The application of electrosprayed minocycline-loaded PLGA microparticles for the treatment of glioblastoma

The survival of patients with glioblastoma multiforme (GBM), the most common and invasive form of malignant brain tumors, remains poor despite advances in current treatment methods including surgery, radiotherapy, and chemotherapy. Minocycline is a semi-synthetic tetracycline derivative that has been widely used as an antibiotic and more recently, it has been utilized as an antiangiogenic factor to inhibit tumorigenesis. The objective of this study was to investigate the utilization of electrospraying process to fabricate minocycline-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles with high drug loading and loading efficiency and to evaluate their ability to induce cell toxicity in human glioblastoma (i.e., U87-MG) cells. The results from this study demonstrated that solvent mixture of dicholoromethane (DCM) and methanol is the optimal solvent combination for minocycline and larger amount of methanol (i.e., 70:30) resulted in a higher drug loading. All three solvent ratios of DCM:methanol tested produced microparticles that were both spherical and smooth, all in the micron size range. The electrosprayed microparticles were able to elicit a cytotoxic response in U87-MG glioblastoma cells at a lower concentration of drug compared to the free drug. This work provides proof of concept to the hypothesis that electrosprayed minocycline-loaded PLGA microparticles can be a promising agent for the treatment of GBM and could have potential application for cancer therapies.

Abstract 2000: Injectable alginate scaffolds for the delivery of minocycline for the treatment of glioblastoma

Glioblastoma Multiforme (GBM) is a Grade IV malignant brain cancer that is associated with a high recurrence and low survival rate amongst affected patients. Despite advances in the different methods of therapy, the prognosis for GBM has not improved through the years and, thus, alternative treatment methods for GBM are needed. Minocycline (MINO) is known as a semi-synthetic tetracycline that serves as an antibiotic and has also been shown to be able to suppress angiogenesis for GBM treatment. Collected from brown seaweed, alginate is a biodegradable polysaccharide that can be used to form a hydrogel for drug delivery due to its biocompatibility properties. Injectable alginate scaffolds may be a promising component for an adjuvant treatment method against GBM as the injectability property of the scaffold will allow for the site of interest to be filled precisely after tumor resection. The objective of this study is to develop injectable alginate scaffolds for the delivery of MINO for the treatment of GBM. The effects of the concentration of sodium alginate (SA) and calcium carbonate (CaCO3) (i.e., 0.75, 1.00, 1.50, and 2.00 wt./vol.%) with a 0.25 wt./vol.% of glucono-delta lactone (GDL) on the pH, gelation time, dimensions, degradation, and drug release kinetics of alginate scaffolds were investigated. Injectable alginate scaffolds were fabricated by dissolving SA and CaCO3 (1:1) in water, homogenized with GDL for 20 sec., and then injected into a 24-well plate to develop uniform scaffolds. Their properties were evaluated by testing pH values via a pH meter, timing gelation with a digital timer, utilizing a digital microcaliper to investigate dimensions, an analytical scale to evaluate the mass of dried scaffolds to determine scaffold degradation, and evaluating the release rate of MINO using a microplate reader at a wavelength of 350 nm. As the concentration of SA and CaCO3 increased, an increase in pH, gelation time, and overall stability of the scaffold were observed. All four concentrations of SA and CaCO3 tested resulted in scaffolds with desired pH and workable gelation time; however, the 1 wt./vol.% group may be the most ideal as an optimal pH was reached after 10 minutes and the gelation time for these scaffolds was ~8 minutes. Lower concentration scaffolds (0.75 and 1.00 wt./vol.%) degraded faster in comparison to those made with higher concentrations. Drug release kinetics data revealed that the scaffolds can sustain short term release but could be improved by incorporating the drug into micro or nanoparticles before incorporation into the scaffolds. In conclusion, the injectable alginate scaffolds developed in this study may be promising biomaterials for the delivery of drugs for GBM treatment.

Citation Format: Kaitlyn D. Ybáñez, Marco A. Arriaga, Rene N. Rico, Theresia Rookstool, Sue Anne Chew. Injectable alginate scaffolds for the delivery of minocycline for the treatment of glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2000.

Abstract 1744: Injectable alginate scaffolds for the dual delivery of Minocycline and Temozolomide for the treatment of glioblastoma

