Yu-Chih Chen

Oct-4 Expression Maintained Cancer Stem-Like Properties in Lung Cancer-Derived CD133-Positive Cells

CD133 (prominin-1), a 5-transmembrane glycoprotein, has recently been considered to be an important marker that represents the subset population of cancer stem-like cells. Herein we report the isolation of CD133-positive cells (LC-CD133+) and CD133-negative cells (LC-CD133−) from tissue samples of ten patients with non-small cell lung cancer (LC) and five LC cell lines. LC-CD133+ displayed higher Oct-4 expressions with the ability to self-renew and may represent a reservoir with proliferative potential for generating lung cancer cells. Furthermore, LC-CD133+, unlike LC-CD133−, highly co-expressed the multiple drug-resistant marker ABCG2 and showed significant resistance to chemotherapy agents (i.e., cisplatin, etoposide, doxorubicin, and paclitaxel) and radiotherapy. The treatment of Oct-4 siRNA with lentiviral vector can specifically block the capability of LC-CD133+ to form spheres and can further facilitate LC-CD133+ to differentiate into LC-CD133−. In addition, knock-down of Oct-4 expression in LC-CD133+ can significantly inhibit the abilities of tumor invasion and colony formation, and increase apoptotic activities of caspase 3 and poly (ADP-ribose) polymerase (PARP). Finally, in vitro and in vivo studies further confirm that the treatment effect of chemoradiotherapy for LC-CD133+ can be improved by the treatment of Oct-4 siRNA. In conclusion, we demonstrated that Oct-4 expression plays a crucial role in maintaining the self-renewing, cancer stem-like, and chemoradioresistant properties of LC-CD133+. Future research is warranted regarding the up-regulated expression of Oct-4 in LC-CD133+ and malignant lung cancer.

Aldehyde dehydrogenase 1 is a putative marker for cancer stem cells in head and neck squamous cancer

Aldehyde dehydrogenase 1 (ALDH1) has been considered to be a marker for cancer stem cells. However, the role of ALDH1 in head and neck squamous cell carcinoma (HNSCC) has yet to be determined. In this study, we isolated ALDH1-positive cells from HNSCC patients and showed that these HNSCC-ALDH1+ cells displayed radioresistance and represented a reservoir for generating tumors. Based on microarray findings, the results of Western blotting and immunofluorescent assays further confirmed that ALDH1+-lineage cells showed evidence of having epithelial-mesenchymal transition (EMT) shifting and endogenously co-expressed Snail. Furthermore, the knockdown of Snail expression significantly decreased the expression of ALDH1, inhibited cancer stem-like properties, and blocked the tumorigenic abilities of CD44+CD24(-)ALDH1+ cells. Finally, in a xenotransplanted tumorigenicity study, we confirmed that the treatment effect of chemoradiotherapy for ALDH1+ could be improved by Snail siRNA. In summary, it is likely that ALDH1 is a specific marker for the cancer stem-like cells of HNSCC.

Functional Improvement of Focal Cerebral Ischemia Injury by Subdural Transplantation of Induced Pluripotent Stem Cells with Fibrin Glue

Ischemic stroke is the leading cause of disability in the world. Cell transplantation has emerged in various neurological diseases as a potential therapeutic approach in the postacute stroke phase. Recently, inducible pluripotent stem (iPS) cells showed potential for multilineage differentiation and provide a resource for stem cell-based therapies. However, whether iPS transplantation could improve the function of stroke-like model is still an open question. The aim of this study is to investigate the therapeutic effects of subdural transplantation of iPS mixed with fibrin glue (iPS-FG) on cerebral ischemic rats induced by middle cerebral artery occlusion (MCAO). We demonstrated an efficient method to differentiate iPS into astroglial-like and neuron-like cells which display functional electrophysiological properties. In vivo study firstly showed that the direct injection of iPS into damaged areas of rat cortex significantly decreased the infarct size and improved the motor function in rats with MCAO. Furthermore, we found that the subdural iPS-FG can also effectively reduce the total infarct volume and greatly improve the behavior of rats with MCAO to perform rotarod and grasping tasks. Importantly, analysis of cytokine expression in iPS-FG-treated ischemic brains revealed a significant reduction of pro-inflammatory cytokines and an increase of anti-inflammatory cytokines. Taken together, these results suggest that iPS cells could improve the motor function, reduce infarct size, attenuate inflammation cytokines, and mediate neuroprotection after ischemic stroke. Subdural iPS-FG could be considered as a more safe approach because this method can avoid iatrogenic injury to brain parenchyma and enhance recovering from stoke-induced impairment.

