Retinoids inhibit human glioma cell proliferation and migration in primary cell cultures but not in established cell lines

Application of Ethyl Cellulose and Ethyl Cellulose + Polyethylene Glycol for the Development of Polymer-Based Formulations using Spray-Drying Technology for Retinoic Acid Encapsulation

Ethyl cellulose (EC)-based microparticles, with and without the incorporation of polyethylene glycol (PEG) as a second encapsulating agent, were prepared using the spray-drying process for the encapsulation of retinoic acid (RA). The production of a suitable controlled delivery system for this retinoid will promote its antitumor efficiency against acute promyelocytic leukemia (APL) due to the possibility of increasing the bioavailability of RA. Product yield ranged from 12 to 28% in all the microparticle formulations, including unloaded microparticles and RA-loaded microparticles. Microparticles with a mean diameter between 0.090 ± 0.002 and 0.54 ± 0.02 µm (number size distribution) and with an irregular form and rough surface were obtained. Furthermore, regarding RA-loaded microparticles, both polymer-based formulations exhibited an encapsulation efficiency of around 100%. A rapid and complete RA release was reached in 40 min from EC− and EC + PEG-based microparticles.

Current Opportunities for Targeting Dysregulated Neurodevelopmental Signaling Pathways in Glioblastoma

Glioblastoma (GBM) is the most common and highly lethal type of brain tumor, with poor survival despite advances in understanding its complexity. After current standard therapeutic treatment, including tumor resection, radiotherapy and concomitant chemotherapy with temozolomide, the median overall survival of patients with this type of tumor is less than 15 months. Thus, there is an urgent need for new insights into GBM molecular characteristics and progress in targeted therapy in order to improve clinical outcomes. The literature data revealed that a number of different signaling pathways are dysregulated in GBM. In this review, we intended to summarize and discuss current literature data and therapeutic modalities focused on targeting dysregulated signaling pathways in GBM. A better understanding of opportunities for targeting signaling pathways that influences malignant behavior of GBM cells might open the way for the development of novel GBM-targeted therapies.

Pre-diagnostic circulating concentrations of fat-soluble vitamins and risk of glioma in three cohort studies

Few prospective studies have evaluated the relation between fat-soluble vitamins and glioma risk. Using three cohorts-UK Biobank (UKB), Nurses' Health Study (NHS), and Health Professionals Follow-Up Study (HPFS), we investigated associations of pre-diagnostic concentrations of fat-soluble vitamins D, A, and E with incident glioma. In 346,785 participants (444 cases) in UKB, associations with vitamin D (25-hydroxyvitamin D [25(OH)D]) were evaluated by Cox proportional hazards regression. In NHS (52 cases, 104 controls) and HPFS (32 cases, 64 controls), associations with 25(OH)D, vitamin A (retinol), and vitamin E (α- and γ-tocopherol) were assessed using conditional logistic regression. Our results suggested plasma concentrations of 25(OH)D and retinol were not associated with glioma risk. Comparing the highest to lowest tertile, the multivariable hazard ratio (MVHR) for 25(OH)D was 0.87 (95% confidence interval [CI] 0.68-1.11) in UKB and the multivariable risk ratio (MVRR) was 0.97 (95% CI 0.51-1.85) in NHS and HPFS. In NHS and HPFS, the MVRR for the same comparison for retinol was 1.16 (95% CI 0.56-2.38). Nonsignificant associations were observed for α-tocopherol (MVRRtertile3vs1 = 0.61, 95% CI 0.29-1.32) and γ-tocopherol (MVRR tertile3vs1 = 1.30, 95% CI 0.63-2.69) that became stronger in 4-year lagged analyses. Further investigation is warranted on a potential association between α- and γ-tocopherol and glioma risk.

Daily Lifestyle Modifications to Improve Quality of Life and Survival in Glioblastoma: A Review

Survival in glioblastoma remains poor despite advancements in standard-of-care treatment. Some patients wish to take a more active role in their cancer treatment by adopting daily lifestyle changes to improve their quality of life or overall survival. We review the available literature through PubMed and Google Scholar to identify laboratory animal studies, human studies, and ongoing clinical trials. We discuss which health habits patients adopt and which have the most promise in glioblastoma. While results of clinical trials available on these topics are limited, dietary restrictions, exercise, use of supplements and cannabis, and smoking cessation all show some benefit in the comprehensive treatment of glioblastoma. Marital status also has an impact on survival. Further clinical trials combining standard treatments with lifestyle modifications are necessary to quantify their survival advantages.

Novel bexarotene derivatives: Synthesis and cytotoxicity evaluation for glioma cells in 2D and 3D in vitro models

Glioblastoma (GBM) is an aggressive and lethal form of brain cancer with a high invasion capacity and a lack of effective chemotherapeutics. Retinoid bexarotene (BXR) inhibits the neurospheroidal colony formation and migration of primary glioblastoma cells but has side effects. To enhance the BXR glioblastoma selectivity and cytotoxicity, we chemically modified it at the carboxyl group with either nitroethanolamine (NEA) bearing a NO-donating group (a well-known bioactivity enhancer; BXR-NEA) or with a dopamine (DA) moiety (to represent the highly toxic for various tumor cells N-acyldopamine family; BXR-DA). These two novel compounds were tested in the 2D (monolayer culture) and 3D (multicellular tumor spheroids) in vitro models. Both BXR-DA and BXR-NEA were found to be more toxic for rat C6 and human U-87MG glioma cells than the initial BXR. After 24 h incubation of the cells (monolayer culture) with the drugs, the IC₅₀ values were in the range of 28-42, and 122-152 μM for BXR derivatives and BXR, respectively. The cell death occurred via apoptosis according to the annexin staining and caspase activation. The tumor spheroids demonstrated higher resistance to the treatment compared to that one of the monolayer cultures. BXR-DA and BXR-NEA were more specific against tumor cells than the parental drug, in particular the selectivity index was 1.8-2.7 vs. 1.3-1.5, respectively. Moreover, they inhibited cell migration more effectively than parental BXR according to a scratch assay. Cell spreading from the tumor spheroids was also inhibited. Thus, the obtained BXR derivatives could be promising for glioblastoma treatment.

