MODL-41. ORGANOTYPIC BRAIN SLICE CULTURE PLATFORM AS A NOVEL PRE-CLINICAL MODEL FOR PATIENT DERIVED CELL LINES

The lack of experimentally tractable models that recapitulate brain structure and function represents a major impediment in the development of novel treatment options for brain cancer. In vitro assays, though fast and high throughput, produce artificial results which do not fully encompass the clinically relevant outcome. Low passage patient derived cell lines offer an advantage over immortalized cell lines in terms of relation to the clinical presentation. Low passage patient derived cell lines, however, show slower growth and decreased tumorgenicity. We have previously shown that the use of organotypic brain slice culture (OBSCs) can recapitulate growth patterns and migration which is seen in vivo. We have further expanded the OBSCs to study their use as a model for patient derived cell lines. Some cell lines such as MS21, a human glioblastoma, or IFF109-DMG, a human pediatric diffuse midline glioma, are simply supported over a four-day time period, whereas other lines such as IFF105-DIPG, a pediatric human diffuse intrinsic pontine glioma, can grow over 3-fold in a 4-day time period. Additionally, we can assess treatment response to a variety of clinically relevant chemotherapeutics. The decreased variability with the OBSCs allows for the assessment of minute differences in treatment response. Overall, these results suggest the OBSC with patient derived cell lines have the potential to be effective models to accelerate preclinical evaluation of therapeutics and guide drug development towards more effective treatment strategies.

MODL-14. MODELING THE INTRATUMORAL HETEROGENEITY OF AGGRESSIVE GLIOBLASTOMA ON ORGANOTYPIC BRAIN SLICES TO OPTIMIZE TUMOR-HOMING TUMORICIDAL INSC TREATMENT

BACKGROUND

Tumor-homing tumoricidal neural stem cell (tNSC) therapy is a promising new strategy that recently entered human patient testing for glioblastoma (GBM). Developing strategies for tNSC therapy to overcome intratumoral heterogeneity, variable cancer cell invasiveness, and differential drug response of GBM will be essential for efficacious treatment response in the clinical setting. We sought to create novel hybrid tumor models and investigate the impact of GBM heterogeneity on tNSC tumor response and treatment durability.

METHODS

We utilized organotypic brain slice explants and human cells with varied properties to generate heterogeneous GBM models ex vivo and in vivo. We first investigated the treatment response and durability of mono- and combination therapy with primary NSCs and fibroblast-derived human induced neural stem cells (iNSCs) engineered with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or enzyme-prodrug therapy. Next, we utilized the ex vivo models and molecular assays to explore mechanisms driving tumor adaption and escape.

RESULTS

Non-invasive imaging, molecular assays, and immunohistochemistry showed the new hybrid GBM models recapitulated key aspects of the clinical disease. Testing in multiple in vivo models showed that tNSC-TRAIL therapy induced robust initial inhibitions in tumor growth and significantly increased survival. However, tumors rebounded in multiple models and patterns of tumor regrowth varied with therapeutic, dose, and route of administration. We found that adjusting iNSC delivery strategies increased spatiotemporal TRAIL coverage and significantly decreased GBM volume throughout the brain, reducing tumor burden 100-fold as quantified in live ex vivo brain slices and resulting in varied impact on treatment durability and median survival across models of both solid and invasive tumors.

CONCLUSIONS

These studies report new hybrid models that accurately capture key aspects of GBM heterogeneity which markedly impact treatment response while demonstrating the ability of tNSC mono- and combination therapy to overcome certain aspects of heterogeneity for robust tumor kill.

MODL-27. An organotypic brain slice culture platform as a novel pre-clinical model for diffuse intrinsic pontine glioma and diffuse midline glioma

High-grade pediatric brain tumors (PBTs) such as diffuse intrinsic pontine glioma (DIPG) and diffuse midline glioma (DMG) are devastating diseases with a median survival of just 11 months. Little progress has been made in identifying effective treatments due to the lack of effective pre-clinical models to accurately assess drug sensitivity. Historically, models of DIPG and DMG have been limited due to the low availability of surgical biopsies and small patient populations. Existing in vitro models are often unable to recapitulate growth and migration patterns seen in patients, while in vivo work is costly, time intensive, and many biopsies fail to establish in mice. We have developed an ex vivo organotypic brain slice culture (OBSC) platform to model DIPG and DMG. Through our partnership with the Ian’s Friends Foundation and Children’s Healthcare of Atlanta Biobank, we have seeded, grown, and treated several low-passage patient-derived PBT lines such as DIPG and DMG. Additionally, we can assess treatment response to a variety of agents used in clinical patient care. Viability assays revealed differences in the sensitivity of cell lines to individual agents, indicating that OBSCs have the potential to capture minute differences in efficacy between cell lines and drugs. When we assessed combination treatments, we found low doses of radiation with low doses of temozolomide were synergistic, but using higher doses of radiation was antagonistic, suggesting the OBSC platform has the potential to guide dosing strategies to maximize therapeutic synergy. Overall, these results suggest that OBSC PBT models have the potential to effectively model PBTs, including DIPG and DMG, to accelerate preclinical evaluation of therapeutics and guide drug development towards more effective treatment strategies.

