Monitoring the growth effect of xenotransplanted human medulloblastoma in an immunocompromised mouse model using in vitro and ex vivo green fluorescent protein imaging

Enhanced antioxidant capacity of dental pulp-derived iPSC-differentiated hepatocytes and liver regeneration by injectable HGF-releasing hydrogel in fulminant hepatic failure

Acute hepatic failure (AHF) is a severe liver injury leading to sustained damage and complications. Induced pluripotent stem cells (iPSCs) may be an alternative option for the treatment of AHF. In this study, we reprogrammed human dental pulp-derived fibroblasts into iPSCs, which exhibited pluripotency and the capacity to differentiate into tridermal lineages, including hepatocyte-like cells (iPSC-Heps). These iPSC-Heps resembled human embryonic stem cell-derived hepatocyte-like cells in gene signature and hepatic markers/functions. To improve iPSC-Heps engraftment, we next developed an injectable carboxymethyl-hexanoyl chitosan hydrogel (CHC) with sustained hepatocyte growth factor (HGF) release (HGF-CHC) and investigated the hepatoprotective activity of HGF-CHC-delivered iPSC-Heps in vitro and in an immunocompromised AHF mouse model induced by thioacetamide (TAA). Intrahepatic delivery of HGF-CHC-iPSC-Heps reduced the TAA-induced hepatic necrotic area and rescued liver function and recipient viability. Compared with PBS-delivered iPSC-Heps, the HGF-CHC-delivered iPSC-Heps exhibited higher antioxidant and antiapoptotic activities that reduced hepatic necrotic area. Importantly, these HGF-CHC-mediated responses could be abolished by administering anti-HGF neutralizing antibodies. In conclusion, our findings demonstrated that HGF mediated the enhancement of iPSC-Hep antioxidant/antiapoptotic capacities and hepatoprotection and that HGF-CHC is as an excellent vehicle for iPSC-Hep engraftment in iPSC-based therapy against AHF.

Reprogramming induced pluripotent stem cells in the absence of c-Myc for differentiation into hepatocyte-like cells

Induced pluripotent stem cells (iPSCs) with four reprogramming factors (Oct-4/Sox2/Klf-4/c-Myc) have been shown to differentiate into hepatic lineages. However, it was unclear whether obviation of the c-Myc oncogene in iPSCs affected hepatic differentiation or inhibited in vivo tumor formation. In this study, we demonstrated that iPSCs without c-Myc had the capacity to differentiate into hepatocyte-like cells (iPSC-Heps) with biological functions. As detected using planar-radionuclide imaging and Hoechst labeling assays, these iPSCs and iPSC-Heps tended to mobilize to the injured liver area in thioacetamide (TAA)-treated mice. Intravenous transplantation of both iPSCs and iPSC-Heps but not mouse embryonic fibroblasts (MEFs) reduced the hepatic necrotic area, improved liver functions, and rescued TAA-treated mice from lethal acute hepatic failure (AHF). In addition, microarray-based bioinformatics and quantitative RT-PCR showed high expression of antioxidant genes in iPSCs and iPSC-Heps compared to MEFs. In vivo and in vitro studies of NAC pretreatment confirmed that iPSCs and iPSC-Heps potentially suppressed ROS production and activated antioxidant enzymes in TAA-injured livers. Six months after transplantation in TAA-treated mice, tumor formation was not seen in non-c-Myc iPSC grafts. Therefore, reprogramming adult somatic cells without c-Myc may prevent oxidative stress-induced damage and provide a safer alternative for hepatic regeneration in AHF.

Celecoxib and radioresistant glioblastoma-derived CD133+ cells: improvement in radiotherapeutic effects. Laboratory investigation

OBJECT

Glioblastoma, the most common primary brain tumor, has a poor prognosis, even with aggressive resection and chemoradiotherapy. Recent studies indicate that CD133(+) cells play a key role in radioresistance and recurrence of glioblastoma. Cyclooxygenase-2 (COX-2), which converts arachidonic acid to prostaglandins, is over-expressed in a variety of tumors, including CD133(+) glioblastomas. The COX-2-derived prostaglandins promote neovascularization during tumor development, and conventional radiotherapy increases the proportion of CD133(+) cells rather than eradicating them. The aim of the present study was to investigate the role of celecoxib, a selective COX-2 inhibitor, in enhancing the therapeutic effects of radiation on CD133(+) glioblastomas.

METHODS

Cells positive for CD133 were isolated from glioblastoma specimens and characterized by flow cytometry, then treated with celecoxib and/or ionizing radiation (IR). Clonogenic assay, cell irradiation, cell cycle analysis, Western blot, and xenotransplantation were used to assess the effects of celecoxib alone, IR alone, and IR with celecoxib on CD133(+) and CD133(-) glioblastoma cells. Three separate xenotransplantation experiments were carried out using 310 severe combined immunodeficient (SCID) mice: 1) an initial tumorigenicity evaluation in which 3 different quantities of untreated CD133(-) cells or untreated or pretreated CD133(+) cells (5 treatment conditions) from 7 different tumors were injected into the striatum of 2 mice (210 mice total); 2) a tumor growth study (50 mice); and 3) a survival study (50 mice). For these last 2 studies the same 5 categories of cells were used as in the tumorigenicity (untreated CD133(-) cells, untreated or pretreated CD133(+) cells, with pretreatment consisting of celecoxib alone, IR alone, or IR and celecoxib), but only 1 cell source (Case 2) and quantity (5 × 10(4) cells) were used.

