MRI T2 and T2* relaxometry to visualize neuromelanin in the dorsal substantia nigra pars compacta.

Visualizing gradual changes in neuromelanin distribution within the substantia nigra is an important metric used to monitor the progression of Parkinsonism. This study aimed to identify the origin of the mismatch region between magnetic resonance transverse relaxation times (T2 and T2*) in the substantia nigra and investigate its feasibility and implications for in vivo detection of neuromelanin as a clinical biomarker. The relationships between neuromelanin distribution assessed by histological staining and the area of T2 and T2* mismatch determined by high- and low-resolution magnetic resonance relaxometry at 7T were directly compared in two normal and one depigmented substantia nigra collected at postmortem. In vivo feasibility of assessing T2 and T2* mismatch, clinically, was investigated using 3T magnetic resonance imaging. In the normal postmortem substantia nigra tissue, the T2 and T2* mismatch region exhibiting a linear pattern was strongly colocalized with neuromelanin distribution along the dorsal substantia nigra pars compacta, but a negligible amount of dorsal mismatch was observed in the depigmented brain. The regions of T2 and T2* mismatch from MRI, neuromelanin pigments from histology, and elevated iron signals from mass spectrometry were spatially overlapped for a normal postmortem brain. In preliminary in vivo studies, a similar, linear T2 and T2* mismatch region was observed in the dorsal area of the substantia nigra in eight normal subjects; this mismatch was significantly obscured in eight Parkinson's disease patients. The length of the dorsal linear mismatch line based on the T2*-T2 mask was significantly shorter in the Parkinson's disease patients compared to normal controls; this result was corroborated by reduced striatal uptake of [18F] FP-CIT dopamine transporters assessed by positron emission tomography scans. In conclusion, the measurement of T2 and T2* mismatch could serve as a complementary imaging biomarker to visualize the dorsal region of the substantia nigra pars compacta, which contains large amounts of neuromelanin.

Impact of video feedback system on medical students' perception of their clinical performance assessment.

BACKGROUND: Providing feedback on student performance in the clinical performance assessment (CPA) is meaningful in that it helps students understand their strengths and weaknesses. This study compared students' perception of their CPA scores before and after providing personalized video feedback. METHODS: Two identical online surveys of Year 1 medical students (N = 103) that had undergone CPA were conducted to evaluate students' perceptions about their CPA scores before and after video feedback. Students were given their test scores with assessment analysis reports immediately after completing the CPA. Top-scored students from each station agreed to provide their video-recorded performance to the rest of the students. RESULTS: After comparing their performance video and top-scored video at each station, medical students were more aware of their CPA total score, clinical performance examination (CPX) total score, score of each CPX station, section score for the CPX station, history taking section score, physical examination section score, and doctor-patient relationship section score. Moreover, students became more convinced of their own weaknesses from their history taking and patient education section after viewing video feedback than before. CONCLUSION: The use of the video feedback system might help students recognize their CPA results and identify their strengths and weaknesses.

Holistic rubric vs. analytic rubric for measuring clinical performance levels in medical students.

BACKGROUND: Task-specific checklists, holistic rubrics, and analytic rubrics are often used for performance assessments. We examined what factors evaluators consider important in holistic scoring of clinical performance assessment, and compared the usefulness of applying holistic and analytic rubrics respectively, and analytic rubrics in addition to task-specific checklists based on traditional standards. METHODS: We compared the usefulness of a holistic rubric versus an analytic rubric in effectively measuring the clinical skill performances of 126 third-year medical students who participated in a clinical performance assessment conducted by Pusan National University School of Medicine. We conducted a questionnaire survey of 37 evaluators who used all three evaluation methods-holistic rubric, analytic rubric, and task-specific checklist-for each student. The relationship between the scores on the three evaluation methods was analyzed using Pearson's correlation. Inter-rater agreement was analyzed by Kappa index. The effect of holistic and analytic rubric scores on the task-specific checklist score was analyzed using multiple regression analysis. RESULTS: Evaluators perceived accuracy and proficiency to be major factors in objective structured clinical examinations evaluation, and history taking and physical examination to be major factors in clinical performance examinations evaluation. Holistic rubric scores were highly related to the scores of the task-specific checklist and analytic rubric. Relatively low agreement was found in clinical performance examinations compared to objective structured clinical examinations. Meanwhile, the holistic and analytic rubric scores explained 59.1% of the task-specific checklist score in objective structured clinical examinations and 51.6% in clinical performance examinations. CONCLUSION: The results show the usefulness of holistic and analytic rubrics in clinical performance assessment, which can be used in conjunction with task-specific checklists for more efficient evaluation.

