Report of the 2023 AACP Council of Deans Taskforce on Pharmacy Research and Scholarship

OBJECTIVE

The objective of this review is to provide the conclusions from the American Association of Colleges of Pharmacy (AACP) Council of Deans (COD) Taskforce on Research and Scholarship.

FINDINGS

The charges and the findings of the committee are: (1) Define the scholarship needs/opportunities to strengthen the outputs. The committee recommends that AACP update its definitions of research/scholarship to include discovery, integration, application/practice, and teaching/learning. A deployed survey demonstrated a high Special Interest Groups research/scholarship interest. (2) Assemble a toolkit of grant and scholarship resources to assist colleges/schools. The AACP should update the existing funding opportunity listing and combine it with additional resources. (3) Create a framework for effective research collaboration and mentorship. The AACP should identify key areas of pharmacy research and experts to serve as mentors and to meet with external stakeholders. (4) and (5) Consider the need for and purpose of a COD standing committee for research and scholarship. Explore the value of a formal research dean's subcommittee. It was recommended that AACP form a research/scholarship committee or Special Interest Groups and create the Pharmacy Scholarship, Research, and Graduate Education pre-meeting to the Interim Meeting. (6) Identify key statements/outputs of the COD that need to be prepared for publication/sharing. We recommended the key statement/outputs in the areas of discovery, integration, application/practice, and teaching and learning.

SUMMARY

The taskforce reviewed the state of research and scholarship across the Academy and provided recommendations with the goal of advancing research across all areas of the pharmacy profession.

Profiling of Circulating Tumor Cells for Screening of Selective Inhibitors of Tumor-Initiating Stem-Like Cells

A critical barrier to effective cancer therapy is the improvement of drug selectivity, toxicity, and reduced recurrence of tumors expanded from tumor-initiating stem-like cells (TICs). The aim is to identify circulating tumor cell (CTC)-biomarkers and to identify an effective combination of TIC-specific, repurposed federal drug administration (FDA)-approved drugs. Three different types of high-throughput screens targeting the TIC population are employed: these include a CD133 (+) cell viability screen, a NANOG expression screen, and a drug combination screen. When combined in a refined secondary screening approach that targets Nanog expression with the same FDA-approved drug library, histone deacetylase (HDAC) inhibitor(s) combined with all-trans retinoic acid (ATRA) demonstrate the highest efficacy for inhibition of TIC growth in vitro and in vivo. Addition of immune checkpoint inhibitor further decreases recurrence and extends PDX mouse survival. RNA-seq analysis of TICs reveals that combined drug treatment reduces many Toll-like receptors (TLR) and stemness genes through repression of the lncRNA MIR22HG. This downregulation induces PTEN and TET2, leading to loss of the self-renewal property of TICs. Thus, CTC biomarker analysis would predict the prognosis and therapy response to this drug combination. In general, biomarker-guided stratification of HCC patients and TIC-targeted therapy should eradicate TICs to extend HCC patient survival.

Abstract 1529: Characterizing antibody internalization for rational selection of ADC linker design

Antibody-drug conjugates (ADC), which target a highly potent cytotoxin to a specific protein overexpressed on tumor cells, are a promising class of anticancer therapeutics. In addition to the antibody characteristics, intracellular reactivity of the antibody-cytotoxin linker (which affects drug release) is a key determinant of ADC efficacy. While many different linkers have been used in approved ADCs, the intracellular trafficking profile of an antibody will likely impact the effectiveness of different linkers differently. Here, we determined the cellular internalization of two antibodies, anti-perlecan antibody (‘AM6’), and anti-EGFR antibody (cetuximab; ‘Ctx’), in MDA-MB-231-LM2 cells (a lung-metastatic TNBC cell line). Using live-cell confocal microscopy, we investigated the effect of endocytosis inhibitors on intracellular trafficking of AM6 and Ctx. While AM6 was internalized quicker compared to Ctx, the internalization of both antibodies was reduced significantly by 5-(N-Ethyl-N-isopropyl)-amiloride, a macropinocytosis inhibitor and, to a lesser extent, by chlorpromazine, an inhibitor of clathrin-mediated-endocytosis. The results suggest both AM6 and Ctx were internalized by both macropinocytosis and clathrin-mediated endocytosis. We then investigated whether acidic pH in the lysosomes and the reductive environment in the endosomal vesicles would facilitate drug release from ADC. We conjugated thiol-reactive doxorubicin to reduced interchain disulfides of Ctx via either the acid and glutathione (GSH)-labile pyridinyldithio-hydrazide linker or the non-cleavable C6-maleimide linker. Intracellular doxorubicin release for the two ADCs was evaluated by live-cell confocal microscopy. Doxorubicin was successfully conjugated to Ctx, with a DAR of 4.8 and 8.6 for the cleavable and non-cleavable linkers, respectively. Conjugation of doxorubicin to the antibody was confirmed by fluorescent gel imaging after SDS-PAGE and by using hydrophobic interaction chromatography. Confocal microscopic studies showed that the ADC with cleavable linker resulted in greater doxorubicin accumulation in the nucleus compared to the ADC with non-cleavable linker, which was predominantly sequestered in the lysosomes. These results suggest that the cleavable linker results in better drug release compared to the non-cleavable linker for the Ctx-doxorubicin ADC. Studies examining the effect of linker chemistry on drug release from the anti-perlecan ADC and on the anticancer efficacy of the two ADCs are ongoing.

Citation Format: Zekun Shao, Jayanth Panyam. Characterizing antibody internalization for rational selection of ADC linker design [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 1529.

Combination of STING and TLR 7/8 Agonists as Vaccine Adjuvants for Cancer Immunotherapy

Immunostimulatory adjuvants that potently activate antigen-presenting cells and (in turn) prime cytotoxic T cells are a key component of anticancer vaccines. In this study, we investigated a multi-adjuvant approach combining a TLR 7/8 agonist (522) and a STING agonist (DMXAA) to promote enhanced antigen cross-presentation, stimulate specific antitumor T-cell responses, and provide improved anticancer efficacy. In vitro experiments using bone marrow-derived dendritic cells (BMDCs) confirmed enhanced activation with the 522-DMXAA combination based on both co-stimulatory molecule expression and pro-inflammatory cytokine secretion. The immunization of mice with vaccines comprising both 522 and DMXAA resulted in greater antitumor efficacy in B16F10 melanoma and MB49 bladder tumor models relative to mono-agonist vaccines. Flow cytometry-based analysis of immune cells from immunized mice revealed the significant activation of antigen-presenting cells, increased numbers of activated and Ag-specific CD8+ T cells in the spleen and lymph nodes, modest NK cell activation, and an overall reduction in CD206⁺ macrophages. These results were supported by an increase in the levels of IFN-γ and a reduction in IL-10 levels in the sera. Taken together, these findings demonstrate the potential of the TLR7/8 and STING agonist combination as vaccine adjuvants to activate both innate and adaptive immune responses.

Abstract 5587: STING and TLR 7/8 Agonist combination can improve immune checkpoint blockade therapy efficiency

Despite significant advancements in immune checkpoint blockade (ICB) therapy, only few patients respond to the treatment. Non-immunogenic cold tumors lack T-cell infiltration, which results in reduced ICB therapeutic efficiency. Immune adjuvants can reprogram the non-immunogenic cold tumor microenvironment (TME) to inflamed hot TME by activating antigen presenting cells and improving T-cell homing. Here, we investigate the potentials of 558 (a novel TLR 7/8 agonist) and ADU-S100 (stimulator of interferon gene (STING) agonist in clinical trials) combination on improving the activity of ICB. Human TLR-specific reporter cell assay using HEK-Blue™-hTLR7 and 8, confirmed the activation of both TLR 7 and TLR 8 with EC50 of 0.18 µM and 5.34 µM respectively, when treated with 558. In addition, treatment of human PBMCs with 558 increased the IFN-γ and TNF-α cytokine secretions. Moreover, the levels of IL-10, an anti-inflammatory cytokine were not increased upon treatment with 558. Although treatment of bone marrow derived dendritic cells (BMDC) with 558 resulted in CD40 expression, a reduced expression of CD80 and CD86, costimulatory molecules that are required for T-cell activation, was observed. Interestingly, 558 in combination with ADU-S100 not only increased the CD40 expression but also improved the expression of CD80 (4-fold) and CD86 on BMDCs. Furthermore, the levels of pro-inflammatory cytokines TNF-α and IL-6 was significantly increased when BMDCs were treated with 558 and ADU-S100 combination compared to the individual treatments. TME constitute M2 polarized macrophages that promote secretion of anti-inflammatory cytokines and favor tumor progression. Interestingly, 558 and ADU-S100 combination reduced the expression of CD206, a mannose receptor that is highly expressed on M2 macrophages and improved the expression of CD80 (25-fold) and CD86 (6-fold) compared to 558 treatments alone. These results confirmed the polarization of M2 macrophages to immunogenic M1 macrophages. Overall, these studies indicate promising potential of 558 and ADU-S100 combination in reprogramming the TME to aid in effective cancer treatments.

Citation Format: Vishnu Revuri, Shubhmita Bhatnagar, John Schultz, Peter Larson, David M. Ferguson, Jayanth Panyam. STING and TLR 7/8 Agonist combination can improve immune checkpoint blockade therapy efficiency [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 5587.