The Influence of Nutritional and Lifestyle Factors on Glioma Incidence

Cancers are the first main cause of premature death in developed countries. Since brain tumors, especially gliomas, are the most lethal type of cancers, risk factors for their prevalence are still being discussed. Nearly 30–50% of all cancers could be prevented by proper nutritional habits and other lifestyle factors, but their influence on the tumors of the central nervous system has not been explained completely and still requires further studies. That is why we attempted to review the available research in this field, with a special focus on the factors with the proven protective activity observed in other cancers. Adequate vegetables and antioxidants (such as vitamins C and A) provided with a diet could have a protective effect, while other factors have shown no correlation with the incidence of glioma. However, further studies are necessary to determine whether fish, coffee, and tea consumption may prevent glioma. Maintaining proper body weight and undertaking a sufficient level of daily physical activity also seem to be important. Excessive body mass index (BMI) and higher attained height have increased the risk of glioma. In order to link more accurately the chosen factors to the prevalence of gliomas, it seems necessary to conduct large cohort, prospective, controlled studies in different world regions.

The association between the dietary inflammatory index and glioma: A case-control study

BACKGROUND & AIMS

Dietary inflammatory potential has been associated with several cancers. However, the relationship between the dietary inflammatory index (DII®) and glioma is not clear. The aim of this study was to examine DII in relation to glioma.

METHODS

In a hospital-based case-control study, we selected 128 newly-diagnosed cases of glioma and 256 controls. Cases were medically confirmed glioma patients, with no history of other cancers. A validated food frequency questionnaire was used to assess diet. DII scores were calculated based on the quantity of dietary components with inflammatory or anti-inflammatory potential. We used conditional logistic regression models to examine the association between the DII and glioma.

RESULT

Study participants were on average 43 years old and predominantly male (58%). After controlling for age, sex and energy intake, individuals in the highest quartile of DII had 87% (95% CI: 1.00-3.47) increased risk of glioma compared to those in the lowest quartile. Additional adjustment for environmental confounders strengthened the relationship; participants with the greatest DII scores had approximately 2.1 times (95% CI: 1.06, 3.83) increased odds of glioma than those with the lowest intake scores. The association was not substantially altered by further adjustment for BMI (2.76; 1.15-6.60).

CONCLUSION

In conclusion, diets with high anti-inflammatory and low inflammatory nutrient contents are recommended to prevent glioma.

Recent progress in natural dietary non-phenolic bioactives on cancers metastasis

From several decades ago to now, cancer continues to be the leading cause of death worldwide, and metastasis is the major cause of cancer-related deaths. For health benefits, there is a great desire to use non-chemical therapy such as nutraceutical supplementation to prevent pathology development. Over 10,000 different natural bioactives or phytochemicals have been known that possessing potential preventive or supplementary effects for various diseases including cancer. Previously, the in vitro and in vivo anti-invasive and anti-metastatic activities of phenolic acids, monophenol, polyphenol and their derivatives and flavonoids and their derivatives have been reviewed. However, a vast number of natural dietary compounds other than phenolics have been demonstrated to potentially possess the ability to inhibit the invasion and metastasis of various cancers. In this review, we summarize the studies in recent decade on in vitro and in vivo effects and molecular mechanisms of natural bioactives, excluding the phenolics in food, in cancer invasion and metastasis. By combining this review of non-phenolics with the previous phenolics reviews, the puzzle for the contribution of natural dietary bioactives on cancer invasive or/and metastatic progress will be almost complete and more clear.

Small Molecule and Monoclonal Antibody Therapies in Neurooncology

Background:

The prognosis for most patients with primary brain tumors remains poor. Recent advances in molecular and cell biology have led to a greater understanding of molecular alterations in brain tumors. These advances are being translated into new therapies that will hopefully improve the prognosis for patients with brain tumors.

Methods:

We reviewed the literature on small molecule targeted agents and monoclonal antibodies used in brain tumor research and brain tumor clinical trials for the past 20 years.

Results:

Brain tumors commonly express molecular abnormalities. These alterations can lead to the activation of cell pathways involved in cell proliferation. This knowledge has led to interest in novel anti-brain-tumor therapies targeting key components of these pathways. Many drugs and monoclonal antibodies have been developed that modulate these pathways and are in various stages of testing.

Conclusions:

The use of targeted therapies against brain tumors promises to improve the prognosis for patients with brain tumors. However, as the molecular pathogenesis of brain tumors has not been linked to a single genetic defect or target, molecular agents may need to be used in combinations or in tandem with cytotoxic agents. Further study of these agents in well-designed cooperative clinical trials is needed.

The Role of Glucose Modulation and Dietary Supplementation in Patients With Central Nervous System Tumors

OPINION STATEMENT

Central nervous system gliomas are the most common primary brain tumor, and these are most often high-grade gliomas. Standard therapy includes a combination of surgery, radiation, and chemotherapy which provides a modest increase in survival, but virtually, no patients are cured, the overall prognosis remains poor, and new therapies are desperately needed. Tumor metabolism is a well-recognized but understudied therapeutic approach to treating cancers. Dietary and nondietary modulation of glucose homeostasis and the incorporation of dietary supplements and other natural substances are potentially important interventions to affect cancer cell growth, palliate symptoms, reduce treatment-associated side effects, and improve the quality and quantity of life in patients with cancer. These approaches are highly desired by patients. However, they can be financially burdensome, associated with toxicities, and have, on occasion, reduced the efficacy of proven therapies and negatively impacted patient outcomes. The lack of rigorous scientific data evaluating almost all diet and supplement-based therapies currently limits their incorporation into standard oncologic practice. Rigorous studies are needed to document and improve these potentially useful approaches in patients with brain and other malignancies.

