Novel mesenchymal stem cell delivery system as targeted therapy against neuroblastoma using the TH-MYCN mouse model

A Comparison of in vivo Tumor-Homing Abilities of Placental-Derived and Bone Marrow-Derived Mesenchymal Stromal Cells in High-Risk Neuroblastoma

BACKGROUND

Neuroblastoma is a highly lethal malignancy of young children. Mesenchymal stromal cells (MSCs) may represent a novel cellular delivery vehicle due to their innate tumor-homing properties. We compared in vivo homing abilities of placental-derived MSCs (PMSCs) and bone marrow-derived MSCs (BM-MSCs) in an orthotopic neuroblastoma xenograft.

METHODS

28 mice underwent direct implantation of neuroblastoma cells (cell line NB1643) into the adrenal gland followed by intraperitoneal injection of 5 × 106 MSCs (PMSC n = 13, BM-MSC n = 13, PBS controls n = 2). MSC migration was monitored with in vivo imaging system (IVIS) radiance measurements at multiple timepoints post-MSC injection. Necropsy timepoints were 72 h (n = 10) and 7 days (n = 16). Ex vivo imaging was performed on all adrenal masses and select organ tissues. Immunohistochemistry (IHC) assessed the presence of MSCs in tumors.

RESULTS

IVIS demonstrated initial diffuse signal that migrated to the left abdomen. Radiance decreased over time, but MSC signal persisted at day 7 in all animals. Ex vivo IVIS demonstrated signal in the adrenal tumor but not other organs. There was no significant difference in average ex vivo adrenal mass radiance between MSC groups (p = 0.74). IHC confirmed presence of both MSC types within the tumor.

CONCLUSION

PMSCs and BM-MSCs successfully migrated to neuroblastoma tumor tissues in vivo without evidence of migration to other organs. MSCs migrate within 72 h and persisted within the tumor up to 7 days. There was no significant difference in homing capabilities of PMSCs compared to BM-MSCs, indicating that either cell type has potential as a drug delivery vehicle.

TYPE OF STUDY

Original Research.

LEVEL OF EVIDENCE

n/a.

Proliferative Effects of Mesenchymal Stromal Cells on Neuroblastoma Cell Lines: Are They Tumor Promoting or Tumor Inhibiting?

BACKGROUND

Neuroblastoma is a common pediatric malignancy with poor survival for high-risk disease. Mesenchymal stromal cells (MSCs) have innate tumor-homing properties, enabling them to serve as a cellular delivery vehicle, but MSCs have demonstrated variable effects on tumor growth. We compared how placental MSCs (PMSCs) and bone marrow-derived MSCs (BM-MSCs) affect proliferation of neuroblastoma (NB) cells in vitro.

METHODS

Indirect co-culture assessed proliferative effects of 18 MSCs (early-gestation PMSCs (n = 9), term PMSCs (n = 5), BM-MSCs (n = 4) on three high-risk NB cell lines (NB1643, SH-SY5Y, and CHLA90). Controls were NB cells cultured in media alone. Proliferation was assessed using MTS assay and measured by fold change (fc) over controls. PMSCs were sub-grouped by neuroprotective effect: strong (n = 7), intermediate (n = 3), and weak (n = 4). The relationship between MSC type, PMSC neuroprotection, and PMSC gestational age on NB cell proliferation was assessed.

RESULTS

NB cell proliferation varied between MSC groups. BM-MSCs demonstrated lower proliferative effects than PMSCs (fc 1.18 vs 1.44, p < 0.001). Neither gestational age nor neuroprotection significantly predicted degree of proliferation. Proliferative effects of MSCs varied among NB cell lines. BM-MSCs had less effect on CHLA90 (fc 1.01) compared to NB1643 (fc 1.33) and SH-SY5Y (fc 1.20). Only NB1643 showed a difference between early and term PMSCs (p = 0.04).

CONCLUSION

Effects of MSCs on NB cell proliferation vary by MSC source and NB cell line. BM-MSCs demonstrated lower proliferative effects than most PMSCs. MSC neuroprotection was not correlated with proliferation. Improved understanding of MSC proliferation-promoting mechanisms may provide valuable insight into selection of cells best suited as drug delivery vehicles.

LEVEL OF EVIDENCE

N/A.

TYPE OF STUDY

Original Research.

The therapeutic effect of MSCs and their extracellular vesicles on neuroblastoma

Neuroblastoma is a common inflammatory-related cancer during infancy. Standard treatment modalities including surgical interventions, high-dose chemotherapy, radiotherapy, and immunotherapy are not able to increase survival rate and reduce tumor relapse in high-risk patients. Mesenchymal stem cells (MSCs) are known for their tumor-targeting and immunomodulating properties. MSCs could be engineered to express anticancer agents (i.e., growth factors, cytokines, pro-apoptotic agents) or deliver oncolytic viruses in the tumor microenvironment. As many functions of MSCs are mediated through their secretome, researchers have tried to use extracellular vesicles (EVs) from MSCs for targeted therapy of neuroblastoma. Here, we reviewed the studies to figure out whether the use of MSCs could be worthwhile in neuroblastoma therapy or not. Native MSCs have shown a promoting or inhibiting role in cancers including neuroblastoma. Therefore, MSCs are proposed as a vehicle to deliver anticancer agents such as oncolytic viruses to the neuroblastoma tumor microenvironment. Although modified MSCs or their EVs have been shown to suppress the tumorigenesis of neuroblastoma, further pre-clinical and clinical studies are required to come to a conclusion.