Glioblastoma Multiforme (GBM) is the most frequent and aggressive malignant primary brain tumor in adults with a life expectancy of less than fifteen months after diagnosis. The standard care for GBM includes surgical resection followed by radiotherapy and chemotherapy. Despite advances in the different methods of therapy, the prognosis for gliomas has not been dramatically improved through the years due to high levels of reoccurrence therefore, alternative treatment methods are needed for GBM. Minocycline (MINO) is a common antibiotic with potential anticancer effects by acting as an anti-angiogenic agent which can help in the treatment and reduction of gliomas by reducing blood vessel formation. Temozolomide (TMZ) is a chemotherapy alkylating agent that has demonstrated antitumor activity against highly resistant malignancies as high-grade gliomas. Injectable alginate scaffolds can serve as a local delivery system for controlled drug release and can be an important component for the development of a treatment method against GBM. The objective of this study was to investigate the optimal concentration of TMZ and MINO alone or in combination against glioblastoma cells (U87-MG) and human umbilical vein endothelial cells (HUVEC) and to evaluate the ability of an injectable alginate scaffold to control the rate of drug release for the treatment of GBM. In this study, U87-MG were treated with MINO (0-4000 µM) and TMZ (0-6000 µM), while HUVEC were treated with MINO (0-1000 µM) and TMZ (0-2000 µM) alone or in combination and a MTT assay was used to determine cell viability. Injectable alginate scaffolds were fabricated by dissolving sodium alginate and calcium carbonate in water and then homogenized with glucanolactone and drugs for 20 seconds. The mixture was then injected into a 24-well plate. After fabrication, scaffolds with MINO, TMZ and MINO/TMZ were incubated in PBS at 37 °C. At each timepoint (1, 4, 7, 10 and 14 days), the amount of drug released was measured by reading the absorbance of MINO and TMZ at 350 and 327 nm, respectively using a microplate reader. The 50% inhibitory concentration (IC50) of MINO and TMZ were found to be 950 µM and 900 µM, respectively in U87-MG. In HUVEC, the IC50 of MINO and TMZ were found to be 150 µM and 400 µM, respectively. MINO and TMZ alone reduced cell viability by 39% and 41%, respectively, in U87-MG and in HUVEC by 36% and 34%, respectively. In combination, both drugs reduced cell viability in U87-MG by 58% and in HUVEC by 56%, resulting in synergistic effects for both cell lines. In addition, the application of the injectable alginate scaffold resulted in a controlled release of the drugs alone or in combination. In conclusion, the combination of MINO and TMZ resulted in synergistic effects on cell viability in both cell lines and the controlled delivery of both drugs with an injectable scaffold can be a promising method for the treatment of GBM.

Citation Format: Marco A. Arriaga, Rene N. Rico, Kaitlyn D. Ybanez, Daniela Lopez-Lorenzo, Sue Anne Chew. Injectable alginate scaffolds for the dual delivery of Minocycline and Temozolomide for the treatment of glioblastoma  [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1744.

Effect of drug-to-lipid ratio on nanodisc-based tenofovir drug delivery to the brain for HIV-1 infection

Background

Combination antiretroviral therapy has significantly advanced HIV-1 infection treatment. However, HIV-1 remains persistent in the brain; the inaccessibility of the blood–brain barrier allows for persistent HIV-1 infections and neuroinflammation. Nanotechnology-based drug carriers such as nanodiscoidal bicelles can provide a solution to combat this challenge.

Methods

This study investigated the safety and extended release of a combination antiretroviral therapy drug (tenofovir)-loaded nanodiscs for HIV-1 treatment in the brain both in vitro and in vivo.

Result

The nanodiscs entrapped the drug in their interior hydrophobic core and released the payload at the desired location and in a controlled release pattern. The study also included a comparative pharmacokinetic analysis of nanodisc formulations in in vitro and in vivo models.

Conclusion

The study provides potential applications of nanodiscs for HIV-1 therapy development.

Application of iron oxide nanoparticles to control the release of minocycline for the treatment of glioblastoma

Background: The utilization of iron oxide nanoparticles (Fe3O4 NPs) to control minocycline release rates from poly(lactic-co-glycolic acid) scaffolds fabricated from an easy/economical technique is presented. Results & methodology: A larger change in temperature and amount of minocycline released was observed for scaffolds with higher amounts of Fe3O4 NPs, demonstrating that nanoparticle concentration can control heat generation and minocycline release. Temperatures near a polymer's glass transition temperature can result in the polymer's chain becoming more mobile and thus increasing drug diffusion out of the scaffold. Elevated temperature and minocycline released from the scaffold can work synergistically to enhance glioblastoma cell death. Conclusion: This study suggests that Fe3O4 NPs are promising materials for controlling minocycline release from polymeric scaffolds by magnetic hyperthermia for the treatment of glioblastoma.

Strategies to better treat glioblastoma: antiangiogenic agents and endothelial cell targeting agents

Glioblastoma multiforme (GBM) is the most prevalent and aggressive form of glioma, with poor prognosis and high mortality rates. As GBM is a highly vascularized cancer, antiangiogenic therapies to halt or minimize the rate of tumor growth are critical to improving treatment. In this review, antiangiogenic therapies, including small-molecule drugs, nucleic acids and proteins and peptides, are discussed. The authors further explore biomaterials that have been utilized to increase the bioavailability and bioactivity of antiangiogenic factors for better antitumor responses in GBM. Finally, the authors summarize the current status of biomaterial-based targeting moieties that target endothelial cells in GBM to more efficiently deliver therapeutics to these cells and avoid off-target cell or organ side effects.

