MiR-196a exerts its oncogenic effect in glioblastoma multiforme by inhibition of IκBα both in vitro and in vivo

Background

Recent studies have revealed that miR-196a is upregulated in glioblastoma multiforme (GBM) and that it correlates with the clinical outcome of patients with GBM. However, its potential regulatory mechanisms in GBM have never been reported.

Methods

We used quantitative real-time PCR to assess miR-196a expression levels in 132 GBM specimens in a single institution. Oncogenic capability of miR-196a was detected by apoptosis and proliferation assays in U87MG and T98G cells. Immunohistochemistry was used to determine the expression of IκBα in GBM tissues, and a luciferase reporter assay was carried out to confirm whether IκBα is a direct target of miR-196a. In vivo, xenograft tumors were examined for an antiglioma effect of miR-196a inhibitors.

Results

We present for the first time evidence that miR-196a could directly interact with IκBα 3′-UTR to suppress IκBα expression and subsequently promote activation of NF-κB, consequently promoting proliferation of and suppressing apoptosis in GBM cells both in vitro and in vivo. Our study confirmed that miR-196a was upregulated in GBM specimens and that high levels of miR-196a were significantly correlated with poor outcome in a large cohort of GBM patients. Our data from human tumor xenografts in nude mice treated with miR-196 inhibitors demonstrated that inhibition of miR-196a could ameliorate tumor growth in vivo.

Conclusions

MiR-196a exerts its oncogenic effect in GBM by inhibiting IκBα both in vitro and in vivo. Our findings provide new insights into the pathogenesis of GBM and indicate that miR-196a may predict clinical outcome of GBM patients and serve as a new therapeutic target for GBM.     

Survival effect of first- and second-line treatments for patients with primary glioblastoma: a cohort study from a prospective registry, 1997–2010

Background

Prospective follow-up studies of large cohorts of patients with glioblastoma (GBM) are needed to assess the effectiveness of conventional treatments in clinical practice. We report GBM survival data from the Brain Cancer Register of the Fondazione Istituto Neurologico Carlo Besta (INCB) in Milan, Italy, which collected longitudinal data for all consecutive patients with GBM from 1997 to 2010.

Methods

Survival data were obtained from 764 patients (aged>16 years) with histologically confirmed primary GBM who were diagnosed and treated over a 7-year period (2004–2010) with follow-up to April 2012 (cohort II). Equivalent data from 490 GBM patients diagnosed and treated over the preceding 7 years (1997–2003) with follow-up to April 2005 (cohort I) were available for comparison. Progression-free survival (PFS) was available from 361 and 219 patients actively followed up at INCB in cohorts II and I, respectively.

Results

Survival probabilities were 54% at 1 year, 21% at 2 years, and 11% at 3 years, respectively, in cohort II compared with 47%, 11%, and 5%, respectively, in cohort I. PFS was 22% and 12% at 1 year in cohorts II and I. Better survival and PFS in cohort II was significantly associated with introduction of the Stupp protocol into clinical practice, with adjusted hazard ratios (HRs) of 0.78 for survival and 0.73 for PFS, or a 22% relative decrease in the risk of death and a 27% relative decrease in the risk of recurrence. After recurrence, reoperation was performed in one-fifth of cohort I and in one-third of cohort II but was not effective (HR, 1.05 in cohort I and 1.02 in cohort II). Second-line chemotherapy, mainly consisting of nitrosourea-based chemotherapy, temozolomide, mitoxantrone, fotemustine, and bevacizumab, improved survival in both cohorts (HR, 0.57 in cohort I and 0.74 in cohort II). Radiosurgery was also effective (HR, 0.52 in cohort II).

Conclusions

We found a significant increase in overall survival, PFS, and survival after recurrence after 2004, likely due to improvements in surgical techniques, introduction of the Stupp protocol as a first-line treatment, and new standard protocols for second-line chemotherapy and radiosurgery after tumor recurrence. In both cohorts, reoperation after tumor recurrence did not improve survival.     

