A Lesson from a Measles Outbreak among Healthcare Workers in a Single Hospital in South Korea: The Importance of Knowing the Prevalence of Susceptibility.

BACKGROUND: Despite the high vaccination coverage rate, in-hospital transmission of measles continues to occur in South Korea. We present a measles outbreak in which two healthcare workers (HCWs) with presumptive evidence of measles immunity were infected by a patient with typical measles at a single hospital in South Korea. This facilitated the evaluation of measles seroprevalence in all HCWs. METHODS: In 2018, suspected patients and contacts exposed during a measles outbreak were investigated based on their medical histories and vaccination status. Cases were confirmed by the detection of measles-specific immunoglobulin M or RNA. After the measles outbreak in 2018, measles IgG testing was conducted on a total of 972 HCWs for point-prevalence, including those exposed to the measles. In addition, we have routinely performed measles IgG tests on newly employed HCWs within one week of their hire date since 2019. The measles vaccine was administered to HCWs who tested negative or equivocally negative for IgG antibodies. RESULTS: An index patient who returned from China with fever and rash was diagnosed with measles at a hospital in Korea. Two additional HCWs were revealed as measles cases: one was vaccinated with the two-dose measles-mumps-rubella (MMR) vaccine, and the other, who was born in 1967, was presumed to have immunity from natural infection in South Korea. All three patients harbored the same D8 genotype. No additional measles cases were identified among the 964 contacts of secondary patients. A total of 2310 HCWs, including those tested during the 2018 outbreak, underwent measles IgG tests. The average age at the time of the test was 32.6 years, and 74.3% were female. The overall seropositivity of measles was 88.9% (95% confidence interval, 87.5-90.1). Although the birth cohorts between 1985 and 1994 were presumed to have received the measles-rubella (MR) catch-up vaccination in 2001, 175 (89.3%) HCWs were born after 1985 among the 195 seronegative cases. CONCLUSION: Despite high population immunity, imported measles transmission occurred among HCWs with presumed immunity. This report underscores the importance of understanding the prevalence of measles susceptibility among newly employed HCWs. This is important for policymaking regarding hospital-wide vaccinations to prevent the spread of vaccine-preventable diseases.

Glioblastoma-educated mesenchymal stem-like cells promote glioblastoma infiltration via extracellular matrix remodelling in the tumour microenvironment.

BACKGROUND: The biological function of mesenchymal stem-like cells (MSLCs), a type of stromal cells, in the regulation of the tumour microenvironment is unclear. Here, we investigated the molecular mechanisms underlying extracellular matrix (ECM) remodelling and crosstalk between MSLCs and glioblastomas (GBMs) in tumour progression. METHODS: In vitro and in vivo co-culture systems were used to analyze ECM remodelling and GBM infiltration. In addition, clinical databases, samples from patients with GBM and a xenografted mouse model of GBM were used. RESULTS: Previous studies have shown that the survival of patients with GBM from whom MSLCs could be isolated is substantially shorter than that of patients from whom MSLCs could not be isolated. Therefore, we determined the correlation between changes in ECM-related gene expression in MSLC-isolatable patients with that in MSLC non-isolatable patients using gene set enrichment analysis (GSEA). We found that lysyl oxidase (LOX) and COL1A1 expressions increased in MSLCs via GBM-derived clusters of differentiation 40 ligand (CD40L). Mechanistically, MSLCs are reprogrammed by the CD40L/CD40/NFκB2 signalling axis to build a tumour infiltrative microenvironment involving collagen crosslinking. Importantly, blocking of CD40L by a neutralizing antibody-suppressed LOX expression and ECM remodelling, decreasing GBM infiltration in mouse xenograft models. Clinically, high expression of CD40L, clusters of differentiation 40 (CD40) and LOX correlated with poor survival in patients with glioma. This indicated that GBM-educated MSLCs promote GBM infiltration via ECM remodelling in the tumour microenvironment. CONCLUSION: Our findings provide mechanistic insights into the pro-infiltrative tumour microenvironment produced by GBM-educated MSLCs and highlight a potential therapeutic target that can be used for suppressing GBM infiltration.

Cholesterol Granuloma of the Maxillary Sinus Misdiagnosed as Nasal Polyp or Mucocele: Four Cases.