The Role of Angiogenesis-Inducing microRNAs in Vascular Tissue Engineering

Angiogenesis is an important process in tissue repair and regeneration as blood vessels are integral to supply nutrients to a functioning tissue. In this review, the application of microRNAs (miRNAs) or anti-miRNAs that can induce angiogenesis to aid in blood vessel formation for vascular tissue engineering in ischemic diseases such as peripheral arterial disease and stroke, cardiac diseases, and skin and bone tissue engineering is discussed. Endothelial cells (ECs) form the endothelium of the blood vessel and are recognized as the primary cell type that drives angiogenesis and studied in the applications that were reviewed. Besides ECs, mesenchymal stem cells can also play a pivotal role in these applications, specifically, by secreting growth factors or cytokines for paracrine signaling and/or as constituent cells in the new blood vessel formed. In addition to delivering miRNAs or cells transfected/transduced with miRNAs for angiogenesis and vascular tissue engineering, the utilization of extracellular vesicles (EVs), such as exosomes, microvesicles, and EVs collectively, has been more recently explored. Proangiogenic miRNAs and anti-miRNAs contribute to angiogenesis by targeting the 3'-untranslated region of targets to upregulate proangiogenic factors such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor, and hypoxia-inducible factor-1 and increase the transduction of VEGF signaling through the PI3K/AKT and Ras/Raf/MEK/ERK signaling pathways such as phosphatase and tensin homolog or regulating the signaling of other pathways important for angiogenesis such as the Notch signaling pathway and the pathway to produce nitric oxide. In conclusion, angiogenesis-inducing miRNAs and anti-miRNAs are promising tools for vascular tissue engineering for several applications; however, future work should emphasize optimizing the delivery and usage of these therapies as miRNAs can also be associated with the negative implications of cancer.

The Application of microRNAs in Biomaterial Scaffold-Based Therapies for Bone Tissue Engineering

In recent years, the application of microRNAs (miRNAs) or anti-microRNAs (anti-miRNAs) that can induce expression of the runt-related transcription factor 2 (RUNX2), a master regulator of osteogenesis, has been investigated as a promising alternative bone tissue engineering strategy. In this review, biomaterial scaffold-based applications that have been used to deliver cells expressing miRNAs or anti-miRNAs that induce expression of RUNX2 for bone tissue engineering are discussed. An overview of the components of the scaffold-based therapies including the miRNAs/anti-miRNAs, cell types, gene delivery vectors, and scaffolds that have been applied are provided. To date, there have been nine miRNAs/anti-miRNAs (i.e., miRNA-26a, anti-miRNA-31, anti-miRNA-34a, miRNA-135, anti-miRNA-138, anti-miRNA-146a, miRNA-148b, anti-miRNA-221, and anti-miRNA-335) that have been incorporated into scaffold-based bone tissue engineering applications and investigated in an in vivo bone critical-sized defect model. For all of the biomaterial scaffold-based miRNA therapies that have been developed thus far, cells that are transfected or transduced with the miRNA/anti-miRNA are loaded into the scaffolds and implanted at the site of interest instead of locally delivering the miRNA/anti-miRNAs directly from the scaffolds. Thus, future work may focus on developing biomaterial scaffolds to deliver miRNAs or anti-miRNAs into cells in vivo.

Effects of solvent used for fabrication on drug loading and release kinetics of electrosprayed temozolomide-loaded PLGA microparticles for the treatment of glioblastoma

Glioblastoma multiforme (GBM) is the most common and invasive form of malignant brain tumors and despite advances in surgery, radiotherapy, and chemotherapy, the survival of patients with GBM still remains poor. Temozolomide (TMZ) is the chemotherapy drug that is most commonly given orally after surgical resection of these tumors. In this study, the effects of solvents (i.e., dichloromethane and acetonitrile) used for the fabrication of electrosprayed TMZ-loaded poly(lactic-co-glycolic acid) (PLGA) on drug loading, loading efficiency, drug release kinetics, surface morphology, and particle size were investigated. The results from this study demonstrated that by using a larger volume of a solvent with higher polarity (i.e., acetonitrile) which allows for a higher amount of hydrophilic TMZ to dissolve into the polymer solution, higher drug loading could be achieved. However, the particles fabricated with high amount of acetonitrile, which has a lower vapor pressure, had large pores and a smaller diameter which led to an initial burst release and high cumulative release at the end of the study. An optimal combination of the two solvents is needed to result in particles with a good amount of loading and minimal initial burst release. The electrosprayed microparticles were able to illicit a cytotoxic response in U-87 MG glioblastoma cells at a lower concentration of drug compared to the free drug. This work indicated that electrospraying is a promising method for the fabrication of TMZ-loaded PLGA microparticles for the treatment of GBM and solvent composition can be altered to control drug loading and release kinetics. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2317-2324, 2019.

Abstract 3719: Fabrication of chemotherapy drug temozolomide-loaded poly(lactic-co-glycolic acid) microparticles by electrospraying for the treatment of glioma