MRI biomarkers identify the differential response of glioblastoma multiforme to anti-angiogenic therapy

Background

Although anti-angiogenic therapy (AATx) holds great promise for treatment of malignant gliomas, its therapeutic efficacy is not well understood and can potentially increase the aggressive recurrence of gliomas. It is essential to establish sensitive, noninvasive biomarkers that can detect failure of AATx and tumor recurrence early so that timely adaptive therapy can be instituted. We investigated the efficacy of MRI biomarkers that can detect response to different classes of AATxs used alone or in combination with radiation.

Methods

Murine intracranial glioma xenografts (NOD/SCID) were treated with sunitinib, VEGF-trap or B20 (a bevacizumab equivalent) alone or in combination with radiation. MRI images were acquired longitudinally before and after treatment, and various MRI parameters (apparent diffusion coefficient, T₁w + contrast, dynamic contrast-enhanced [DCE], initial area under the contrast enhancement curve, and cerebral blood flow) were correlated to tumor cell proliferation, overall tumor growth, and tumor vascularity.

Results

Combinatorial therapies reduced tumor growth rate more efficiently than monotherapies. Apparent diffusion coefficient was an accurate measure of tumor cell density. Vascular endothelial growth factor (VEGF)-trap or B20, but not sunitinib, resulted in significant reduction or complete loss of contrast enhancement. This reduction was not due to a reduction in tumor growth or microvascular density, but rather was explained by a reduction in vessel permeability and perfusion. We established that contrast enhancement does not accurately reflect tumor volume or vascular density; however, DCE-derived parameters can be used as efficient noninvasive biomarkers of response to AATx.

Conclusions

MRI parameters following therapy vary based on class of AATx. Validation of clinically relevant MRI parameters for individual AATx agents is necessary before incorporation into routine practice.     

Targeting adaptive glioblastoma: an overview of proliferation and invasion

Glioblastoma is one of the most devastating cancers, in which tumor cell infiltration into surrounding normal brain tissue confounds clinical management. This review describes basic and translational research into glioma proliferation and invasion, in particular the phenotypic switch underlying a stochastic “go or grow” model of tumor cell behavior. We include recent progress in system genomics, cancer stem cell theory, and tumor–microenvironment interaction, from which novel therapeutic strategies may emerge for managing this malignant disease. We suggest that an effective therapeutic strategy should target both adaptive glioblastoma cells and the stroma–tumor interaction.     

Differential expression of miR200a-3p and miR21 in grade II–III and grade IV gliomas: Evidence that miR200a-3p is regulated by O6-methylguanine methyltransferase and promotes temozolomide responsiveness

Glioblastoma multiforme (GBM) is the most common primary brain tumor and is among the deadliest of human cancers. Dysregulation of microRNAs (miRNAs) expression is an important step in tumor progression as miRNAs can act as tumor suppressors or oncogenes and may affect cell sensitivity to chemotherapy. Whereas the oncogenic miR21 has been shown to be overexpressed in gliomas, the expression and function of the tumor-supressor miR200a in GBMs remains unknown. In this study, we show that miR21 is upregulated in grade IV (GBMs) vs. grade II–III (LGs) gliomas, confirming that miR21 expression level is correlated with tumor grade, and that it may be considered as a marker of tumor progression. Conversely, miR200a is demonstrated for the first time to be downregulated in GBMs compared with LGs, and overexpression of miR200a in GBM cells is shown to promote TMZ-sensitivity. Interestingly, miR200a but not miR21 expression level is significantly higher in TMZ-responsive vs. -unresponsive tumoral glial cells in primary culture. Furthermore, miR200a appears negatively correlated with the expression of the DNA repair enzyme O⁶-methylguanine methyltransferase (MGMT), and the inhibition of MGMT activity results in an increase of miR200a expression in GBM cells. Taken together, these data strongly suggest that miR200a is likely to act as a crucial antitumoral factor regarding glioma progression. Interplay between miR200a and MGMT should be considered as potential mechanism involved in therapeutic response.     