Co-targeting of Tiam1/Rac1 and Notch ameliorates chemoresistance against doxorubicin in a biomimetic 3D lymphoma model.

Lymphoma is a heterogeneous disease with a highly variable clinical course and prognosis. Improving the prognosis for patients with relapsed and treatment-resistant lymphoma remains challenging. Current in vitro drug testing models based on 2D cell culture lack natural tissue-like structural organization and result in disappointing clinical outcomes. The development of efficient drug testing models using 3D cell culture that more accurately reflects in vivo behaviors is vital. Our aim was to establish an in vitro 3D lymphoma model that can imitate the in vivo 3D lymphoma microenvironment. Using this model, we explored strategies to enhance chemosensitivity to doxorubicin, an important chemotherapeutic drug widely used for the treatment of hematological malignancies. Lymphoma cells grown in this model exhibited excellent biomimetic properties compared to conventional 2D culture including (1) enhanced chemotherapy resistance, (2) suppressed rate of apoptosis, (3) upregulated expression of drug resistance genes (MDR1, MRP1, BCRP and HIF-1α), (4) elevated levels of tumor aggressiveness factors including Notch (Notch-1, -2, -3, and -4) and its downstream molecules (Hes-1 and Hey-1), VEGF and MMPs (MMP-2 and MMP-9), and (5) enrichment of a lymphoma stem cell population. Tiam1, a potential biomarker of tumor progression, metastasis, and chemoresistance, was activated in our 3D lymphoma model. Remarkably, we identified two synergistic therapeutic oncotargets, Tiam1 and Notch, as a strategy to combat resistance against doxorubicin in EL4 T and A20 B lymphoma. Therefore, our data suggest that our 3D lymphoma model is a promising in vitro research platform for studying lymphoma biology and therapeutic approaches.

Specific visualization of neuromelanin-iron complex and ferric iron in the human post-mortem substantia nigra using MR relaxometry at 7T.

Neuromelanin (NM) is an endogenous iron chelating molecule of pigmented neurons in the human substantia nigra (SN). Along with the increase in iron deposition, the reduction in NM-containing dopaminergic neurons and the variation of iron load on NM are generally considered to be important factors participating to pathogenesis of Parkinson's disease (PD). The aim of this study was to non-invasively delineate the spatial distributions of paramagnetic magnetic susceptibility perturbers, such as NM-iron complex and ferric iron in SN. Multiple quantitative MR parameters of T1, T2, T2*, susceptibility weighted image (SWI), quantitative susceptibility map (QSM), and T1 weighted image with magnetization transfer (MT) effects were acquired for six post-mortem SN samples without a history of neurological disease. Co-registered quantitative histological validations were performed to identify and correlate NM pigments, iron deposits, and myelin distributions with respect to associated MR parameters. The regions with NM pigments and iron deposits showed positive magnetic susceptibility (paramagnetic) values, while myelinated areas showed negative magnetic susceptibility (diamagnetic) values from the QSM. The region of reduced T2 values in SN mostly coincided with high iron deposits, but not necessarily with the NM pigments. The correlations between T2*/T2 (or T2*/T22) values and NM pigments were higher than those between T2* values and NM pigments, due to the effective size differences between NM-iron complex and ferric iron. Consequently, separate segmentations of ferric iron from the T2 map and NM-iron complex from the T2*/T2 map (or T2*/T22 map) were possible with the boundary of the SN determined from the T1 weighted image.