Glioblastoma (GBM) is a form of brain tumor with a low median survival rate of 16 months after diagnosis despite the many efforts to treat it. The main approach to treat GBM consists of surgery followed by radiation and chemotherapy drugs, such as Temozolomide (TMZ). However, TMZ tends to degrade fast making it hard to deliver enough amounts of the drug to the site of the tumor. The overall goal of our project is to develop a biodegradable composite system to locally deliver both an anti-angiogenic and chemotherapy agent for the treatment of glioma. The objective of this particular work was to successfully fabricate TMZ loaded biodegradable poly (lactic-co-glycolic acid) (PLGA) microparticles as carriers of the drug to protect TMZ from rapid degradation, and providing a method for controlling the release of the drug. In this study, three different methods of fabricating the microparticles were investigated and compared: single-emulsion solvent evaporation, double-emulsion solvent evaporation, and electrospraying to determine which method will result in high drug loading and sustained release of the drug. For the drug release study, 5 mg of each type of microparticle were added to 1 ml of phosphate-buffered saline (PBS) and stored and shaken in a non-CO2 incubator set at 37°C. At each time point (1, 3, 7, 10, and 14 days), the microparticles were frozen down and at the end of the study, the microparticles were dissolved in dimethyl sulfoxide (DMSO) and the drug concentration was determined by absorbance using a spectrophotometer at a wavelength of 328 nm. Compared to the two emulsion solvent evaporation methods investigated, electrospraying provides a way to fabricate TMZ loaded microparticles with a high drug loading efficiency (60% to 97% of the drug used for fabrication was loaded into the particles compared to 0.05% for the emulsion solvent evaporation methods). The lower drug loading efficiency of the emulsion solvent-evaporation technique resulted from the loss of the drug into the PVA solution during the microparticle hardening process which is avoided with the electrospraying method. The electrospraying method showed a constant controlled release of the drug over 14 days and resulted in a drug cumulative release of 90% from the microparticles at the end of the study. However, the amount of drug loaded is still low (0.72% to 1.2% of the total weight of the particles) due to the low solubility of TMZ in the solvent (i.e. dichloromethane) used for electrospraying. Thus, our future work consists of investigating other solvents to increase the amount of drug loaded. In conclusion, electrospraying is a promising method to fabricate microparticles with high drug loading efficiency and sustained release of the drug, however optimization of the solvent used to prepare the electrospraying solution is needed to increase the amount of drug loaded.

Citation Format: Daniel A. Rodriguez De Anda, Sue Anne Chew. Fabrication of chemotherapy drug temozolomide-loaded poly(lactic-co-glycolic acid) microparticles by electrospraying for the treatment of glioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3719.

Biomaterial-Based Implantable Devices for Cancer Therapy

This review article focuses on the current local therapies mediated by implanted macroscaled biomaterials available or proposed for fighting cancer and also highlights the upcoming research in this field. Several authoritative review articles have collected and discussed the state-of-the-art as well as the advancements in using biomaterial-based micro- and nano-particle systems for drug delivery in cancer therapy. On the other hand, implantable biomaterial devices are emerging as highly versatile therapeutic platforms, which deserve an increased attention by the healthcare scientific community, as they are able to offer innovative, more effective and creative strategies against tumors. This review summarizes the current approaches which exploit biomaterial-based devices as implantable tools for locally administrating drugs and describes their specific medical applications, which mainly target resected brain tumors or brain metastases for the inaccessibility of conventional chemotherapies. Moreover, a special focus in this review is given to innovative approaches, such as combined delivery therapies, as well as to alternative approaches, such as scaffolds for gene therapy, cancer immunotherapy and metastatic cell capture, the later as promising future trends in implantable biomaterials for cancer applications.

Abstract 1366: Fabrication of minocycline loaded PLGA microparticles for the treatment of intracranial tumors

Minocycline is a tetracycline derivative that was originally used clinically as an antibiotic and is currently being investigated as an anti-angiogenic factor for the treatment of different cancers including intracranial tumors such as glioblastomas. Due to its lipophilic nature, it has difficulty dissolving completely in organic or aqueous solvents and thus, presents a challenge for the fabrication of these particles via the emulsion-solvent evaporation method. The aim of this study is to investigate the effects of different methods of fabricating minocycline loaded microparticles on particle properties, such as the diameter, drug loading and release kinetics of the microparticles. Microparticles loaded with drug during the fabrication process were produced via two different methods: 1) an oil-in-water (O/W) single emulsion-solvent evaporation method where the drug was dissolved in the oil phase (denoted as “O/W particles”) and 2) a water-in-oil-in-water (W/O/W) double emulsion-solvent evaporation method where the drug was dissolved in the first water phase (denoted as “W/O/W particles”). Empty microparticles were also fabricated by a W/O/W method and loaded with drug after fabrication by dripping a drug solution onto freeze dried particles which were then left overnight at 4°C to allow the drug to adsorb onto and absorb into the particles (denoted as “prefabricated particles”). Light microscopy images of the particles were obtained and used to measure the diameters of the particles with the ImageJ software. The drug loading and release kinetics were determined by measuring the absorbance of minocycline at 350 nm with a microplate reader. The prefabricated particles resulted in larger diameters compared to the O/W and W/O/W particles which were loaded during the fabrication process. This could have resulted from the use of a vortex instead of a homogenizer/sonicator for the prefabricated scaffold which produces an emulsion with a lower speed compared to a homogenizer/sonicator. The prefabricated particles had a higher amount of drug loaded compared to O/W and W/O/W particles which were loaded during the fabrication process. By loading the drug after fabricating the particles, almost all of the drug can be adsorbed onto and/or absorbed into the particles without resulting in much loss of the drug. Alternatively, by loading the particles during the fabrication process, a lot of drug is lost into the water and/or oil phase and thus reducing the loading efficiencies of the particles. However, the particles loaded during the fabrication process were able to prolong the release of the loaded drug compared to the prefabricated scaffold which lost almost all of its drug by Day 1. In conclusion, although the prefabricated particles allow for the complete loading of the drug, the particles loaded during the fabrication process are more promising as controlled release vehicles as they are able to better sustain the release of the loaded drug.

Citation Format: Sue Anne Chew, Marco Arriaga, Jesus R. Franco, Daniela Barbosa, Victor A. Hinojosa, Jose-Carlos Martinez, Paul Lenz. Fabrication of minocycline loaded PLGA microparticles for the treatment of intracranial tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1366.