CRABP-II- and FABP5-independent responsiveness of human glioblastoma cells to all-trans retinoic acid

Glioblastomas respond differently to all-trans retinoic acid (RA) for unknown reasons. Because CRABP-II and FABP5 mediate RA intracellular signaling respectively and lead to distinct biological consequences, their expression patterns in different grades of astrocytomas and the glioblastoma cells lines LN18, LN428 and U251 were examined to identify potential correlations with RA sensitivities. The response of glioblastoma cells to RA, decitabine or the FABP5 competitive inhibitor, BMS309403, was analyzed. CRABP-II and FABP5 were expressed to varying degrees by the 84-astrocytoma cases examined. Treatment of LN428, U251 and LN18 cells with RA failed to suppress their growth; however, U251 proliferation was inhibited by decitabine. The combination of decitabine and RA suppressed the growth of all three cell lines and induced significant apoptosis of LN428 and U251 cells. Both CRABP-II and FABP5 were transcribed in the three cell lines but FABP5 proteins were undetectable in U251 cells. The ratio of CRABP-II to FABP5 was not altered after RA, decitabine or RA and decitabine treatment and the resistance of cells to RA was not reversed by BMS309403 treatment. In conclusion, CRABP-II and FABP5 expression patterns are neither related to the tumor grades nor correlated with RA sensitivity. Additional molecular factors may be present that determines the sensitivity of glioblastoma cells to RA. Dicitabine may improve the sensitivity of glioblastoma cells to RA, however, its underlying mechanism and its in vivo feasibility need to be investigated.

Biodegradable Elastomers with Antioxidant and Retinoid-like Properties

Intimal hyperplasia (IH) is a type of scarring that involves complex pathophysiological responses of the vasculature to injury, including overproliferation and migration of vascular smooth muscle cells (VSMCs), adventitial fibroblasts, and the activation of macrophages. The objective of this research was to develop a biodegradable polymer with intrinsic properties that would combat the cellular processes that contribute to IH. Citric acid, 1,8-octanediol, and all-trans retinoic acid (atRA) were incorporated into a polyester network via a condensation reaction to form the thermoset poly(1,8-octamethylene-citrate-co-retinate) (POCR). POCR was chemically characterized and assessed for the presence of antioxidant and retinoidlike properties. ^HNMR and ATR-FTIR confirmed the incorporation of atRA into the backbone of the polymer network. POCR was able to scavenge radicals and inhibit lipid peroxidation. The proliferation and migration of vascular smooth muscle cells cultured on POCR were inhibited, whereas endothelial cell proliferation and migration were not. These results are consistent with the biological effects of atRA. These results are the first to demonstrate the synthesis of a polymer with intrinsic antirestenotic properties for potential use in the fabrication of vascular devices such as stents and vascular grafts.

Radiotherapy and temozolomide for anaplastic astrocytic gliomas

We previously reported results of a phase II non-comparative trial that randomized patients with glioblastoma following radiotherapy to one of two different temozolomide schedules, followed by 13-cis-retinoic acid (RA) maintenance. Here we report the results of an exploratory cohort of patients accrued with anaplastic astrocytic tumors. Patients with newly diagnosed anaplastic astrocytoma (AA) or anaplastic oligo-astrocytoma (AOA) were treated with concurrent radiotherapy (60 Gy over 6 weeks) and temozolomide (75 mg/m(2)), and six adjuvant 28-day cycles of either dose-dense (150 mg/m(2), days 1-7, 15-21) or metronomic (50 mg/m(2), days 1-28) temozolomide. Subsequently, maintenance RA (100 mg/m(2), days 1-21/28) was administered until disease progression. All outcome measures were descriptive without intention to compare between treatment arms. Survival was measured by the Kaplan-Meier method. There were 31 patients (21 men, 10 women) with median age 48 years (range 28-74), median KPS 90 (range 60-100). Extent of resection was gross-total in 35%, subtotal 23%, and biopsy 42%. Histology was AA in 90%, and AOA in 10%. MGMT promoter methylation was methylated in 20%, unmethylated in 50%, and uninformative in 30% of 30 tested. Median progression-free survival was 2.1 years (95% CI 0.95-Not Reached), and overall survival 2.9 years (95 % CI 2.0-Not Reached). We report outcomes among a homogeneously treated population with anaplastic astrocytic tumors. Survival was unexpectedly short compared to other reports. These data may be useful as a contemporary historic control for other ongoing or future randomized trials.

Polymeric nanoparticles based on chitooligosaccharide as drug carriers for co-delivery of all-trans-retinoic acid and paclitaxel

An amphiphilic all-trans-retinoic acid (ATRA)-chitooligosaccharide (RCOS) conjugate was synthesized to form self-assembled polymeric nanoparticles to facilitate the co-delivery of ATRA and paclitaxel (PTX). The blank RCOS nanoparticles possessed low hemolytic activity and cytotoxicity, and could efficiently load PTX with a drug loading of 22.2% and a high encapsulation efficiency of 71.3%. PTX-loaded RCOS nanoparticles displayed a higher cytotoxicity to HepG2 cells compared to PTX plus ATRA solution when corrected by the accumulated drug release. Cellular uptake profiles of RCOS nanoparticles were evaluated via confocal laser scanning microscope and flow cytometry with FITC as a fluorescent mark. The RCOS nanoparticles could be rapidly and continuously taken up by HepG2 cells via endocytosis and transported into the nucleus, and the uptake rates increased with particle concentration. These results revealed the promising potential of RCOS nanoparticles as drug carriers for co-delivery of ATRA and PTX or other hydrophobic therapeutic agents.

Treatment of recurrent malignant gliomas with 13-cis-retinoic acid naphthalene triazole

Glioblastoma multiforme and anaplastic astrocytoma are challenges to clinical biologists at present. The patients with glioblastoma have median survival of less than 12 months, despite advances in radiotherapeutical, chemotherapeutical and conventional surgical modalities. Retinoic acids are known to effect in vitro proliferation, differentiation, and apoptosis in colon, prostate, lung, and leukemia cancers. Retinoids are known to have anti-proliferation, anti-migration, and anti-invasive activity against human malignant gliomas, suggesting that retinoids are suitable anticancer agents to inhibit progression of tumors. Recurrent malignant cerebral gliomas have been treated with ATRA and 13-cis RA. However, the side effects associated with the use of high doses of retinoic acid demand for some more potent derivative free from such effects. The present clinical trials are undertaken to investigate the clinical safety and possible efficacy of administering retinoic acid naphthalene triazole (RANT) to patients with recurrent malignant gliomas. The toxicities observed in the patients during RANT treatment were mild. These preliminary results suggest that RANT is more potent compared to RA against recurrent malignant gliomas.

