Seung Ah Choi

Human adipose tissue-derived mesenchymal stem cells: Characteristics and therapeutic potential as cellular vehicles for prodrug gene therapy against brainstem gliomas

Human mesenchymal stem cells (hMSCs) have emerged as attractive cellular vehicles for gene therapy against brain malignancy because of their targeted tropism for cancer and the intrinsic attribute of autologous transplantation. We evaluated the characteristics and therapeutic potential of human adipose tissue-derived MSCs (hAT-MSCs) and prodrug gene therapy against diffuse pontine gliomas. The hAT-MSCs were isolated from human adipose tissue and characterised for morphology, surface markers and potential to differentiate into mesenchymal and neuronal lineages. We genetically modified hAT-MSCs to express rabbit carboxylesterase (rCE) enzyme, which can efficiently convert the prodrug CPT-11 (irinotecan-7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin), into the active drug SN-38 (7-ethyl-10-hydroxycamptothecin). The migratory capacity of hAT-MSCs expressing rCE (hAT-MSC.rCE), their ability to convert CPT-11 to SN-38 and cytotoxic effect on F98 cells were evaluated in vitro. The therapeutic potential of hAT-MSC.rCE was confirmed using a rat brainstem glioma model. The hAT-MSCs showed fibroblast-like morphology and expressed hMSC-specific markers including CD73, CD90 and CD105. The hAT-MSCs could differentiate into a mesenchymal lineage and transdifferentiate into a neuronal lineage under optimum culture conditions. The hAT-MSC.rCE converted CPT-11 to SN-38 and preserved the tumour tropism of hAT-MSCs. Brainstem glioma-bearing rats treated with hAT-MSC.rCE and CPT-11 survived 5d more than rats treated with CPT-11 only (p=0.0018). Our study demonstrates that hAT-MSCs can be easily prepared and genetically modified as cellular vehicles for prodrug gene therapy and that they have therapeutic potential against brainstem gliomas.

Therapeutic efficacy and safety of TRAIL- producing human adipose tissue-derived mesenchymal stem cells against experimental brainstem glioma

Mesenchymal stem cells (MSCs) have an extensive migratory capacity for gliomas, which is comparable to that of neural stem cells. Among the various types of MSCs, human adipose tissue-derived MSCs (hAT-MSC) emerge as one of the most attractive vehicles for gene therapy because of their high throughput, lack of ethical concerns, and availability and ease of isolation. We evaluated the therapeutic potential and safety of genetically engineered hAT-MSCs encoding the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) against brainstem gliomas. Human AT-MSCs were isolated from human fat tissue, characterized, and transfected with TRAIL using nucleofector. The therapeutic potential of TRAIL-producing hAT-MSCs (hAT-MSC.TRAIL) was confirmed using in vitro and in vivo studies. The final fate of injected hAT-MSCs was traced in long-survival animals. The characterization of hAT-MSCs revealed the expression of MSC-specific cell-type markers and their differentiation potential into mesenchymal lineage. Short-term outcomes included a 56.3% reduction of tumor volume (P < .001) with increased apoptosis (3.03-fold, P < .05) in animals treated with hAT-MSC.TRAIL compared with the control groups. Long-term outcomes included a significant survival benefit in the hAT-MSC.TRAIL-treated group (26 days of median survival in the control group vs 84 days in the hAT-MSC.TRAIL-treated group, P < .0001), without any evidence of mesenchymal differentiation in vivo. Our study demonstrated the therapeutic efficacy and safety of nonvirally engineered hAT-MSCs against brainstem gliomas and showed the possibility of stem-cell-based targeted gene therapy for clinical application.

Identification of brain tumour initiating cells using the stem cell marker aldehyde dehydrogenase

