The expression of DNA damage checkpoint proteins and prognostic implication in metastatic brain tumors.

The most important therapeutic tool in brain metastasis is radiation therapy. However, resistance to radiation is a possible cause of recurrence or treatment failure. Recently, DNA damage checkpoint signaling pathway activation after irradiation has received increasing attention. The association between the expression levels and survival outcome was evaluated to find possible therapeutic targets in brain metastasis. Radiosensitivity of human non-small cell lung cancer cell lines was determined by checking their viability after treatment with varying doses of ionizing radiation (IR). The expression of DNA checkpoint proteins was analyzed by Western blots and immunohistochemistry. On the basis of the clinical data for the patients, the association between the expression of the components and patients' survival was investigated. The expression levels of TopBP1 and phosphorylated Chk1 (P-Chk1) protein were higher in radioresistant lung cancer cell lines compared to radiosensitive cell lines. We previously assessed radiation survival of lung cancer cell lines after treating them with Chk1 inhibitor, AZD7762. AZD7762 significantly sensitized both radioresistant and radiosensitive cells to IR. We also observed a strong inverse relationship between progression-free survival (PFS) and expression level of P-Chk1 and TopBP1. This study, which is the first clinical report that connects DNA damage checkpoints and prognosis of brain metastasis, supports these two proteins to be promising targets for overcoming the radioresistance in brain metastasis.

Clinical and biological implications of CD133-positive and CD133-negative cells in glioblastomas.

A number of recent reports have demonstrated that only CD133-positive cancer cells of glioblastoma multiforme (GBM) have tumor-initiating potential. These findings raise an attractive hypothesis that GBMs can be cured by eradicating CD133-positive cancer stem cells (CSCs), which are a small portion of GBM cells. However, as GBMs are known to possess various genetic alterations, GBMs might harbor heterogeneous CSCs with different genetic alterations. Here, we compared the clinical characteristics of two GBM patient groups divided according to CD133-positive cell ratios. The CD133-low GBMs showed more invasive growth and gene expression profiles characteristic of mesenchymal or proliferative subtypes, whereas the CD133-high GBMs showed features of cortical and well-demarcated tumors and gene expressions typical of proneuronal subtype. Both CD133-positive and CD133-negative cells purified from four out of six GBM patients produced typical GBM tumor masses in NOD-SCID brains, whereas brain mass from CD133-negative cells showed more proliferative and angiogenic features compared to that from CD133-positive cells. Our results suggest, in contrast to previous reports that only CD133-positive cells of GBMs can initiate tumor formation in vivo CD133-negative cells also possess tumor-initiating potential, which is indicative of complexity in the identification of cancer cells for therapeutic targeting.

Clinical outcomes of an endoscopic transclival and transpetrosal approach for primary skull base malignancies involving the clivus.

OBJECTIVE The endoscopic endonasal approach for treating primary skull base malignancies involving the clivus is a formidable task. The authors hypothesized that tumor involvement of nearby critical anatomical structures creates hurdles to endoscopic gross-total resection (GTR). The aim of this study was to retrospectively review the clinical outcomes of patients who underwent an endoscopic endonasal approach to treat primary malignancies involving the clivus and to analyze prognostic factors for GTR. METHODS Between January 2009 and November 2015, 42 patients underwent the endoscopic endonasal approach for resection of primary skull base malignancies involving the clivus at 2 independent institutions. Clinical data; tumor locations within the clivus; and anatomical involvement of the cavernous or paraclival internal carotid artery, cisternal trigeminal nerve, hypoglossal canal, and dura mater were investigated to assess the extent of resection. Possible prognostic factors affecting GTR were also analyzed. RESULTS Of the 42 patients, 37 were diagnosed with chordomas and 5 were diagnosed with chondrosarcomas. The mean (± SD) preoperative tumor volume was 25.2 ± 30.5 cm3 (range 0.8-166.7 cm3). GTR was achieved in 28 patients (66.7%) and subtotal resection in 14 patients (33.3%). All tumors were classified as upper (n = 17), middle (n = 17), or lower (n = 8) clival tumors based on clival involvement, and as central (24 [57.1%]) or paramedian (18 [42.9%]) based on laterality of the tumor. Univariate analysis identified the tumor laterality (OR 6.25, 95% CI 1.51-25.86; p = 0.011) as significantly predictive of GTR. In addition, the laterality of the tumor was found to be a statistically significant predictor in multivariate analysis (OR 41.16, 95% CI 1.12-1512.65; p = 0.043). CONCLUSIONS An endoscopic endonasal approach can provide favorable clinical and surgical outcomes. However, the tumor laterality should be considered as a potential obstacle to total removal.