Abstract 4215: Combination of STING and TLR 7/8 agonists as vaccine adjuvants for cancer immunotherapy

Various classes of molecules including toll-like receptor (TLR) agonists, exosomes, and metallo compounds have been evaluated as adjuvants for cancer vaccines. However, their wide-spread clinical use has been limited by transient immune responses and serious side-effects. Here, we propose the use of a multi-adjuvant approach that combines two different classes of adjuvants, STING and TLR 7/8 agonists, based on their distinct immune cell targets, signalling pathways, and significant roles in the activation and maintenance of immune responses. We evaluated the potential of combining 522, a novel TLR 7/8 agonist, and DMXAA, a STING agonist, for stronger DC activation and greater CD8 T cell responses. Mouse bearing B16F10-OVA (murine melanoma cell line which expresses ovalbumin) tumors were immunized with OVA mixed with 522 or DMXAA or a combination of 522 and DMXAA daily for 5 days. Immunization with OVA+DMXAA+522 resulted in significant tumor growth inhibition (p < 0.05) and improved survival (p<0.05) compared to other controls. Using flow cytometry, the costimulatory molecule expression and immune cell infiltration in mouse lymph node, spleen and tumor were evaluated. Immunization with OVA+DMXAA+522 resulted in the activation of antigen presenting cells (APCs) in lymph nodes, spleen and tumor (additive or equivalent to single treated groups). The combination also elicited stronger antigen specific CD8 T cell and natural killer (NK) cell responses than control or individual treatment groups. OVA + DMXAA+ 522 immunization increased the number of OVA-specific CD44high CD8 T cells by over 4-fold compared to other treatment groups and control mice in spleen and lymph nodes. A reduction in the frequency of M2 macrophages was observed with OVA+DMXAA+522 treatment. Cytokine analysis demonstrated higher levels of pro-inflammatory cytokines like IFNγ and lower levels of pro-tumorigenic cytokines in the serum of OVA+DMXAA+522 immunized mice compared to that in untreated or OVA-only treated mice. Taken together, these results suggest that combination of TLR7/8 and STING agonists is a promising multi-adjuvant approach for cancer vaccination

Citation Format: Shubhmita Bhatnagar, Vishnu Revuri, Manan Shah, Peter Larson, David Ferguson, Jayanth Panyam. Combination of STING and TLR 7/8 agonists as vaccine adjuvants for cancer immunotherapy [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 4215.

Abstract 2880: CD133-targeting silicate prodrug nanoparticles for effective cancer stem cell targeting

Cancer stem cells (CSCs) are considered to be key contributors to drug resistance and tumor recurrence in many solid tumors. Therapeutic approaches that specifically target these cells are needed to improve treatment outcomes in these tumor types. We are investigating CD133, a widely used surface marker to identify CSCs in colon, brain, and breast tumors. Here, we report the use of polymeric nanoparticles targeting CD133 by conjugating an anti-CD133 scFv-Fc to poly(L-lactide)-PEG-maleimide nanoparticles (anti-CD133 NPs) for effective CSC targeting. The Fc tagged anti-CD133 scFv was prepared and purified using an Expi293 expression system. Nanoparticles were prepared using flash nanoprecipitation and loaded with a hydrophobic, hydrolytically labile, silicate prodrug of paclitaxel. Flash nanoprecipitation allowed for generation of particles with a size of 232 ± 17 nm (increased to 289 ± 23 nm upon scFv conjugation), a zeta potential of -11.5 mV and a drug loading of 57 ± 8 wt% measured by HPLC. The anti-CD133 scFv-Fc was thiolated using 2-iminothiolane (2-IT) and conjugated to nanoparticles using thiol-maleimide chemistry. Thiolation of the antibody was optimized using different molar excesses of 2-IT. A binding assay using Caco-2 cells (which overexpress CD133) confirmed that thiolation of the antibody did not affect its binding, even at the highest molar excess of 2-IT used. With 200x molar excess of 2-IT, 2.9 thiols per antibody were added. Antibody conjugation was confirmed using gel electrophoresis; bands corresponding to the heavy and light chains of antibody were observed for anti-CD133 NPs after reduction but were not seen for non-reduced anti-CD133 NPs or for unconjugated particles. Cytotoxicity studies in MDA-MB-231-LM2 cells revealed maximum kill in drug loaded anti-CD133 NPs, which was significantly higher than for either non-targeted, drug-loaded nanoparticles or blank nanoparticles (p<0.05). Overall, these studies indicate the potential for using anti-CD133 scFv-Fc in conjunction with FNP-produced silicate prodrug nanoparticles of paclitaxel for efficient targeting of CSCs.

Citation Format: Shubhmita Bhatnagar, Mengyuan Jin, Thomas Hoye, Jayanth Panyam. CD133-targeting silicate prodrug nanoparticles for effective cancer stem cell targeting [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 2880.

Abstract 1808: Impact of nanoengineering on redox regulation and CXCR4-mediated homing of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are being investigated for several therapeutic applications, including cancer, inflammation, tissue repair, and transplantation because of their ability to home to injured and inflamed tissues. Despite the large number of preclinical studies investigating engineered MSCs as therapeutic agents and numerous clinical trials investigating MSCs for other therapeutic applications, there have only been a handful of clinical trials investigating MSCs for treating solid tumors, and none have progressed beyond Phase I/II. Inefficient tumor homing ability and a lack of understanding of fundamental mechanisms may contribute to the limited translational success of MSC-based therapies. We hypothesized that nanoengineering MSCs with anticancer drugs induces oxidative stress, and MSCs counteract this stress by activating Nrf2, which increases the expression of various antioxidant proteins, including CXCR4, a key mediator of MSC tumor homing. We performed global label-free, unbiased proteomics on nanoengineered MSCs using modified in-Stage technology. Our studies indicated that MSCs nanoengineered with paclitaxel underwent significant changes in the overall proteome compared to either untreated MSCs or MSCs loaded with blank nanoparticles. Analysis of molecular function profile revealed that loading paclitaxel in MSCs significantly enhanced the expression of proteins involved in the antioxidant and catalytic activity and protein binding. The biological process profile also showed a similar increase in defense response and an increase in metabolic processes. It was further found that MSCs nanoengineered with PTX lead to significant upregulation of nrf2, the master regulator of antioxidant responses, and CXCR4, a direct target of Nrf2 and a key mediator of tumor homing. Also, an increase in CXCR4 expression was directly proportional to paclitaxel loading in cells. These studies suggest nanoengineering of MSCs impacts their biology, which likely contributes to their improved tumor homing capacity in vivo.

Citation Format: Drishti Sehgal, Susheel Kumar Nethi, Carmen Merali, Salim Merali, Jayanth Panyam, Swayam Prabha. Impact of nanoengineering on redox regulation and CXCR4-mediated homing of mesenchymal stem cells [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 1808.

Cancer stem cells and strategies for targeted drug delivery

Cancer stem cells (CSCs) are a small proportion of cancer cells with high tumorigenic activity, self-renewal ability, and multilineage differentiation potential. Standard anti-tumor therapies including conventional chemotherapy, radiation therapy, and molecularly targeted therapies are not effective against CSCs, and often lead to enrichment of CSCs that can result in tumor relapse. Therefore, it is hypothesized that targeting CSCs is key to increasing the efficacy of cancer therapies. In this review, CSC properties including CSC markers, their role in tumor growth, invasiveness, metastasis, and drug resistance, as well as CSC microenvironment are discussed. Further, CSC-targeted strategies including the use of targeted drug delivery systems are examined.

Encapsulation of Andrographolide in poly(lactide-co-glycolide) Nanoparticles: Formulation Optimization and in vitro Efficacy Studies

Andrographolide is a potential chemopreventive and chemotherapeutic agent that suffers from poor aqueous solubility. Encapsulation in poly(lactide-co-glycolide) (PLGA) nanoparticles can overcome solubility issues and enable sustained release of the drug, resulting in improved therapeutic efficacy. In this study, andrographolide was encapsulated in PLGA nanoparticles via emulsion solvent evaporation technique. Effect of various formulation parameters including polymer composition, polymer molecular weight, polymer to drug ratio, surfactant concentration and the organic solvent used on nanoparticle properties were investigated. A selected formulation was used to determine the effect of encapsulation in nanoparticles on andrographolide's in vitro anticancer efficacy. Nanoparticles formulated using a polymer with 85:15 lactide to glycolide ratio and ethyl acetate as the organic solvent were found to be optimal based on average hydrodynamic particle size (135 ± 4 nm) and drug loading (2.6 ± 0.6%w/w). This formulation demonstrated sustained release of andrographolide over 48 h and demonstrated significantly greater in vitro anticancer efficacy compared to free drug in a metastatic breast cancer cell line. These results suggest that additional, more in-depth efficacy studies are warranted for the nanoparticle formulation of andrographolide.

Abstract 6255: Augmented lung tumor infiltration of chemotherapeutics using synthetic antigen receptor- mesenchymal stem cells (SAR-MSCs)

Targeted delivery can improve drug accumulation in tumor tissue and treatment outcomes. However, currently available options suffer from a lack of selectivity for tumor cells. Mesenchymal Stem cells (MSCs) can be engineered with chemotherapeutic-loaded polymeric nanoparticles (PNPs) for tumor-targeted delivery, owing to their characteristic tumor tropic properties. Although nano-engineered MSCs demonstrated significant anticancer activity in multiple ovarian cancer models, their non-specific accumulation in clearance organs such as lungs and liver remains a concern. Parallel to the concept of chimeric antigen receptor (CAR)-T cell therapy, we advance here a strategy of modifying MSCs with synthetic antigen receptors (SARs) that target specific antigens overexpressed on cancer cells. Our approach consists of stably incorporating recombinant protein G (PG) on the surface of MSCs, followed by binding of a full-length IgG to the PG handle. Because protein G binds to the Fc region of IgG, antigen-binding affinity of the antibody is conserved. Epidermal growth factor receptor (EGFR) has been reported to be overexpressed and implicated in the pathogenesis of several malignancies especially lung cancer. Cetuximab (Cmab) is an anti-EGFR monoclonal antibody used in the treatment of metastatic lung cancer. In the current study, SAR-MSCs were developed by coating the nano-engineered MSCs with palmitated PG, followed by incorporating Cmab on the cell surface. Flow cytometry and confocal microscopy were used to confirm the incorporation of fluorescently labeled PAPG handle on MSC surface. Similarly, the installation of fluorescently labeled antibody on PAPG-functionalized MSCs was confirmed by flow cytometry. Preliminary efficacy studies in a mouse orthotopic A549-luc human lung adenocarcinoma model demonstrated significantly (P<0.05) improved survival of mice treated with Cmab-modified nano-engineered MSCs compared to isotype IgG-modified nano-engineered MSCs control group. These results suggest that the SAR technology could further improve the effectiveness of MSCs as tumor targeted drug delivery vehicles.

Citation Format: Susheel Kumar Nethi, Drishti Sehgal, Jayanth Panyam, Swayam Prabha. Augmented lung tumor infiltration of chemotherapeutics using synthetic antigen receptor- mesenchymal stem cells (SAR-MSCs) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6255.