Aldehyde dehydrogenase (ALDH) has been identified in stem cells from both normal and cancerous tissues. This study aimed to evaluate the potential of ALDH as a universal brain tumour initiating cell (BTIC) marker applicable to primary brain tumours and their biological role in maintaining stem cell status. Cells from various primary brain tumours (24paediatric and 6 adult brain tumours) were stained with Aldefluor and sorted by flow cytometry. We investigated the impact of ALDH expression on BTIC characteristics in vitro and on tumourigenic potential in vivo. Primary brain tumours showed universal expression of ALDH, with 0.3-28.9% of the cells in various tumours identified as ALDH(+). The proportion of CD133(+) cells within ALDH(+) is higher than ALDH cells. ALDH(+) cells generate neurospheres with high proliferative potential, express neural stem cell markers and differentiate into multiple nervous system lineages. ALDH(+) cells tend to show high expression of induced pluripotent stem cell-related genes. Notably, targeted knockdown of ALDH1 by shRNA interference in BTICs potently disturbed their self-renewing ability. After 3months, ALDH(+) cells gave rise to tumours in 93% of mice whereas ALDH cells did not. The characteristic pathology of mice brain tumours from ALDH(+) cells was similar to that of human brain tumours, and these cells are highly proliferative in vivo. Our data suggest that primary brain tumours contain distinct subpopulations of cells that have high expression levels of ALDH and BTIC characteristics. ALDH might be a potential therapeutic target applicable to primary brain tumours.

A distinct subpopulation within CD133 positive brain tumor cells shares characteristics with endothelial progenitor cells.

The cell surface marker CD133 has been proposed as a brain tumor stem cell marker. However, there have been substantial controversies regarding the necessity and role of CD133 in tumorigenesis. This study aimed to characterize CD133(+) cells in brain tumors. Human brain tumor specimens and whole blood were collected from the same patients (N=12). We carried out dual FACS staining for CD133/CD34 and functional tumorigenesis and angiogenesis analyses of CD133(+) cells from different origins. We also investigated the in vivo tumorigenic potential and histological characteristics of four distinct groups on the basis of expression of CD133/CD34 markers (CD133(+), CD133(+)/CD34(+), CD133(+)/CD34(-), and CD133(-)). CD133(+) brain tumor cells coexpressed significantly higher positivity for CD34 (70.7±5.2% in CD133(+) vs. 12.3±4.2% in CD133(-) cells, P<0.001). CD133(+) brain tumor cells formed neurosphere-like spheroids and differentiated into multiple nervous system lineages unlike CD133(+) blood cells. They showed biological characteristics of endothelial cells, including vWF expression, LDL uptake and tube formation in vitro, unlike CD133(-) brain tumors cells. Pathologic analysis of brains implanted with CD133(+) cells showed large, markedly hypervascular tumors with well-demarcated boundary. CD133(+)/CD34(-) cells produced smaller but highly infiltrative tumors. Notably, pure angiogenic cell fractions (CD133(+)/CD34(+)) and CD133(-) tumor cells did not generate tumors in vivo. Our data suggest the presence of a distinct subpopulation of CD133(+) cells isolated from human brain tumors, with characteristics of endothelial progenitor cells (EPCs).

Human Adipose Tissue-Derived Mesenchymal Stem Cells Target Brain Tumor-Initiating Cells.

In neuro-oncology, the biology of neural stem cells (NSCs) has been pursued in two ways: as tumor-initiating cells (TICs) and as a potential cell-based vehicle for gene therapy. NSCs as well as mesenchymal stem cells (MSCs) have been reported to possess tumor tropism capacities. However, there is little data on the migratory capacity of MSCs toward brain tumor-initiating cells (BTICs). This study focuses on the ability of human adipose tissue derived MSCs (hAT-MSCs) to target BTICs and their crosstalk in the microenvironment. BTICs were isolated from three different types of brain tumors. The migration capacities of hAT-MSCs toward BTICs were examined using an in vitro migration assay and in vivo bioluminescence imaging analysis. To investigate the crosstalk between hAT-MSCs and BTICs, we analyzed the mRNA expression patterns of cyto-chemokine receptors by RT-qPCR and the protein level of their ligands in co-cultured medium. The candidate cyto-chemokine receptors were selectively inhibited using siRNAs. Both in vitro and in vivo experiments showed that hAT-MSCs possess migratory abilities to target BTICs isolated from medulloblastoma, atypical teratoid/rhabdoid tumors (AT/RT) and glioblastoma. Different types of cyto-chemokines are involved in the crosstalk between hAT-MSCs and BTICs (medulloblastoma and AT/RT: CXCR4/SDF-1, CCR5/RANTES, IL6R/IL-6 and IL8R/IL8; glioblastoma: CXCR4/SDF-1, IL6R/IL-6, IL8R/IL-8 and IGF1R/IGF-1). Our findings demonstrated the migratory ability of hAT-MSCs for BTICs, implying the potential use of MSCs as a delivery vehicle for gene therapy. This study also confirmed the expression of hAT-MSCs cytokine receptors and the BTIC ligands that play roles in their crosstalk.

