Chemotherapeutic options for primary brain tumors

Targeted brain delivery nanoparticles for malignant gliomas

Brain tumors display the highest mortality rates of all childhood cancers, and over the last decade its prevalence has steadily increased in elderly. To date, effective treatments for brain tumors and particularly for malignant gliomas remain a challenge mainly due to the low permeability and high selectivity of the blood-brain barrier (BBB) to conventional anticancer drugs. In recent years, the elucidation of the cellular mechanisms involved in the transport of substances into the brain has boosted the development of therapeutic-targeted nanoparticles (NPs) with the ability to cross the BBB. Here, we present a comprehensive overview of the available therapeutic strategies developed against malignant gliomas based on 'actively targeted' NPs, the challenges of crossing the BBB and blood-brain tumor barrier as well as its mechanisms and a critical assessment of clinical studies that have used targeted NPs for the treatment of malignant gliomas. Finally, we discuss the potential of actively targeted NP-based strategies in clinical settings, its possible side effects and future directions for therapeutic applications. First draft submitted: 4 October 2016; Accepted for publication: 14 October 2016; Published online: 23 November 2016.

Proteomic analysis of human glioblastoma cell lines differently resistant to a nitric oxide releasing agent

Glioblastoma multiforme is the most aggressive astrocytoma characterized by the development of resistant cells to various cytotoxic stimuli. Nitric oxide (NO) is able to overcome tumor resistance in PTEN mutated rat C6 glioma cells due to its ability to inhibit cell growth by influencing the intracellular distribution of ceramide. The aim of this study is to monitor the effects of NO donor PAPANONOate on ceramide trafficking in human glioma cell lines, CCF-STTG1 (PTEN-mutated, p53-wt) and T98G (PTEN-harboring, p53-mutated), together with the assessment of their differential molecular signature by 2D-DIGE and MALDI mass spectrometry. In the CCF-STTG1 cell line, the results indicate that treatment with PAPANONOate decreased cell proliferation (<50%) and intracellular trafficking of ceramide, assessed by BODIPY-C5Cer, while these events were not observed in the T98G cell line. Proteomic results suggest that CCF-STTG1 cells are characterized by an increased expression of proteins involved in NO-associated ER stress (i.e. protein disulfide-isomerase A3, calreticulin, 78 kDa glucose-regulated protein), which could compromise ceramide delivery from ER to Golgi, leading to ceramide accumulation in ER and partial growth arrest. Conversely, T98G cell lines, resistant to NO exposure, are characterized by increased levels of cytosolic antioxidant proteins (i.e. glutathione-S-transferase P, peroxiredoxin 1), which might buffer intracellular NO. By providing differential ceramide distribution after NO exposure and differential protein expression of two high grade glioma cell lines, this study highlights specific proteins as possible markers for tumor aggressiveness. This study demonstrates that, in two different high grade glioma cell lines, NO exposure results in a different ceramide distribution and protein expression. Furthermore, this study highlights specific proteins as possible markers for tumor aggressiveness.

Advances in diagnostic and treatment modalities for intracranial tumors

Intracranial neoplasia is a common clinical condition in domestic companion animals, particularly in dogs. Application of advances in standard diagnostic and therapeutic modalities together with a broad interest in the development of novel translational therapeutic strategies in dogs has resulted in clinically relevant improvements in outcome for many canine patients. This review highlights the status of current diagnostic and therapeutic approaches to intracranial neoplasia and areas of novel treatment currently in development.

A novel intracellular peptide derived from g1/s cyclin d2 induces cell death

Intracellular peptides are constantly produced by the ubiquitin-proteasome system, and many are probably functional. Here, the peptide WELVVLGKL (pep5) from G1/S-specific cyclin D2 showed a 2-fold increase during the S phase of HeLa cell cycle. pep5 (25-100 μm) induced cell death in several tumor cells only when it was fused to a cell-penetrating peptide (pep5-cpp), suggesting its intracellular function. In vivo, pep5-cpp reduced the volume of the rat C6 glioblastoma by almost 50%. The tryptophan at the N terminus of pep5 is essential for its cell death activity, and N terminus acetylation reduced the potency of pep5-cpp. WELVVL is the minimal active sequence of pep5, whereas Leu-Ala substitutions totally abolished pep5 cell death activity. Findings from the initial characterization of the cell death/signaling mechanism of pep5 include caspase 3/7 and 9 activation, inhibition of Akt2 phosphorylation, activation of p38α and -γ, and inhibition of proteasome activity. Further pharmacological analyses suggest that pep5 can trigger cell death by distinctive pathways, which can be blocked by IM-54 or a combination of necrostatin-1 and q-VD-OPh. These data further support the biological and pharmacological potential of intracellular peptides.