A novel terpenoid class for prevention and treatment of KRAS-driven cancers: Comprehensive analysis using in situ, in vitro, and in vivo model systems

Inhibiting the disease progression in KRAS-driven cancers after diagnosis has been a difficult task for clinicians to manage due to the lack of effective intervention/preventive therapies. KRAS-driven cancers depend on sustained KRAS signaling. Although developing inhibitors of KRAS signaling has proven difficult in the past, the quest for identifying newer agents has not stopped. Based on studies showing terpenoids as modulators of KRAS-regulated downstream molecular pathways, we asked if this chemical family has an affinity of inhibiting KRAS protein activity. Using crystal structure as a bait in silico, we identified 20 terpenoids for their KRAS protein-binding affinity. We next carried out biological validation of in silico data by employing in situ, in vitro, patient-derived explant ex vivo, and KPC transgenic mouse models. In this report, we provide a comprehensive analysis of a lup-20(29)-en-3b-ol (lupeol) as a KRAS inhibitor. Using nucleotide exchange, isothermal titration calorimetry, differential scanning fluorimetry, and immunoprecipitation assays, we show that lupeol has the potential to reduce the guanosine diphosphate/guanosine triphosphate exchange of KRAS protein including mutant KRASG12V . Lupeol treatment inhibited the KRAS activation in KRAS-activated cell models (NIH-panel, colorectal, lung, and pancreatic intraepithelial neoplasia) and patient tumor explants ex vivo. Lupeol reduced the three-dimensional growth of KRAS-activated cells. The pharmacokinetic analysis showed the bioavailability of lupeol after consumption via oral and intraperitoneal routes in animals. Tested under prevention settings, the lupeol consumption inhibited the development of pancreatic intraepithelial neoplasia in LSL-KRASG12D/Pdx-cre mice (pancreatic ductal adenocarcinoma progression model). These data suggest that the selected members of the triterpene family (such as lupeol) could be exploited as clinical agents for preventing the disease progression in KRAS-driven cancers which however warrants further investigation.

TLR7/8 Agonist-Loaded Nanoparticles Augment NK Cell-Mediated Antibody-Based Cancer Immunotherapy

Activated natural killer (NK) cells can kill malignant tumor cells via granule exocytosis and secretion of IFN-γ, a key regulator of the TH1 response. Thus, mobilization of NK cells can augment cancer immunotherapy, particularly when mediated through antibody-dependent cellular cytotoxicity (ADCC). Stimulation of toll-like receptor (TLR)7/8 activity in dendritic cells promotes pro-inflammatory cytokine secretion and costimulatory molecule upregulation, both of which can potentiate NK cell activation. However, currently available TLR7/8 agonists exhibit unfavorable pharmacokinetics, limiting their in vivo efficacy. To enable efficient delivery to antigen-presenting cells, we encapsulated a novel imidazoquinoline-based TLR7/8 agonist in pH-responsive polymeric NPs. Enhanced costimulatory molecule expression on dendritic cells and a stronger pro-inflammatory cytokine response were observed with a NP-encapsulated agonist, compared to that with the soluble form. Treatment with NP-encapsulated agonists resulted in stronger in vivo cytotoxicity and prolonged activation of NK cells compared to that with a soluble agonist. In addition, TLR7/8 agonist-loaded NPs potentiated stronger NK cell degranulation, which resulted in enhanced in vitro and in vivo ADCC mediated by the epidermal growth factor receptor-targeting antibody cetuximab. TLR7/8 agonist-loaded NP treatment significantly enhanced the antitumor efficacy of cetuximab and an anti-HER2/neu antibody in mouse tumor models. Collectively, our data show that a pH-responsive NP-encapsulating TLR7/8 agonist could be used as a potent immunostimulatory adjuvant for antibody-based cancer immunotherapy by promoting NK cell activation.

Exploiting antibody biology for the treatment of cancer

Over the last decade, antibodies have become an important component in the arsenal of cancer therapeutics. High-specificity, low off-target effects, desirable pharmacokinetics and high success rate are a few of the many attributes that make antibodies amenable for development as drugs. To design antibodies for successful clinical applications, however, it is critical to have an understanding of their structure, functions, mechanisms of action and pharmacokinetic/pharmacodynamic properties. This review highlights some of these key aspects, as well as certain limitations encountered, with monoclonal antibody therapy. Further, we discuss rational combination therapies for clinical applications, some of which could help overcome the limitations.

Abstract 4985: TLR agonists for anticancer immunotherapy

Introduction: Toll-like receptors (TLRs) are important pattern recognition receptors through which innate immune cells recognize invasive microorganisms. The immunostimulatory property of TLR agonists allows for activation of dendritic cells (DCs) and enables their use as anticancer vaccine adjuvants. Because TLR 7 and 8 can be activated by synthetic small molecules, they are of particular interest as a target in vaccine adjuvant discovery. However, a key drawback of these synthetic small molecules is that they also induce immunosuppressive cytokines, resulting in immunosuppression.

Methods: We have previously developed a suite of highly substituted imidazoquinolines, which potently activate TLR 7 and/or 8. In this study, we tested some selected TLR7, TLR8 and TLR7/8 dual agonists for their ability to activate DCs without inducing immune suppressive cytokines. Murine bone marrow-derived dendritic cells (BMDCs) were generated from C57BL/6 mice. BMDCs were treated with one of seven TLR agonists for 72 hrs. Cells were collected and stained for flow cytometry analysis, and the culture supernatants were examined for secretion of pro-inflammatory cytokines, IL-12p70 and IFN-γ, and an immunosuppressive cytokine, IL-10, by ELISA. We also investigated activation of T cells by these agonists. Human peripheral blood mononuclear cells (hPBMCs) from healthy donors were incubated with one of seven TLR agonists overnight and cells were analyzed by flow cytometry for the expression of T cell activation marker CD69 and production of IFN-γ.

Results: All the TLR agonists investigated activated BMDCs, as evidenced by the upregulation of costimulatory markers CD40, CD80 and CD86 on DCs. In addition, all the agonists examined induced the secretion of IL-12p70 and IFN-γ. TLR 8 agonists showed the least induction of IL-10 secretion. All the TLR agonists activated both CD4 and CD8 T cells. TLR 8 agonists induced higher production of IFN-γ in both type of T cells than other candidates.

Conclusion: Both TLR 8 and TLR 7/8 agonists activated BMDCs and stimulated strong pro-inflammatory cytokine production. However, TLR8 activation was associated with less immunosuppression. These results suggest that these new imidazoquinoline esters are promising candidates for use as anti-cancer vaccine adjuvants.

Citation Format: Wenqiu Zhang, Hyunjoon Kim, Vidhi Khanna, David M. Ferguson, Thomas Griffith, Jayanth Panyam. TLR agonists for anticancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4985.

Abstract 3623: Mesenchymal stem cells engineered with TAT peptide functionalized nanoparticles improve therapeutic efficacy of paclitaxel in an orthotopic lung tumor model

Tumors are characterized by uneven vascular perfusion with near normal blood flow in the outer most regions, while the inner regions can be avascular. In addition, elevated interstitial fluid pressure and rigid extracellular matrix compromise intra-tumoral solute transport and hence limited drug efficacy. Mesenchymal stem cells (MSCs) have the unique advantage of being able to migrate specifically to both primary tumors and metastases following systemic administration. However, poor payload capacity of MSCs limits their use as drug delivery carriers. To address this issue, we investigated polymeric nanoparticles that were functionalized with transactivator of transcription (TAT) peptide. Paclitaxel loaded PLGA nanoparticles (15-16 % w/w paclitaxel; diameter of 225 ± 7 nm; and zeta potential of −15 ± 4 mV) were prepared by emulsion-solvent evaporation method, followed by TAT-conjugation to the surface of nanoparticles via maleimide-thiol chemistry. Nanoengineered MSCs were generated by incubating MSCs in suspension with 100 µg/mL paclitaxel loaded nanoparticles for 4 hours at 37°C. Our studies demonstrated that TAT functionalization improved the paclitaxel loading in MSCs. In addition, engineering MSCs with TAT functionalized nanoparticles did not affect the differentiation and migration properties of MSCs. Further, MSCs engineered with TAT peptide functionalized nanoparticles resulted in significant inhibition of tumor growth and overall improved survival in a mouse orthotopic model of lung cancer compared to that with free drug treatment. In summary, our results demonstrated that MSCs nanoengineered using TAT functionalized nanoparticles can serve as an efficient carrier for tumor specific delivery of anticancer drugs, resulting in greatly improved therapeutic efficacy.

Citation Format: Swayam Prabha, Gopikrishna Moku, Buddhadev Layek, Jayanth Panyam. Mesenchymal stem cells engineered with TAT peptide functionalized nanoparticles improve therapeutic efficacy of paclitaxel in an orthotopic lung tumor model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3623.

Abstract 2167: Antibody glycoengineering for drug delivery applications

Antibody-drug conjugates (ADC) hold considerable promise as anticancer agents. A critical determinant of the effectiveness of ADCs is the chemistry that is used to conjugate the payload. Currently used approaches include primarily conjugation to either side-chain amine or carboxylic acid groups or conjugation to thiols. Because these reactions are not site specific and not easily controlled, these chemistries can result in reduced affinity for the target antigen. Further, these conjugation reactions lack selectivity and can result in heterogeneous mixtures of products that differ in the sites and stoichiometry of modification. We investigated a glycoengineering strategy that enables the introduction of artificial azide groups in the antibody without affecting their antigen affinity. This is based on the observation that glycosyltransferases can incorporate non-natural sugars (e.g., azido mannose) at different sites on an IgG molecule. The azide groups in these artificial sugars are then available to react with alkynes through copper-catalyzed ‘click’ chemistry or with strained alkynes such as dibenzyl cyclooctyne (DBCO) allowing for biorthogonal, copper-free ‘click’ chemistry. Because the sugars are added reproducibly and at a site that does not affect antigen binding, the glycoengineering technology would overcome problems associated with traditional conjugation strategies. Using this approach, azide groups were introduced in anti-CD133 and anti-perlecan antibodies. Further, the azide groups were available to react with various DBCO conjugates including fluorophores, drug molecules and nanoparticles. Importantly, the addition of artificial sugar and subsequent azide-alkyne reaction did not affect the affinity of the antibody for the target antigen. Conjugation of a cytotoxin to the antibody resulted in enhanced cell kill in vitro and efficacy in vivo. We plan on further improving the effectiveness of this approach by investigating cleavable linker technology in combination with the glycoengineering strategy. We expect that this strategy will prove to be a unique platform technology that will have a significant impact on antibody-based therapeutics.

Citation Format: Drishti Navin Sehgal, Stephen Kalscheuer, Jayanth Panyam. Antibody glycoengineering for drug delivery applications [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2167.