ABSTRACT: Cholesterol granuloma is commonly found in the mastoid air cells but is rare in the paranasal sinuses. The most commonly affected sinuses are the frontal sinus, followed by the maxillary sinus. Cholesterol granuloma can be difficult to diagnose because clinical manifestations and radiologic findings are similar to those of other sinonasal disorders. The authors observed 4 cases of cholesterol granuloma that were preoperatively suspected to be nasal polyps or mucoceles. Here, the authors report on their clinical presentation and their successful treatment using the endoscopic sinus approach. These cases expand the current literature on cholesterol granuloma in the paranasal sinuses.

Crosstalk between GBM cells and mesenchymal stemlike cells promotes the invasiveness of GBM through the C5a/p38/ZEB1 axis.

BACKGROUND: Mesenchymal stemlike cells (MSLCs) have been detected in many types of cancer including brain tumors and have received attention as stromal cells in the tumor microenvironment. However, the cellular mechanisms underlying their participation in cancer progression remain largely unexplored. The aim of this study was to determine whether MSLCs have a tumorigenic role in brain tumors. METHODS: To figure out molecular and cellular mechanisms in glioma invasion, we have cultured glioma with MSLCs in a co-culture system. RESULTS: Here, we show that MSLCs in human glioblastoma (GBM) secrete complement component C5a, which is known for its role as a complement factor. MSLC-secreted C5a increases expression of zinc finger E-box-binding homeobox 1 (ZEB1) via activation of p38 mitogen-activated protein kinase (MAPK) in GBM cells, thereby enhancing the invasion of GBM cells into parenchymal brain tissue. CONCLUSION: Our results reveal a mechanism by which MSLCs undergo crosstalk with GBM cells through the C5a/p38 MAPK/ZEB1 signaling loop and act as a booster in GBM progression. KEY POINTS: 1. MSLCs activate p38 MAPK-ZEB1 signaling in GBM cells through C5a in a paracrine manner, thereby boosting the invasiveness of GBM cells in the tumor microenvironment.2. Neutralizing of C5a could be a potential therapeutic target for GBM by inhibition of mesenchymal phenotype.

Force-mediated proinvasive matrix remodeling driven by tumor-associated mesenchymal stem-like cells in glioblastoma.

In carcinoma, cancer-associated fibroblasts participate in force-mediated extracellular matrix (ECM) remodeling, consequently leading to invasion of cancer cells. Likewise, the ECM remodeling actively occurs in glioblastoma (GBM) and the consequent microenvironmental stiffness is strongly linked to migration behavior of GBM cells. However, in GBM the stromal cells responsible for force-mediated ECM remodeling remain unidentified. We show that tumor-associated mesenchymal stem-like cells (tMSLCs) provide a proinvasive matrix condition in GBM by force-mediated ECM remodeling. Importantly, CCL2-mediated Janus kinase 1 (JAK1) activation increased phosphorylation of myosin light chain 2 in tMSLCs and led to collagen assembly and actomyosin contractility. Collectively, our findings implicate tMSLCs as stromal cells providing force-mediated proinvasive ECM remodeling in the GBM microenvironment, and reminiscent of fibroblasts in carcinoma. [BMB Reports 2018; 51(4): 182-187].

Long-term effect of noise exposure during military service in South Korea.

OBJECTIVE: Most Korean men spend at least two years in the military service usually in their early twenties. The aim of this study was to identify the long-term effect of exposure to military noise during military service by comparing two regressions of age-related hearing loss between groups with and without exposure to military noise. DESIGN: Cross-sectional observational study. STUDY SAMPLE: Finally, 4079 subjects were included, among 10,286 data of men's audiogram from January 2004 to April 2010. We excluded repeated testers and any subjects who had other known external causes or had an asymmetric audiogram. We grouped subjects with exposure to military noise (N = 3163) and those without as the control group (N = 916). RESULTS: There was a significant effect of exposure to military noise at 4 and 8 kHz after controlling for the effect of age. The annual threshold deterioration rates were faster in the military noise exposed group than in the control group at 1, 2 and 4 kHz (p < 0.05). CONCLUSION: The long-term effect of exposure to military noise on age-related hearing loss showed an adding effect at 8 kHz and an accelerating effect in the frequency region from 1 to 4 kHz.

Tumor-associated mesenchymal stem-like cells provide extracellular signaling cue for invasiveness of glioblastoma cells.