RESULTS

High levels of COX-2 protein were detected in the CD133(+) but not the CD133(-) glioblastoma cells. The authors further demonstrated that 30 μM celecoxib was able to effectively enhance the IR effect in inhibiting colony formation and increasing IR-mediated apoptosis in celecoxib-treated CD133(+) glioblastoma cells. Furthermore, reduction in radioresistance was correlated with the induction of G2/M arrest, which was partially mediated through the increase in the level of phosphorylated-cdc2. In vivo xenotransplant analysis further confirmed that CD133(+)-associated tumorigenicity was significantly suppressed by celecoxib treatment. Importantly, pretreatment of CD133(+) glioblastoma cells with a combination of celecoxib and IR before injection into the striatum of SCID mice resulted in a statistically significant reduction in tumor growth and a statistically significant increase in the mean survival rate of the mice.

CONCLUSIONS

Celecoxib combined with radiation plays a critical role in the suppression of growth of CD133(+) glioblastoma stemlike cells. Celecoxib is therefore a radiosensitizing drug for clinical application in glioblastoma.

Celecoxib enhances radiosensitivity in medulloblastoma-derived CD133-positive cells

OBJECTS

Cyclooxygenase-2 (COX-2), the enzyme that converts arachidonic acid to prostaglandins, is overexpressed in a variety of tumors, including medulloblastoma (MB). CD133, a transmembrane glycoprotein, has been suggested as a marker for cancer stem cells in brain tumors. The aim of the present study was to investigate the role of celecoxib, a selective COX-2 inhibitor, in enhancing the effects of ionizing radiotherapy (IR) on medulloblastoma-derived CD133-positive cells (MB-CD133(+)).

MATERIALS AND METHODS

MB-CD133(+) were isolated from two medulloblastoma cell lines (Daoy and UW228). Then, they were treated with celecoxib in different concentrations, and cell viability was assessed. The assays of cell survival, soft agar, radiosensitivity, colony formation, and apoptotic activity in MB-CD133(+) treated with celecoxib alone, radiation alone, or celecoxib combined with radiation were further evaluated.

RESULTS

MB-CD133(+) showed the self-renew ability to form sphere bodies in vitro and regenerate tumors in vivo. The levels of COX-2 mRNA and protein in MB-CD133(+) were significantly higher than those in MB-CD133(-). The treatment of 30 μM celecoxib could effectively inhibit the abilities of cell proliferation and colony formation and increase IR-induced apoptosis in treated MB-CD133(+). Furthermore, in vivo study demonstrated that celecoxib significantly enhanced radiosensitivity in MB-CD133(+)-transplanted grafts. Notably, xenotransplantation analysis demonstrated that the treatment of celecoxib could further suppress the expressions of angiogenic and stemness-related genes in treated MB-CD133(+) grafts of SCID mice.

CONCLUSIONS

Celecoxib presents the potential of radiosensitizing effect in MB-derived cancer stem cells. Therefore, it should be warranted in future trials to enhance the radiotherapeutic effects in MB patients.

Caffeic acid phenethyl ester preferentially enhanced radiosensitizing and increased oxidative stress in medulloblastoma cell line

OBJECTIVES

Caffeic acid phenethyl ester (CAPE), an active component of propolis, was recently reported to have radiosensitizing effects on medulloblastoma (MB) cells. However, the mechanisms of radiosensitivity involved in medulloblastoma cells are still unclear. The specific aim of this study was to investigate the role of CAPE-induced oxidative stress to influence of radiosensitivity and anti-proliferative effects in medulloblastoma cells.

MATERIALS AND METHODS

Medulloblastoma (Daoy) cells were treated with CAPE in different concentrations and assessed for cell viability. The following were also evaluated: migratory ability, reduced glutathione (GSH) level, reactive oxygen species (ROS) level, nuclear factor-kappaB (NF-kappaB) activity, and apoptosis in CAPE alone, radiation alone, or radiation combined with CAPE in Daoy cells.

RESULTS

The results indicated that CAPE inhibited the growth of Daoy cells. CAPE treatment in Daoy cells could effectively decrease glutathione reductase and significantly increase glutathione peroxidase. Radiation-activated NF-kappaB was reversed by CAPE pretreatment. Finally, the result of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay showed that CAPE treatment can enhance radiation-induced apoptosis in Daoy cells.

CONCLUSIONS

Our study demonstrated the anti-proliferative and radiosensitizing effects of CAPE on MB cells, which may be achievable through depleting GSH, increased ROS activity, and inhibiting NF-kappaB activity.