Abstract 2175: Synthetic antigen receptor mesenchymal stem cells (SAR-MSCs) targeting perlecan for drug delivery to ovarian cancer

Mesenchymal stem cells (MSCs) can be engineered with polymeric nanoparticles for tumor-targeted delivery of small molecule drugs. Such nano-engineered MSCs have demonstrated exciting anticancer activity in multiple ovarian cancer models. Despite significantly improved delivery of chemotherapeutics to tumor tissues, non-specific accumulation of MSCs in clearance organs remains a concern. Paralleling the concept of CAR-T cells, we advance here a strategy for synthetic modification of MSCs with antibodies targeting specific antigens overexpressed on cancer cells. Our approach consists of stably incorporating recombinant protein G (PG) on the surface of MSCs, followed by binding of a full-length IgG to the PG handle. Because protein G binds to the Fc region of IgG, antigen-binding affinity of the antibody is conserved. We have previously shown the overexpression of perlecan (HSPG2) on ovarian cancer cells and its correlation to poor patient survival. In the current study, we investigated the incorporation of anti-perlecan antibody on the surface of nano-engineered MSCs. The anti-perlecan IgG antibody was first derivatized with palmitic acid (PA), which was then used to insert PG on MSCs cell membrane. We characterized the PAPG derivative by LC/Q-TOF/MS. Flow cytometry and confocal microscopy were used to confirm the incorporation of fluorescently labeled PAPG handle on MSC surface. Similarly, the binding of fluorescently labeled anti-perlecan IgG to PAPG-functionalized MSCs was confirmed by flow cytometry. We are currently investigating the anticancer efficacy of paclitaxel-loaded, anti-perlecan SAR-MSCs using in vitro and mouse models of ovarian cancer.

Citation Format: Susheel Kumar Nethi, Dristhi Sehgal, Shen Cheng, Jayanth Panyam, Swayam Prabha. Synthetic antigen receptor mesenchymal stem cells (SAR-MSCs) targeting perlecan for drug delivery to ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2175.

Abstract 4129: Novel small molecule TLR7/8 agonists for enhancing NK cell-mediated ADCC

Antibody-dependent cell-mediated cytotoxicity (ADCC) is a key mechanism of action for some therapeutic antibodies. ADCC involves killing of an antibody-coated target cell by an effector cell through the release of cytotoxic or cell death-inducing molecules. ADCC is triggered through interaction of Fcγ receptors present on the effector cell surface with the Fc region of the target-bound antibody. Natural killer (NK) cells are one of the primary effector cells that mediate ADCC. There is significant interest in designing therapeutic agents that can enhance ADCC because this can result in improved clinical responses with approved antibodies. We have developed a suite of highly substituted imidazoquinolines, which activate TLR 7 and/or 8 and induce significantly higher levels of cytokines compared to the FDA-approved TLR7 agonist imiquimod. In the current study, we evaluated our series of TLR7-specific, 8-specific and 7/8 dual selective agonists for their ability to improve ADCC with Cetuximab. We investigated NK cell activation in the presence of these compounds, as well as NK cell mediated ADCC against an EGFR expressing lung cancer cell line, A549. In addition, we also measured cytokine induction in human peripheral blood mononuclear cells in response to these compounds. Our studies show dual TLR 7/8 and 8-specific agonists induce robust pro-inflammatory cytokine secretion and activate NK cells. however, mixed agonists also induce greater immunosuppressive cytokines compared to TLR8-specific agonists. Further, these agonists also significantly enhanced Cetuximab mediated ADCC in vitro. In vivo studies examining the anticancer efficacy of the combination of selected TLR7/8 agonists and Cetuximab are ongoing.

Citation Format: Vidhi Khanna, Hyunjoon Kim, Wenqui Zhang, Peter Larson, David Ferguson, Jayanth Panyam. Novel small molecule TLR7/8 agonists for enhancing NK cell-mediated ADCC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4129.

Abstract 987: Glycoengineered MSCs for targeting platinum resistant ovarian tumors

Tumor-targeted delivery of chemotherapeutics can improve efficacy while mitigating their debilitating side effects. However, current drug delivery approaches rely on inefficient passive accumulation of delivery systems in the tumor and suffer from significant non-specific distribution. Here, we propose a novel two-step tumor targeting strategy that can improve delivery of cytotoxic agents to both primary tumor as well as metastatic lesions, resulting in effective tumor inhibition. This strategy involves introduction of non-natural targets in the tumor tissue via glycoengineered mesenchymal stem cells (MSCs expressing targetable synthetic azide groups) followed by the delivery of drug-loaded polymeric nanoparticles (surface functionalized with dibenzyl cyclooctyne; DBCO) that have high affinity for these synthetic targets. DBCO surface functionalized, paclitaxel (PTX)-loaded nanoparticles (DBCO-PTX NP; 17.6% w/w PTX; diameter 313.7 ± 13 nm; and zeta potential -12.5 ± 1.9 mV) were formulated using poly (DL-lactide-co-glycolide) (PLGA) polymer by emulsion-solvent evaporation method. Glycoengineered MSCs (MSC-Az) were generated by culturing MSCs in N-azidoacetylmannosamine-tetraacylated supplemented media without affecting their viability or tumor homing properties. Binding of MSC-Az to DBCO-PTX NP was confirmed with confocal microscopy and flow cytometry analysis. Anticancer efficacy of two-step targeting strategy was evaluated in murine model of platinum-resistant orthotopic ovarian C200-luc tumors. Treatment with MSC-Az + DBCO-PTX nanoparticles resulted in significant inhibition of the tumor growth (p < 0.05) and improved survival (p < 0.05) compared to that with other controls. In summary, our results demonstrate the potential of two-step tumor targeting strategy to enhance the anticancer efficacy of conventional chemotherapeutic drugs.

Citation Format: Buddhadev Layek, Drishti Sehgal, Jayanth Panyam, Swayam Prabha. Glycoengineered MSCs for targeting platinum resistant ovarian tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 987.

Improving Payload Capacity and Anti-Tumor Efficacy of Mesenchymal Stem Cells Using TAT Peptide Functionalized Polymeric Nanoparticles

Mesenchymal stem cells (MSCs) accumulate specifically in both primary tumors and metastases following systemic administration. However, the poor payload capacity of MSCs limits their use in small molecule drug delivery. To improve drug payload in MSCs, we explored polymeric nanoparticles that were functionalized with transactivator of transcription (TAT) peptide. Paclitaxel loaded poly(DL-lactide-co-glycolide) (PLGA) nanoparticles (15–16% w/w paclitaxel; diameter of 225 ± 7 nm; and zeta potential of −15 ± 4 mV) were fabricated by emulsion-solvent evaporation method, followed by TAT-conjugation to the surface of nanoparticles via maleimide-thiol chemistry. Our studies demonstrated that TAT functionalization improved the intracellular accumulation and retention of nanoparticles in MSCs. Further, nano-engineering of MSCs did not alter the migration and differentiation potential of MSCs. Treatment with nano-engineered MSCs resulted in significant (p < 0.05) inhibition of tumor growth and improved survival (p < 0.0001) in a mouse orthotopic model of lung cancer compared to that with free or nanoparticle encapsulated drug. In summary, our results demonstrated that MSCs engineered using TAT functionalized nanoparticles serve as an efficient carrier for tumor specific delivery of anticancer drugs, resulting in greatly improved therapeutic efficacy.

Combination of Sunitinib and PD-L1 Blockade Enhances Anticancer Efficacy of TLR7/8 Agonist-Based Nanovaccine

Cancer vaccines composed of tumor-associated antigens (TAAs) and toll-like receptor (TLR) agonists have shown promising antitumor efficacy in preclinical studies by generating antigen-specific CD8 T cells, but translation of cancer vaccines to the clinic has been limited due to variables responses and development of resistance. The tumor microenvironment deploys various immune escape mechanisms that neutralize CD8 T cell-mediated tumor rejection. Therefore, we hypothesized that modulation of the tumor microenvironment can augment CD8 T cell activation and enhance therapeutic efficacy of cancer vaccines. To accomplish this, we aimed to eliminate immune suppressive cells and block their inhibitory signaling. Combination of the tyrosine kinase inhibitor (TKI) sunitinib with a nanoparticle-based cancer vaccine (nanovaccine) resulted in the reduction of immune-suppressive myeloid-derived suppressive cells (MDSCs) and regulatory T cells (Tregs). Blockade of programmed death-ligand 1 (PD-L1) using anti-PD-L1 antibody was used to reduce CD8 T cell exhaustion. Combination of nanovaccine+sunitinib+PD-L1 antibody treatment reduced PD-L1^high M2 macrophages and MDSCs and upregulated activation of CD8 T cells in the tumor. Nanovaccine+sunitinib+PD-L1 antibody treatment also stimulated antigen-specific CD8 T cell response, which led to improved therapeutic efficacy in MB49 and B16F10 murine tumor models. These results suggest that modulation of tumor microenvironment using sunitinib and PD-L1 blockade can significantly enhance the antitumor efficacy of cancer nanovaccine.

Poly(d,l-lactide-co-glycolide) Nanoparticles as Delivery Platforms for TLR7/8 Agonist-Based Cancer Vaccine

Targeted drug delivery can significantly influence the efficacy of a drug. In the past decades, diverse drug-delivery technologies, including nano- and microparticles, co-crystals, and microneedles have been developed to maximize therapeutic efficacy and minimize undesired side effects of therapeutics. Nanoparticles-submicron-sized drug carriers-have been actively investigated for the delivery of antibiotics, nucleic acids, peptide/proteins, and chemotherapeutics. Recently, nanoparticles have gained attention as a vaccine delivery platform for tumor-associated antigens (TAAs) and/or vaccine adjuvants. Agonists of imidazoquinoline-based Toll-like receptor (TLR) 7/8 are potent cytokine inducers that are used as cancer vaccine adjuvants to elicit robust T-cell response by activating dendritic cells (DCs). Despite their in vitro potency, the translation of TLR7 agonists as cancer vaccine adjuvants in the clinic has been limited by their poor retention at the injection site. Therefore, a formulation that could improve the availability of TLR7/8 agonists to DCs via conventional vaccine administration routes (subcutaneous, intramuscular) can broaden the application of TLR7/8 agonists for cancer immunotherapy. Polymeric nanoparticles fabricated with poly(d,l-lactide-co-glycolide) (PLGA) can be an efficient TLR7/8 agonist delivery platform. PLGA is a biocompatible polymer, and nanoparticles prepared from this polymer are stable in saline and are small enough to be administered by subcutaneous or intramuscular injections. Furthermore, nanoparticulate TLR7/8 delivery can enhance DC uptake and facilitate lymphatic drainage, both of which can enhance the adjuvanticity of TLR7/8 agonists compared with soluble forms. In this review, we discuss the use of PLGA nanoparticles with TLR7/8 agonists for improving cancer immunotherapy.