Development of minimally invasive cancer immunotherapy using anti-disialoganglioside GD2 antibody-producing mesenchymal stem cells for a neuroblastoma mouse model

PURPOSE

Mouse IgG anti-disialoganglioside GD2 antibody-secreting mouse mesenchymal stem cells (anti-GD2-MSCs) were developed, and their anti-tumor effects were validated in an in vivo neuroblastoma mouse model.

METHODS

Anti-GD2 antibody constructs were generated, incorporating FLAG-tagged single-chain fragment variables against GD2 fused to a linker sequence, and a fragment of a stationary portion was changed from human IgG to mouse IgG and GFP protein. The construct was lentivirally introduced into mouse MSCs. A syngeneic mouse model was established through the subcutaneous transplantation of a tumor tissue fragment from a TH-MYCN transgenic mouse, and the homing effects of anti-GD2-MSCs were validated by In vivo imaging system imaging. The syngeneic model was divided into three groups according to topical injection materials: anti-GD2-MSCs with IL-2, IL-2, and PBS. The tumors were removed, and natural killer (NK) cells were counted.

RESULTS

Anti-GD2-MSCs showed homing effects in syngeneic models. The growth rate of subcutaneous tumors was significantly suppressed by anti-GD2-MSCs with IL-2 (p < 0.05). Subcutaneous tumor immunostaining showed an increased NK cell infiltration in the same group (p < 0.01).

CONCLUSION

Anti-GD2-MSCs using mouse IgG showed a homing effect and significant tumor growth suppression in syngeneic models. Anti-GD2-MSC-based cellular immunotherapy could be a novel therapeutic strategy for intractable neuroblastoma.

Exosome mimetics derived from bone marrow mesenchymal stem cells ablate neuroblastoma tumor in vitro and in vivo

PURPOSE

To develop exosome-mimetics derived from bone marrow mesenchymal stem cells (EM) as a novel nanoscale drug delivery system(nanoDDS) with improved tumor targeting activity, therapeutic effect, and biosafety, and to evaluate the therapeutic effect of doxorubicin loaded EM (EM-Dox) on neuroblastoma (NB) in vitro and in vivo.

METHODS

EM was prepared by serial extrusion of bone marrow mesenchymal stem cells (BMSCs), ammonium sulfate gradient method was used to promote the active loading of doxorubicin, and EM-Dox was obtained after removal of free doxorubicin by dialysis. The obtained EM and EM-Dox were characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), Western Blot assay(WB), and the yield of exosomes and EM was further compared. Confocal fluorescent microscopy was used to verify the uptake of EM-Dox and free doxorubicin (Free-Dox) by NB cells. CCK-8 assay, cell cycle assay, and cell apoptosis assay were used to evaluate the antitumor effect of EM-Dox on NB cells in vitro. In addition, the targeted therapeutic effect and biosafety of EM-Dox against NB were evaluated in tumor-bearing nude mice.

RESULTS

TEM, NTA, and WB verified that both EM and EM-Dox feature highly similar morphology, size and marker protein expression in comparison with naturally occurred exosomes, but the particle size of EM-Dox increased slightly after loading doxorubicin. The protein yield and particle yield of EM-Dox were 16.8 and 26.3-folds higher than those of exosomes, respectively. Confocal fluorescent microscopy showed that EM and doxorubicin had a definite co-localization. EM-Dox was readily internalized in two well-established human NB cell lines. The intracellular content of doxorubicin in cells treated with EM-Dox was significantly higher than that treated with Free-Dox. CCK-8 assay and flow cytometry confirmed that EM-Dox could inhibit NB cell proliferation, induce G2/M phase cell cycle arrest, and promote NB cell apoptosis in vitro. In vivo bioluminescence imaging results demonstrated that EM-Dox effectively targets NB tumors in vivo. Compared with Free-Dox, EM-Dox had a significantly increased inhibitory effect against NB tumor proliferation and progression in vivo, without inducing any myocardial injury.

CONCLUSIONS

EM-Dox showed significantly increased anti-tumor activity in comparison with free doxorubicin in vitro and in vivo, and scalable EMs may represent a new class of NanoDDS that can potentially replace naturally occurred exosomes in preclinical or clinical translations.