TMOD-31. AN ORGANOTYPIC TISSUE PLATFORM TO BRIDGE IN VITRO AND IN VIVO ASSAYS FOR BRAIN CANCER TREATMENT

Brain cancers remain one of the greatest medical challenges. The lack of experimentally tractable models that recapitulate brain structure/function represents a major impediment. Platforms that enable functional testing in high-fidelity models are urgently needed to accelerate the identification and translation of therapies to improve outcomes for patients suffering from brain cancer. In vitro assays are often too simple and artificial while in vivo studies can be time-intensive and complicated. Our live, organotypic brain slice platform can be used to seed and grow brain cancer cell lines, allowing us to bridge the existing gap in models. These tumors can rapidly establish within the brain slice microenvironment, and morphologic features of the tumor can be seen within a short period of time. The growth, migration, and treatment dynamics of tumors seen on the slices recapitulate what is observed in vivo yet is missed by in vitro models. Additionally, the brain slice platform allows for the dual seeding of different cell lines to simulate characteristics of heterogeneous tumors. Furthermore, live brain slices with embedded tumor can be generated from tumor-bearing mice. This method allows us to quantify tumor burden more effectively and allows for treatment and retreatment of the slices to understand treatment response and resistance that may occur in vivo. This brain slice platform lays the groundwork for a new clinically relevant preclinical model which provides physiologically relevant answers in a short amount of time leading to an acceleration of therapeutic translation.

SCIDOT-20. ADAPTING ENGINEERED CELL THERAPIES TO UNDERSTAND AND OVERCOME GLIOBLASTOMA RESISTANCE USING INTEGRATED IN VIVO AND EX VIVO MODELS

Genetically engineered neural stem cells (NSCs) are a promising therapy for the highly aggressive brain cancer glioblastoma (GBM), yet treatment durability remains a major challenge. We sought to define the events that contribute to dynamic adaption of GBM during NSC treatment and develop strategies to convert initial tumor kill into sustained GBM suppression. Using a unique hybrid tumor model treated with human skin-derived induced NSCs (iNSCs) releasing the pro-apoptotic agent TRAIL, we investigated how spatial distribution of tumor and iNSCs affects GBM adaption throughout recurrence. Serial bioluminescent imaging (BLI) was used to track tumor volumes in vivo, while a subset of mice were sacrificed 6, 13, and 20 days post-treatment to harvest brains and generate living ex vivo tissue slices. Live animal imaging showed iNSC-TRAIL treatment rapidly decreased tumor volumes when delivered into the primary tumor mass; however, minimal impact on tumor growth was observed when cells were delivered into distal regions of the brain. In contrast, high-resolution imaging of living brain sections showed extensive impacts of iNSC-TRAIL therapy that could not be visualized with BLI. The living slices showed iNSC-TRAIL treatment into the primary tumor decreased the solid, but not the invasive, tumor burden. Treatment into the lateral ventricles did impact tumor kill and was more effective at treating the invasive tumor burden and maintaining inhibition than treatment into the contralateral parenchyma. We next utilized the living tissue slices to explore the sensitivity of the recurrent tumors to TRAIL. When therapy was applied to slices harboring recurrent tumor, treatment again significantly reduced tumor volumes, suggesting tumors had not acquired TRAIL resistance. These results informed an additional in vivo survival study and subsequent PCR analysis of untreated and recurrent tumors, and combine the fidelity of in vivo studies with the speed and spatial resolution of living brain slice technology.