Acidic pH-responsive polymer nanoparticles as a TLR7/8 agonist delivery platform for cancer immunotherapy

Synthetic imidazoquinoline-based toll-like receptor (TLR) 7/8 bi-specific agonists are promising vaccine adjuvants that can induce maturation of dendritic cells (DCs) and activate them to secrete pro-inflammatory cytokines. However, in vivo efficacy of these small molecule agonists is often hampered by their fast clearance from the injection site, limiting their use to topical treatments. In this study, we investigated the use of acidic pH-responsive poly(lactide-co-glycolide) (PLGA) nanoparticles for endo-lysosome specific release of 522, a novel TLR7/8 agonist. Bicarbonate salt was incorporated into the new formulation to generate carbon dioxide (CO2) gas at acidic pH, which can disrupt the polymer shell to rapidly release the payload. Compared to conventional PLGA nanoparticles, the pH responsive formulation resulted in 33-fold higher loading of 522. The new formulation demonstrated acid-responsive CO2 gas generation and drug release. The acid-responsive formulation increased the in vitro expression of co-stimulatory molecules on DCs and improved antigen-presentation via MHC I, both of which are essential for CD8 T cell priming. In vivo studies showed that the pH-responsive formulation elicited stronger antigen-specific CD8 T cell and natural killer (NK) cell responses than conventional PLGA nanoparticles, resulting in enhanced anticancer efficacy in a murine melanoma tumor model. Our results suggest that acidic-pH responsive, gas-generating nanoparticles are an efficient TLR7/8 agonist delivery platform for cancer immunotherapy.

Inhibition of Chlamydia trachomatis Growth During the Last Decade: A Mini-Review

Chlamydia trachomatis is responsible for the most frequent sexually transmitted bacterial infection in the world and for trachoma, the world's leading infectious cause of blindness. Genital chlamydial infection is very common among sexually active young people, and when untreated, leads to serious complications. No vaccine is yet available for this bacterial infection. Although Chlamydia resistance to antibiotics is rarely observed in vivo, studies showed that 10-20% of patients remain infected at the end of antibiotherapy, without being reinfected. The present review gives a global and comprehensive overview of the different targets and the related inhibitors proposed during the last decade, with a view to limiting the growth of this human pathogen. Metallic and polymeric nanoparticles in this field are also briefly presented.

Chemopreventive efficacy of curcumin-loaded PLGA microparticles in a transgenic mouse model of HER-2-positive breast cancer

Curcumin has shown promising inhibitory activity against HER-2-positive tumor cells in vitro but suffers from poor oral bioavailability in vivo. Our lab has previously developed a polymeric microparticle formulation for sustained delivery of curcumin for chemoprevention. The goal of this study was to examine the anticancer efficacy of curcumin-loaded polymeric microparticles in a transgenic mouse model of HER-2 cancer, Balb-neuT. Microparticles were injected monthly, and mice were examined for tumor appearance and growth. Initiating curcumin microparticle treatment at 2 or 4 weeks of age delayed tumor appearance by 2-3 weeks compared to that in control mice that received empty microparticles. At 12 weeks, abnormal (lobular hyperplasia, carcinoma in situ, and invasive carcinoma) mammary tissue area was significantly decreased in curcumin microparticle-treated mice, as was CD-31 staining. Curcumin treatment decreased mammary VEGF levels significantly, which likely contributed to slower tumor formation. When compared to saline controls, however, blank microparticles accelerated tumorigenesis and curcumin treatment abrogated this effect, suggesting that PLGA microparticles enhance tumorigenesis in this model. PLGA microparticle administration was shown to be associated with higher plasma lactic acid levels and increased activation of NF-κΒ. The unexpected side effects of PLGA microparticles may be related to the high dose of the microparticles that was needed to achieve sustained curcumin levels in vivo. Approaches that can decrease the overall dose of curcumin (for example, by increasing its potency or reducing its clearance rate) may allow the development of sustained release curcumin dosage forms as a practical approach to cancer chemoprevention.

Abstract 2897: Therapeutic efficacy of antibodies targeting domain 1 of HSPG2 in breast cancer

Significant advancements in chemotherapy have improved the survival rates of patients presenting with local or regional breast cancer to as high as 99% and 85%, respectively. On the contrary, patients with metastatic breast cancer have a dismal 5-year survival rate of 26%. Thus, there is an urgent need for research strategies directed towards treatment of metastasis. Our lab used a phage display-based cell panning procedure to develop two fully humanized antibodies (Clone 6 and AM6) that are able to bind specifically to breast cancer metastatic cells. Target deconvolution revealed HSPG2/Perlecan Domain 1 as the cell surface antigen bound by the antibodies. Immunohistochemistry studies revealed high HSPG2 expression across various tumor subtypes including melanoma, bladder cancer, glioblastoma and ovarian cancer. There was a significant correlation between high HSPG2 and with poor survival in bladder and ovarian cancers. Interestingly, we observed significant tumor growth inhibition in the triple-negative MDA-MB-231 breast cancer xenograft model. This efficacy was significantly reduced when the tumor growth inhibition studies were repeated in NSG mice, suggesting NK cell-mediated antibody dependent cellular cytotoxicity (ADCC) as the potential mechanism of action. The data presented here point to the relevance of HSPG2 as a novel target for not only breast cancer but also other malignancies. We also show the potential of Clone 6 and AM6 as therapeutic and targeting agents. Further studies are required to understand the significance of HSPG2 overexpression and its correlation with tumor progression as well as to confirm the mechanism of action with Clone 6 and AM6 antibodies.

Citation Format: Vidhi Khanna, Stephen Kalscheuer, Jayanth Panyam, Da Yang, Sihan Li. Therapeutic efficacy of antibodies targeting domain 1 of HSPG2 in breast cancer [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 2897.

Abstract 3723: Nanoengineered mesenchymal stem cells successfully inhibit tumor progression in a syngeneic mouse model

Active tumor-targeted drug delivery holds great promise for enhancing therapeutic efficacy and mitigating toxic side effects resulting from nonspecific distribution of chemotherapeutic agents to healthy tissues. However, the majority of current drug delivery strategies depend on inefficient passive accumulation of the drug carrier in the tumor. We have developed a novel and truly active tumor-targeting approach that relies on the tumor tropism of mesenchymal stem cells (MSCs). Our work emphases nanoengineering of MSCs with paclitaxel-loaded nanoparticles to create cellular drug depots capable of selectively homing to tumor sites and releasing the drug over an extended duration. Paclitaxel-loaded PLGA nanoparticles (18.1 ± 1.9 % w/w paclitaxel; diameter of 282.5 ± 5.2 nm; and zeta potential of −18.4 ± 2.5 mV) were formulated by emulsion-solvent evaporation method. Nanoengineered MSCs were generated by incubating MSCs with 100 µg/mL paclitaxel-loaded nanoparticles for 4 hours at 37°C without altering their viability and migration potential. Anticancer efficacy of nanoengineered MSCs was evaluated in C57BL/6 albino female mice bearing orthotopic Lewis Lung Carcinoma (LL/2-luc) tumors. Despite significantly lower doses of paclitaxel (~2.5 mg/kg total dose for nanoengineered MSCs vs. 120 mg/kg for free- and nanoparticle-encapsulated drug), nanoengineered MSCs resulted in significant greater tumor inhibition and superior survival. Furthermore, administration of human MSCs did not elicit any overt immunologic responses in mice. In summary, our results demonstrate that nanoengineered MSCs can serve as an efficient carrier for tumor-specific delivery of anticancer drugs, resulting in greatly improved therapeutic efficacy.

Citation Format: Buddhadev Layek, Jayanth Panyam, Swayam Prabha. Nanoengineered mesenchymal stem cells successfully inhibit tumor progression in a syngeneic mouse model [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 3723.

Abstract 718: Nanoparticle-based tumor cell lysate vaccine for cancer immunotherapy

Introduction Combination of tumor-associated antigen (TAA) and toll-like receptor (TLR) agonists can facilitate a potent anticancer immune response. Synthetic peptides, which are derived from antigens that are highly elevated or only expressed in tumor tissue, have been investigated as a source of TAA. However, these peptides are not available for all tumor types and often poorly immunogenic. Whole tumor cell lysate is a promising alternate antigen source that seeks to overcome some of the limitations associated with peptide-based vaccines. In this study, we utilized whole tumor cell lysate as antigen source and a novel TLR 7/8 agonist encapsulating nanoparticles as adjuvant to formulate the cancer vaccine and examined its efficacy against subcutaneous (S.C.) tumor models.

Methods A new imidazaquinoline-based TLR 7/8 agonist (termed ‘522') was encapsulated in poly(lactide-co-glycolide) (PLGA) nanoparticles using emulsion solvent evaporation method to formulate the vaccine adjuvant. The adjuvant (522NP) was used in combination with whole tumor cell lysate (CL) prepared from murine bladder carcinoma (MB49) cells. Immunocompetent C57BL/6 mice were immunized subcutaneously with 5 doses of cell-lysate vaccine or various control treatments. Two days after the final vaccination dose, mice were sacrificed and organs were harvested. Splenocytes were analyzed using flow cytometry to measure antigen (Ag)-specific CD8 T cell response. We investigated whether prophylactic and therapeutic CL+522NP immunization can delay tumor growth and improve survival in MB49 S.C. tumor models.

Results CD11ahighCD8low CD8 T cells were examined as they represent Ag-experienced CD8 T cells that can respond to Ag. Frequency of CD11ahigh CD8low CD8 T cells increased in mice vaccinated with CL+522NP. In the prophylactic model, CL+522NP significantly delayed tumor growth compared to that in other control groups. On d 30, average tumor volumes reached ~1000 mm3 in untreated mice compared to ~500 mm3 in CL alone and CL+Soluble522 treated groups. However, CL+522NP vaccinated mice showed remarkably very little tumor growth (~122 mm3) over the same time period. In the therapeutic model, only CL+522NP treatment was effective in delaying tumor growth. Unlike in the prophylactic study, where CL alone had a moderate effect, therapeutic effects were not observed from CL alone or CL+Soluble522 groups.