Pathologic Correlation of Paramagnetic White Matter Lesions in Adult-Onset Leukoencephalopathy With Axonal Spheroids and Pigmented Glia.

It has been proposed that susceptibility-weighted imaging is a sensitive magnetic resonance imaging (MRI) technique for identifying white matter (WM) pathologic changes involving demyelination and iron accumulation. We identified the tree silhouette-like configuration with a paramagnetic phase shift in the frontal subcortical WM lesions of 4 patients with adult-onset leukoencephalopathy with axonal spheroids and pigmented glia who underwent 3T MRI. According to our postmortem 7T MRI and histologic correlation study to investigate the origin of the susceptibility-related phase contrast, changes in the subcortical WM architecture and central WM loss with the relative preservation of iron-rich U-fibers may contribute to the paramagnetic susceptibility.

Fish Scale Collagen Peptides Protect against CoCl2/TNF-α-Induced Cytotoxicity and Inflammation via Inhibition of ROS, MAPK, and NF-κB Pathways in HaCaT Cells.

Skin diseases associated with inflammation or oxidative stress represent the most common problem in dermatology. The present study demonstrates that fish scale collagen peptides (FSCP) protect against CoCl2-induced cytotoxicity and TNF-α-induced inflammatory responses in human HaCaT keratinocyte cells. Our study is the first to report that FSCP increase cell viability and ameliorate oxidative injury in HaCaT cells through mechanisms mediated by the downregulation of key proinflammatory cytokines, namely, TNF-α, IL-1ß, IL-8, and iNOS. FSCP also prevent cell apoptosis by repressing Bax expression, caspase-3 activity, and cytochrome c release and by upregulating Bcl-2 protein levels in CoCl2- or TNF-α-stimulated HaCaT cells. In addition, the inhibitory effects of FSCP on cytotoxicity and the induction of proinflammatory cytokine expression were found to be associated with suppression of the ROS, MAPK (p38/MAPK, ERK, and JNK), and NF-κB signaling pathways. Taken together, our data suggest that FSCP are useful as immunomodulatory agents in inflammatory or immune-mediated skin diseases. Furthermore, our results provide new insights into the potential therapeutic use of FSCP in the prevention and treatment of various oxidative- or inflammatory stress-related inflammation and injuries.

IL-7 Induces an Epitope Masking of γc Protein in IL-7 Receptor Signaling Complex.

IL-7 signaling via IL-7Rα and common γ-chain (γc) is necessary for the development and homeostasis of T cells. Although the delicate mechanism in which IL-7Rα downregulation allows the homeostasis of T cell with limited IL-7 has been well known, the exact mechanism behind the interaction between IL-7Rα and γc in the absence or presence of IL-7 remains unclear. Additionally, we are still uncertain as to how only IL-7Rα is separately downregulated by the binding of IL-7 from the IL-7Rα/γc complex. We demonstrate here that 4G3, TUGm2, and 3E12 epitope masking of γc protein are induced in the presence of IL-7, indicating that the epitope alteration is induced by IL-7 binding to the preassembled receptor core. Moreover, the epitope masking of γc protein is inversely correlated with the expression of IL-7Rα upon IL-7 binding, implying that the structural alteration of γc might be involved in the regulation of IL-7Rα expression. The conformational change in γc upon IL-7 binding may contribute not only to forming the functional IL-7 signaling complex but also to optimally regulating the expression of IL-7Rα.

The Neuromelanin-related T2* Contrast in Postmortem Human Substantia Nigra with 7T MRI.