Effects of surface area to volume ratio of PLGA scaffolds with different architectures on scaffold degradation characteristics and drug release kinetics

In this work, PLGA scaffolds with different architectures were fabricated to investigate the effects of surface area to volume ratio (SVR) (which resulted from the different architectures) on scaffold degradation characteristics and drug release kinetics with minocycline as the model drug. It was hypothesized that the thin strand scaffolds, which had the highest SVR, would degrade faster than the thick strand and globular scaffolds as the increase in surface area will allow more contact between water molecules and degradable ester groups in the polymer. However, it was found that globular scaffolds, which had the lowest SVR, resulted in the fastest degradation which demonstrated that the amount of degradation of the scaffolds does not only depend on the SVR but also on other factors such as the retention of acidic degradation byproducts in the scaffold and scaffold porosity. PLGA 50 : 50 globular scaffolds resulted in a biphasic release profile, with a burst release in the beginning and the middle of the release study which may be beneficial for some drug delivery applications. A clear correlation between SVR and release rates was not observed, indicating that besides the availability of more surface area for drug to diffuse out of the polymer matrix, other factors such as amount of scaffold degradation and scaffold porosity may play a role in determining drug release kinetics. Further studies, such as scanning electron microscopy, need to be performed in the future to further evaluate the porosity, morphology and structure of the scaffolds.

Comprehensive proteomic profiling identifies the androgen receptor axis and other signaling pathways as targets of microRNAs suppressed in metastatic prostate cancer

MicroRNAs are important epigenetic regulators of protein expression by triggering degradation of target mRNAs and/or inhibiting their translation. Dysregulation of microRNA expression has been reported in several cancers, including prostate cancer (PC). We comprehensively characterized the proteomic footprint of a panel of 12 microRNAs that are potently suppressed in metastatic PC (SiM-miRNAs: miR-1, miR-133a, miR-133b, miR-135a, miR-143-3p, miR-145-3p, miR-205, miR-221-3p, miR-221-5p, miR-222-3p, miR-24-1-5p, and miR-31) using reverse-phase proteomic arrays. Re-expression of these SiM-miRNAs in PC cells suppressed cell proliferation and targeted key oncogenic pathways, including cell cycle, apoptosis, Akt/mammalian target of rapamycin signaling, metastasis and the androgen receptor (AR) axis. However, only 12%, at most, of these observed protein expression changes could be explained by predicted direct binding of miRNAs to corresponding mRNAs, suggesting that the majority of these proteomic effects result indirectly. AR and its steroid receptor coactivators (SRCs; SRC-1, -2 and -3) were recurrently affected by these SiM-miRNAs. In agreement, we identified inverse correlations between expression of these SiM-miRNAs and early clinical recurrence, as well as with AR transcriptional activity in human PC tissues. We also identified robust induction of miR-135a by androgen and strong direct binding of AR to the miR-135a locus. As miR-135a potently suppresses AR expression, this results in a negative feedback loop that suppresses AR protein expression in an androgen-dependent manner, while de-repressing AR expression upon androgen deprivation. Our results demonstrate that epigenetic silencing of these SiM-miRNAs can result in increased AR axis activity and cell proliferation, thus contributing to disease progression. We further demonstrate that a negative feedback loop involving miR-135a can restore AR expression under androgen-deprivation conditions, thus contributing to the upregulation of AR protein expression in castration-resistant PC. Finally, our unbiased proteomic profiling demonstrates that the majority of actual protein expression changes induced by SiM-miRNAs cannot be explained based on predicted direct interactions.

miR-137 Targets p160 Steroid Receptor Coactivators SRC1, SRC2, and SRC3 and Inhibits Cell Proliferation

The p160 family of steroid receptor coactivators (SRCs) are pleiotropic transcription factor coactivators and "master regulators" of gene expression that promote cancer cell proliferation, survival, metabolism, migration, invasion, and metastasis. Cancers with high p160 SRC expression exhibit poor clinical outcomes and resistance to therapy, highlighting the SRCs as critical oncogenic drivers and, thus, therapeutic targets. microRNAs are important epigenetic regulators of protein expression. To examine the regulation of p160 SRCs by microRNAs, we used and combined 4 prediction algorithms to identify microRNAs that could target SRC1, SRC2, and SRC3 expression. For validation of these predictions, we assessed p160 SRC protein expression and cell viability after transfection of corresponding microRNA mimetics in breast cancer, uveal melanoma, and prostate cancer (PC) cell lines. Transfection of selected microRNA mimetics into breast cancer, uveal melanoma, and PC cells depleted SRC protein expression levels and exerted potent antiproliferative activity in these cell types. In particular, microRNA-137 (miR-137) depleted expression of SRC1, SRC2, and very potently, SRC3. The latter effect can be attributed to the presence of 3 miR-137 recognition sequences within the SRC3 3'-untranslated region. Using reverse phase protein array analysis, we identified a network of proteins, in addition to SRC3, that were modulated by miR-137 in PC cells. We also found that miR-137 and its host gene are epigenetically silenced in human cancer specimens and cell lines. These results support the development and testing of microRNA-based therapies (in particular based on restoring miR-137 levels) for targeting the oncogenic family of p160 SRCs in cancer.