Conclusion CL+522NPs vaccination triggered a robust anti-cancer immune response that resulted in the expansion of CD11ahigh CD8low CD8 T cells, which suggests that 522NPs enhance the immunogenicity of cell lysate and elicit Ag-specific CD8 T cell response. Furthermore, CD8 T cells generated by CL+522NPs vaccination appeared to be effective in killing tumors in both prophylactic and therapeutic tumor models. These results suggest that 522NPs are effective vaccine adjuvants capable of improving the outcome of cancer immunotherapy.

Citation Format: Hyunjoon Kim, Peter Larson, Tamara A. Kucaba, Katherine A. Murphy, David M. Ferguson, Thomas S. Griffith, Jayanth Panyam. Nanoparticle-based tumor cell lysate vaccine for cancer immunotherapy [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 718.

Nano-Engineered Mesenchymal Stem Cells Increase Therapeutic Efficacy of Anticancer Drug Through True Active Tumor Targeting

Tumor-targeted drug delivery has the potential to improve therapeutic efficacy and mitigate non-specific toxicity of anticancer drugs. However, current drug delivery approaches rely on inefficient passive accumulation of the drug carrier in the tumor. We have developed a unique, truly active tumor-targeting strategy that relies on engineering mesenchymal stem cells (MSC) with drug-loaded nanoparticles. Our studies using the A549 orthotopic lung tumor model show that nano-engineered MSCs carrying the anticancer drug paclitaxel (PTX) home to tumors and create cellular drug depots that release the drug payload over several days. Despite significantly lower doses of PTX, nano-engineered MSCs resulted in significant inhibition of tumor growth and superior survival. Anticancer efficacy of nano-engineered MSCs was confirmed in immunocompetent C57BL/6 albino female mice bearing orthotopic Lewis Lung Carcinoma (LL/2-luc) tumors. Furthermore, at doses that resulted in equivalent therapeutic efficacy, nano-engineered MSCs had no effect on white blood cell count, whereas PTX solution and PTX nanoparticle treatments caused leukopenia. Biodistribution studies showed that nano-engineered MSCs resulted in greater than 9-fold higher AUC_lung of PTX (1.5 μg.day/g) than PTX solution and nanoparticles (0.2 and 0.1 μg.day/g tissue, respectively) in the target lung tumors. Furthermore, the lung-to-liver and the lung-to-spleen ratios of PTX were several folds higher for nano-engineered MSCs relative to those for PTX solution and nanoparticle groups, suggesting that nano-engineered MSCs demonstrate significantly less off-target deposition. In summary, our results demonstrate that nano-engineered MSCs can serve as an efficient carrier for tumor-specific drug delivery and significantly improved anti-cancer efficacy of conventional chemotherapeutic drugs. Mol Cancer Ther; 17(6); 1196-206. ©2018 AACR.

Triptolide suppresses the in vitro and in vivo growth of lung cancer cells by targeting hyaluronan-CD44/RHAMM signaling

Higher levels of hyaluronan (HA) and its receptors CD44 and RHAMM have been associated with poor prognosis and metastasis in NSCLC. In the current study, our goal was to define, using cellular and orthotopic lung tumor models, the role of HA-CD44/RHAMM signaling in lung carcinogenesis and to assess the potential of triptolide to block HA-CD44/RHAMM signaling and thereby suppress the development and progression of lung cancer. Triptolide reduced the viability of five non-small cell lung cancer (NSCLC) cells, the proliferation and self-renewal of pulmospheres, and levels of HA synthase 2 (HAS2), HAS3, HA, CD44, RHAMM, EGFR, Akt and ERK, but increased the cleavage of caspase 3 and PARP. Silencing of HAS2, CD44 or RHAMM induced similar effects. Addition of excess HA to the culture media completely abrogated the effects of triptolide and siRNAs targeting HAS2, CD44, or RHAMM. In an orthotopic lung cancer model in nude rats, intranasal administration of liposomal triptolide (400 μg/kg) for 8 weeks significantly reduced lung tumor growth as determined by bioluminescence imaging, lung weight measurements and gross and histopathological analysis of tumor burden. Also, triptolide suppressed expressions of Ki-67, a marker for cell proliferation, HAS2, HAS3, HA, CD44, and RHAMM in lung tumors. Overall, our results provide a strong rationale for mitigating lung cancer by targeting the HA-CD44/RHAMM signaling axis.

Honokiol suppresses lung tumorigenesis by targeting EGFR and its downstream effectors

Since epidermal growth factor receptor (EGFR) is commonly deregulated in pre-malignant lung epithelium, targeting EGFR may arrest the development of lung cancer. Here, we showed that honokiol (2.5–7.5 μM), a bioactive compound of Magnolia officinalis, differentially suppressed proliferation (up to 93%) and induced apoptosis (up to 61%) of EGFR overexpressing tumorigenic bronchial cells and these effects were paralleled by downregulation of phospho-EGFR, phospho-Akt, phospho-STAT3 and cell cycle-related proteins as early as 6–12 h post-treatment. Autocrine secretion of EGF sensitized 1170 cells to the effects of honokiol. Molecular docking studies indicated that honokiol binds to the tyrosine kinase domain of EGFR although it was less efficient than erlotinib. However, the anti-proliferative and pro-apoptotic activities of honokiol were stronger than those of erlotinib. Upon combinatory treatment, honokiol sensitized bronchial cells and erlotinib resistant H1650 and H1975 cells to erlotinib. Furthermore, in a mouse lung tumor bioassay, intranasal instillation of liposomal honokiol (5 mg/kg) for 14 weeks reduced the size and multiplicity (49%) of lung tumors and the level of total- and phospho-EGFR, phospho-Akt and phospho-STAT3. Overall, our results indicate that honokiol is a promising candidate to suppress the development and even progression of lung tumors driven by EGFR deregulation.

The effects of collagen-rich extracellular matrix on the intracellular delivery of glycol chitosan nanoparticles in human lung fibroblasts

Recent progress in nanomedicine has shown a strong possibility of targeted therapy for obstinate chronic lung diseases including idiopathic pulmonary fibrosis (IPF). IPF is a fatal lung disease characterized by persistent fibrotic fibroblasts in response to type I collagen-rich extracellular matrix. As a pathological microenvironment is important in understanding the biological behavior of nanoparticles, in vitro cellular uptake of glycol chitosan nanoparticles (CNPs) in human lung fibroblasts was comparatively studied in the presence or absence of type I collagen matrix. Primary human lung fibroblasts from non-IPF and IPF patients (n=6/group) showed significantly increased cellular uptake of CNPs (>33.6-78.1 times) when they were cultured on collagen matrix. To elucidate the underlying mechanism of enhanced cellular delivery of CNPs in lung fibroblasts on collagen, cells were pretreated with chlorpromazine, genistein, and amiloride to inhibit clathrin-mediated endocytosis, caveolae-mediated endocytosis, and macropinocytosis, respectively. Amiloride pretreatment remarkably reduced the cellular uptake of CNPs, suggesting that lung fibroblasts mainly utilize the macropinocytosis-dependent mechanism when interacted with collagen. In addition, the internalization of CNPs was predominantly suppressed by a phosphoinositide 3-kinase (PI3K) inhibitor in IPF fibroblasts, indicating that enhanced PI3K activity associated with late-stage macropinocytosis can be particularly important for the enhanced cellular delivery of CNPs in IPF fibroblasts. Our study strongly supports the concept that a pathological microenvironment which surrounds lung fibroblasts has a significant impact on the intracellular delivery of nanoparticles. Based on the property of enhanced intracellular delivery of CNPs when fibroblasts are made to interact with a collagen-rich matrix, we suggest that CNPs may have great potential as a drug-carrier system for targeting fibrotic lung fibroblasts.

Abstract 4593: Glycoengineered antibodies for click chemistry applications

Antibody-drug conjugates (ADC) hold considerable promise as anticancer agents. A critical determinant of the effectiveness of ADCs is the chemistry that is used to conjugate the payload. Currently used approaches include primarily conjugation to either side-chain amine or carboxylic acid groups or conjugation to thiols. Because these reactions are not site specific and not easily controlled, these chemistries can result in reduced affinity for the target antigen. Further, these conjugation reactions lack selectivity and can result in heterogeneous mixtures of products that differ in the sites and stoichiometry of modification. We investigated a glycoengineering strategy that enables the introduction of artificial azide groups in the antibody without affecting their antigen affinity. This is based on the observation that glycosyltransferases can incorporate non-natural sugars (e.g., azido mannose) at different sites on an IgG molecule. The azide groups inthese artificial sugars are then available to react with alkynes through copper-catalyzed ‘click’ chemistry or with strained alkynes such as dibenzyl cyclooctyne (DBCO) allowing for biorthogonal, copper-free ‘click’ chemistry. Because the sugars are added reproducibly and at asite that does not affect antigen binding, the glycoengineering technology would overcome problems associated with traditional conjugation strategies. Using this approach, azide groups were introduced in anti-CD133 and anti-perlecan antibodies. Further, the azide groups were available to react with various DBCO conjugates including fluorophores, drug molecules and nanoparticles. Importantly, the addition of artificial sugar and subsequent azide-alkyne reactiondid not affect the affinity of the antibody for the target antigen. Conjugation of nanoparticles to antibodies using this approach resulted in enhanced cellular uptake of the nanoparticles. Similarly, conjugation of a cytotoxin to the antibody resulted in enhanced cell kill in vitro. Weexpect that this glycoengineering strategy will prove to be a unique platform technology that will have a significant impact on antibody-based therapeutics.