Significance of interleukin-13 receptor alpha 2–targeted glioblastoma therapy

Glioblastoma multiforme (GBM) remains one of the most lethal primary brain tumors despite surgical and therapeutic advancements. Targeted therapies of neoplastic diseases, including GBM, have received a great deal of interest in recent years. A highly studied target of GBM is interleukin-13 receptor α chain variant 2 (IL13Rα2). Targeted therapies against IL13Rα2 in GBM include fusion chimera proteins of IL-13 and bacterial toxins, nanoparticles, and oncolytic viruses. In addition, immunotherapies have been developed using monoclonal antibodies and cell-based strategies such as IL13Rα2-pulsed dendritic cells and IL13Rα2-targeted chimeric antigen receptor–modified T cells. Advanced therapeutic development has led to the completion of phase I clinical trials for chimeric antigen receptor–modified T cells and phase III clinical trials for IL-13–conjugated bacterial toxin, with promising outcomes. Selective expression of IL13Rα2 on tumor cells, while absent in the surrounding normal brain tissue, has motivated continued study of IL13Rα2 as an important candidate for targeted glioma therapy. Here, we review the preclinical and clinical studies targeting IL13Rα2 in GBM and discuss new advances and promising applications.     

Potential novel role of bevacizumab in glioblastoma and cervical cancer

The VEGF-A binding monoclonal antibody bevacizumab is a widely prescribed angiogenesis inhibitor and indicated for many types of cancer. As shown by three randomized phase 3 trials recently published in the New England Journal of Medicine, novel indications for this drug are still being explored. In the RTOG 0825 and AVAglio trials the effect of bevacizumab addition to standard therapy in newly diagnosed glioblastoma (radiotherapy plus temozolomide) was investigated, while in GOG 240 the combination of platinum-based chemotherapy plus bevacizumab was explored in advanced cervical cancer. In RTOG 0825, addition of bevacizumab to standard therapy did not result in survival benefit, and moreover, quality of life was more deteriorated in the bevacizumab arm. In AVAglio, however, progression-free survival (PFS) was significantly increased in the bevacizumab group and these patients also experienced a longer deterioration-free survival. These conflicting results do not fully support the incorporation of bevacizumab in the first-line treatment of glioblastoma. In contrast, in GOG 240 the bevacizumab group (including paclitaxel plus topotecan or paclitaxel) experienced a significant longer PFS and overall survival, and quality of life was not negatively affected in these patients. Thus, these results favor the use of bevacizumab in the treatment of advanced cervical cancer.     

The role of basic fibroblast growth factor in glioblastoma multiforme and glioblastoma stem cells and in their in vitro culture

Glioblastoma multiforme (GBM) is the most malignant form of central nervous system tumor, and current therapies are largely ineffective at treating the cancer. Developing a more complete understanding of the mechanisms controlling the tumor is important in order to explore new possible treatment options. It is speculated that the presence of glioblastoma stem or stem-like cells (GSCs), a rare type of pluripotent cancer cell that possesses the ability to self-renew and generate tumors, could be an important factor contributing to the resistance to treatment and deadliness of the cancer. A comprehensive knowledge of the mechanisms controlling the expression and properties of GSCs is currently lacking, and one promising area for further exploration is in the influence of basic fibroblast growth factor (FGF-2) on GSCs. Recent studies reveal that FGF-2 plays a significant part in regulating GBM, and the growth factor is commonly included as a supplement in media used to culture GSCs in vitro. However, the particular role that FGF-2 plays in GSCs has not been as extensively explored. Therefore, understanding how FGF-2 is involved in GSCs and in GBMs could be an important step towards a more complete comprehension of the managing the disease. In this review, we look at the structure, signaling pathways, and specific role of FGF-2 in GBM and GSCs. In addition, we explore the use of FGF-2 in cell culture and using its synthetic analogs as a potential alternative to the growth factor in culture medium.