Androgen receptor is the key transcriptional mediator of the tumor suppressor SPOP in prostate cancer

Somatic missense mutations in the substrate-binding pocket of the E3 ubiquitin ligase adaptor SPOP are present in up to 15% of human prostate adenocarcinomas, but are rare in other malignancies, suggesting a prostate-specific mechanism of action. SPOP promotes ubiquitination and degradation of several protein substrates, including the androgen receptor (AR) coactivator SRC-3. However, the relative contributions that SPOP substrates may make to the pathophysiology of SPOP-mutant (mt) prostate adenocarcinomas are unknown. Using an unbiased bioinformatics approach, we determined that the gene expression profile of prostate adenocarcinoma cells engineered to express mt-SPOP overlaps greatly with the gene signature of both SRC-3 and AR transcriptional output, with a stronger similarity to AR than SRC-3. This finding suggests that in addition to its SRC-3-mediated effects, SPOP also exerts SRC-3-independent effects that are AR-mediated. Indeed, we found that wild-type (wt) but not prostate adenocarcinoma-associated mutants of SPOP promoted AR ubiquitination and degradation, acting directly through a SPOP-binding motif in the hinge region of AR. In support of these results, tumor xenografts composed of prostate adenocarcinoma cells expressing mt-SPOP exhibited higher AR protein levels and grew faster than tumors composed of prostate adenocarcinoma cells expressing wt-SPOP. Furthermore, genetic ablation of SPOP was sufficient to increase AR protein levels in mouse prostate. Examination of public human prostate adenocarcinoma datasets confirmed a strong link between transcriptomic profiles of mt-SPOP and AR. Overall, our studies highlight the AR axis as the key transcriptional output of SPOP in prostate adenocarcinoma and provide an explanation for the prostate-specific tumor suppressor role of wt-SPOP.

Protein kinase C inhibitors sensitize GNAQ mutant uveal melanoma cells to ionizing radiation

PURPOSE

Uveal melanoma (UM) tumors require large doses of radiation therapy (RT) to achieve tumor ablation, which frequently results in damage to adjacent normal tissues, leading to vision-threatening complications. Approximately 50% of UM patients present with activating somatic mutations in the gene encoding for G protein αq-subunit (GNAQ), which lead to constitutive activation of downstream pathways, including protein kinase C (PKC). In this study, we investigated the impact of small-molecule PKC inhibitors bisindolylmaleimide I (BIM) and sotrastaurin (AEB071), combined with ionizing radiation (IR), on survival in melanoma cell lines.

METHODS

Cellular radiosensitivity was determined by using a combination of proliferation, viability, and clonogenic assays. Cell-cycle effects were measured by flow cytometry. Transcriptomic and proteomic profiling were performed by quantitative real-time PCR, reverse-phase protein array analysis, and immunofluorescence.

RESULTS

We found that the PKC inhibitors combined with IR significantly decreased the viability, proliferation, and clonogenic potential of GNAQ(mt), but not GNAQ(wt)/BRAF(mt) cells, compared with IR alone. Combined treatment increased the antiproliferative and proapoptotic effects of IR in GNAQ(mt) cells through delayed DNA-damage resolution and enhanced induction of proteins involved in cell-cycle arrest, cell-growth arrest, and apoptosis.

CONCLUSIONS

Our preclinical results suggest that combined modality treatment may allow for reductions in the total RT dose and/or fraction size, which may lead to better functional organ preservation in the treatment of primary GNAQ(mt) UM. These findings suggest future clinical trials combining PKC inhibitors with RT in GNAQ(mt) UM warrant consideration.

Abstract P6-10-03: The PKC inhibitor PKC412 antagonizes breast cancer cell growth and enhances tamoxifen sensitivity

Background: AIB1 (SRC-3, NCoA3), a member of the p160/steroid receptor coactivators family, plays a critical role in cell growth and proliferation. In estrogen receptor-alpha positive (ER+) breast cancer (BC) cells, it coactivates estrogen- and additional transcription factors-dependent gene transcription, reducing the antagonistic activity of tamoxifen and resulting in tamoxifen resistance (TR). We have previously shown that BC patients whose tumors expressed high levels of both AIB1 and HER-2 had worse outcomes with tamoxifen therapy, suggesting that AIB1 may be an important diagnostic and therapeutic target. Our findings that knocking down AIB1 attenuates ER signaling and inhibits breast cancer cell growth further indicate that the manipulation of AIB1 level could be an approach to treating BC and overcoming TR. Recently, it has been shown that protein kinase C (PKC) isoforms phosphorylate AIB1 and prevent its proteasome-mediated degradation. The present study was carried out to test if the multi-targeted kinase and PKC inhibitor PKC412 (midostaurin) is capable of promoting degradation of AIB1, inhibiting BC cell growth, and promoting tamoxifen antagonistic activity.

Methods: The ER+ MCF7, T47D, and ZR75-B BC cells and their tamoxifen-resistant derivatives (TR) were used. The Methylene Blue assay was employed to measure cell viability of BC cell lines after treatment with PKC412 or the combination of PKC412 with tamoxifen. To determine the impact of PKC412 on AIB1 and ER proteins and mRNA levels, we used immunoblotting and RT-qPCR, respectively.