Cucurbitacin I suppressed stem-like property and enhanced radiation-induced apoptosis in head and neck squamous carcinoma--derived CD44(+)ALDH1(+) cells.

Head and neck squamous cell carcinoma (HNSCC) is a prevalent cancer worldwide. Signal transducers and activators of transcription 3 (STAT3) signaling is reported to promote tumor malignancy and recurrence in HNSCC. Cucurbitacins, triterpenoid derivatives, are strong STAT3 inhibitors with anticancer properties. Recent studies have shown aldehyde dehydrogenase 1 (ALDH1) to be a marker of cancer stem cells (CSC) in HNSCC. The aim of this study was to investigate the therapeutic effect of cucurbitacin I in HNSCC-derived CSCs. Using immunohistochemical analysis, we firstly showed that CD44, ALDH1, and phosphorylated STAT3 (p-STAT3) were higher in high-grade HNSCCs, and that triple positivity for CD44/ALDH1/p-STAT3 indicated a worse prognosis for HNSCC patients. Secondly, CD44+ALDH1+ cells isolated from seven HNSCC patients showed greater tumorigenicity, radioresistance, and high expression of stemness (Bmi-1/Oct-4/Nanog) and epithelial-mesenchymal-transitional (Snail/Twist) genes as p-STAT3 level increased. Furthermore, we found that cucurbitacin I (JSI-124) can effectively inhibit the expression of p-STAT3 and capacities for tumorigenicity, sphere formation, and radioresistance in HNSCC-CD44+ALDH1+. Notably, 150 nmol/L cucurbitacin I effectively blocked STAT3 signaling and downstream survivin and Bcl-2 expression, and it induced apoptosis in HNSCC-CD44+ALDH1+. Moreover, microarray data indicated that 100 nmol/L cucurbitacin I facilitated CD44+ALDH1+ cells to differentiate into CD44−ALDH1− and enhanced the radiosensitivity of HNSCC-CD44+ALDH1+. Xenotransplant experiments revealed that cucurbitacin I combined with radiotherapy significantly suppressed tumorigenesis and lung metastasis and further improved the survival rate in HNSCC-CD44+ALDH1+-transplanted immunocompromised mice. Taken together, our data show that cucurbitacin I, STAT3 inhibitor, reduces radioresistant, distant-metastatic, and CSC-like properties of HNSCC-CD44+ALDH1+ cells. The potential of cucurbitacin I as a radiosensitizer should be verified in future anti-CSC therapy. Mol Cancer Ther; 9(11); 2879–92. ©2010 AACR.

Inhibition of tumorigenicity and enhancement of radiochemosensitivity in head and neck squamous cell cancer-derived ALDH1-positive cells by knockdown of Bmi-1

Bmi-1, a member of the Polycomb family of transcriptional repressors, is essential for maintaining the self-renewal abilities of adult stem cells. Bmi-1 has been demonstrated to play a role in tumorigenesis in head and neck squamous cell carcinomas (HNSCCs). A recent study has further suggested that ALDH1 may be considered to be a putative marker for HNSCC-derived cancer stem cells. However, the role that Bmi-1 plays in HNSCC-derived ALDH1-positive cells (HNSCC-ALDH1(+)) has yet to be determined. In this study, we demonstrated that HNSCC-ALDH1(+) cells possess tumor initiating properties, are capable of self-renewal, and express higher levels of Bmi-1 as compared to HNSCC-ALDH1(-) cells. To further explore the functional role of Bmi-1 in HNSCC-ALDH1(+) cells, we used a lentiviral vector expressing shRNA to knock down Bmi-1 expression (sh-Bmi-1) in HNSCC-ALDH1(+) cells. Silencing of Bmi-1 significantly enhanced the sensitivity of HNSCC-ALDH1(+) cells to chemoradiation and increased the degree of chemoradiation-mediated apoptosis that occurred. Importantly, knockdown of Bmi-1 increased the effectiveness of radiotherapy and led to the inhibition of tumor growth in nude mice transplanted with HNSCC-ALDH1(+) cells. Kaplan-Meier survival analysis indicated that the mean survival rate of HNSCC-ALDH1(+) tumor-bearing immunocompromised mice treated with radiotherapy was significantly improved by treatment with sh-Bmi-1 as well. In summary, these results suggest that Bmi-1 is a potential target for increasing the sensitivity of HNSCC cancer stem cells to chemoradiotherapy.