Relationship between malignant subtypes of meningioma and clinical outcome.

We evaluated the relationship between histological malignant subtypes (WHO grade II or III) of meningioma and clinical outcome. Of 485 patients treated surgically for intracranial meningioma at our hospital between 1994 and 2004, 49 (10%; 18 male, 31 female) had potentially malignant features. The histological tumor subtypes within this group of patients included: atypical (n=23); clear cell (n=3); chordoid (n=5); rhabdoid (n=16); and anaplastic (n=4). Correlations among prognosis, recurrence, and the following factors were analyzed for each histological subtype: the Simpson grade of surgical resection (grades I-III vs. grade IV), tumor location (convexity vs. other), the Ki-67 index, and use of postoperative radiotherapy. The median value of the Ki-67 index was 16.2% (range: 1.0-57.2%). The surgical resections were of Simpson grades I-III and IV in 43 and six of the 49 patients, respectively. Tumors recurred after the initial surgical resection in 14 of the 49 patients. In view of the relatively high proportion of malignant subtypes (10%), we suggest that all meningiomas should be evaluated for malignancy. The extent of surgical resection, the histological subtype, and the Ki-67 index can help to predict the clinical outcome for meningioma patients.

Genetically-engineered human neural stem cells with rabbit carboxyl esterase can target CNS lymphoma.

BACKGROUND: Despite advances in its treatment, CNS lymphoma remains a devastating disease. Taking advantage of the tumour-tropic properties of neural stem cells (NSCs) is a novel therapeutic strategy. To apply this strategy to the treatment of CNS lymphoma, we investigated the role of NSCs expressing carboxyl esterase (HB1.F3.CE), which activates irinotecan. MATERIALS AND METHODS: In order to find in vitro bystander effects of engineered NSCs, we performed cell viability assays. In vivo, the HB1.F3.CE cells were injected into the brain of mice with orthotopic CNS lymphoma. Mice were then treated with irinotecan by systemic administration. RESULTS: The HB1.F3.CE cells significantly inhibited the growth of Raji cells with irinotecan treatment. In vivo, the HB1.F3.CE cells migrated into the tumour and significantly reduced tumour volume. In addition, survival of mice was prolonged by treatment with HB1.F3.CE and irinotecan. CONCLUSION: Transplantation of human NSCs encoding CE into brain, combined with irinotecan therapy, may be an effective treatment regimen for CNS lymphoma.

Trans-differentiation of neural stem cells: a therapeutic mechanism against the radiation induced brain damage.

Radiation therapy is an indispensable therapeutic modality for various brain diseases. Though endogenous neural stem cells (NSCs) would provide regenerative potential, many patients nevertheless suffer from radiation-induced brain damage. Accordingly, we tested beneficial effects of exogenous NSC supplementation using in vivo mouse models that received whole brain irradiation. Systemic supplementation of primarily cultured mouse fetal NSCs inhibited radiation-induced brain atrophy and thereby preserved brain functions such as short-term memory. Transplanted NSCs migrated to the irradiated brain and differentiated into neurons, astrocytes, or oligodendrocytes. In addition, neurotrophic factors such as NGF were significantly increased in the brain by NSCs, indicating that both paracrine and replacement effects could be the therapeutic mechanisms of NSCs. Interestingly, NSCs also differentiated into brain endothelial cells, which was accompanied by the restoration the cerebral blood flow that was reduced from the irradiation. Inhibition of the VEGF signaling reduced the migration and trans-differentiation of NSCs. Therefore, trans-differentiation of NSCs into brain endothelial cells by the VEGF signaling and the consequential restoration of the cerebral blood flow would also be one of the therapeutic mechanisms of NSCs. In summary, our data demonstrate that exogenous NSC supplementation could prevent radiation-induced functional loss of the brain. Therefore, successful combination of brain radiation therapy and NSC supplementation would provide a highly promising therapeutic option for patients with various brain diseases.