The Role of Chemotherapy in the Treatment of Malignant Astrocytomas

Malignant astrocytomas are aggressive neoplasms with a dismal prognosis despite optimal treatment. Maximal resective surgery is traditionally complemented by radiation therapy. Chemotherapy is now used on patients as initial therapy when their functional status is congruent with further treatment. The classic agents used are nitrosoureas, but temozolomide has taken the front seat recently, with recent data demonstrating increased survival when this agent is used concurrently with radiation therapy in newly diagnosed glioblastoma patients. A new class of agents, refered to as biological modifiers, are increasingly used in clinical trials in an effort to affect the intrinsic biologic aberrations harboured by tumor cells. These drugs comprise differentiation agents, anti-angiogenic agents, matrix-metalloproteinase inhibitors and signal transduction inhibitors, among others. This article reviews the standard cytotoxic agents that have been used to treat malignant astrocytomas, and the different combination regimens offering promise. In addition, recent advances with biological modifiers are also discussed.

Topographical control of cell-cell interaction in C6 glioma by nanodot arrays

Nanotopography modulates the physiological behavior of cells and cell-cell interactions, but the manner of communication remains unclear. Cell networking (syncytium) of astroglia provides the optimal microenvironment for communication of the nervous system. C6 glioma cells were seeded on nanodot arrays with dot diameters ranging from 10 to 200 nm. Cell viability, morphology, cytoskeleton, and adhesion showed optimal cell growth on 50-nm nanodots if sufficient incubation was allowed. In particular, the astrocytic syncytium level maximized at 50 nm. The gap junction protein Cx43 showed size-dependent and time-dependent transport from the nucleus to the cell membrane. The transport efficiency was greatly enhanced by incubation on 50-nm nanodots. In summary, nanotopography is capable of modulating cell behavior and influencing the cell-cell interactions of astrocytes. By fine-tuning the nanoenvironment, it may be possible to regulate cell-cell communications and optimize the biocompatibility of neural implants.

Isotretinoin maintenance therapy for glioblastoma: a retrospective review

OBJECTIVES

The current standard treatment of glioblastoma includes maximal safe surgical resection, radiation, and temozolomide. Although isotretinoin has been used for maintenance therapy to delay tumor recurrence, this approach has not been proven to be effective. The objectives of the study are to compare the overall survival, progression-free survival and tolerability of isotretinoin maintenance therapy in patients who received isotretinoin maintenance therapy to patients who did not receive this treatment.

METHODS

This study is a retrospective review of adult patients with glioblastoma treated at MD Anderson Cancer Center from 2004 to 2009. Patients who underwent surgical resection, radiation with concurrent temozolomide, and adjuvant treatment with temozolomide were included in the control group, and compared to similarly treated patients who received isotretinoin maintenance following adjuvant temozolomide.

RESULTS

Eighteen patients who received isotretinoin maintenance therapy and 70 control patients were included in the analysis. Progression-free survival was 25.3 months with maintenance therapy versus 8.3 months for those not receiving maintenance (p = 0.04). There was no difference in the 2-year or 3-year overall survival estimates (p = 0.11). The common toxicities of isotretinoin included dermatologic-, metabolic-, and psychiatric-related adverse effects.

CONCLUSIONS

Isotretinoin maintenance therapy was associated with increased progression-free survival, but did not increase the overall survival in this retrospective review. The potential benefit of maintenance therapy should be weighed against toxicities and negative impact on quality of life in this patient population.

Effect of lomeguatrib-temozolomide combination on MGMT promoter methylation and expression in primary glioblastoma tumor cells

Temozolomide (TMZ) is commonly used in the treatment of glioblastoma (GBM). The MGMT repair enzyme (O (6)-methylguanine-DNA methyltransferase) is an important factor causing chemotherapeutic resistance. MGMT prevents the formation of toxic effects of alkyl adducts by removing them from the DNA. Therefore, MGMT inhibition is an interesting therapeutic approach to circumvent TMZ resistance. The aim of the study was to investigate the effect of the combination of lomeguatrib (an MGMT inactivator) with TMZ, on MGMT expression and methylation. Primary cell cultures were obtained from GBM tumor tissues. The sensitivity of primary GBM cell cultures and GBM cell lines to TMZ, and to the combination of TMZ and lomeguatrib, was determined by a cytotoxicity assay (MTT). MGMT and p53 expression, and MGMT methylation were investigated after drug application. In addition, the proportion of apoptotic cells and DNA fragmentation was analyzed. The combination of TMZ and lomeguatrib in primary GBM cell cultures and glioma cell lines decreased MGMT expression, increased p53 expression, and did not change MGMT methylation. Moreover, apoptosis was induced and DNA fragmentation was increased in cells. In addition, we also showed that lomeguatrib-TMZ combination did not have any effect on the cell cycle. Finally, we determined that the sensitivity of each primary GBM cells and glioma cell lines to the lomeguatrib-TMZ combination was different and significantly associated with the structure of MGMT methylation. Our study suggests that lomeguatrib can be used with TMZ for GBM treatment, although further clinical studies will be needed so as to determine the feasibility of this therapeutic approach.

All-trans retinoic acid-incorporated nanoparticles of deoxycholic acid-conjugated dextran for treatment of CT26 colorectal carcinoma cells

PURPOSE

All-trans retinoic acid (RA)-incorporated nanoparticles were prepared using deoxycholic acid-conjugated dextran (DexDA). Anticancer activity of RA-incorporated DexDA nanoparticles were tested in vitro and in vivo.

METHODS

RA-incorporated nanoparticles were prepared by dialysis. Antiproliferative and anti-invasive potential of RA-incorporated nanoparticles were studied using CT26 colorectal carcinoma cells.

RESULTS

RA-incorporated nanoparticles have small particle sizes of around 70-300 nm and spherical shapes. The higher drug-feeding ratio and higher substitution degree of deoxycholic acid in the conjugates resulted in higher drug contents, lower loading efficiency, and larger particle size. RA release rate became slower at higher drug contents and higher substitution degree of deoxycholic acid in the DexDA conjugates. The antiproliferation activity, anti-invasive activity, and matrix metalloproteinase 2 expression of RA-incorporated nanoparticles against CT26 cells in vitro was similar to RA. However, RA-incorporated nanoparticles had superior antimetastatic activity in an animal pulmonary metastatic model of CT26 cells compared to RA itself.