Hyaluronic acid (HA) is abundant in tumor microenvironment and closely associated with invasiveness of glioblastoma (GBM) cells. However, the cellular mechanism underlying HA-rich microenvironment in GBM remains unexplored. Here, we show that tumor-associated mesenchymal stem-like cells (tMSLCs) contribute to abundance of hyaluronic acid (HA) in tumor microenvironment through HA synthase-2 (HAS2) induction, and thereby enhances invasiveness of GBM cells. In an autocrine manner, C5a secreted by tMSLCs activated ERK MAPK for HAS2 induction in tMSLCs. Importantly, HA acted as a signaling ligand of its cognate receptor RHAMM for intracellular signaling activation underlying invasiveness of GBM cells. Taken together, our study suggests that tMSLCs contribute to HA-rich proinvasive ECM microenvironment in GBM.

Intraosseous hemangioma of the middle turbinate misdiagnosed as a nasal polyp.

Intraosseous hemangiomas account for 1% of all bone tumors and primarily originate from the vertebral column and skull bones. However, intraosseous hemangiomas of the nasal cavity are extremely rare. Here, we report a case of intraosseous hemangioma with a cavernous pattern arising from the middle turbinate that was preoperatively misdiagnosed as chronic rhinosinusitis with polyps. Except for nasal obstruction, there were no specific rhinologic symptoms. The tumor was excised en bloc by the endoscopic endonasal approach without preoperative embolization.

Radiation promotes malignant progression of glioma cells through HIF-1alpha stabilization.

Given its contribution to malignant phenotypes of cancer, tumor hypoxia has been considered as a potential therapeutic problem. In the stressful microenvironment condition, hypoxia inducible factor 1 (HIF1) is well known to mediate the transcriptional adaptation of cells to hypoxia and acts as a central player for the process of hypoxia-driven malignant cancer progression. Here, we found that irradiation causes the HIF1α protein to stabilize, even in normoxia condition through activation of p38 MAPK, thereby promoting angiogenesis in tumor microenvironment and infiltrative property of glioma cells. Notably, irradiation reduced hydroxylation of HIF1α through destabilization of prolyl hydroxylases (PHD)-2. Moreover, radiation also decreased the half-life of protein von Hippel-Lindau (pVHL), which is a specific E3 ligase for HIF1α. Of note, inhibition of p38 MAPK attenuated radiation-induced stabilization of HIF1α through destabilization of PHD-2 and pVHL. In agreement with these results, targeting of either p38 MAPK, HIF1α, pVHL or PHD-2 effectively mitigated the radiation-induced tube formation of human brain-derived micro-vessel endothelial cells (HB-MEC) and infiltration of glioma cells. Taken together, our findings suggest that targeting HIF1α in combination with ionizing radiation might increase the efficacy of radiotherapy for glioma treatment.

A novel 2-pyrone derivative, BHP, impedes oncogenic KRAS-driven malignant progression in breast cancer.

Elevated KRAS expression has been frequently associated with cancer progression including breast cancer; however, therapeutic approaches targeting KRAS have been widely unsuccessful and KRAS mutant cancers remain unsolved problem in cancer therapy. In this study, we found that a new 2-pyrone derivative, 5-bromo-3-(3-hydroxyprop-1-ynyl)-2H-pyran-2-one (BHP) can block KRAS-driven breast cancer progression. Importantly, treatment with BHP effectively suppressed the migratory and invasive properties along with epithelial-mesenchymal transition (EMT) in MDA-MB231 breast cancer cells that carry oncogenic KRAS and mesenchymal malignant phenotypes. In parallel, BHP also sensitized the cells to anticancer treatment. Consistently, forced-expression of oncogenic KRAS bestowed the migratory and invasive properties, mesenchymal transition and resistance to anticancer treatment into normal human mammalian breast cells MCF10A and relatively non-malignant MCF7 and SK-BR3 breast cancer cells; however, treatment with BHP blocked those KRAS-induced malignant phenotypes. Notably, BHP interfered the interaction of KRAS with Raf-1 in concentration-dependent manner, thereby blocking the downstream effectors of KRAS signaling that is PI3K/AKT and ERK. Taken together, our findings indicate that the BHP, an α-pyrone derivative, suppresses malignant breast cancer progression by targeting of oncogenic KRAS signaling pathways.

Fractionated radiation-induced nitric oxide promotes expansion of glioma stem-like cells.