Chemotherapeutic resistance in anaplastic astrocytoma cell lines treated with a temozolomide-lomeguatrib combination

The treatment of anaplastic astrocytoma (AA) is controversial. New chemotherapeutic approaches are needed for AA treatment. Temozolomide (TMZ) is one of the chemotherapeutic drugs for the treatment of AA. The cytotoxic effects of TMZ can be removed by the MGMT (O(6)-methylguanine-DNA methyltransferase) enzyme. Then, chemotherapeutic resistance to TMZ occurs. MGMT inhibition by MGMT inactivators (such as lomeguatrib) is an important anticancer therapeutic approach to circumvent TMZ resistance. We aim to investigate the effect of TMZ-lomeguatrib combination on MGMT expression and TMZ sensitivity of SW1783 and GOS-3 AA cell lines. The sensitivity of SW1783 and GOS-3 cell lines to TMZ and to the combination of TMZ and lomeguatrib was determined by a cytotoxicity assay. MGMT methylation was detected by MS-PCR. MGMT and p53 expression were investigated by real-time PCR after drug treatment, and the proportion of apoptotic cells was analyzed by flow cytometry. When the combination of TMZ-lomeguatrib (50 μM) was used in AA cell lines, IC50 values were reduced compared to only using TMZ. MGMT expression was decreased, p53 expression was increased, and the proportion of apoptotic cells was induced in both cell lines. The lomeguatrib-TMZ combination did not have any effect on the cell cycle and caused apoptosis by increasing p53 expression and decreasing MGMT expression. Our study is a pilot study investigating a new therapeutic approach for AA treatment, but further research is needed.

Characterizing the role of PCDH9 in the regulation of glioma cell apoptosis and invasion

PCDH9, a member of the protocadherin superfamily, is frequently lost in many different cancer types. This study aimed to detect PCDH9 expression in glioma tissues. This study also assessed the effects of PCDH9 expression in two different glioma cell lines. This was accomplished by manipulating PCDH9 expression in these glioma cell lines. The data showed that the expression of PCDH9 mRNA and protein was significantly decreased in gliomas compared to normal brain tissues. Lentivirus carrying PCDH9 cDNA restored PCDH9 expression in the U87 and U251 glioma cell lines. PCDH9 restoration in these cell lines reduced tumor cell viability, induced apoptosis, and caused G0/G1 cell cycle arrest. PCDH9 expression also suppressed the colony formation ability and invasion capacity of U87 and U251 cells. Molecularly, the restoration of PCDH9 expression upregulated Bax protein expression, but downregulated Bcl-2 and cyclin D1 expression. These data from the current study suggest that the loss of PCDH9 expression could contribute to glioma development and/or progression. Further studies will evaluate PCDH9 expression as a biomarker for the early detection of gliomas and as a prognostic indicator for this cancer type.

Chemotherapy wafers for high grade glioma

BACKGROUND

Standard treatment for high grade glioma (HGG) usually entails surgery (either biopsy or resection) followed by radiotherapy plus or minus temozolomide. Implanting wafers impregnated with chemotherapy agents into the resection cavity represents a novel means of delivering drugs directly to the resection cavity with potentially fewer systemic side effects. It is not clear how effective this modality is or whether it should be recommended as part of standard care for patients with HGG.

OBJECTIVES

To estimate the clinical effectiveness of chemotherapy wafers for patients with HGG.