Prognostic implications of the DNA damage response pathway in glioblastoma.

Genomic instability and resistance to genotoxic therapies for glioblastoma (GBM) suggest aberrant DNA damage response (DDR), since DDR maintains the genomic integrity against genotoxic insults including anti-tumor therapies. To elucidate the biological and clinical meaning of DDR in GBM, we retrospectively investigated the immunohistochemical expression of DDR proteins (ATM, Chk1, Chk2, TopBP1, Rad17, p53, Nbs1, MDC1, γH2AX and RPA1) in 69 GBM surgical samples and their relation with GBM patient survival. Remarkably, higher expression of ATM revealed significantly longer overall survival (OS) and progression-free survival (PFS) (p<0.05). Upon multivariate analysis, expression level of ATM was an independent factor for longer OS (p=0.020) and longer PFS (p=0.019). Since ATM induces cell cycle arrest or apoptosis through cell cycle regulators in response to genotoxic insults, these results indicate that aberrant DDR signaling through ATM in GBM may be associated with resistance to genotoxic anti-tumor therapeutics. Conclusively, we emphasize that the identification of DDR machinery, which can be involved in unstable genomic status or genotoxic therapies in GBM, is very important to predict patient outcome.

Genetically engineered human neural stem cells with rabbit carboxyl esterase can target brain metastasis from breast cancer.

Neural stem cells (NSCs) led to the development of a novel strategy for delivering therapeutic genes to tumors. NSCs expressing rabbit carboxyl esterase (F3.CE), which activates CPT-11, significantly inhibited the growth of MDA-MB-435 cells in the presence of CPT-11. F3.CE cells migrated selectively into the brain metastases located in the opposite hemisphere. The treatment also significantly decreased tumor volume in immune-deficient mice bearing MDA-MB-435 tumors when F3.CE cells were transplanted into the contralateral hemisphere. The survival rate was significantly prolonged with the treatment with F3.CE and CPT-11. This strategy may be considered as an effective treatment regimen for brain metastases.

Morphological and functional MRI, MRS, perfusion and diffusion changes after radiosurgery of brain metastasis.

Radiosurgery is a noninvasive procedure where spatially accurate and highly conformal doses of radiation are targeted at brain lesions with an ablative intent. Recently, radiosurgery has been established as an effective technique for local treatment of brain metastasis. After radiosurgery, magnetic resonance (MR) imaging plays an important role in the assessment of the therapeutic response and of any complications. The therapeutic approach depends on the imaging findings obtained after radiosurgery, which have a role in the decision making to perform additional invasive modalities (repeat resection, biopsy) to obtain a definite diagnosis and to improve the survival of patients. Conventional MR imaging findings are mainly based on morphological alterations of tumors. However, there are variable imaging findings of radiation-induced changes including radiation necrosis in the brain. Radiologists are sometimes confused by radiation-induced injuries, including radiation necrosis, that are seen on conventional MR imaging. The pattern of abnormal enhancement on follow-up conventional MR imaging closely mimics that of a recurrent brain metastasis. So, classifying newly developed abnormal enhancing lesions in follow-up of treated brain metastasis with correct diagnosis is one of the key goals in neuro-oncologic imaging. To overcome limitations of the use of morphology-based conventional MR imaging, several physiological-based functional MR imaging methods have been used, namely diffusion-weighted imaging, perfusion MR imaging, and proton MR spectroscopy, for the detection of hemodynamic, metabolic, and cellular alterations. These imaging modalities provide additional information to allow clinicians to make proper decisions regarding patient treatment.