Upregulation of SOX2, NOTCH1, and ID1 in supratentorial primitive neuroectodermal tumors: a distinct differentiation pattern from that of medulloblastomas

OBJECT Supratentorial primitive neuroectodermal tumor (PNET) and medulloblastoma are highly malignant embryonal brain tumors. They share morphological similarities, but differ in their differentiation patterns and global gene expression. The authors compared the expression of specific genes involved in neuroglial differentiation in supratentorial PNETs and medulloblastomas to define the distinct characters of these tumors. METHODS The mRNA expression of 8 genes (SOX2, NOTCH1, ID1, ASCL-1, NEUROD1, NEUROG1, NEUROG2, and NRG1) was evaluated in 25 embryonal tumors (12 supratentorial PNETs and 13 medulloblastomas) by quantitative real-time polymerase chain reaction. The expression levels of the transcripts of these genes were compared between the tumor groups. Activation of the JAK/STAT3 pathway was assessed by immunoblotting. Relative expression levels of STAT3 and phosphorylated STAT3 proteins were compared. RESULTS Supratentorial PNETs expressed significantly higher levels of SOX2, NOTCH1, ID1, and ASCL-1 transcripts, whereas the transcription of proneural basic helix-loop-helix factors, NEUROD1, NEUROG1 (significantly), and NEUROG2 (not significantly) was upregulated in medulloblastomas. The proportion of phosphorylated STAT3alpha relative to STAT3alpha was significantly greater in supratentorial PNETs than in medulloblastomas, indicating activation of the JAK/STAT3 pathway in supratentorial PNETs. CONCLUSIONS These results indicate that supratentorial PNET predominantly has glial features and medulloblastoma largely follows a neuronal differentiation pattern. These divergent differentiation patterns may be related to the location and origin of each tumor.

Disulfiram modulates stemness and metabolism of brain tumor initiating cells in atypical teratoid/rhabdoid tumors

BACKGROUND Atypical teratoid/rhabdoid tumors (AT/RT) are among the most malignant pediatric brain tumors. Cells from brain tumors with high aldehyde dehydrogenase (ALDH) activity have a number of characteristics that are similar to brain tumor initiating cells (BTICs). This study aimed to evaluate the therapeutic potential of ALDH inhibition using disulfiram (DSF) against BTICs from AT/RT. METHODS Primary cultured BTICs from AT/RT were stained with Aldefluor and isolated by fluorescence activated cell sorting. The therapeutic effect of DSF against BTICs from AT/RT was confirmed in vitro and in vivo. RESULTS AT/RT cells displayed a high expression of ALDH. DSF demonstrated a more potent cytotoxic effect on ALDH(+) AT/RT cells compared with standard anticancer agents. Notably, treatment with DSF did not have a considerable effect on normal neural stem cells or fibroblasts. DSF significantly inhibited the ALDH enzyme activity of AT/RT cells. DSF decreased self-renewal ability, cell viability, and proliferation potential and induced apoptosis and cell cycle arrest in ALDH(+) AT/RT cells. Importantly, DSF reduced the metabolism of ALDH(+) AT/RT cells by increasing the nicotinamide adenine dinucleotide ratio of NAD(+)/NADH and regulating Silent mating type Information Regulator 2 homolog 1 (SIRT1), nuclear factor-kappaB, Lin28A/B, and miRNA let-7g. Animals in the DSF-treated group demonstrated a reduction of tumor volume (P < .05) and a significant survival benefit (P = .02). CONCLUSION Our study demonstrated the therapeutic potential of DSF against BTICs from AT/RT and suggested the possibility of ALDH inhibition for clinical application.