High field magnetic resonance imaging (MRI)-based delineation of the substantia nigra (SN) and visualization of its inner cellular organization are promising methods for the evaluation of morphological changes associated with neurodegenerative diseases; however, corresponding MR contrasts must be matched and validated with quantitative histological information. Slices from two postmortem SN samples were imaged with a 7 Tesla (7T) MRI with T1 and T2* imaging protocols and then stained with Perl's Prussian blue, Kluver-Barrera, tyrosine hydroxylase, and calbindin immunohistochemistry in a serial manner. The association between T2* values and quantitative histology was investigated with a co-registration method that accounts for histology slice preparation. The ventral T2* hypointense layers between the SNr and the crus cerebri extended anteriorly to the posterior part of the crus cerebri, which demonstrates the difficulty with an MRI-based delineation of the SN. We found that the paramagnetic hypointense areas within the dorsolateral SN corresponded to clusters of neuromelanin (NM). These NM-rich zones were distinct from the hypointense ventromedial regions with high iron pigments. Nigral T2* imaging at 7T can reflect the density of NM-containing neurons as the metal-bound NM macromolecules may decrease T2* values and cause hypointense signalling in T2* imaging at 7T.

Effects of micro- and subtle-expression reading skill training in medical students: A randomized trial.

OBJECTIVE: to investigate the effectiveness of the Micro Expression Training Tool (METT) and the Subtle Expression Training Tool (SETT) to help improve the non-verbal communication skills of medical students. METHODS: In a randomized controlled trial, all participants were randomly allocated to either a training (n=41) or control group (n=41) and were pre-tested before education with METT and SETT at baseline. Then, training students took second tests after a 1-h class about interpreting micro and subtle expressions and control students took the second tests without the class. RESULTS: METT pre-test scores were positively related with female gender, agreeableness, whereas SETT pre-test scores were negatively related with age and positively related with female gender. Mean METT score increases of 29.3% and mean SETT score increases of 36.2% were observed after training, whereas the control group achieved only a mean METT score increase of 11.0% at second testing. Increases in both test scores in the training group were significantly higher than in the control group. CONCLUSION: METT and SETT are effective, simple tools for improving the micro- and subtle-expression reading skills of medical students. PRACTICE IMPLICATIONS: METT and SETT can be effective for improving the non-verbal communication skills of medical students.

Epidermal growth factor-like domain 8 inhibits the survival and proliferation of mouse thymocytes.

Thymic epithelial cells (TECs) play a critical role in T-cell development through their intercellular interactions and by producing various soluble proteins, such as growth factors, cytokines and chemokines. In this study, we report a new role for epidermal growth factor-like domain 8 (EGFL8) in the regulation of the survival and proliferation of mouse thymocytes. Mouse recombinant EGFL8 (rEGFL8) protein was produced using an E. coli system and its biological role in mouse thymocytes was determined. The injection of rEGFL8 in mice in vivo resulted in a decrease in the weight of the thymus, as well as in the number of total thymocytes; rEGFL8 also inhibited thymocyte proliferation and induced thymocyte apoptosis. Furthermore, rEGFL8 suppressed the expression of the Notch downstream targets, Hes1 and Hey1, in mouse thymocytes and TECs, indicating that EGFL8 negatively regulates the Notch signaling pathway in these cells. The identification of the role of EGFL8 in thymocytes may aid in the determination of the fate of thymocytes during T-cell development.

Hexane extract of aged black garlic reduces cell proliferation and attenuates the expression of ICAM-1 and VCAM­1 in TNF-α-activated human endometrial stromal cells.