A novel in vitro retinal differentiation model by co-culturing adult human bone marrow stem cells with retinal pigmented epithelium cells

Human retinal pigment epithelium (HRPE) cells are important in maintaining the normal physiology within the neurosensory retina and photoreceptors. Recently, transplantation of HRPE has become a possible therapeutic approach for retinal degeneration. By negative immunoselection (CD45 and glycophorin A), in this study, we have isolated and cultivated adult human bone marrow stem cells (BMSCs) with multilineage differentiation potential. After a 2- to 4-week culture under chondrogenic, osteogenic, adipogenic, and hepatogenic induction medium, these BMSCs were found to differentiate into cartilage, bone, adipocyte, and hepatocyte-like cells, respectively. We also showed that these BMSCs could differentiate into neural precursor cells (nestin-positive) and mature neurons (MAP-2 and Tuj1-positive) following treatment of neural selection and induction medium for 1 month. Furthermore, the plasticity of BMSCs was confirmed by initiating their differentiation into retinal cells and photoreceptor lineages by co-culturing with HRPE cells. The latter system provides an ex vivo expansion model of culturing photoreceptors for the treatment of retinal degeneration diseases.

Delivery of Oct4 and SirT1 with cationic polyurethanes-short branch PEI to aged retinal pigment epithelium

Cationic polyurethane, a biodegradable non-viral vector, protects DNA from nuclease degradation and helps to deliver genes efficiently. Oct4, a POU-domain transcription factor, is highly expressed in maintaining pluripotency and cellular reprogramming process in stem cells. SirT1, a NAD-dependent histone deacetylase, is an essential mediator of cellular longevity. Herein we demonstrated that both Oct4 and SirT1 (Oct4/SirT1) expression was decreased in an age-dependent manner in retina with aged-related macular degeneration and retinal pigment epithelium cells (RPEs). To investigate the possible rescuing role of Oct4/SirT1, polyurethane-short branch polyethylenimine (PU-PEI) was used to deliver Oct4/SirT1 into aged RPEs (aRPEs) or light-injured rat retinas. Oct4/SirT1 overexpression increased the expression of several progenitor-related genes and the self-renewal ability of aRPEs. Moreover, Oct4/SirT1 overexpression resulted in the demethylation of the Oct4 promoter and enhanced the expression of antioxidant enzymes, which was accompanied by a decrease in intracellular ROS production and hydrogen peroxide-induced oxidative stress. Importantly, PU-PEI-mediated Oct4/SirT1 gene transfer rescued retinal cell loss and improved electroretinographic responses in light-injured rat retinas. In summary, these data suggest that PU-PEI-mediated delivery of Oct4/SirT1 reprograms aRPEs into a more primitive state and results in cytoprotection by regulating the antioxidative capabilities of these cells.

Targeting Signal Transducer and Activator of Transcription 3 Pathway by Cucurbitacin I Diminishes Self-Renewing and Radiochemoresistant Abilities in Thyroid Cancer-Derived CD133+ Cells