Results: PKC412 successfully inhibited the growth of MCF7, T47D, and ZR75-B cells, and their tamoxifen-resistant derivatives. Treatment with PKC412 depleted AIB1 protein and reduced the level of ER protein without significant alteration in AIB1 mRNA level. Consequently, ER signaling was disrupted, as reflected by decreased expression of ER target genes such as GREB1. PKC412 also enhanced tamoxifen's antagonistic activity in the parental cell lines and sensitized tamoxifen-resistant MCF7 and ZR75-B cells to tamoxifen.

Conclusions: The results of this study suggest that the multi-targeted kinase and PKC inhibitor PKC412 can post-translationally destabilize AIB1 protein and ER, inhibiting BC cell growth and viability. PKC412 enhances tamoxifen's antagonistic activity on BC growth; furthermore, it sensitizes tamoxifen-resistant cells to tamoxifen. Thus, PKC412 is a promising agent to treat BC and, in combination with tamoxifen, to delay or overcome TR.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-10-03.

Engineering a polymeric gene delivery vector based on poly(ethylenimine) and hyaluronic acid

In this work, the effects of primary amines, ligand targeting, and overall charge on the effectiveness of branched poly(ethylenimine)-hyaluronic acid conjugate (bPEI-HA) zwitterionic gene delivery vectors are investigated. To elucidate the relative importance of each of these parameters, we explored the zeta potential, cytotoxicity, and transfection efficiency for a variety of formulations of bPEI-HA. It was found that the length of the hyaluronic acid (HA) oligosaccharide had the most significant effect on cytotoxicity and transfection efficiency with human mesenchymal stem cells. Test groups of bPEI incorporating HA with a length of 10 saccharides had significantly higher transfection efficiency (14.6 ± 2.0%) and lower cytotoxicity than other formulations tested, with the cytotoxicity of the group containing the greatest mass of 10 saccharide showing similar results as the positive controls at the highest polymer concentration (100 μg/mL). Additionally, molar incorporation of HA, as opposed to the saccharide length and HA mass incorporation, had the greatest effect on zeta potential but a minor effect on both cytotoxicity and transfection efficiency. This work demonstrates the relative importance of each of these tunable design criteria when creating a zwitterionic polymeric gene delivery vector and provides useful specific information regarding the design of bPEI-HA gene delivery vectors.

Genotype-dependent sensitivity of uveal melanoma cell lines to inhibition of B-Raf, MEK, and Akt kinases: rationale for personalized therapy

PURPOSE

Inhibitors of B-Raf and MEK kinases hold promise for the management of cutaneous melanomas harboring BRAF mutations. BRAF mutations are rare in uveal melanomas (UMs), but somatic mutations in the G protein α subunits Gαq and Gα11 (encoded by GNAQ and GNA11, respectively) occur in a mutually exclusive pattern in ∼80% of UMs. The impact of B-Raf and MEK inhibitors on Gα-mutant UMs remains unknown.

METHODS

The impact of the B-Raf inhibitor PLX4720, the MEK inhibitor AZD6244, and the Akt inhibitor MK2206 on UM cell lines was assessed with the use of cell viability, proliferation, and apoptosis assays and immunoblot analysis.

RESULTS

BRAF-mutant UM cells were sensitive to both PLX4720 and AZD6244, undergoing cell cycle arrest but not apoptosis. UM cells with a Gα-protein mutation (GNAQ or GNA11) were mildly sensitive to AZD6244 but completely resistant to PLX4720. In fact, PLX4720 paradoxically increased ERK phosphorylation in Gα-mutant UM cells. The combination of AZD6244 with PLX4720 had synergistic anticancer activity in BRAF-mutant cells but not in Gα-mutant cells. The Akt inhibitor MK2206 sensitized BRAF-mutant cells to both PLX4720 and AZD6244 and sensitized Gα-mutant cells to AZD6244 but did not overcome the resistance of the Gα-mutant cells to PLX4720.

CONCLUSIONS

The response of UM cells to inhibition of B-Raf, MEK, and Akt depends on their genotype. Future use of such targeted therapies in clinical trials of UM patients will require careful design and patient selection based on genotype to provide personalized and effective therapy.

Controlled release of anti-inflammatory siRNA from biodegradable polymeric microparticles intended for intra-articular delivery to the temporomandibular joint

PURPOSE

As the next step in the development of an intra-articular controlled release system to treat painful temporomandibular joint (TMJ) inflammation, we developed several biodegradable poly(DL-lactic-co-glycolic acid) (PLGA)-based microparticle (MP) formulations encapsulating a model anti-inflammatory small interfering RNA (siRNA) together with branched poly(ethylenimine) (PEI) as a transfecting agent. The effect of siRNA loading and N:P ratio on the release kinetics of siRNA-PEI polyplexes was determined, and the size and N:P ratio of the polyplexes released over time was characterized.

METHODS

Polyplex-loaded PLGA MPs were prepared using an established double emulsion technique. Increasing the pH of the release samples enabled siRNA-PEI dissociation and subsequent measurement of the release of each component over 28 days. Polyplex diameter was measured for all release samples and compared to freshly prepared siRNA-PEI under simulated physiologic conditions.

RESULTS

Systematic variation of siRNA loading and N:P ratio resulted in distinct siRNA and PEI release profiles. Polyplex diameter remained constant despite large variations in the relative amounts of siRNA and PEI. Excess PEI was sequestered through complexation with 500-1,000 nm diameter PLGA MP-derived particles, including small MPs and PLGA degradation products.