Glioblastoma remains an incurable brain disease due to the prevalence of its recurrence. Considerable evidence suggests that glioma stem-like cells are responsible for glioma relapse after treatment, which commonly involves ionizing radiation. Here, we found that fractionated ionizing radiation (2 Gy/day for 3 days) induced glioma stem-like cell expansion and resistance to anticancer treatment such as cisplatin (50 µM) or taxol (500 nM), or by ionizing radiation (10 Gy) in both glioma cell lines (U87, U373) and patient-derived glioma cells. Of note, concomitant increase of nitric oxide production occurred with the radiation-induced increase of the glioma stem-like cell population through upregulation of inducible nitric oxide synthase (iNOS). In line with this observation, downregulation of iNOS effectively reduced the glioma stem-like cell population and decreased resistance to anticancer treatment. Collectively, our results suggest that targeting iNOS in combination with ionizing radiation might increase the efficacy of radiotherapy for glioma treatment.

Protective effects of Acanthopanax divaricatus vat. albeofructus and its active compound on ischemia-reperfusion injury of rat liver.

In the present study, the potential antioxidant and anti-inflammatory effects of Acanthopanax divaricatus vat. albeofructus (AE) and acanthoside-D (AD) isolated from AE against hepatic ischemia-reperfusion (I/R) injury were investigated in a rat model. Male Sprague-Dawley rats (200-220 g) were randomized into seven groups: normal controls; sham-operated controls; I/R injury model; I/R injury model with AE pretreatment at 150, 300, and 600 mg/kg body weight; and I/R injury model with AD pretreatment at 600 µg/kg body weight (equivalent to high dose of AE). The AE and AD pretreatments were administered orally for 2 weeks prior to I/R injury surgery. All rats recovered for 1 week with AE and AD treatment after surgery. Compared to the normal control groups, the I/R injury model group without supplemental treatment showed a significantly lower level of serum superoxide dismutase (SOD) and significantly higher levels of tumor necrosis factor-alpha (TNF-α, interleukin (IL)-6, serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP), as well as lactate dehydrogenase (LDH) activity. The I/R-induced decrease in SOD and increases in TNF-α and IL-6 were resolved, at least partially, by AE and AD treatments, as evidenced by significantly higher antioxidant activities and significantly lower inflammatory cytokine levels in the treatment groups as compared to the I/R injury model group. The AE and AD treatment groups also showed significantly higher levels of serum IL-10 than I/R injury model group. Histological examination revealed that the AE and AD treated groups had less extensive liver necrosis than I/R injury model group. Concomitantly, AE lowered the I/R-induced increases in AST, ALT, ALP levels and LDH activity. In conclusion, AE and AD are capable of alleviating I/R-induced hepatic injury by inhibiting inflammatory cell infiltration, thereby mitigating the release of inflammatory cytokines and balancing the oxidant-antioxidant status mediated by p38 MAPK and JNK/SAPK signaling.

A new 2-pyrone derivative, 5-bromo-3-(3-hydroxyprop-1-ynyl)-2H-pyran-2-one, suppresses stemness in glioma stem-like cells.

Glioma cells with stem cell properties, termed glioma stem-like cells (GSCs), have been linked to tumor formation, maintenance, and progression and are responsible for the failure of chemotherapy and radiotherapy. Because conventional glioma treatments often fail to eliminate GSCs completely, residual surviving GSCs are able to repopulate the tumor. Compounds that target GSCs might be helpful in overcoming resistance to anticancer treatments in human brain tumors. In this study, we showed that 5-bromo-3-(3-hydroxyprop-1-ynyl)-2H-pyran-2-one (BHP), a new 2-pyrone derivative, suppressed the maintenance of the GSC population in both a glioma cell line and patient-derived glioma cells. Treatment of GSCs with BHP effectively inhibited sphere formation and suppressed the CD133(+) cell population. Treatment with BHP also suppressed expression of the stemness-regulating transcription factors Sox2, Notch2, and ß-catenin in sphere-cultured glioma cells. Treatment of GSCs with BHP significantly suppressed two fundamental characteristics of cancer stem cells: self-renewal and tumorigenicity. BHP treatment dramatically inhibited clone-forming ability at the single-cell level and suppressed in vivo tumor formation. BHP markedly inhibited both phosphoinositide 3-kinase/Akt and Ras/Raf-1/extracellular signal-regulated kinase signaling, which suggests that one or both of these pathways are involved in BHP-induced suppression of GSCs. In addition, treatment with BHP effectively sensitized GSCs to chemotherapy and radiotherapy. Taken together, these results indicate that BHP targets GSCs and enhances their sensitivity to anticancer treatments and suggest that BHP treatment may be useful for treating brain tumors by eliminating GSCs.