SEARCH STRATEGY

The following databases were searched: CENTRAL (issue 4. 2010); MEDLINE and EMBASE. The original search strategy also included: Science Citation Index; Physician Data Query; and the meta-Register of Controlled Trials. Reference lists of all identified studies were searched. The Journal of Neuro-Oncology and Neuro-oncology were hand searched from 1999 to 2010, including all conference abstracts. Neuro-oncologists, trial authors and drug manufacturers were contacted regarding ongoing and unpublished trials.

SELECTION CRITERIA

Patients included those of all ages with a histologically proven diagnosis of HGG (using intra-operative analysis when undergoing first resection). Therapy could be instigated for either newly diagnosed disease (primary therapy) or at recurrence. Interventions included insertion of chemotherapy wafers to the resection cavity. Included studies had to be randomised controlled trials (RCTs).

DATA COLLECTION AND ANALYSIS

Two independent review authors assessed the search results for relevance and undertook critical appraisal according to pre-specified guidelines.

MAIN RESULTS

In primary disease two RCTs assessing the effect of carmustine impregnated wafers (Gliadel®) and enrolling a total of 272 participants were identified. Survival was increased with Gliadel® compared to placebo (hazard ratio (HR) 0.65, 95% Confidence Interval (CI) 0.48 to 0.86, P = 0.003). In recurrent disease a single RCT was included comparing Gliadel® with placebo and enrolled 222 participants. It did not demonstrate a significant survival increase (HR 0.83, 95% CI 0.62 to 1.10, P = 0.2). There was no suitable data for any of the secondary outcome measures. Adverse events were not more common in either arm and are presented in a descriptive fashion.

AUTHORS' CONCLUSIONS

Carmustine impregnated wafers (Gliadel®) result in improved survival without an increased incidence of adverse events over placebo wafers when used for primary disease therapy. There is no evidence of benefit for any other outcome measures. In recurrent disease Gliadel® does not appear to confer any additional benefit.

PPARgamma agonists inhibit growth and expansion of CD133+ brain tumour stem cells

Brain tumour stem cells (BTSCs) are a small population of cells that has self-renewal, transplantation, multidrug resistance and recurrence properties, thus remain novel therapeutic target for brain tumour. Recent studies have shown that peroxisome proliferator-activated receptor gamma (PPARgamma) agonists induce growth arrest and apoptosis in glioblastoma cells, but their effects on BTSCs are largely unknown. In this study, we generated gliospheres with more than 50% CD133+ BTSC by culturing U87MG and T98G human glioblastoma cells with epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF). In vitro treatment with PPARgamma agonist, 15-Deoxy-Delta(12,14)-Prostaglandin J(2) (15d-PGJ2) or all-trans retinoic acid resulted in a reversible inhibition of gliosphere formation in culture. Peroxisome proliferator-activated receptor gamma agonists inhibited the proliferation and expansion of glioma and gliosphere cells in a dose-dependent manner. Peroxisome proliferator-activated receptor gamma agonists also induced cell cycle arrest and apoptosis in association with the inhibition of EGF/bFGF signalling through Tyk2-Stat3 pathway and expression of PPARgamma in gliosphere cells. These findings demonstrate that PPARgamma agonists regulate growth and expansion of BTSCs and extend their use to target BTSCs in the treatment of brain tumour.

Pharmacogenomics of brain cancer and personalized medicine in malignant gliomas

The pharmacogenetics of cancer treatment has been aimed at identifying genetic components of interindividual variability in patients' response to cancer chemotherapy and toxicity. This, in turn, will establish an individually based treatment, and also elucidate the molecular basis of the treatment regimen for further improvements. Brain cancer is an instructive example for the potential contributions of pharmacogenomics to improved treatment in the 21st century. Patients with oligodendrogliomas have benefited from phamacogenomics, as there is a clear relationship between response to chemotherapy and chromosomal profile. Drug efficacy, safety and response could be improved by using pharmacogenomics to identify genetic markers that differentiate responder from nonresponder patient groups, as well as identifying patients likely to develop adverse drug reactions. This review will focus on how pharmacogenomics by microarray studies may lead to much more accurate tumor classification, drug and biomarker discovery, and drug efficacy testing. We will discuss relevant scientific advances in pharmacogenetics for more personalized chemotherapy.