Increasing evidence indicates the potentially crucial roles of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in the pathological process underlying endometriosis. The present study aimed to investigate the effects of a hexane extract of aged black garlic (HEABG) on the proliferation and expression of ICAM-1 and VCAM-1 in tumor necrosis factor-α (TNF-α)-activated human endometrial stromal cells (HESCs) isolated from patients with endometriosis. HESCs were isolated from endometriotic tissues obtained from women with advanced endometriosis who underwent laparoscopic surgery for ovarian endometrioma (n=18). Cell proliferation and cell cycle analysis were assessed by WST-1 assay and flow cytometry, respectively. The expression of ICAM-1 and VCAM-1 was measured by flow cytometry, immunofluorescence staining, immunoblotting and quantitative reverse transcriptase-PCR. The secretion of interleukin-6 (IL-6) was determined by enzyme-linked immunosorbent assay (ELISA). The activation of nuclear factor-κB (NF-κB) and activator protein-1 (AP-1) was detected by electrophoretic mobility shift assay (EMSA) and the activation of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and p38 MAPK was analyzed by immunoblotting. Cell proliferation and cell cycle progression were significantly suppressed by HEABG in the TNF-α-induced HESCs through the inhibition of the ERK and JNK signaling pathways. Remarkably, the treatment of the HESCs with HEABG potently suppressed the TNF-α-induced ICAM-1 and VCAM-1 transcript and protein expression by inhibiting the activation of NF-κB and AP-1 transcription factors. Our results suggest that HEABG may be effective in the prevention and treatment of endometriosis in humans.

Regulatory role of mouse epidermal growth factor-like protein 8 in thymic epithelial cells.

Unlike epidermal growth factor-like protein 7 (EGFL7), which is a secreted protein implicated in the regulation of blood vessel formation and cell migration, little is known about the physiological function of EGFL8. Thymic epithelial cells (TECs) play a pivotal role in T-cell development by regulating cellular interactions and expression of growth factors, cytokines, and chemokines. In order to investigate the functional role of EGFL8 in TECs, we transfected TECs with an EGFL8-expressing vector to overexpress EGFL8 protein and with an EGFL8 siRNA to knockdown EGFL8 expression. EGFL8-silenced TECs showed significant increase in the number of adherent thymocytes by enhancing the expression of intercellular adhesion molecule-1 (ICAM-1), while the overexpression of EGFL8 inhibited the adherence of TECs to thymocytes by suppressing ICAM-1 expression. Furthermore, in vitro co-culture study revealed that knockdown of EGFL8 facilitated the maturation of thymocytes to CD4(+) and CD8(+) single-positive populations. These regulatory effects of EGFL8 in T-cell development were further confirmed by the results that knockdown of EGFL8 enhanced the expression of genes involved in thymopoiesis, such as interleukin-7 (IL-7), granulocyte/macrophage-colony stimulating factor (GM-CSF), and thymus-expressed chemokine (TECK). Our data show that EGFL8 exerts inhibitory effects on TECs and thymocytes, suggesting that EGFL8 acts as a negative regulatory molecule in the development of T cells in the mouse thymus.

LAP2 is widely overexpressed in diverse digestive tract cancers and regulates motility of cancer cells.

BACKGROUND: Lamina-associated polypeptides 2 (LAP2) is a nuclear protein that connects the nuclear lamina with chromatin. Although its critical roles in genetic disorders and hematopoietic malignancies have been described, its expression and roles in digestive tract cancers have been poorly characterized. METHODS: To examine the expression of LAP2 in patient tissues, we performed immunohistochemistry and real-time PCR. To examine motility of cancer cells, we employed Boyden chamber, wound healing and Matrigel invasion assays. To reveal its roles in metastasis in vivo, we used a liver metastasis xenograft model. To investigate the underlying mechanism, a cDNA microarray was conducted. RESULTS: Immunohistochemistry in patient tissues showed widespread expression of LAP2 in diverse digestive tract cancers including stomach, pancreas, liver, and bile duct cancers. Real-time PCR confirmed that LAP2ß is over-expressed in gastric cancer tissues. Knockdown of LAP2ß did not affect proliferation of most digestive tract cancer cells except pancreatic cancer cells. However, knockdown of LAP2ß decreased motility of all tested cancer cells. Moreover, overexpression of LAP2ß increased motility of gastric and pancreatic cancer cells. In the liver metastasis xenograft model, LAP2ß increased metastatic efficacy of gastric cancer cells and mortality in tested mice. cDNA microarrays showed the possibility that myristoylated alanine-rich C kinase substrate (MARCKS) and interleukin6 (IL6) may mediate LAP2ß-regulated motility of cancer cells. CONCLUSIONS: From the above results, we conclude that LAP2 is widely overexpressed in diverse digestive tract cancers and LAP2ß regulates motility of cancer cells and suggest that LAP2ß may have utility for diagnostics and therapeutics in digestive tract cancers.

