Si-Jian Pan

Over-expression of tetraspanin 8 in malignant glioma regulates tumor cell progression.

Tumor cell invasion and proliferation remain the overwhelming causes of death for malignant glioma patients. To establish effective therapeutic methods, new targets implied in these processes have to be identified. Tetraspanin 8 (Tspn8) forms complexes with a large variety of trans-membrane and/or cytosolic proteins to regulate several important cellular functions. In the current study, we found that Tspn8 was over-expressed in multiple clinical malignant glioma tissues, and its expression level correlated with the grade of tumors. Tspn8 expression in malignant glioma cells (U251MG and U87MG lines) is important for cell proliferation and migration. siRNA-mediated knockdown of Tspn8 markedly reduced in vitro proliferation and migration of U251MG and U87MG cells. Meanwhile, Tspn8 silencing also increased the sensitivity of temozolomide (TMZ), and significantly increased U251MG or U87MG cell death and apoptosis by TMZ were achieved with Tspn8 knockdown. We observed that Tspn8 formed a complex with activated focal adhesion kinase (FAK) in both human malignant glioma tissues and in above glioma cells. This complexation appeared required for FAK activation, since Tspn8 knockdown inhibited FAK activation in U251MG and U87MG cells. These results provide evidence that Tspn8 contributes to the pathogenesis of glioblastoma probably by promoting proliferation, migration and TMZ-resistance of glioma cells. Therefore, targeting Tspn8 may provide a potential therapeutic intervention for malignant glioma.

Tetraspanin 8-Rictor-Integrin α3 Complex Is Required for Glioma Cell Migration

The malignant glioma remains one of the most aggressive human malignancies with extremely poor prognosis. Glioma cell invasion and migration are the main causes of death. In the current study, we studied the expression and the potential functions of tetraspanin 8 (Tspan8) in malignant gliomas. We found that Tspan8 expression level is high in both malignant glioma tissues and in several human glioma cell lines, where it formed a complex integrin α3 and rictor, the latter is a key component of mammalian target of rapamycin (mTOR) complex 2 (mTORC2). Disruption of this complex, through siRNA-mediated knockdown of anyone of these three proteins, inhibited U251MG glioma cell migration in vitro. We further showed that Tspan8-rictor association appeared required for mTORC2 activation. Knockdown of Tspan8 by the targeted siRNAs prevented mTOR-rictor (mTORC2) assembly as well as phosphorylation of AKT (Ser-473) and protein kinase C α (PKCα) in U251MG cells. Together, these results demonstrate that over-expressed Tspan8 in malignant glioma forms a complex with rictor and integrin α3 to mediate mTORC2 activation and glioma cell migration. Therefore, targeting Tspan8-rictor-integrin α3 complex may provide a potential therapeutic intervention for malignant glioma.

Cold inducible RNA binding protein upregulation in pituitary corticotroph adenoma induces corticotroph cell proliferation via Erk signaling pathway

Cushings disease is caused by pituitary corticotroph adenoma, and the pathogenesis of it has remained obscure. Here, we showed that cold inducible RNA binding protein (CIRP) was markedly elevated in corticotroph tumors. Forced overexpression of CIRP in murine AtT20 pituitary corticotroph cell line increased corticotroph precursor hormone proopiomelanocortin (POMC) transcription, ACTH secretion and cellular proliferation. In vivo, CIRP overexpression promotes murine corticotroph tumor growth and enhances ACTH production. Mechanistically, we show that CIRP could promote AtT20 cells proliferation by inducing cyclinD1 and decreasing p27 expression via Erk1/2 signaling pathway. Clinically, CIRP overexpression is significantly correlated with Cushings disease recurrence. CIRP appears to play a critical tumorigenesis function in Cushings disease and its expression might be a useful biomarker for tumor recurrence.

GSK621 Targets Glioma Cells via Activating AMP-Activated Protein Kinase Signalings

Here, we studied the anti-glioma cell activity by a novel AMP-activated protein kinase (AMPK) activator GSK621. We showed that GSK621 was cytotoxic to human glioma cells (U87MG and U251MG lines), possibly via provoking caspase-dependent apoptotic cell death. Its cytotoxicity was alleviated by caspase inhibitors. GSK621 activated AMPK to inhibit mammalian target of rapamycin (mTOR) and downregulate Tetraspanin 8 (Tspan8) in glioma cells. AMPK inhibition, through shRNA knockdown of AMPKα or introduction of a dominant negative (T172A) AMPKα, almost reversed GSK621-induced AMPK activation, mTOR inhibition and Tspan8 degradation. Consequently, GSK621’s cytotoxicity in glioma cells was also significantly attenuated by AMPKα knockdown or mutation. Further studies showed that GSK621, at a relatively low concentration, significantly potentiated temozolomide (TMZ)’s sensitivity and lethality against glioma cells. We summarized that GSK621 inhibits human glioma cells possibly via activating AMPK signaling. This novel AMPK activator could be a novel and promising anti-glioma cell agent.