CONCLUSIONS

These PLGA MP formulations show exciting potential as the first intra-articular TMJ controlled release system.

Delivery of plasmid DNA encoding bone morphogenetic protein-2 with a biodegradable branched polycationic polymer in a critical-size rat cranial defect model

This study investigated the delivery of plasmid DNA (pDNA) encoding bone morphogenetic protein-2 in the form of polyplexes with a biodegradable branched triacrylate/amine polycationic polymer (TAPP) that were complexed with gelatin microparticles (GMPs) loaded within a porous tissue engineering scaffold. More specifically, the study investigated the interplay between TAPP degradation, gelatin degradation, pDNA release, and bone formation in a critical-size rat cranial defect model. The pDNA release kinetics in vitro were not affected by the crosslinking density of the GMPs but depended, rather, on the degradation rates of the TAPPs. Besides the initial release of polyplexes not bound to the GMPs and the minimal release of polyplexes through diffusion or dissociation from the GMPs, the pDNA was likely released as naked pDNA or as part of an incomplete polyplex, after the degradation of fragments of the polycationic polymer. After 30 days, significantly higher amounts of pDNA were released (93%-98%) from composite scaffolds containing naked pDNA or pDNA complexed with P-AEPZ (synthesized with 1-[2-aminoethyl]piperazine, a faster degrading TAPP) compared with those containing pDNA complexed with P-DED (synthesized with N,N-dimethylethylenediamine, a slower degrading TAPP) (74%-82%). Composite scaffolds containing GMPs complexed with TAPP/pDNA polyplexes did not result in enhanced bone formation, as analyzed by microcomputed tomography and histology, in a critical-size rat cranial defect at 12 weeks postimplantation compared with those loaded with naked pDNA. The results demonstrate that polycationic polymers with a slow degradation rate can prolong the release of pDNA from the composite scaffolds and suggest that a gene delivery system comprising biodegradable polycationic polymers should be designed to release the pDNA in an intact polyplex form.

Altering amine basicities in biodegradable branched polycationic polymers for nonviral gene delivery

In this work, biodegradable branched polycationic polymers were synthesized by Michael addition polymerization from different amine monomers and the triacrylate monomer trimethylolpropane triacrylate. The polymers varied in the number of amines that dissociate in different pH ranges, which are considered to be beneficial to different parts of the gene delivery process. P-DED, a polymer synthesized from trimethylolpropane triacrylate and dimethylethylenediamine, had the highest number of protonated amines that are available for plasmid DNA (pDNA) complexation at pH 7.4 of all polymers synthesized. P-DED formed a positive polyplex (13.9 +/- 0.5 mV) at a polymer/pDNA weight ratio of 10:1 in contrast with the other polymers synthesized, which formed positive polyplexes only at higher weight ratios. Polyplexes formed with the synthesized polymers at the highest polymer/pDNA weight ratio tested (300:1) resulted in higher transfection with enhanced green fluorescent protein reporter gene (5.3 +/- 1.0 to 30.6 +/- 6.6%) compared with naked pDNA (0.8 +/- 0.4%), as quantified by flow cytometry. Polyplexes formed with P-DED (weight ratio of 300:1) also showed higher transfection (30.6 +/- 6.6%) as compared with polyplexes formed with branched polyethylenimine (weight ratio of 2:1, 25.5 +/- 2.7%). The results from this study demonstrated that polymers with amines that dissociate above pH 7.4, which are available as positively charged groups for pDNA complexation at pH 7.4, can be synthesized to produce stable polyplexes with increased zeta potential and decreased hydrodynamic size that efficiently transfect cells. This work indicated that polymers containing varying amine functionalities with different buffering capabilities can be synthesized by using different amine monomers and used as effective gene delivery vectors.

Biodegradable branched polycationic polymers with varying hydrophilic spacers for nonviral gene delivery

Biodegradable branched polycationic polymers with varying hydrophilic spacer lengths were synthesized from different triacrylate monomers and the amine monomer 1-(2-aminoethyl)piperazine by Michael addition polymerization. The hydrophilic spacers were varied by the number of ethyleneoxy groups in the triacrylate monomer (E/M) that ranged from 0 to 14. The polymer degradation depended on the spacer length and pH; the amount of ester degraded as determined by (1)H NMR after 14 days was 43.4 +/- 2.1% (pH 5.0) and 89.7 +/- 1.3% (pH 7.4) for the polymer with 0 E/M compared to 55.7 +/- 2.6% (pH 5.0) and 98.5 +/- 1.6% (pH 7.4) for the polymer with 14 E/M. Cell viability of rat fibroblasts after exposure to polymer solutions of concentrations up to 1000 microg/mL remained high (above 66.9 +/- 12.1% compared to below 7.6 +/- 1.1% for polyethylenimine at a concentration of 50 microg/mL or higher) and increased with the spacer length. The polyplexes made with all the synthesized polymers showed higher transfection efficiency (4.5 +/- 1.7% to 9.4 +/- 2.0%, dependent on the polymer/pDNA weight ratio) with an enhanced green fluorescent protein reporter gene compared to naked pDNA (0.8 +/- 0.4%) as quantified by flow cytometry. This study demonstrates that hydrophilic spacers can be incorporated into polycationic polymers to reduce their cytotoxicity and enhance their degradability for nonviral gene delivery.