Mechanisms involved in selecting and maintaining neuroblastoma cancer stem cell populations, and perspectives for therapeutic targeting

Pediatric neuroblastomas (NBs) are heterogeneous, aggressive, therapy-resistant embryonal tumours that originate from cells of neural crest (NC) origin and in particular neuroblasts committed to the sympathoadrenal progenitor cell lineage. Therapeutic resistance, post-therapeutic relapse and subsequent metastatic NB progression are driven primarily by cancer stem cell (CSC)-like subpopulations, which through their self-renewing capacity, intermittent and slow cell cycles, drug-resistant and reversibly adaptive plastic phenotypes, represent the most important obstacle to improving therapeutic outcomes in unfavourable NBs. In this review, dedicated to NB CSCs and the prospects for their therapeutic eradication, we initiate with brief descriptions of the unique transient vertebrate embryonic NC structure and salient molecular protagonists involved NC induction, specification, epithelial to mesenchymal transition and migratory behaviour, in order to familiarise the reader with the embryonic cellular and molecular origins and background to NB. We follow this by introducing NB and the potential NC-derived stem/progenitor cell origins of NBs, before providing a comprehensive review of the salient molecules, signalling pathways, mechanisms, tumour microenvironmental and therapeutic conditions involved in promoting, selecting and maintaining NB CSC subpopulations, and that underpin their therapy-resistant, self-renewing metastatic behaviour. Finally, we review potential therapeutic strategies and future prospects for targeting and eradication of these bastions of NB therapeutic resistance, post-therapeutic relapse and metastatic progression.

The Potential of Mesenchymal Stromal Cells in Neuroblastoma Therapy for Delivery of Anti-Cancer Agents and Hematopoietic Recovery

Neuroblastoma is one of the most common pediatric cancers and a major cause of cancer-related death in infancy. Conventional therapies including high-dose chemotherapy, stem cell transplantation, and immunotherapy approach a limit in the treatment of high-risk neuroblastoma and prevention of relapse. In the last two decades, research unraveled a potential use of mesenchymal stromal cells in tumor therapy, as tumor-selective delivery vehicles for therapeutic compounds and oncolytic viruses and by means of supporting hematopoietic stem cell transplantation. Based on pre-clinical and clinical advances in neuroblastoma and other malignancies, we assess both the strong potential and the associated risks of using mesenchymal stromal cells in the therapy for neuroblastoma. Furthermore, we examine feasibility and safety aspects and discuss future directions for harnessing the advantageous properties of mesenchymal stromal cells for the advancement of therapy success.

Mesenchymal Stromal Cells in Neuroblastoma: Exploring Crosstalk and Therapeutic Implications

Neuroblastoma (NB) is the second most common solid cancer in childhood, accounting for 15% of cancer-related deaths in children. In high-risk NB patients, the majority suffers from metastasis. Despite intensive multimodal treatment, long-term survival remains <40%. The bone marrow (BM) is among the most common sites of distant metastasis in patients with high-risk NB. In this environment, small populations of tumor cells can persist after treatment (minimal residual disease) and induce relapse. Therapy resistance of these residual tumor cells in BM remains a major obstacle for the cure of NB. A detailed understanding of the microenvironment and its role in tumor progression is of utmost importance for improving the treatment efficiency of NB. In BM, mesenchymal stromal cells (MSCs) constitute an important part of the microenvironment, where they support hematopoiesis and modulate immune responses. Their role in tumor progression is not completely understood, especially for NB. Although MSCs have been found to promote epithelial-mesenchymal transition, tumor growth, and metastasis and to induce chemoresistance, some reports point toward a tumor-suppressive effect of MSCs. In this review, we aim to compile current knowledge about the role of MSCs in NB development and progression. We evaluate arguments that depict tumor-supportive versus -suppressive properties of MSCs in the context of NB and give an overview of factors involved in MSC-NB crosstalk. A focus lies on the BM as a metastatic niche, since that is the predominant site for NB metastasis and relapse. Finally, we will present opportunities and challenges for therapeutic targeting of MSCs in the BM microenvironment.

Emerging therapeutic targets for neuroblastoma

INTRODUCTION

Neuroblastoma (NB) is the prime cancer of infancy, and accounts for 9% of pediatric cancer deaths. While children diagnosed with clinically stable NB experience a complete cure, those with high-risk disease (HR-NB) do not recover, despite intensive therapeutic strategies. Development of novel and effective targeted therapies is needed to counter disease progression, and to benefit long-term survival of children with HR-NB.

AREAS COVERED

Recent studies (2017-2020) pertinent to NB evolution are selectively reviewed to recognize novel and effective therapeutic targets. The prospective and promising therapeutic targets/strategies for HR-NB are categorized into (a) targeting oncogene-like and/or reinforcing tumor suppressor (TS)-like lncRNAs; (b) targeting oncogene-like microRNAs (miRs) and/or mimicking TS-miRs; (c) targets for immunotherapy; (d) targeting epithelial-to-mesenchymal transition and cancer stem cells; (e) novel and beneficial combination approaches; and (f) repurposing drugs and other strategies in development.

EXPERT OPINION

It is highly unlikely that agents targeting a single candidate or signaling will be beneficial for an HR-NB cure. We must develop efficient drug deliverables for functional targets, which could be integrated and advance clinical therapy. Fittingly, the looming evidence indicated an aggressive evolution of promising novel and integrative targets, development of efficient drugs, and improvised strategies for HR-NB treatment.