Santosh Kesari

Malignant gliomas in adults.

Approximately 5% of patients with malignant gliomas have a family history of gliomas. Some of these familial cases are associated with rare genetic syndromes, such as neurofibromatosis types 1 and 2, the Li−Fraumeni syndrome (germ-line p53 mutations associated with an increased risk of several cancers), and Turcot’s syndrome (intestinal polyposis and brain tumors). 10 However, most familial cases have

Malignant Gliomas in Adults

Approximately 5% of patients with malignant gliomas have a family history of gliomas. Some of these familial cases are associated with rare genetic syndromes, such as neurofibromatosis types 1 and 2, the Li−Fraumeni syndrome (germ-line p53 mutations associated with an increased risk of several cancers), and Turcot’s syndrome (intestinal polyposis and brain tumors). 10 However, most familial cases have

Bevacizumab for recurrent malignant gliomas: efficacy, toxicity, and patterns of recurrence.

Background: Bevacizumab, a humanized monoclonal antibody against vascular endothelial growth factor, may have activity in recurrent malignant gliomas. At recurrence some patients appear to develop nonenhancing infiltrating disease rather than enhancing tumor. Methods: We retrospectively reviewed 55 consecutive patients with recurrent malignant gliomas who received bevacizumab and chemotherapy to determine efficacy, toxicity, and patterns of recurrence. Using a blinded, standardized imaging review and quantitative volumetric analysis, the recurrence patterns of patients treated with bevacizumab were compared to recurrence patterns of 19 patients treated with chemotherapy alone. Results: A total of 2.3% of patients had a complete response, 31.8% partial response, 29.5% minimal response, and 29.5% had stable disease. Median time to radiographic progression was 19.3 weeks. Six-month progression-free survival (PFS) was 42% for patients with glioblastoma and 32% for patients with anaplastic glioma. In 23 patients who progressed on their initial therapy, bevacizumab was continued and the concurrent chemotherapy agent changed. In no case did the change produce a radiographic response, but two patients had prolonged PFS of 20 and 31 weeks. Recurrence pattern analysis identified a significant increase in the volume of infiltrative tumor relative to enhancing tumor in bevacizumab responders. Conclusions: Combination therapy with bevacizumab and chemotherapy is well-tolerated and active against recurrent malignant gliomas. At recurrence, continuing bevacizumab and changing the chemotherapy agent provided long-term disease control only in a small subset of patients. Bevacizumab may alter the recurrence pattern of malignant gliomas by suppressing enhancing tumor recurrence more effectively than it suppresses nonenhancing, infiltrative tumor growth.

MicroRNA 21 promotes glioma invasion by targeting matrix metalloproteinase regulators.

ABSTRACT Substantial data indicate that microRNA 21 (miR-21) is significantly elevated in glioblastoma (GBM) and in many other tumors of various origins. This microRNA has been implicated in various aspects of carcinogenesis, including cellular proliferation, apoptosis, and migration. We demonstrate that miR-21 regulates multiple genes associated with glioma cell apoptosis, migration, and invasiveness, including the RECK and TIMP3 genes, which are suppressors of malignancy and inhibitors of matrix metalloproteinases (MMPs). Specific inhibition of miR-21 with antisense oligonucleotides leads to elevated levels of RECK and TIMP3 and therefore reduces MMP activities in vitro and in a human model of gliomas in nude mice. Moreover, downregulation of miR-21 in glioma cells leads to decreases of their migratory and invasion abilities. Our data suggest that miR-21 contributes to glioma malignancy by downregulation of MMP inhibitors, which leads to activation of MMPs, thus promoting invasiveness of cancer cells. Our results also indicate that inhibition of a single oncomir, like miR-21, with specific antisense molecules can provide a novel therapeutic approach for “physiological” modulation of multiple proteins whose expression is deregulated in cancer.

Olig2-Regulated Lineage-Restricted Pathway Controls Replication Competence in Neural Stem Cells and Malignant Glioma

Recent studies have identified stem cells in brain cancer. However, their relationship to normal CNS progenitors, including dependence on common lineage-restricted pathways, is unclear. We observe expression of the CNS-restricted transcription factor, OLIG2, in human glioma stem and progenitor cells reminiscent of type C transit-amplifying cells in germinal zones of the adult brain. Olig2 function is required for proliferation of neural progenitors and for glioma formation in a genetically relevant murine model. Moreover, we show p21(WAF1/CIP1), a tumor suppressor and inhibitor of stem cell proliferation, is directly repressed by OLIG2 in neural progenitors and gliomas. Our findings identify an Olig2-regulated lineage-restricted pathway critical for proliferation of normal and tumorigenic CNS stem cells.