TMOD-31. ADAPTING ENGINEERED CELL THERAPIES TO UNDERSTAND AND OVERCOME GLIOBLASTOMA RESISTANCE USING INTEGRATED IN VIVO AND EX VIVO MODELS

Genetically engineered neural stem cells (NSCs) are a promising therapy for the highly aggressive brain cancer glioblastoma (GBM), yet treatment durability remains a major challenge. We sought to define the events that contribute to dynamic adaption of GBM during NSC treatment and develop strategies to convert initial tumor kill into sustained GBM suppression. Using a unique hybrid tumor model treated with human skin-derived induced NSCs (iNSCs) releasing the pro-apoptotic agent TRAIL, we investigated how spatial distribution of tumor and iNSCs affects GBM adaption throughout recurrence. Serial bioluminescent imaging (BLI) was used to track tumor volumes in vivo, while a subset of mice were sacrificed 6, 13, and 20 days post-treatment to harvest brains and generate living ex vivo tissue slices. Live animal imaging showed iNSC-TRAIL treatment rapidly decreased tumor volumes when delivered into the primary tumor mass; however, minimal impact on tumor growth was observed when cells were delivered into distal regions of the brain. In contrast, high-resolution imaging of living brain sections showed extensive impacts of iNSC-TRAIL therapy that could not be visualized with BLI. The living slices showed iNSC-TRAIL treatment into the primary tumor decreased the solid, but not the invasive, tumor burden. Treatment into the lateral ventricles did impact tumor kill and was more effective at treating the invasive tumor burden and maintaining inhibition than treatment into the contralateral parenchyma. We next utilized the living tissue slices to explore the sensitivity of the recurrent tumors to TRAIL. When therapy was applied to slices harboring recurrent tumor, treatment again significantly reduced tumor volumes, suggesting that tumors had not acquired TRAIL resistance. These results informed an additional in vivo survival study and subsequent PCR analysis of untreated and recurrent tumors, and combine the fidelity of in vivo studies with the speed and spatial resolution of living brain slice technology.

Intra-cavity stem cell therapy inhibits tumor progression in a novel murine model of medulloblastoma surgical resection

Background

Cytotoxic neural stem cells (NSCs) have emerged as a promising treatment for Medulloblastoma (MB), the most common malignant primary pediatric brain tumor. The lack of accurate pre-clinical models incorporating surgical resection and tumor recurrence limits advancement in post-surgical MB treatments. Using cell lines from two of the 5 distinct MB molecular sub-groups, in this study, we developed an image-guided mouse model of MB surgical resection and investigate intra-cavity NSC therapy for post-operative MB.

Methods

Using D283 and Daoy human MB cells engineered to express multi-modality optical reporters, we created the first image-guided resection model of orthotopic MB. Brain-derived NSCs and novel induced NSCs (iNSCs) generated from pediatric skin were engineered to express the pro-drug/enzyme therapy thymidine kinase/ganciclovir, seeded into the post-operative cavity, and used to investigate intra-cavity therapy for post-surgical MB.

Results

We found that surgery reduced MB volumes by 92%, and the rate of post-operative MB regrowth increased 3-fold compared to pre-resection growth. Real-time imaging showed NSCs rapidly homed to MB, migrating 1.6-fold faster and 2-fold farther in the presence of tumors, and co-localized with MB present in the contra-lateral hemisphere. Seeding of cytotoxic NSCs into the post-operative surgical cavity decreased MB volumes 15-fold and extended median survival 133%. As an initial step towards novel autologous therapy in human MB patients, we found skin-derived iNSCs homed to MB cells, while intra-cavity iNSC therapy suppressed post-surgical tumor growth and prolonged survival of MB-bearing mice by 123%.

Conclusions

We report a novel image-guided model of MB resection/recurrence and provide new evidence of cytotoxic NSCs/iNSCs delivered into the surgical cavity effectively target residual MB foci.

Dual Functional LipoMET Mediates Envelope-type Nanoparticles to Combinational Oncogene Silencing and Tumor Growth Inhibition

The success of small interfering RNA (siRNA)-mediated gene silencing for cancer therapy is still limited because of its instability and poor intracellular internalization. Traditional cationic carriers cannot adequately meet the need for clinical application of siRNA. We herein report a dual-functional liposome containing a cholesterol derivative of metformin, i.e., LipoMET, which takes advantage of the fusogenic activity as well as intrinsic tumor apoptosis inducing ability of biguanide moiety to achieve a combinational anti-oncogenic effect. In this study, the vascular endothelial growth factor (VEGF)-specific siRNAs were first electrostatically condensed into a ternary nanocomplex composed of polycation and hyaluronate, which was subsequently enveloped by LipoMET through membrane fusion. In comparison with common cationic control group, the resulting envelope-type nanoparticles (PH@LipoMET nanoparticles [NPs]) showed the ability of rapid cellular internalization and effective endosomal escape of siRNA during intracellular trafficking studies. Systemic administration of the targeted LipoMETs was capable of inducing apoptosis and tumor growth inhibition in the NCI-H460 xenograft model. When carrying VEGF-specific siRNAs, PH@LipoMET NPs remarkably downregulated the expression of VEGF and led to even more tumor suppression in vivo. Thus, LipoMET originated envelope-type nanoparticles may serve as a potential dual-functional siRNA delivery system to improve therapeutic effect of oncogene silencing.