CONCLUSION

RA-incorporated nanoparticles showed similar anticancer activity in vitro and superior antimetastatic activity in vivo in a pulmonary metastatic model of CT26 cells. We suggest that RA-incorporated nanoparticles are promising vehicles for efficient delivery of RA.

Differential activation of catalase expression and activity by PPAR agonists: implications for astrocyte protection in anti-glioma therapy

Glioma survival is dismal, in part, due to an imbalance in antioxidant expression and activity. Peroxisome proliferator-activated receptor (PPAR) agonists have antineoplastic properties which present new redox-dependent targets for glioma anticancer therapies. Herein, we demonstrate that treatment of primary cultures of normal rat astrocytes with PPAR agonists increased the expression of catalase mRNA protein, and enzymatic activity. In contrast, these same agonists had no effect on catalase expression and activity in malignant rat glioma cells. The increase in steady-state catalase mRNA observed in normal rat astrocytes was due, in part, to de novo mRNA synthesis as opposed to increased catalase mRNA stability. Moreover, pioglitazone-mediated induction of catalase activity in normal rat astrocytes was completely blocked by transfection with a PPARγ-dominant negative plasmid. These data suggest that defects in PPAR-mediated signaling and gene expression may represent a block to normal catalase expression and induction in malignant glioma. The ability of PPAR agonists to differentially increase catalase expression and activity in normal astrocytes but not glioma cells suggests that these compounds might represent novel adjuvant therapeutic agents for the treatment of gliomas.

Extended adjuvant temozolomide with cis-retinoic acid for adult glioblastoma

OBJECTIVE

To determine the toxicity and effectiveness of 24 months of adjuvant temozolomide (tmz) with cis-retinoic acid (cra) for patients with glioblastoma.

METHODS

This retrospective population-based review considered the charts of all patients diagnosed with glioblastoma in Manitoba and referred to a provincial cancer centre during 2002-2008. Consecutive patients came from a population-based referral centre and provincial cancer registry. All patients were treated according to the local standard of care with surgical resection followed by concurrent radiotherapy and tmz 75 mg/m(2) daily, followed by tmz 150-200 mg/m(2) for days 1-5, repeated every 28 days for up to 24 cycles, and cra 50 mg/m(2) twice daily for days 1-21, repeated every 28 days. The main outcome measures were safety, tolerability, and effectiveness of long-term tmz and cra.

RESULTS

Of 247 patients diagnosed with glioblastoma in Manitoba during the study period, 116 started concurrent chemoradiotherapy, and 80 received adjuvant tmz. Of the patients who started concurrent chemoradiotherapy, 80 began adjuvant chemotherapy. Patients completed a median of 5.5 cycles of tmz and 3 cycles of cra. Grade 3 or 4 hematologic toxicity was noted in 16% of patients. Median overall survival was 15.1 months, and 26.7% of patients remained alive at 2 years.

CONCLUSIONS

Extended adjuvant tmz and cra is well tolerated. However, the population-based effectiveness of this regimen is similar to the clinical trial efficacy of 6 months of adjuvant tmz. Future studies in glioblastoma should incorporate duration of adjuvant chemotherapy into the study design.

Anti-tumor activity of all-trans retinoic acid-incorporated glycol chitosan nanoparticles against HuCC-T1 human cholangiocarcinoma cells

The aim of this study is to investigate antitumor activity of all-trans retinoic acid (RA)-incorporated glycol chitosan (GC) nanoparticles. RA-incorporated GC nanoparticles were prepared by electrostatic interaction between RA and amine group of GC. RA-incorporated GC nanoparticles have spherical shape and their particle size was 317 ± 34.5 nm. They were simply reconstituted into aqueous solution without changes of intrinsic properties. RA-incorporated GC nanoparticles were evidently inhibited the proliferation of HuCC-T1 cholangiocarcinoma cells at higher than 20 μg/ml of RA concentration while empty GC vegicles did not affect to the viablity of tumor cells. Apoptosis and necrosis analysis of tumor cells with treatment of RA or RA-incorporated GC nanoparticles also supported these results. Invasion test using Matrigel also showed that invasion of tumor cells was significantly inhibited at higher than 20 μg/ml of RA concentration. Wound healing assay also showed that RA-incorporated GC nanoparticles were inhibited migration of tumor cells as similar to RA itself. Our results suggested that RA-incorporated GC nanoparticles is a promising vehicles for RA delivery to HuCC-T1 cholangiocarcinoma cells.

Modulation of glioma risk and progression by dietary nutrients and antiinflammatory agents

Gliomas are tumors of glial origin formed in the central nervous system and exhibit profound morphological and genetic heterogeneity. The etiology of this heterogeneity involves an interaction between genetic alterations and environmental risk factors. Scientific evidence suggests that certain natural dietary components, such as phytoestrogens, flavonoids, polyunsaturated fatty acids, and vitamins, may exert a protective effect against gliomas by changing the nature of the interaction between genetics and environment. Similarly, certain antiinflammatory drugs and dietary modifications, such as methionine restriction and the adoption of low-calorie or ketogenic diets, may take advantage of glioma and normal glial cells' differential requirements for glucose, methionine, and ketone bodies and may, therefore, be effective as part of preventive or treatment strategies for gliomas. Treatment trials of glioma patients and chemoprevention trials of individuals with a known genetic predisposition to glioma using the most promising of these agents, such as the antiinflammatory drugs curcumin and gamma-linolenic acid, are needed to validate or refute these agents' putative role in gliomas.

Synergistic effect of retinoic acid and cytokines on the regulation of glial fibrillary acidic protein expression

Glial fibrillary acidic protein (GFAP) is the main astroglial marker during astrogliogenesis, but it is also expressed in other cell types, including neural stem cells and old neurons. Activation of the JAK/STAT pathway by the IL-6 family of cytokines is the canonical pathway regulating GFAP expression, whereas retinoic acid is thought to be the only inducer of GFAP to operate independently of this pathway. Here, we show that retinoic acid receptor α not only links retinoic acid signaling to the canonical cytokine-stimulated pathway leading to GFAP expression but that it also plays a key role in the synergistic actions of retinoic acid and cytokines on this pathway. Cytokines both potentiate retinoic acid receptor α expression and enhance its binding to DNA and to the Stat3-p300/CBP-Smad transcriptional complex, the cornerstone of the canonical pathway. PI3K is upstream to all the key events leading to the expression of GFAP. Our results give new insights about the role of retinoic acid signaling in GFAP expression.