PTTG1 oncogene promotes tumor malignancy via epithelial to mesenchymal transition and expansion of cancer stem cell population.

The prognosis of breast cancer patients is related to the degree of metastasis. However, the mechanisms by which epithelial tumor cells escape from the primary tumor and colonize at a distant site are not entirely understood. Here, we analyzed expression levels of pituitary tumor-transforming gene-1 (PTTG1), a relatively uncharacterized oncoprotein, in patient-derived breast cancer tissues with corresponding normal breast tissues. We found that PTTG1 is highly expressed in breast cancer patients, compared with normal tissues. Also, PTTG1 expression levels were correlated with the degree of malignancy in breast cancer cell lines; the more migratory and invasive cancer cell lines MDA-MB-231 and BT549 displayed the higher expression levels of PTTG1 than the less migratory and invasive MCF7 and SK-BR3 and normal MCF10A cell lines. By modulating PTTG1 expression levels, we found that PTTG1 enhances the migratory and invasive properties of breast cancer cells by inducing epithelial to mesenchymal transition, as evidenced by altered morphology and epithelial/mesenchymal cell marker expression patterns and up-regulation of the transcription factor Snail. Notably, down-regulation of PTTG1 also suppressed cancer stem cell population in BT549 cells by decreasing self-renewing ability and tumorigenic capacity, accompanying decreasing CD44(high) CD24(low) cells and Sox2 expression. Up-regulation of PTTG1 had the opposite effects, increasing sphere-forming ability and Sox2 expression. Importantly, PTTG1-mediated malignant tumor properties were due, at least in part, to activation of AKT, known to be a key regulator of both EMT and stemness in cancer cells. Collectively, these results suggest that PTTG1 may represent a new therapeutic target for malignant breast cancer.

Titanium dioxide induces apoptotic cell death through reactive oxygen species-mediated Fas upregulation and Bax activation.

BACKGROUND: Titanium dioxide (TiO(2)) has been widely used in many areas, including biomedicine, cosmetics, and environmental engineering. Recently, it has become evident that some TiO(2) particles have a considerable cytotoxic effect in normal human cells. However, the molecular basis for the cytotoxicity of TiO(2) has yet to be defined. METHODS AND RESULTS: In this study, we demonstrated that combined treatment with TiO(2) nanoparticles sized less than 100 nm and ultraviolet A irradiation induces apoptotic cell death through reactive oxygen species-dependent upregulation of Fas and conformational activation of Bax in normal human cells. Treatment with P25 TiO(2) nanoparticles with a hydrodynamic size distribution centered around 70 nm (TiO(2) (P25-70)) together with ultraviolet A irradiation-induced caspase-dependent apoptotic cell death, accompanied by transcriptional upregulation of the death receptor, Fas, and conformational activation of Bax. In line with these results, knockdown of either Fas or Bax with specific siRNA significantly inhibited TiO(2)-induced apoptotic cell death. Moreover, inhibition of reactive oxygen species with an antioxidant, N-acetyl-L-cysteine, clearly suppressed upregulation of Fas, conformational activation of Bax, and subsequent apoptotic cell death in response to combination treatment using TiO(2) (P25-70) and ultraviolet A irradiation. CONCLUSION: These results indicate that sub-100 nm sized TiO(2) treatment under ultraviolet A irradiation induces apoptotic cell death through reactive oxygen species-mediated upregulation of the death receptor, Fas, and activation of the preapoptotic protein, Bax. Elucidating the molecular mechanisms by which nanosized particles induce activation of cell death signaling pathways would be critical for the development of prevention strategies to minimize the cytotoxicity of nanomaterials.

TRAIL is involved in CpG ODN-mediated anti-apoptotic signals.