Analysis of questioning technique during classes in medical education.

BACKGROUND: Questioning is one of the essential techniques used by lecturers to make lectures more interactive and effective. This study surveyed the perception of questioning techniques by medical school faculty members and analyzed how the questioning technique is used in actual classes. METHODS: Data on the perceptions of the questioning skills used during lectures was collected using a self-questionnaire for faculty members (N = 33) during the second semester of 2008. The questionnaire consisted of 18 items covering the awareness and characteristics of questioning skills. Recorded video tapes were used to observe the faculty members' questioning skills. RESULTS: Most faculty members regarded the questioning technique during classes as being important and expected positive outcomes in terms of the students' participation in class, concentration in class and understanding of the class contents. In the 99 classes analyzed, the median number of questions per class was 1 (0-29). Among them, 40 classes (40.4 %) did not use questioning techniques. The frequency of questioning per lecture was similar regardless of the faculty members' perception. On the other hand, the faculty members perceived that their usual wait time after question was approximately 10 seconds compared to only 2.5 seconds measured from video analysis. More lecture-experienced faculty members tended to ask more questions in class. CONCLUSIONS: There were some discrepancies regarding the questioning technique between the faculty members' perceptions and reality, even though they had positive opinions of the technique. The questioning skills during a lecture need to be emphasized to faculty members.

Acute effects of capsaicin on proopioimelanocortin mRNA levels in the arcuate nucleus of Sprague-Dawley rats.

OBJECTIVE: Capsaicin, a noxious stimulant and main component of the hot flavor of red peppers, has an analgesic effect when administered to humans. We investigated the expression of proopioimelanocortin (POMC) mRNA in the arcuate nucleus of Sprague-Dawley (SD) rats after administering capsaicin, hypothesizing that administering capsaicin activates the central opioid system. METHODS: SD rats were divided randomly into two groups; one group received a saline injection and the other received a capsaicin injection. The POMC mRNA level in the arcuate nucleus of the hypothalamus was measured by the reverse transcription-polymerase chain reaction at 0, 20, 40, 60, and 120 minutes after capsaicin administration. RESULTS: Capsaicin administration resulted in a significantly increased POMC mRNA level, compared to that in saline-treated rats at the 20-minute time point (t=-4.445, p=0.001). However, no significant group differences were observed at other times (t=-1.886, p=0.089; t= -0.973, p=0.353; t=-2.193, p=0.053 for 40, 60, and 120 minutes, respectively). CONCLUSION: The analgesic effect of capsaicin might be associated with increased activity of the cerebral opioid system. This finding suggests that capsaicin acted for nociception and analgesia and could affect alcohol-intake behavior, which might further imply that a food culture could affect drinking behavior.

Expression and roles of NUPR1 in cholangiocarcinoma cells.

Nuclear protein-1 (NUPR1) is a small nuclear protein that is responsive to various stress stimuli. Although NUPR1 has been associated with cancer development, its expression and roles in cholangiocarcinoma have not yet been described. In the present study, we found that NUPR1 was over-expressed in human cholangiocarcinoma tissues, using immunohistochemistry. The role of NUPR1 in cholangiocarcinoma was examined by its specific siRNA. NUPR1 siRNA decreased proliferation, migration and invasion of human cholangiocarcinoma cell lines (HuCCT1 and SNU1196 cells). From these results, we conclude that NUPR1 is over-expressed in cholangiocarcinoma and regulates the proliferation and motility of cancer cells.

Vitamin D3 regulates cell viability in gastric cancer and cholangiocarcinoma.