Randomized phase II trial of chemoradiotherapy followed by either dose-dense or metronomic temozolomide for newly diagnosed glioblastoma

PURPOSE

Alternative dosing schedules of temozolomide may improve survival in patients with newly diagnosed glioblastoma (GBM) by increasing the therapeutic index, overcoming common mechanisms of temozolomide resistance, or both. The goal of this randomized phase II study was to evaluate two different temozolomide regimens in the adjuvant treatment of newly diagnosed GBM.

PATIENTS AND METHODS

Adult patients with newly diagnosed GBM were randomly assigned to receive standard radiotherapy with concurrent daily temozolomide followed by six adjuvant cycles of either dose-dense (150 mg/m(2) days 1 to 7 and 15 to 21) or metronomic (50 mg/m(2) continuous daily) temozolomide. Maintenance doses of 13-cis-retinoic acid were then administered until tumor progression. The primary end point was overall survival (OS) at 1 year. Tumor tissue was assayed to determine O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation status.

RESULTS

Eighty-five eligible patients were enrolled; 42 were randomly assigned to dose-dense and 43 to metronomic temozolomide. The 1-year survival rate was 80% for the dose-dense arm and 69% for the metronomic arm; median OS was 17.1 months (95% CI, 14.0 to 28.1 months) and 15.1 months (95% CI, 12.3 to 18.9 months), respectively. The most common toxicities were myelosuppression (leukopenia, neutropenia, and thrombocytopenia) and elevated liver enzymes. Pseudoprogression was observed in 37% of assessable patients and may have had an impact on estimates of progression-free survival (6.6 months in the dose-dense arm and 5.0 months in the metronomic arm).

CONCLUSION

Both dose-dense and metronomic temozolomide regimens were well tolerated with modest toxicity. The dose-dense regimen appears promising, with 1-year survival of 80%.

PPARgamma and RXRgamma ligands act synergistically as potent antineoplastic agents in vitro and in vivo glioma models

Glioblastoma represent the most common primary brain tumor in adults and are currently considered incurable. We investigated antiproliferative and anti-invasive mechanisms of 6-OH-11-O-hydroxyfenantrene (IIF), a retinoid X receptor ligand, and pioglitazone (PGZ), a peroxisome proliferator-activated receptor gamma activator, in three different glioblastoma cell lines. A dose-dependent reduction of tumor invasion and strong decrease of matrix metalloproteinases 2 and 9 expression was observed, especially when a combination therapy of IIF and PGZ was administered. Combined treatment also markedly reduced proliferation and induced apoptosis in all glioma cell lines tested. This was in particular accompanied by decrease of antiapoptotic proteins Bcl2 and p53, while simultaneously pro-apoptotic cytochrome c, cleaved caspase 3, Bax and Bad levels increased. These in vitro findings were further substantiated in a murine glioma model in vivo, where oral administration of PGZ and IIF resulted in significantly reduced tumor volume and proliferation. Of note, treatment with nuclear receptor ligands was not only effective when the treatment was initiated shortly after the intraparenchymal seeding of the glioma cells, but even when initiated in the last third of the observation period. Collectively, our results demonstrate the effectiveness of a combined treatment of ligands of proliferator-activated receptor and retinoid X receptor against glioblastoma.

Inhibition of all-trans retinoic acid on MDM2 gene expression in astrocytoma cell line SHG-44

OBJECTIVE

To investigate the impact of all-trans retinoic acid (ATRA) on MDM2 gene expression in astrocytoma cell line SHG-44, and to provide basic data for further research on the progression mechanism and gene therapy of human astrocytoma.

METHODS

The differential expressions of MDM2 gene and protein in SHG-44 cells were detected by cDNA microarray and Western blot, respectively, before and after treatment of ATRA. The expressions of MDM2 protein in WHO grade II and grade IV astrocytomas were determined by immunohistochemical streptavidin-peroxidase method. Some differentially expressed genes were selected randomly for Northern blot analysis.

RESULTS

The intensity ratio of ATRA-treated to untreated SHG-44 cell was 0.37 in the cDNA microarray, suggesting that the expression of MDM2 gene was down-regulated in SHG-44 cells after treatment with ATRA. Some genes differentially expressed in the microarray were confirmed by Northern blot. Western blot demonstrated that the optical density ratios of MDM2 to beta-actin in ATRA-treated and untreated SHG-44 were 14.02+/-0.35 and 21.40+/-0.58 (t = 24.728, P = 0.000), respectively, suggesting that the expression of MDM2 protein was inhibited in ATRA-treated SHG-44 cells. Moreover, the percentages of MDM2-positive protein were 24.00% (6/25) and 56.52% (13/23) (chi(2) = 5.298, P = 0.021) in WHO grade II and grade IV astrocytomas, respectively, suggesting that the expression of MDM2 protein may increase along with the elevation of astrocytoma malignancy.

CONCLUSION

ATRA can inhibit MDM2 gene expression in SHG-44 cells, and MDM2 is related to astrocytoma progression.

Pressure-loaded MSCs during early osteodifferentiation promote osteoclastogenesis by increase of RANKL/OPG ratio

Mechanical stress plays an important role in bone remodeling. However, it is still unclear whether mechanical stress regulates osteoclastogenesis mediated by mesenchymal stem cells (MSCs) during initial osteodifferentiation. We investigated the effects of static and dynamic pressures on osteoclast-inducing potential of MSCs during early osteodifferentiation. The osteoclastogenesis was examined using TRAP staining. The mRNA levels of receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) genes were analyzed using real-time RT-PCR. It was shown that MSCs exposed to either pressure during initial osteodifferentiation promoted osteoclastogenesis with the up-regulation of RANKL/OPG ratio. MSCs displayed diverse responses to pressures at different points of initial osteodifferentiation. The RANKL/OPG ratio was significantly increased after osteoinduction in the primary MSCs without pressures exposure, which contradicted the previous report. These results suggest novel mechanisms of the initial biological responses of bone remodeling upon mechanical stimuli.