ID3 contributes to cerebrospinal fluid seeding and poor prognosis in medulloblastoma

BackgroundThe inhibitor of differentiation (ID) genes have been implicated as promoters of tumor progression and metastasis in many human cancers. The current study investigated the expression and functional roles of ID genes in seeding and prognosis of medulloblastoma.MethodsID gene expression was screened in human medulloblastoma tissues. Knockdown of ID3 gene was performed in medulloblastoma cells in vitro. The expression of metastasis-related genes after ID3 knockdown was assessed. The effect of ID3 knockdown on tumor seeding was observed in an animal model in vivo. The survival of medulloblastoma patients was plotted according to the ID3 expression levels.ResultsSignificantly higher ID3 expression was observed in medulloblastoma with cerebrospinal fluid seeding than tumors without seeding. Knockdown of ID3 decreased proliferation, increased apoptosis, and suppressed the migration of D283 medulloblastoma cells in vitro. In a seeding model of medulloblastoma, ID3 knockdown in vivo with shRNA inhibited the growth of primary tumors, prevented the development of leptomeningeal seeding, and prolonged animal survival. High ID3 expression was associated with shorter survival of medulloblastoma patients, especially in Group 4 medulloblastomas.ConclusionsHigh ID3 expression is associated with medullolbastoma seeding and is a poor prognostic factor, especially in patients with Group 4 tumors. ID3 may represent the metastatic/ aggressive phenotype of a subgroup of medulloblastoma.

miR-192 suppresses leptomeningeal dissemination of medulloblastoma by modulating cell proliferation and anchoring through the regulation of DHFR, integrins, and CD47

Background The main cause of death in medulloblastoma is recurrence associated with leptomeningeal dissemination. During this process, the role of microRNAs (miRs) in the acquisition of metastatic phenotype remains poorly understood. This study aimed to identify the miR involved in leptomeningeal dissemination and to elucidate its biological functional mechanisms. Materials and methods We analyzed the miR expression profiles of 29 medulloblastomas according to the presence of cerebrospinal fluid (CSF) seeding. Differentially expressed miRs (DEmiRs) were validated in 29 medulloblastoma tissues and three medulloblastoma cell lines. The biological functions of the selected miRs were evaluated using in vitro and in vivo studies. Results A total of 12 DEmiRs were identified in medulloblastoma with seeding, including miR-192. The reduced expression of miR-192 was confirmed in the tumor seeding group and in the medulloblastoma cells. Overexpression of miR-192 inhibited cellular proliferation by binding DHFR. miR-192 decreased cellular anchoring via the repression of ITGAV, ITGB1, ITGB3, and CD47. Animals in the miR-192-treated group demonstrated a reduction of spinal seeding (P < 0.05) and a significant survival benefit (P < 0.05). Conclusions Medulloblastoma with seeding showed specific DEmiRs compared with those without. miR-192 suppresses leptomeningeal dissemination of medulloblastoma by modulating cell proliferation and anchoring ability.

Genomic analysis reveals secondary glioblastoma after radiotherapy in a subset of recurrent medulloblastomas

Despite great advances in understanding of molecular pathogenesis and achievement of a high cure rate in medulloblastoma, recurrent medulloblastomas are still dismal. Additionally, misidentification of secondary malignancies due to histological ambiguity leads to misdiagnosis and eventually to inappropriate treatment. Nevertheless, the genomic characteristics of recurrent medulloblastomas are poorly understood, largely due to a lack of matched primary and recurrent tumor tissues. We performed a genomic analysis of recurrent tumors from 17 pediatric medulloblastoma patients. Whole transcriptome sequencing revealed that a subset of recurrent tumors initially diagnosed as locally recurrent medulloblastomas are secondary glioblastomas after radiotherapy, showing high similarity to the non-G-CIMP proneural subtype of glioblastoma. Further analysis, including whole exome sequencing, revealed missense mutations or complex gene fusion events in PDGFRA with augmented expression in the secondary glioblastomas after radiotherapy, implicating PDGFRA as a putative driver in the development of secondary glioblastomas after treatment exposure. This result provides insight into the possible application of PDGFRA-targeted therapy in these second malignancies. Furthermore, genomic alterations of TP53 including 17p loss or germline/somatic mutations were also found in most of the secondary glioblastomas after radiotherapy, indicating a crucial role of TP53 alteration in the process. On the other hand, analysis of recurrent medulloblastomas revealed that the most prevalent alterations are the loss of 17p region including TP53 and gain of 7q region containing EZH2 which already exist in primary tumors. The 7q gain events are frequently accompanied by high expression levels of EZH2 in both primary and recurrent medulloblastomas, which provides a clue to a new therapeutic target to prevent recurrence. Considering the fact that it is often challenging to differentiate between recurrent medulloblastomas and secondary glioblastomas after radiotherapy, our findings have major clinical implications both for correct diagnosis and for potential therapeutic interventions in these devastating diseases.