A low serum level of vitamin D has been associated with an increased incidence of gastrointestinal tract cancers. However, the effects of vitamin D3 have not been investigated in gastric cancer and cholangiocarcinoma. In the present study, we found that vitamin D3 treatment significantly suppressed the viability of gastric cancer and cholangiocarcinoma cells. Moreover, vitamin D3 had a synergistic effect with other anti-cancer drugs, such as paclitaxel, adriamycin, and vinblastine, for suppressing cell viability. To determine the underlying mechanism involved in the regulation of viability by vitamin D3, we examined the effects of vitamin D3 on expression of hedgehog signaling target genes, which has been associated with gastric cancer and cholangiocarcinoma. Vitamin D3 treatment decreased the level of mRNA expression of patched1, Gli1, cyclin D1, and Bcl2, suggesting the possibility that vitamin D3 may act through regulation of hedgehog signaling. From the above results, we conclude that vitamin D3 regulates cell viability in gastric cancer and cholangiocarcinoma.

Characterization of the expression of cytokeratins 5, 8, and 14 in mouse thymic epithelial cells during thymus regeneration following acute thymic involution.

The thymus is a central lymphoid organ for T cell development. Thymic epithelial cells (TECs) constitute a major component of the thymic stroma, which provides a specialized microenvironment for survival, proliferation, and differentiation of immature T cells. In this study, subsets of TECs were examined immunohistochemically to investigate their cytokeratin (CK) expression patterns during thymus regeneration following thymic involution induced by cyclophosphamide treatment. The results demonstrated that both normal and regenerating mouse thymuses showed a similar CK expression pattern. The major medullary TECs (mTEC) subset, which is stellate in appearance, exhibited CK5 and CK14 staining, and the minor mTEC subset, which is globular in appearance, exhibited CK8 staining, whereas the vast majority of cortical TECs (cTECs) expressed CK8 during thymus regeneration. Remarkably, the levels of CK5 and CK14 expression were enhanced in mTECs, and CK8 expression was upregulated in cTECs during mouse thymus regeneration after cyclophosphamide-induced acute thymic involution. Of special interest, a relatively high number of CK5(+)CK8(+) TEC progenitors occurred in the thymic cortex during thymus regeneration. Taken together, these findings shed more light on the role of CK5, CK8, and CK14 in the physiology of TECs during mouse thymus regeneration, and on the characterization of TEC progenitors for restoration of the epithelial network and for concomitant regeneration of the adult thymus.

Cancer spheres from gastric cancer patients provide an ideal model system for cancer stem cell research.

Cancer stem cells have been hypothesized to drive the growth and metastasis of tumors. Because they need to be targeted for cancer treatment, they have been isolated from many solid cancers. However, cancer stem cells from primary human gastric cancer tissues have not been isolated as yet. For the isolation, we used two cell surface markers: the epithelial cell adhesion molecule (EpCAM) and CD44. When analyzed by flow cytometry, the EpCAM(+)/CD44(+) population accounts for 4.5% of tumor cells. EpCAM(+)/CD44(+) gastric cancer cells formed tumors in immunocompromised mice; however, EpCAM(-)/CD44(-), EpCAM(+)/CD44(-) and EpCAM(-)/CD44(+) cells failed to do so. Xenografts of EpCAM(+)/CD44(+) gastric cancer cells maintained a differentiated phenotype and reproduced the morphological and phenotypical heterogeneity of the original gastric tumor tissues. The tumorigenic subpopulation was serially passaged for several generations without significant phenotypic alterations. Moreover, EpCAM(+)/CD44(+), but not EpCAM(-)/CD44(-), EpCAM(+)/CD44(-) or EpCAM(-)/CD44(+) cells grew exponentially in vitro as cancer spheres in serum-free medium, maintaining the tumorigenicity. Interestingly, a single cancer stem cell generated a cancer sphere that contained various differentiated cells, supporting multi-potency and self-renewal of a cancer stem cell. EpCAM(+)/CD44(+) cells had greater resistance to anti-cancer drugs than other subpopulation cells. The above in vivo and in vitro results suggest that cancer stem cells, which are enriched in the EpCAM(+)/CD44(+) subpopulation of gastric cancer cells, provide an ideal model system for cancer stem cell research.