Citation Format: Drishti Sehgal, Stephen Kalscheuer, Tanmoy Sadhukha, Jayanth Panyam. Glycoengineered antibodies for click chemistry applications [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4593. doi:10.1158/1538-7445.AM2017-4593

Abstract 2181: Antibody-conjugated nanoparticles for targeting metastatic triple-negative breast cancer

Early detection and the availability of new treatments have improved the survival rates of patients presenting with local or regional breast cancer to as high as 99% and 85%, respectively. On the contrary, patients with metastatic disease have a dismal 5-year survival rate of 17%. Thus, there is an urgent need for treatment strategies directed towards metastasis. Our lab has developed antibodies (Clone 6 and AM6) capable of recognizing tumor cells that have undergone epithelial-to-mesenchymal transition (EMT), a key step in the generation of circulating tumor cells and metastasis. The goal of the current study was to determine whether we use these antibodies as targeting ligands for directing anticancer drug-loaded polymeric nanoparticles to metastatic triple negative breast cancer cells as a novel therapeutic option. Polymeric PLGA nanoparticles loaded with paclitaxel, a chemotherapeutic agent, were functionalized with the antibodies using thiol-maleimide chemistry. We optimized the conjugation reaction in order to achieve maximal cell uptake of nanoparticles without compromising antibody binding. In vitro studies were carried out in an MDA-MB-231 derivative cell line with enhanced lung metastatic potential as well as a melanoma metastatic cell line M12. Clone 6 nanoparticles and AM6 nanoparticles showed significant improvement in cellular uptake as well as retention. A competition experiment confirmed target-mediated uptake of nanoparticles. Cytotoxicity studies showed improved cell kill using Clone 6 nanoparticles and AM6 nanoparticles. Based on these promising in vitro results, we are currently carrying out in vivo studies in mice. The development of a targeted drug delivery system for the treatment of metastatic triple negative breast cancer can significantly enhance the survival rate for patients who often have a life-expectancy of less than one year.

Citation Format: Vidhi Khanna, Stephen Kalscheuer, Ameya Kirtane, Jayanth Panyam. Antibody-conjugated nanoparticles for targeting metastatic triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2181. doi:10.1158/1538-7445.AM2017-2181

Evaluation of Vaginal Drug Levels and Safety of a Locally Administered Glycerol Monolaurate Cream in Rhesus Macaques

The human immunodeficiency virus epidemic affects millions of people worldwide. As women are more vulnerable to infection, female-controlled interventions can help control the spread of the disease significantly. Glycerol monolaurate (GML), an inexpensive and safe compound, has been shown to protect against simian immunodeficiency virus infection when applied vaginally. However, on account of its low aqueous solubility, fabrication of high-dose formulations of GML has proven difficult. We describe the development of a vaginal cream that could be loaded with up to 35% GML. Vaginal drug levels and safety of 3 formulations containing increasing concentrations of GML (5%w/w, 15%w/w, and 35%w/w) were tested in rhesus macaques after vaginal administration. GML concentration in the vaginal tissue increased as the drug concentration in the cream increased, with 35% GML cream resulting in tissue concentration of ∼0.5 mg/g, albeit with high interindividual variability. Compared with the vehicle control, none of the GML creams had any significant effect on the vaginal flora and cytokine (macrophage inflammatory protein 3α and interleukin 8) levels, suggesting that high-dose GML formulations do not induce local adverse effects. In summary, we describe the development of a highly loaded vaginal cream of GML, and vaginal drug levels and safety after local administration in macaques.

Engineering of Anti-CD133 Trispecific Molecule Capable of Inducing NK Expansion and Driving Antibody-Dependent Cell-Mediated Cytotoxicity

Purpose

The selective elimination of cancer stem cells (CSCs) in tumor patients is a crucial goal because CSCs cause drug refractory relapse. To improve the current conventional bispecific immune-engager platform, a 16133 bispecific natural killer (NK) cell engager (BiKE), consisting of scFvs binding FcγRIII (CD16) on NK cells and CD133 on carcinoma cells, was first synthesized and a modified interleukin (IL)-15 crosslinker capable of stimulating NK effector cells was introduced.

Materials and Methods

DNA shuffling and ligation techniques were used to assemble and synthesize the 1615133 trispecific NK cell engager (TriKE). The construct was tested for its specificity using flow cytometry, cytotoxic determinations using chromium release assays, and lytic degranulation. IL-15–mediated expansion was measured using flow-based proliferation assays. The level of interferon (IFN)-γ release was measured because of its importance in the anti-cancer response.

Results

1615133 TriKE induced NK cell–mediated cytotoxicity and NK expansion far greater than that achieved with BiKE devoid of IL-15. The drug binding and induction of cytotoxic degranulation was CD133⁺ specific and the anti-cancer activity was improved by integrating the IL-15 cross linker. The NK cell–related cytokine release measured by IFN-γ detection was higher than that of BiKE. NK cytokine release studies showed that although the IFN-γ levels were elevated, they did not approach the levels achieved with IL-12/IL-18, indicating that release was not at the supraphysiologic level.

Conclusion

1615133 TriKE enhances the NK cell anti-cancer activity and provides a self-sustaining mechanism via IL-15 signaling. By improving the NK cell performance, the new TriKE represents a highly active drug against drug refractory relapse mediated by CSCs.

Fibrinolytic Enzyme Cotherapy Improves Tumor Perfusion and Therapeutic Efficacy of Anticancer Nanomedicine

Elevated interstitial fluid pressure and solid stress within tumors contribute to poor intratumoral distribution of nanomedicine. In this study, we hypothesized that the presence of fibrin in tumor extracellular matrix contributes to hindered intratumoral distribution of nanocarriers and that this can be overcome through the use of a fibrinolytic enzyme such as tissue plasminogen activator (tPA). Analysis of fibrin expression in human tumor biopsies showed significant fibrin staining in nearly all tumor types evaluated. However, staining was heterogeneous across and within tumor types. We determined the effect of fibrin on the diffusion, intratumoral distribution, and therapeutic efficacy of nanocarriers. Diffusivity of nanocarriers in fibrin matrices was limited and could be improved significantly by coincubation with tPA. In vivo, coadministration of tPA improved the anticancer efficacy of nanoparticle-encapsulated paclitaxel in subcutaneous syngeneic mouse melanoma and orthotopic xenograft lung cancer models. Furthermore, treatment with tPA led to decompression of blood vessels and improved tumor perfusion. Cotreatment with tPA resulted in greater intratumoral penetration of a model nanocarrier (Doxil), leading to enhanced availability of the drug in the tumor core. Fibrinolytics such as tPA are already approved for other indications. Fibrinolytic cotherapy is therefore a rapidly translatable strategy for improving therapeutic effectiveness of anticancer nanomedicine. Cancer Res; 77(6); 1465-75. ©2017 AACR.

Freeze concentration-induced PLGA and polystyrene nanoparticle aggregation: Imaging and rational design of lyoprotection

Long-term storage of stable nanoparticulate systems is critical to the utilization of nanotechnology in biomedical applications. Freeze-drying or lyophilization is the most commonly used approach to preparing stable injectable nano formulations. A detailed understanding of the freezing stress on nanoparticles is essential to the successful preservation of original particle attributes and to the development of reliable lyophilization processes. However, visualization of the freezing process and the underlying mechanisms that result in particle aggregation remains challenging. Here, we show a clear causal relationship between the freeze-concentration event and particle aggregation by employing correlative imaging techniques, encompassing both real-time dynamic visualization and super-resolution imaging for frozen systems. Direct evidence was obtained to corroborate the particle isolation hypothesis. Moreover, ice-ice, ice-air and ice-container interfaces were identified as hotspots for generating freezing stress on susceptible nanoparticles. In light of these observations, sphere close packing models were explored. Based on the relationship between jammed particles and void fraction within a confined interfacial space, we are able to define the boundary condition of the minimal 'cryoprotectant to particle ratio' required for effective design space of particle isolation and cryoprotection. These findings clearly demonstrated the utility of visualization techniques and modeling in elucidating the mechanism of freezing stress and protection, providing guiding tools to the rational design of cryoprotectant containing nano formulations and processes.

Assessing the Benefits of Drug Delivery by Nanocarriers: A Partico/Pharmacokinetic Framework

OBJECTIVE

An in vivo kinetic framework is introduced to analyze and predict the quantitative advantage of using nanocarriers to deliver drugs, especially anticancer agents, compared to administering the same drugs in their free form.

METHODS

This framework recognizes three levels of kinetics. First is the particokinetics associated with deposition of nanocarriers into tissues associated with drug effect and toxicity, their residence inside those tissues, and elimination of the nanocarriers from the body. Second is the release pattern in time of free drug from the nanocarriers. Third is the pharmacokinetics of free drug, as it relates to deposition and elimination processes in the target and toxicity associated tissues, and total body clearance. A figure of merit, the drug targeting index (DTI), is used to quantitate the benefit of nanocarrier-based drug delivery by considering the effects of preferential deposition of nanoparticles into target tissues and relative avoidance of tissues associated with drug toxicity, compared to drug that is administered in its free form.

RESULTS

General methods are derived for calculating DTI when appropriate particokinetic, pharmacokinetic, and drug release rate information is available, and it is shown that relatively simple algebraic forms result when some common assumptions are made.

CONCLUSION

This approach may find use in developing and selecting nanocarrier formulations, either for populations or for individuals.

Abstract 4657: Selective inhibitors epigenetically modify and eradicate tumor-initiating stem-like cells through downregulating microRNA 22-mediated TET induction and apoptosis

Tumor-initiating stem-like cells (TICs) are a minor population in bulk tumors that play a critical role in tumor recurrence and therapy-resistance. We previously showed that a key stemness marker Nanog is upregulated that regulates self-renewal and pluripotency of embryonic stem cells and TICs. We demonstrated that alcohol-mediated activation of Toll-like receptor 4 (TLR4) by endotoxin resulted in increased expression of pluripotency stem cell transcription factor NANOG that metabolically reprograms tumor-initiating stem-like cells (TICs: cancer stem cells) via inhibition of oxidative phosphorylation and activation of fatty acid oxidation in our recently accepted Cell Metabolism paper. Discovery of a drug that specifically targets TICs would be a vital goal for cancer therapy. To identify selective TIC inhibitors, we conducted a high throughput screening of an FDA-approved drug library using combination of Nanog promoter-GFP-based screening with viability-based screening and their combination screening of each hit compound. Our high-throughput screening identified the best combination of repurposed FDA-approved drugs: all-trans retinoic acid (ATRA) and the histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) that repressed NANOG and induces apoptosis of TICs. Treatment of ATRA inhibits self-renewal ability in vitro. To specifically target the CD133 (+) population, we encapsulated ATRA into nanoparticles conjugated with CD133 antibody using biodegradable poly(D,L-lactide-co-glycolide) (PLGA) polymer. The combination treatment significantly inhibited tumor growth compared to single drug treatments while the ATRA or SAHA monotherapy groups did not reduce or even promoted tumor growth. The combination of ATRA with SAHA specifically induces apoptosis of TICs. Targeting of TICs by NANOG antagonism increases drug susceptibility in tumor-bearing mice and achieves ∼90% tumor growth suppression. RNA-seq analysis identified that ATRA+SAHA treatment reduced expression of MicroRNA-22 (miR-22), leading to induction of PTEN and ten-eleven translocation enzymes (TET2), which demethylates DNA. PTEN induction promoted P-FOXO3A and induced BIM, leading to induction of apoptosis. The combined treatment Induced TET1/2 to demethylate p53-binding sites of NANOG promoter, leading to downregulation of NANOG. Taken together, combination treatment of ATRA with SAHA may serve as a novel avenue for HCC treatment. Novel combination of repurposed drugs is cost-effective therapeutic strategy to target microRNA for eradication of TICs, leading to inhibition of metastasis and recurrence.