Anaplastic thyroid cancer (ATC) is a lethal solid tumor with poor prognosis because of its invasiveness and its resistance to current therapies. Recently, ATC-CD133+ cells were found to have cancer stem cell (CSC) properties and were suggested to be important contributors to tumorigenicity and cancer metastasis. However, the molecular pathways and therapeutic targets in thyroid cancer-related CSCs remain undetermined. In this study, ATC-CD133+ cells were isolated and found to have increased tumorigenicity, radioresistance, and higher expression of both embryonic stem cell-related and drug resistance-related genes compared with ATC-CD133− cells. Microarray bioinformatics analysis suggested that the signal transducer and activator of transcription 3 (STAT3) pathway could be important in regulating the stemness signature in ATC-CD133+ cells; therefore, the effect of the potent STAT3 inhibitor cucurbitacin I in ATC-CD133+ cells was evaluated in this study. Treatment of ATC-CD133+ cells with cucurbitacin I diminished their CSC-like abilities, inhibited their stemness gene signature, and facilitated their differentiation into ATC-CD133− cells. Of note, treatment of ATC-CD133+ cells with cucurbitacin I up-regulated the expression of thyroid-specific genes and significantly enhanced radioiodine uptake. Furthermore, cucurbitacin I treatment increased the sensitivity of ATC-CD133+ cells to radiation and chemotherapeutic drugs through apoptosis. Finally, xenotransplantation experiments revealed that cucurbitacin I plus radiochemotherapy significantly suppressed tumorigenesis and improved survival in immunocompromised mice into which ATC-CD133+ cells were transplanted. In summary, these results show that the STAT3 pathway plays a key role in mediating CSC properties in ATC-CD133+ cells. Targeting STAT3 with cucurbitacin I in ATC may provide a new approach for therapeutic treatment in the future.

MafA promotes the reprogramming of placenta‐derived multipotent stem cells into pancreatic islets‐like and insulin+ cells

MafA is a pancreatic transcriptional factor that controls β‐cell‐specific transcription of the insulin gene. However, the role of MafA in the regulation of pancreatic transdifferentiation and reprogramming in human stem cells is still unclear. In this study, we investigate the role of MafA in placenta‐derived multipotent stem cells (PDMSCs) that constitutively expressed Oct‐4 and Nanog. PDMSCs were isolated and transfected with MafA using a lentivector. Our results showed that overexpression of MafA in PDMSCs significantly up‐regulated the expression of pancreatic development‐related genes (Sox17, Foxa2, Pdx1 and Ngn3). Microarray analysis suggested that the gene expression profile of MafA‐overexpressing PDMSCs was similar to that of pancreas and islet tissues. MafA increased the expression levels of the mRNAs of NKx2.2, Glut2, insulin, glucagons and somatostatin, and further facilitated the differentiation of PDMSCs into insulin+ cells. The glucose‐stimulated responses to insulin and c‐peptide production in MafA‐overexpressing PDMSCs were significantly higher than in PDMSCs with vector control. Our results indicated that MafA‐overexpressing PDMSCs were more resistant to oxidative damage and oxidative damage‐induced apoptosis than PDMSCs carrying the vector control were. Importantly, the expression of MafA in PDMSCs xenotransplanted into immunocompromised mice improved the restoration of blood insulin levels to control values and greatly prolonged the survival of graft cells in immunocompromised mice with STZ‐induced diabetes. In summary, these data suggest that MafA plays a novel role in the reprogramming of stem cells into pancreatic β‐progenitors, promotes the islet‐like characteristics of PDMSCs, as well as functionally enhances insulin production to restore the regulation of blood glucose levels in transplanted grafts.

SirT1—A Sensor for Monitoring Self-Renewal and Aging Process in Retinal Stem Cells

Retinal stem cells bear potency of proliferation, self-renewal, and differentiation into many retinal cells. Utilizing appropriate sensors one can effectively detect the self-renewal and aging process abilities. Silencing information regulator (SirT1), a member of the sirtuin family, is a NAD-dependent histone deacetylase and an essential mediator for longevity in normal cells by calorie restriction. We firstly investigate the SirT1 mRNA expression in retinal stem cells from rats and 19 human eyes of different ages. Results revealed that SirT1 expression was significantly decreased in in vivo aged eyes, associated with poor self-renewal abilities. Additionally, SirT1 mRNA levels were dose-dependently increased in resveratrol- treated retinal stem cells. The expression of SirT1 on oxidative stress-induced damage was significantly decreased, negatively correlated with the level of intracellular reactive oxygen species production. Treatment with resveratrol could effectively further reduce oxidative stress induced by H2O2 treatment in retinal stem cells. Importantly, the anti-oxidant effects of resveratrol in H2O2-treated retinal stem cells were significantly abolished by knockdown of SirT1 expression (sh-SirT1). SirT1 expression provides a feasible sensor in assessing self-renewal and aging process in retinal stem cells. Resveratrol can prevent reactive oxygen species-induced damages via increased retinal SirT1 expression.