Differentially expressed genes from the glioblastoma cell line SHG-44 treated with all-trans retinoic acid in vitro

Morphology, immunocytochemistry, growth curve assay, and flow cytometry were used to investigate the effects of all-trans retinoic acid (RA) on cell proliferation, cell cycle progression and differentiation of the astrocytoma cell line SHG-44 from glioblastoma multiforme (World Health Organization grade IV). The differentially expressed genes from RA-treated and normal SHG-44 were identified by cDNA microarray after the cell line SHG-44 was treated with 10muM RA for 3 days. Validation of some differentially expressed genes was performed by Northern Blot analysis. The expression of glial fibrillary acidic protein (GFAP) was markedly increased in RA-treated SHG-44 cells. Other changes included a short shuttle shape, small nucleus, decreased karyoplasm proportion, the formation of increased thin cytoplasmic processes, reduced cell growth and a 15% increase in G0/G1 phase cell populations. In addition, 42 known genes were identified with altered expression in our cDNA microarray. There was stable down-regulation of MDM2 and UGB as well as overexpression of SOD2, CSTB, and G3BP when RA-treated SHG-44 was compared with normal SHG-44. RA simultaneously suppressed the proliferation of SHG-44 cells significantly as well as induced differentiation and altered gene expression.

Concurrent radiotherapy with temozolomide followed by adjuvant temozolomide and cis-retinoic acid in children with diffuse intrinsic pontine glioma

The prognosis of children with diffuse intrinsic pontine glioma (DIPG) is very poor. Radiotherapy remains the standard treatment for these patients, but the median survival time is only 9 months. Currently, the use of concurrent radiotherapy with temozolomide (TMZ) has become the standard care for adult patients with malignant gliomas. We therefore investigated this approach in 12 children diagnosed with DIPG. The treatment protocol consisted of concurrent radiotherapy at a dose of 55.8-59.4 Gy at the tumor site with TMZ (75 mg/m(2)/day) for 6 weeks followed by TMZ (200 mg/m(2)/day) for 5 days with cis-retinoic acid (100 mg/m(2)/day) for 21 days with a 28-day cycle after concurrent radiotherapy. Ten of the 12 patients had a clinical response after the completion of concurrent radiotherapy. Seven patients had a partial response, four had stable disease, and one had progressive disease. At the time of the report, 9 of the 12 patients had died of tumor progression, one patient was alive with tumor progression, and two patients were alive with continuous partial response and clinical improvement. The median time to progression was 10.2 +/- 3.0 months (95% confidence interval [CI], 4.2-16.1 months). One-year progression-free survival was 41.7% +/- 14.2%. The median survival time was 13.5 +/- 3.6 months (95% CI, 6.4-20.5 months). One-year overall survival was 58% +/- 14.2%. The patients who had a partial response after completion of concurrent radiotherapy had a longer survival time (p = 0.036) than did the other patients (those with stable or progressive disease). We conclude that the regimen of concurrent radiotherapy and TMZ should be considered for further investigation in a larger series of patients.

Diffuse pontine gliomas in children: changing strategies, changing results? A mono-institutional 20-year experience

Patients with diffuse pontine gliomas have a median survival of less than one year and represent a challenge for pediatric oncologists, prompting them to attempt experimental therapies. From 1987 to 2005, 62 children with diffuse pontine glioma, not amenable to curative surgery, were treated according to four successive pilot protocols: (1) concomitant chemo-radiotherapy (etoposide, cytarabine, ifosfamide, cisplatin, and dactinomycin); (2) intensive high-dose courses chemotherapy (cisplatin/etoposide, cyclophosphamide/vincristine/methotrexate) and a subsequent course of myeloablative thiotepa followed by radiation and maintenance chemotherapy; (3) cisplatin/etoposide followed by isotretinoin before, during and after focal irradiation; and (4) iv vinorelbine before, during, and after irradiation. Considering all patients, 77% experienced a transient response to treatment, always detectable after radiotherapy. The progression-free survival (PFS) rate was 25 +/- 6% at one year, median PFS was seven months; overall survival (OS) was 45 +/- 6%, median OS was eleven months: no statistical differences in the four studies in terms of outcome were detected. Despite improved diagnostic, therapeutic, and supportive tools in pediatric neuro-oncology, little has been achieved for patients with diffuse pontine tumors.

Polyion Complex Micelles Composed of All-TranS Retinoic Acid and Poly (Ethylene Glycol)-Grafted-Chitosan

The goal of this study is to develop novel types of polyion complex micelles for the drug delivery to brain tumor. Methoxy poly(ethylene glycol) (mPEG)-grafted chitosan (CP) was synthesized in order to make polymeric micelles encapsulating all-trans retinoic acid (ATRA) based on polyion complex formation. Polyion complex micelles were found to have spherical shapes with sizes of about 50 approximately 200 nm. The loading efficiency of micelle was higher than 80% (w/w) for all formulations. 1H nuclear magnetic resonance (NMR) spectra confirmed the formation of polymeric micelles. The CP graft copolymer and ATRA have distinguishing peaks in their 1H NMR spectra. The specific peaks of ATRA disappeared in D2O or DMSO while it appeared at mixtures of D2O/DMSO, indicating that ATRA and chitosan formed ion complex inner-core. In the cell cytotoxicity study using U87MG cells in vitro, polyion complex micelles showed similar cytotoxicity to that of free ATRA. A migration test was performed to investigate the inhibition of tumor cell invasion in vitro. The results suggested that the polyion complex micelles was more effective at inhibiting tumor cell migration than free ATRA.