Synthetic oligodeoxynucleotides (ODNs) with the CpG-motifs are recognized by toll-like receptor 9 (TLR9), which elicits an immune response. Serum starvation of Raw264.7 cells increased tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) expression. However, treatment with CpG ODN reduced TRAIL expression as well as apoptosis by serum starvation. In serum starved cells, TLR9 inhibitors recovered the decreasing TRAIL expression and sub-G1 accumulation by CpG ODN. CpG ODN-regulated anti-apoptotic signals which were dependent on the Akt-FoxO3a signaling pathway. CpG ODNs activated Akt and inactivated FoxO3a in serum starved cells. Knockdown of FoxO3a by siRNA decreased TRAIL expression and apoptosis in serum-starved cells. In contrast, FoxO3a overexpression increased apoptosis by serum starvation, and CpG ODNs blocked these effects through TRAIL expression. LY294002, a PI3K-Akt inhibitor, blocked the CpG ODN effect of TRAIL expression and the sub-G1 population in serum starved cells. In contrast, overexpression of wild-type Akt reduced additional sub-G1 cells both in non-CpG ODN- and CpG ODN-treated cells. Taken together, these results demonstrate the involvement of Akt-FoxO3a signaling in TLR9-mediated downregulation of TRAIL and anti-apoptotic signals.

A new 2-pyrone derivative, 5-bromo-3-(3-hydroxyprop-1-ynyl)-2H-pyran-2-one, synergistically enhances radiation sensitivity in human cervical cancer cells.

Radiation resistance can be overcome by a combination treatment with chemical modifiers. Here, we showed that treatment with 5-bromo-3-(3-hydroxyprop-1-ynyl)-2H-pyran-2-one (BHP), a new 2-pyrone derivative, in combination with ionizing radiation enhances the sensitivity of human cervical cancer cells to ionizing radiation through overproduction of reactive oxygen species (ROS). The combined treatment with BHP and ionizing radiation caused a decrease in clonogenic survival and an increase in apoptotic cell death in cervical cancer cells. The combined treatment promoted conformational activation of Bax and led to mitochondrial apoptotic cell death. The combination treatment also induced a marked increase in intracellular ROS level. Inhibition of ROS attenuated the radiosensitizing effect of BHP, concurrent with a decrease in Bax activation, a decrease in mitochondrial cell death, and an increase in clonogenic survival. These results indicate that BHP synergistically enhances sensitivity of human cervical cancer cells to ionizing radiation through elevation of intracellular ROS and that ROS-dependent Bax activation is critically involved in the increase in apoptotic cell death induced by the combined treatment with BHP and ionizing radiation.

Reversible Sensorineural Hearing Loss due to Pachymeningitis Associated with Elevated Serum MPO-ANCA.

Hypertrophic pachymeningitis is a progressive disease resulting in a diffuse thickening of dura mater due to inflammation, tumor or autoimmune diseases, but most cases are idiopathic. It is seldom reported to be related to sensorineural hearing loss, but it can cause sensorineural hearing loss which can be potentially reversed through treatment. Here, we report the case of a 54-year-old woman who had progressive, bilateral, worse in the left, sensorineural hearing loss and visual disturbance with an accompanying headache over several months. Brain MRI showed diffusely thickened dura mater, highly enhanced after gadolinium administration, which was consistent with pachymeningitis. It was assumed to be related to autoimmune pathogenesis on the basis of elevated serum myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) titers. After empirical steroid and cyclophosphamide therapy, auditory impairment improved, especially in the high frequency region of the pure tone audiogram, and significant improvement in the word recognition test. Moreover, a follow-up MRI revealed much decreased enhancement of the dura mater, and the MPO-ANCA titer decreased to within the normal range. In the case of rapidly progressive sensorineural hearing loss or hearing impairment accompanying other cranial neuropathy, pachymeningitis should be taken into consideration, and brain MRI with gadolinium enhancement is the best method of detecting it. Also, to ensure proper treatment, a cautious evaluation including an ANCA work-up should be performed.

The small GTPase Rac1 is involved in the maintenance of stemness and malignancies in glioma stem-like cells.

A subpopulation of cancer cells with stem cell properties is responsible for tumor formation, maintenance, and malignant progression; however, the molecular mechanisms underlying the maintenance of cancer stem-like cell properties have remained unclear. Here, we show that the Rho family GTPase Rac1 is involved in the glioma stem-like cell (GSLC) maintenance and tumorigenicity in human glioma. The Rac1-Pak signaling was markedly activated in GSLCs. Knockdown of Rac1 caused reduction of expression of GSLC markers, self-renewal-related proteins and neurosphere formation. Moreover, down-regulation of Rac1 suppressed the migration, invasion, and malignant transformation in GSLCs. Furthermore, inhibition of Rac1 enhanced radiation sensitivity of GSLCs. These results indicate that the small GTPase Rac1 is involved in the maintenance of stemness and malignancies in GSLCs.