Transdifferentiation of glioblastoma cells into vascular endothelial cells

Glioblastoma (GBM) is the most malignant brain tumor and is highly resistant to intensive combination therapies and anti-VEGF therapies. To assess the resistance mechanism to anti-VEGF therapy, we examined the vessels of GBMs in tumors that were induced by the transduction of p53+/− heterozygous mice with lentiviral vectors containing oncogenes and the marker GFP in the hippocampus of GFAP-Cre recombinase (Cre) mice. We were surprised to observe GFP+ vascular endothelial cells (ECs). Transplantation of mouse GBM cells revealed that the tumor-derived endothelial cells (TDECs) originated from tumor-initiating cells and did not result from cell fusion of ECs and tumor cells. An in vitro differentiation assay suggested that hypoxia is an important factor in the differentiation of tumor cells to ECs and is independent of VEGF. TDEC formation was not only resistant to an anti-VEGF receptor inhibitor in mouse GBMs but it led to an increase in their frequency. A xenograft model of human GBM spheres from clinical specimens and direct clinical samples from patients with GBM also showed the presence of TDECs. We suggest that the TDEC is an important player in the resistance to anti-VEGF therapy, and hence a potential target for GBM therapy.

Maintenance Therapy With Tumor-Treating Fields Plus Temozolomide vs Temozolomide Alone for Glioblastoma: A Randomized Clinical Trial

IMPORTANCE Glioblastoma is the most devastating primary malignancy of the central nervous system in adults. Most patients die within 1 to 2 years of diagnosis. Tumor-treating fields (TTFields) are a locoregionally delivered antimitotic treatment that interferes with cell division and organelle assembly. OBJECTIVE To evaluate the efficacy and safety of TTFields used in combination with temozolomide maintenance treatment after chemoradiation therapy for patients with glioblastoma. DESIGN, SETTING, AND PARTICIPANTS After completion of chemoradiotherapy, patients with glioblastoma were randomized (2:1) to receive maintenance treatment with either TTFields plus temozolomide (n = 466) or temozolomide alone (n = 229) (median time from diagnosis to randomization, 3.8 months in both groups). The study enrolled 695 of the planned 700 patients between July 2009 and November 2014 at 83 centers in the United States, Canada, Europe, Israel, and South Korea. The trial was terminated based on the results of this planned interim analysis. INTERVENTIONS Treatment with TTFields was delivered continuously (>18 hours/day) via 4 transducer arrays placed on the shaved scalp and connected to a portable medical device. Temozolomide (150-200 mg/m2/d) was given for 5 days of each 28-day cycle. MAIN OUTCOMES AND MEASURES The primary end point was progression-free survival in the intent-to-treat population (significance threshold of .01) with overall survival in the per-protocol population (n = 280) as a powered secondary end point (significance threshold of .006). This prespecified interim analysis was to be conducted on the first 315 patients after at least 18 months of follow-up. RESULTS The interim analysis included 210 patients randomized to TTFields plus temozolomide and 105 randomized to temozolomide alone, and was conducted at a median follow-up of 38 months (range, 18-60 months). Median progression-free survival in the intent-to-treat population was 7.1 months (95% CI, 5.9-8.2 months) in the TTFields plus temozolomide group and 4.0 months (95% CI, 3.3-5.2 months) in the temozolomide alone group (hazard ratio [HR], 0.62 [98.7% CI, 0.43-0.89]; P = .001). Median overall survival in the per-protocol population was 20.5 months (95% CI, 16.7-25.0 months) in the TTFields plus temozolomide group (n = 196) and 15.6 months (95% CI, 13.3-19.1 months) in the temozolomide alone group (n = 84) (HR, 0.64 [99.4% CI, 0.42-0.98]; P = .004). CONCLUSIONS AND RELEVANCE In this interim analysis of 315 patients with glioblastoma who had completed standard chemoradiation therapy, adding TTFields to maintenance temozolomide chemotherapy significantly prolonged progression-free and overall survival. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00916409.