Long-Term Follow-Up of MRI-Guided Bilateral Anterior Capsulotomy in Patients with Refractory Schizophrenia

Aim: To determine whether there is a long-term benefit of MRI-guided bilateral anterior capsulotomy in the treatment of refractory schizophrenia. Methods: 116 patients (16 patients did not complete the follow-up evaluation) with refractory schizophrenia who underwent capsulotomy were included. The treatment effect was evaluated using a series of international rating scales. Evaluations were performed at baseline, 3 weeks and 24 months after surgery. Results: The rate of effectiveness was 74% according to the Clinical Global Impression evaluation, and there was an obvious improvement based on the statistical analysis for Positive and Negative Symptom Scale (baseline vs. 24 months after surgery, 6.86 ± 8.12, 10.70 ± 8.70 vs. 26.65 ± 4.85, 21.66 ± 7.19), Brief Psychiatric Rating Scale (14.75 ± 13.21 vs. 44.97 ± 9.36), Activities of Daily Living Scale (18.06 ± 6.58 vs. 24.61 ± 8.95), Social Disability Screening Schedule (6.69 ± 6.12 vs. 15.06 ± 3.18) and Global Assessment Scale (74.35 ± 12.75 vs. 48.74 ± 9.18). Among all the symptoms of schizophrenia, aggressive behavior (82% response rate), hallucination, (71% response rate) and delusion (70% response rate) showed the best response. Conclusion: Our research indicates that capsulotomy is a relatively safe and effective intervention for patients with refractory schizophrenia. It could be an alternative therapy for those patients with chronic and severe schizophrenia. But there must be strict inclusion criteria considering the complications and irreversibility of this procedure.

Volumetric MRI Analysis in Patients with Short-Term Remission of Cushing's Disease

The data on patients with short‐term remission of Cushings disease (CD) might provide information that is not available from previous long‐term remission studies. We aimed to investigate structural changes in the brain in these patients and to examine whether these changes were associated with clinical characteristics.

Decreased expression of SFRP2 promotes development of the pituitary corticotroph adenoma by upregulating Wnt signaling

Cushings disease is primarily caused by pituitary adrenocorticotropin-secreting adenoma. However, its pathogenesis has remained obscure. In the present study, whole transcriptome analysis was performed by RNA sequencing (RNA-Seq) and expression of secreted frizzled-related protein 2 (SFRP2) was decreased in corticotroph tumors compared with normal pituitary glands. Furthermore, the RNA-Seq results were validated and the expression of SFRP2 in tumor tissues was analyzed by comparing another cohort of 23 patients with Cushings disease and 3 normal human pituitary samples using reverse transcription-quantitative polymerase chain reaction, western blot and immunohistochemistry staining. Clinically, there was an association between lower SFRP2 expression and aggressive adenoma characteristics, including larger size and invasiveness. Conversely, SFRP2 overexpression reduced the ability of AtT20 cells to proliferate and migrate, and reduced production of the adrenocorticotrophic hormone in vitro. Mechanistically, overexpressed SFRP2 reduced the level of β-catenin in the cytoplasm and nucleus, and decreased Wnt signaling activity in AtT20 cells. Therefore, SFRP2 appears to act as a tumor suppressor in Cushings disease by regulating the activity of the Wnt signaling pathway.

Altered spontaneous brain activity in Cushing's disease: a resting‐state functional MRI study

Cushings disease (CD) provides a unique and naturalist model for studying the influence of hypercortisolism on the human brain and the reversibility of these effects after resolution of the condition. This cross‐sectional study used resting‐state fMRI (rs‐fMRI) to investigate the altered spontaneous brain activity in CD patients and the trends for potential reversibility after the resolution of the hypercortisolism. We also aim to determine the relationship of these changes with clinical characteristics and cortisol levels.

Altered gray and white matter microstructure in Cushing’s disease: A diffusional kurtosis imaging study

Exposure to chronic hypercortisolism has multiple adverse effects on brain biology in humans. Cushings disease (CD) represents a unique and natural human model for examining the effects of hypercortisolism on the brain. This cross-sectional study used Diffusional Kurtosis Imaging (DKI) to investigate the microstructure alterations in both white matter (WM) and gray matter (GM) of CD patients and to determine the relationship of these changes with clinical characteristics. DKI images were obtained from 15 active CD patients. DKI parametric maps were estimated through voxel-based analyses (VBA) and compared with 15 healthy controls matched for age, sex and education. In addition, correlations were analyzed between the altered DKI parameters and clinical characteristics. Compared with healthy controls, CD patients mainly exhibited significantly altered diffuse parameters in the GM and WM of the left medial temporal lobe (MTL). The mean values of increased radial diffusivity (RD) of CD patients in GM of the left hippocampus/parahippocampal gyrus correlated positively with the clinical severity of CD. Additionally, we also found altered kurtosis parameters in the cerebellum and frontal lobe. DKI imaging of CD patients could represent complementary information in both white matter and gray matter. The impairment of the left MTL might explain some part of the memory and cognition impairments in CD patients.