Chemotherapeutic wafers for High Grade Glioma

BACKGROUND

Standard treatment for high grade glioma (HGG) usually entails biopsy or surgical resection where possible followed by radiotherapy. Systemic chemotherapy is usually only given in selected cases and its use is often limited by side effects. Implanting wafers impregnated with chemotherapy agents into the resection cavity represents a novel means of delivering drugs to the central nervous system (CNS) with fewer side effects. It is not clear how effective this modality is or whether it should be recommended as part of standard care for HGG.

OBJECTIVES

To assess whether chemotherapeutic wafers have any advantage over conventional therapy for HGG.

SEARCH STRATEGY

The following databases were searched: The Cochrane Central Register of Controlled Trials (CENTRAL), Issue 2, 2007, MEDLINE, EMBASE, SCIENCE CITATION INDEX, Physician Data Query and the meta-Register of Controlled Trials. Reference lists of all identified studies were searched. The Journal of Neuro-Oncology was hand searched from 1999 to 2007, including all conference abstracts. Neuro-oncologists were contacted regarding ongoing and unpublished trials.

SELECTION CRITERIA

Patients included those of all ages with a presumed diagnosis of malignant glioma from clinical examination and radiology. Interventions included insertion of chemotherapeutic wafers to the resection cavity at either primary surgery or for recurrent disease. Included studies had to be randomised controlled trials (RCTs).

DATA COLLECTION AND ANALYSIS

Quality assessment and data extraction were undertaken by two review authors. Outcome measures included survival, time to progression, quality of life (QOL) and adverse events.

MAIN RESULTS

In primary disease two RCTs assessing the effect of carmustine impregnated wafers (Gliadel(R)) and enrolling a total of 272 participants were identified. Survival was increased (hazard ratio (HR) 0.65 confidence interval (CI) 0.48 to 0.86 p = 0.003). In recurrent disease a single RCT was included assessing the effect of Gliadel(R) and enrolling 222 participants. It did not demonstrate a significant survival increase (HR 0.83 CI 0.62 to 1.10 p = 0.2). There was no suitable data for time to progression or QOL. Adverse events were not more common in either arm, and were presented in a descriptive fashion.

AUTHORS' CONCLUSIONS

Gliadel(R) results in a prolongation of survival without an increased incidence of adverse events when used as primary therapy. There is no evidence of enhanced progression free survival (PFS) or QOL. In recurrent disease, Gliadel(R) does not appear to confer any added benefit. These findings are based on the results of three RCTs with approximately 500 patients in total.

mTORC2 activity is elevated in gliomas and promotes growth and cell motility via overexpression of rictor

mTORC2 is a multimeric kinase composed of the mammalian target of rapamycin kinase (mTOR), mLST8, mSin1, and rictor. The complex is insensitive to acute rapamycin exposure and has shown functions in controlling cell growth and actin cytoskeletal assembly. mTORC2 has recently been shown to phosphorylate and activate Akt. Because approximately 70% of gliomas harbor high levels of activated Akt, we investigated whether mTORC2 activity was elevated in gliomas. In this study, we found that mTORC2 activity was elevated in glioma cell lines as well as in primary tumor cells as compared with normal brain tissue (P < 0.05). Moreover, we found that rictor protein and mRNA levels were also elevated and correlated with increased mTORC2 activity. Overexpression of rictor in cell lines led to increased mTORC2 assembly and activity. These lines exhibited increased anchorage-independent growth in soft agar, increased S-phase cell cycle distribution, increased motility, and elevated integrin beta(1) and beta(3) expression. In contrast, small interfering RNA-mediated knockdown of rictor inhibited these oncogenic activities. Protein kinase C alpha (PKC alpha) activity was shown to be elevated in rictor-overexpressing lines but reduced in rictor-knockdown clones, consistent with the known regulation of actin organization by mTORC2 via PKC alpha. Xenograft studies using these cell lines also supported a role for increased mTORC2 activity in tumorigenesis and enhanced tumor growth. In summary, these data suggest that mTORC2 is hyperactivated in gliomas and functions in promoting tumor cell proliferation and invasive potential due to increased complex formation as a result of the overexpression of rictor.