Human Glioblastoma–Derived Cancer Stem Cells: Establishment of Invasive Glioma Models and Treatment with Oncolytic Herpes Simplex Virus Vectors

Glioblastoma, the most malignant type of primary brain tumor, is one of the solid cancers where cancer stem cells have been isolated, and studies have suggested resistance of those cells to chemotherapy and radiotherapy. Here, we report the establishment of CSC-enriched cultures derived from human glioblastoma specimens. They grew as neurospheres in serum-free medium with epidermal growth factor and fibroblast growth factor 2, varied in the level of CD133 expression and very efficiently formed highly invasive and/or vascular tumors upon intracerebral implantation into immunodeficient mice. As a novel therapeutic strategy for glioblastoma-derived cancer stem-like cells (GBM-SC), we have tested oncolytic herpes simplex virus (oHSV) vectors. We show that although ICP6 (UL39)-deleted mutants kill GBM-SCs as efficiently as wild-type HSV, the deletion of gamma34.5 significantly attenuated the vectors due to poor replication. However, this was significantly reversed by the additional deletion of alpha47. Infection with oHSV G47Delta (ICP6(-), gamma34.5(-), alpha47(-)) not only killed GBM-SCs but also inhibited their self-renewal as evidenced by the inability of viable cells to form secondary tumor spheres. Importantly, despite the highly invasive nature of the intracerebral tumors generated by GBM-SCs, intratumoral injection of G47Delta significantly prolonged survival. These results for the first time show the efficacy of oHSV against human GBM-SCs, and correlate this cytotoxic property with specific oHSV mutations. This is important for designing new oHSV vectors and clinical trials. Moreover, the new glioma models described in this study provide powerful tools for testing experimental therapeutics and studying invasion and angiogenesis.

Single-agent bortezomib in previously untreated multiple myeloma: efficacy, characterization of peripheral neuropathy, and molecular correlations with response and neuropathy.

PURPOSE To assess efficacy and safety of single-agent bortezomib in previously untreated patients with multiple myeloma, investigate prevalence of baseline and treatment-emergent polyneuropathy, and identify molecular markers associated with response and neuropathy. PATIENTS AND METHODS Patients received bortezomib 1.3 mg/m(2) on days 1, 4, 8, and 11, for up to eight 21-day cycles. A subset of patients underwent neurophysiologic evaluation pre- and post-treatment. Bone marrow aspirates were performed at baseline for exploratory whole-genome analyses. Results Among 64 patients, 41% had partial response or better, including 9% complete/near-complete responses; median duration of response was 8.4 months. Response rates did not differ in the presence or absence of adverse cytogenetics. After median follow-up of 29 months, median time to progression was 17.3 months. Median overall survival had not been reached; estimated 1-year survival was 92%. Thirty-two patients successfully underwent optional stem-cell transplantation. Bortezomib treatment was generally well tolerated. At baseline, 20% of patients had sensory polyneuropathy. Sensory polyneuropathy developed during treatment in 64% of patients (grade 3 in 3%), but proved manageable and resolved in 85% within a median of 98 days. Neurologic examination, neurophysiologic testing, and measurements of epidermal nerve fiber densities in 35 patients confirmed pretreatment sensory neuropathy in 20% and new or worsening neuropathy in 63%. Pharmacogenomic analyses identified molecular markers of response and treatment-emergent neuropathy, which will require future study. CONCLUSION Single-agent bortezomib is effective in previously untreated myeloma. Baseline myeloma-associated neuropathy seems more common than previously reported, and bortezomib-associated neuropathy, although a common toxicity, is reversible in most patients.

Human Glioma Growth Is Controlled by MicroRNA-10b

MicroRNA (miRNA) expression profiling studies revealed a number of miRNAs dysregulated in the malignant brain tumor glioblastoma. Molecular functions of these miRNAs in gliomagenesis are mainly unknown. We show that inhibition of miR-10b, a miRNA not expressed in human brain and strongly upregulated in both low-grade and high-grade gliomas, reduces glioma cell growth by cell-cycle arrest and apoptosis. These cellular responses are mediated by augmented expression of the direct targets of miR-10b, including BCL2L11/Bim, TFAP2C/AP-2γ, CDKN1A/p21, and CDKN2A/p16, which normally protect cells from uncontrolled growth. Analysis of The Cancer Genome Atlas expression data set reveals a strong positive correlation between numerous genes sustaining cellular growth and miR-10b levels in human glioblastomas, while proapoptotic genes anticorrelate with the expression of miR-10b. Furthermore, survival of glioblastoma patients expressing high levels of miR-10 family members is significantly reduced in comparison to patients with low miR-10 levels, indicating that miR-10 may contribute to glioma growth in vivo. Finally, inhibition of miR-10b in a mouse model of human glioma results in significant reduction of tumor growth. Altogether, our experiments validate an important role of miR-10b in gliomagenesis, reveal a novel mechanism of miR-10b-mediated regulation, and suggest the possibility of its future use as a therapeutic target in gliomas.