Citation Format: Chia-Lin Chen, Suresh Swaminathan, Ameya Kirtane, Jayanth Panyam, Keigo Machida. Selective inhibitors epigenetically modify and eradicate tumor-initiating stem-like cells through downregulating microRNA 22-mediated TET induction and apoptosis. [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 4657.

Nanoparticles Containing High Loads of Paclitaxel-Silicate Prodrugs: Formulation, Drug Release, and Anticancer Efficacy

We have investigated particle size, interior structure, drug release kinetics, and anticancer efficacy of PEG-b-PLGA-based nanoparticles loaded with a series of paclitaxel (PTX)-silicate prodrugs [PTX-Si(OR)3]. Silicate derivatization enabled us to adjust the hydrophobicity and hydrolytic lability of the prodrugs by the choice of the alkyl group (R) in the silicate derivatives. The greater hydrophobicity of these prodrugs allows for the preparation of nanoparticles that are stable in aqueous dispersion even when loaded with up to ca. 75 wt % of the prodrug. The hydrolytic lability of silicates allows for facile conversion of prodrugs back to the parent drug, PTX. A suite of eight PTX-silicate prodrugs was investigated; nanoparticles were made by flash nanoprecipitation (FNP) using a confined impingement jet mixer with a dilution step (CIJ-D). The resulting nanoparticles were 80-150 nm in size with a loading level of 47-74 wt % (wt %) of a PTX-silicate, which corresponds to 36-59 effective wt % of free PTX. Cryogenic transmission electron microscopy images show that particles are typically spherical with a core-shell structure. Prodrug/drug release profiles were measured. Release tended to be slower for prodrugs having greater hydrophobicity and slower hydrolysis rate. Nanoparticles loaded with PTX-silicate prodrugs that hydrolyze most rapidly showed in vitro cytotoxicity similar to that of the parent PTX. Nanoparticles loaded with more labile silicates also tended to show greater in vivo efficacy.

Abstract A51: Intradermal delivery of polymeric nanoparticle based vaccine formulation using a hollow microneedle system

Introduction: Nanoparticle (NP)-based anticancer vaccine delivery systems provide a number of advantages including spatial repetitive display of the antigen, size dependent lymphatic and intracellular trafficking, and the depot effect of persistence and sustained release of antigens/adjuvants. However, the optimal NP delivery mode and route of administration need additional investigation. To achieve reproducible intradermal PLGA NP vaccine delivery using an in-vivo rat model, we used a hollow microneedle array system (1). The profile of the resulting humoral and cellular immune responses was compared to that resulting from conventional intramuscular (IM) injection of the same formulation.

Methods: Immunostimulatory Nanoparticles (ISNPs) loaded with imiquimod and monophosphoryl Lipid A (MPL-A) were created using emulsion- solvent evaporation technique. All vaccine formulations for the in vivo study contained 2 mg of ISNPs as the adjuvant component. Antigen was given either in the form of soluble OVA solution or OVA encapsulated PLGA NPs at equivalent doses of OVA (16 µg). Two doses of vaccine (prime and boost) were administered to Crl:CD(SD) rats three weeks apart via IM or ID delivery. ID delivery was enabled by a plastic, hollow microneedle array with 18 microneedles, each &lt;1mm in length, similar to those referenced previously (1). Blood collection was carried out three weeks after each dose. Serially-diluted serum was incubated with OVA coated plate for IgG1/IgG2a titer test by ELISA. Spleens were harvested at the endpoint of the experiment (three weeks after the booster dose) for splenocyte isolation. The T cell response was determined by pulsing the splenocyte culture with OVA antigen using a Mabtech rat Interferon gamma ELISpot kit.

Results and Discussion: ISNPs promoted high antigen-specific antibody response in both IM and ID vaccination groups. Compared to the soluble form, antigen encapsulated in NPs triggered significantly stronger IgG1 antibody response three weeks after priming dose regardless of administration route. Not only did the NP formulation demonstrate faster kinetics in mounting antibody response, but the antibody avidity, determined by Urea ELISA, was also better in the OVA NP formulation when compared to the soluble OVA formulation, indicating quicker progress of antibody affinity maturation. However, three weeks after the boost, IgG1 level of all groups were comparable, reaching a titer plateau. In contrast to the IgG1 response, antigen OVA encapsulated in NPs and delivered intradermally via the microneedles resulted in the highest IgG2a titer among all experimental groups at both time points after both priming and booster doses.

IgG2a is widely considered a surrogate biomarker for Th1 response, while IgG1 is a biomarker for Th2 response. The relative strength of Th1/Th2 response could be assessed from IgG1/IgG2a ratio (2). Among the different groups, ID delivery of the OVA NP formulation demonstrated the highest relative strength of Th1 response. This result was further confirmed by the secretion of Th1 cytokine Interferon gamma by splenocytes upon antigen recall response. These data suggest that for a NP vaccine carrier, the skin is a vaccination priming locus that enhances Th1 response, which is considered essential for effective induction of anti-tumor immunity.

Conclusion: A polymer-based NP vaccine formulation delivered intradermally via hollow microneedles elicited robust humoral and cellular immunity. When compared to IM injection, the unique combination of the polymeric NP formulation and the ID route of administration led to an optimal Th1 immune response.

References:

1. Burton SA, Ng CY, Simmers R, Moeckly C, Brandwein D, Gilbert T, Johnson N, Brown K, Alston T, Prochnow G, Siebenaler K, Hansen K.

Pharm Res. 2011; 28(1): 31–40

2. Brewer JM, Tetley L, Richmond J, Liew FY, Alexander J. J Immunol. 1998 ;161(8):4000-7.

Citation Format: Lin Niu, Leonard Chu, Kris Hansen, Jayanth Panyam. Intradermal delivery of polymeric nanoparticle based vaccine formulation using a hollow microneedle system. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr A51.

Reformulating Tylocrebrine in Epidermal Growth Factor Receptor Targeted Polymeric Nanoparticles Improves Its Therapeutic Index

Several promising anticancer drug candidates have been sidelined owing to their poor physicochemical properties or unfavorable pharmacokinetics, resulting in high overall cost of drug discovery and development. Use of alternative formulation strategies that alleviate these issues can help advance new molecules to the clinic at a significantly lower cost. Tylocrebrine is a natural product with potent anticancer activity. Its clinical trial was discontinued following the discovery of severe central nervous system toxicities. To improve the safety and potency of tylocrebrine, we formulated the drug in polymeric nanoparticles targeted to the epidermal growth factor receptor (EGFR) overexpressed on several types of tumors. Through in vitro studies in different cancer cell lines, we found that EGFR targeted nanoparticles were significantly more effective in killing tumor cells than the free drug. In vivo pharmacokinetic studies revealed that encapsulation in nanoparticles resulted in lower brain penetration and enhanced tumor accumulation of the drug. Further, targeted nanoparticles were characterized by significantly enhanced tumor growth inhibitory activity in a mouse xenograft model of epidermoid cancer. These results suggest that the therapeutic index of drugs that were previously considered unusable could be significantly improved by reformulation. Application of novel formulation strategies to previously abandoned drugs provides an opportunity to advance new molecules to the clinic at a lower cost. This can significantly increase the repertoire of treatment options available to cancer patients.

Immunotoxin targeting CD133(+) breast carcinoma cells

CD133 expression enriches for tumor-initiating cells and is a negative prognostic factor in numerous cancers. We previously developed an immunotoxin against CD133 by fusing a gene fragment encoding the scFv portion of an anti-CD133 antibody to a gene fragment encoding deimmunized PE38KDEL. The resulting fusion protein, dCD133KDEL, demonstrated potent antitumor activity following intratumoral delivery into head neck cell carcinoma xenografts. However, the efficacy against other tumors and the tolerability of systemic administration remained unclear. The purpose of this study was to evaluate the tolerability and efficacy of dCD133KDEL in a systemic human breast carcinoma model. Time course viability studies showed that dCD133KDEL selectively inhibited MDA-MB-231 ductal breast carcinoma cells that contained a minority CD133(+) subpopulation, implicating CD133(+) cells as a source for self-renewal within this cell line. Furthermore, systemic administration of dCD133KDEL caused regression or inhibition of tumor growth in mice bearing an intrasplenic MDA-MB-231 tumor challenge as a model for metastatic disease. In the same model, combined therapy with dCD133KDEL and another immunotoxin designed to target the bulk tumor mass was the most effective therapy, supporting the idea that such combination therapies might better address tumor heterogeneity. dCD133KDEL shows promise as a therapeutic agent and as a biologic tool to study cancer stem cells.

Identification and characterization of a novel scFv recognizing human and mouse CD133

CD133, also known as Prominin-1, is expressed on stem cells present in many tissues and tumors. In this work, we have identified and characterized a single-chain variable fragment (scFv) for the efficient and specific recognition of CD133. Phage display was used to develop the scFv from a previously reported anti-CD133 hybridoma clone 7, which was capable of recognizing both glycosylated and non-glycosylated forms of human CD133. The scFv immunostained CD133(+) Caco-2 cells, but not CD133(-/low) U87 cells. Significantly, it immunostained CD133(-) cells transiently transfected with the mouse CD133 gene as well as CD133(+) mouse cells. Co-immunostaining studies in mouse bone marrow cells, using anti-CD133 scFv-FITC and anti-mouse CD133-PE (clone 13A4) commercial antibody, indicated that the epitopes recognized by these reagents partially overlap. Taken together, these results suggest that the scFv can recognize mouse CD133 protein in addition to recognizing human CD133. This new scFv is expected to be valuable both as a molecular diagnostic reagent for identifying CD133(+) cells and as a ligand for targeting therapeutics to CD133(+) tumor-initiating cells.