Novel murine tumour models depend on strain and route of inoculation

This study describes variations in tumour growth patterns which occur when changes in the routes of inoculation and mouse strain are used to introduce tumours into established murine model systems that are known to vary in location and aggression. Intraperitoneal, subcutaneous, intravenous and hydrodynamic inoculations of B16F10 cells were compared among CD-1, C57BL/6 and Balb/c mice. Most surprisingly, allogeneic tumour growth in Balb/c mice after intravenous and hydrodynamic inoculation of B16F10 cells was faster than tumour growth in the syngeneic C57BL/6 mice. These and other variations in the tumour growth patterns described here can help provide the researcher with more experimental control when planning to use the optimal tumour model for any particular study.

Theranostic etoposide phosphate/indium nanoparticles for cancer therapy and imaging

Etoposide phosphate (EP), a water-soluble anticancer prodrug, is widely used for treatment of many cancers. After administration it is rapidly converted to etoposide, its parent compound, which exhibits anticancer activity. Difficulty in parenteral administration necessitates the development of a suitable nanoparticle delivery system for EP. Here we have used indium both as a carrier to deliver etoposide phosphate to tumor cells and as a SPECT imaging agent through incorporation of (111)In. Etoposide phosphate was successfully encapsulated together with indium in nanoparticles, and exhibited dose dependent cytotoxicity and induction of apoptosis in cultured H460 cancer cells via G2/M cell cycle arrest. In a mouse xenograft lung cancer model, etoposide phosphate/indium nanoparticles induce tumor cell apoptosis, leading to significant enhancement of tumor growth inhibition compared to the free drug.

Delivery of oligonucleotides with lipid nanoparticles

Since their inception in the 1980s, oligonucleotide-based (ON-based) therapeutics have been recognized as powerful tools that can treat a broad spectrum of diseases. The discoveries of novel regulatory methods of gene expression with diverse mechanisms of action are still driving the development of novel ON-based therapeutics. Difficulties in the delivery of this class of therapeutics hinder their in vivo applications, which forces drug delivery systems to be a prerequisite for clinical translation. This review discusses the strategy of using lipid nanoparticles as carriers to deliver therapeutic ONs to target cells in vitro and in vivo. A discourse on how chemical and physical properties of the lipid materials could be utilized during formulation and the resulting effects on delivery efficiency constitutes the major part of this review.

Synergistic anti-tumor effects of combined gemcitabine and cisplatin nanoparticles in a stroma-rich bladder carcinoma model

Tumors grown in a stroma-rich mouse model resembling clinically advanced bladder carcinoma with UMUC3 and NIH 3T3 cells have high levels of fibroblasts and an accelerated tumor growth rate. We used this model to investigate the synergistic effect of combined gemcitabine monophosphate (GMP) nanoparticles and Cisplatin nanoparticles (Combo NP) on tumor-associated fibroblasts (TAFs). A single injection of Combo NP had synergistic anti-tumor effects while the same molar ratio of combined GMP and Cisplatin delivered as free drug (Combo Free) fell outside of the synergistic range. Combo NP nearly halted tumor growth with little evidence of general toxicity while Combo Free had only a modest inhibitory effect at 16mg/kg GMP and 1.6mg/kg Cisplatin. Combo NP increased levels of apoptosis within the tumor by approximately 1.3 folds (TUNEL analysis) and decreased α-SMA-positive fibroblast recruitment by more than 87% (immunofluorescence) after multiple injections compared with Combo Free, GMP NP or Cisplatin NP alone. The TAF-targeting capability of Combo NP was evaluated by double staining for TUNEL and α-SMA at various time points after a single injection. On day one after injection, 57% of the TUNEL-positive cells were identified as α-SMA-positive fibroblasts. By day four, tumor stroma was 85% depleted and 87% of the remaining TAFs were TUNEL-positive. Combo NP-treated tumors became 2.75 folds more permeable than those treated with Combo Free as measured by Evans Blue. We conclude that the antineoplastic effect of Combo NP works by first targeting TAFs and is more effective as an anti-tumor therapy than Combo Free, GMP NP or Cisplatin NP alone.

In vivo gene delivery by nonviral vectors: overcoming hurdles?

The promise of cancer gene therapeutics is hampered by difficulties in the in vivo delivery to the targeted tumor cells, and systemic delivery remains to be the biggest challenge to be overcome. Here, we concentrate on systemic in vivo gene delivery for cancer therapy using nonviral vectors. In this review, we summarize the existing delivery barriers together with the requirements and strategies to overcome these problems. We will also introduce the current progress in the design of nonviral vectors, and briefly discuss their safety issues.