blood and tissues were harvested and assayed for CsA, and resultant pharmacokinetic parameters and tissue distribution of CsA in its polymeric micellar formulation were compared to its commercially available intravenous formulation (Sandimmune). In the pharmacokinetic assessment, a 6.1 fold increase in the area under the blood concentration versus time curve (AUC) was observed for CsA when given as polymeric micellar formulation as compared to Sandimmune. The volume of distribution and clearance of CsA as PEO-b-PCL formulation were observed to be 10.0 and 7.6 fold lower, respectively, compared to the commercial formulation. No significant differences in t(1/2) or MRT could be detected. In the biodistribution study, analysis of tissue samples indicated that the mean AUC of CsA in polymeric micelles was lower in liver, spleen and kidney (1.5, 2.1 and 1.4-fold, respectively). Similar to the pharmacokinetic study in these rats, the polymeric micellar formulation gave rise to 5.7 and 4.9-fold increase in the AUC of CsA in blood and plasma, respectively. Our results show that PEO-b-PCL micelles can effectively solubilize CsA, at the same time confining CsA to the blood circulation and restricting its access to tissues such as kidney, perhaps limiting the onset of toxicity.

Micelles of methoxy poly(ethylene oxide)-b-poly(epsilon-caprolactone) as vehicles for the solubilization and controlled delivery of cyclosporine A

The commercial formulation of Cyclosporine A (CsA) for intravenous administration contains Cremophor EL, a low molecular weight surfactant known to be toxic. In this study, micelles of methoxy poly(ethylene oxide)-b-poly(epsilon-caprolactone) (PEO-b-PCL) were investigated as alternative vehicles for the solubilization and delivery of CsA. PEO-b-PCL block copolymers having identical PEO chain lengths and PCL molecular weights of 5000, 13,000, or 24,000 g mol(-)(1) were synthesized and assembled into polymeric micelles using a co-solvent evaporation method. PEO-b-PCL micelles were then compared to Cremophor EL micelles for their functional properties in drug delivery including micellar size, thermodynamic stability, core viscosity, CsA encapsulation, and in vitro CsA release. Among different PCL block lengths, optimum solubilization was achieved by utilizing polymeric micelles having a PCL block of 13,000 g mol(-)(1). CsA reached an aqueous solubility of 1.3 mg/mL in the presence of PEO-b-PCL micelles. This concentration is comparable to injectable CsA levels in its Cremophor EL formulation (0.5-2.5 mg/mL). In contrast to the Cremophor EL formulation, the in vitro rate of CsA release was significantly sustained by the polymeric micellar carrier. Within 12 h, only 5.8% of CsA was released from polymeric micelles while Cremophor EL micelles released 77% of their drug content. Accordingly, viscosity of the PEO-b-PCL micellar core was found to be significantly higher than Cremophor EL micelles. The results points to a potential for PEO-b-PCL micelles as nanoscopic drug carriers for efficient solubilization and controlled delivery of CsA.