13-cis Retinoic acid induces apoptosis and cell cycle arrest in human SEB-1 sebocytes

Isotretinoin (13-cis retinoic acid (13-cis RA)) is the most potent inhibitor of sebum production, a key component in the pathophysiology of acne, yet its mechanism of action remains largely unknown. The effects of 13-cis RA, 9-cis retinoic acid (9-cis RA), and all-trans retinoic acid (ATRA) on cell proliferation, apoptosis, and cell cycle proteins were examined in SEB-1 sebocytes and keratinocytes. 13-cis RA causes significant dose-dependent and time-dependent decreases in viable SEB-1 sebocytes. A portion of this decrease can be attributed to cell cycle arrest as evidenced by decreased DNA synthesis, increased p21 protein expression, and decreased cyclin D1. Although not previously demonstrated in sebocytes, we report that 13-cis RA induces apoptosis in SEB-1 sebocytes as shown by increased Annexin V-FITC staining, increased TUNEL staining, and increased cleaved caspase 3 protein. Furthermore, the ability of 13-cis RA to induce apoptosis cannot be recapitulated by 9-cis RA or ATRA, and it is not inhibited by the presence of a retinoid acid receptor (RAR) pan-antagonist AGN 193109. Taken together these data indicate that 13-cis RA causes cell cycle arrest and induces apoptosis in SEB-1 sebocytes by a RAR-independent mechanism, which contributes to its sebosuppressive effect and the resolution of acne.

Effects of toxic doses of glutamate on Cu-Zn and Mn/superoxide dismutases activities in human glioma cell lines

Recent research has implicated glutamate in the growth and invasive migration of gliomas. Superoxide dismutase (SOD) is involved in excitotoxicity and may influence cellular proliferative status. Thus, this study investigated the effects of gliotoxic doses of glutamate on Cu-Zn and Mn/SODs activities in human glioma cell lines. To this end, glioma cell lines (U87MG, U138MG and U251MG) were treated with glutamate (5-200 mM) during 48 h. Then, cell viability assays, clonogenic assay and Cu-Zn and Mn/SODs activities of the cell lines were performed. IC50values of glutamate were similar for both U87MG and U138MG cells (56 and 69 mM, respectively), while a higher value was detected for U251MG cells (110 mM). In the long term, 14 days after glutamate was removed from the culture media, cells showed partial or complete recovery. The effects of glutamate treatment on Cu-Zn and Mn/SODs activities varied among the distinct cell lines. While acute treatment with toxic doses of glutamate caused a significant decrease in the Cu-Zn/SOD activity of U138MG and U251MG cells, it did not affect Cu-Zn/SOD activity in U87MG cells. Only in U251MG cells, acute glutamate treatment decreased significantly Mn/SOD activity. In the long term (14 days after the 48 h treatment), glutamate did not affect either Cu-Zn or Mn/SODs activities. Thus, it may be suggested that SOD vulnerability to glutamate-mediated effects may be related to distinct tumoral cell behavior.

A phase II study of concurrent temozolomide and cis-retinoic acid with radiation for adult patients with newly diagnosed supratentorial glioblastoma

PURPOSE

This Phase II study was designed to determine the median survival time of adults with supratentorial glioblastoma treated with a combination of temozolomide (TMZ) and 13-cis-retinoic acid (cRA) given daily with conventional radiation therapy (XRT).

METHODS AND MATERIALS

This was a single arm, open-labeled, Phase II study. Patients were treated with XRT in conjunction with cRA and TMZ. Both drugs were administered starting on Day 1 of XRT, and chemotherapy cycles continued after the completion of XRT to a maximum of 1 year.

RESULTS

Sixty-one patients were enrolled in the study. Time to progression was known for 55 patients and 6 were censored. The estimated 6-month progression-free survival was 38% and the estimated 1-year progression-free survival was 15%. Median time to progression was estimated as 21 weeks. The estimated 1-year survival was 57%. The median survival was 57 weeks.

CONCLUSIONS

The combined therapy was relatively well tolerated, but there was no survival advantage compared with historical studies using XRT either with adjuvant nitrosourea chemotherapy, with TMZ alone, or with the combination of TMZ and thalidomide. Based on this study, cRA does not seem to add a significant synergistic effect to TMZ and XRT.

Phase II study of fenretinide (NSC 374551) in adults with recurrent malignant gliomas: A North American Brain Tumor Consortium study

PURPOSE

Fenretinide induces apoptosis in malignant gliomas in vitro. This two-stage phase II trial was conducted to determine the efficacy of fenretinide in adults with recurrent malignant gliomas.

PATIENTS AND METHODS

Twenty-two patients with anaplastic gliomas (AG) and 23 patients with glioblastoma (GBM) whose tumors had recurred after radiotherapy and no more than two chemotherapy regimens were enrolled. Fenretinide was given orally on days 1 to 7 and 22 to 28 in 6-week cycles in doses of 600 or 900 mg/m(2) bid.

RESULTS

Six of 21 (29%) patients in the AG arm and two of 23 (9%) patients in the GBM arm had stable disease at 6 months. One patient with AG treated at 900 mg/m(2) bid dosage had a partial radiologic response. Median progression-free survival (PFS) was 6 weeks for the AG arm and 6 weeks for the GBM arm. PFS at 6 months was 10% for the AG arm and 0% for the GBM arm. Grade 1 or 2 fatigue, dryness of skin, anemia, and hypoalbuminemia were the most frequent toxicities reported. The trial was closed after the first stage because of the inadequate activity at the fenretinide doses used. The first-administration mean plasma C(max) for fenretinide was 832 +/- 360 ng/mL at the 600 mg/m(2) bid dosage and 1,213 +/- 261 ng/mL at the 900 mg/m(2) bid dosage.

CONCLUSION

Fenretinide was inactive against recurrent malignant gliomas at the dosage used in this trial. However, additional studies using higher doses of the agent are warranted based on the tolerability of the agent and the potential for activity of a higher fenretinide dosage, as suggested in this trial.

All-trans-retinoic acid release from core-shell type nanoparticles of poly(epsilon-caprolactone)/poly(ethylene glycol) diblock copolymer

Poly(epsilon-caprolactone)/poly(ethylene glycol) (abbreviated as CE) diblock copolymers were synthesized to make core-shell type nanoparticles for all-trans-retinoic acid (atRA). Fluorescence spectroscopy showed that critical association concentration (CAC) value decreased at higher MW of CE diblock copolymer. Drug loading characteristics were studied under various experimental conditions. Drug contents and loading efficiency increased as the MW of poly(epsilon-caprolactone) (PCL) block of CE and initial drug feeding amount increased. Solvent used and preparation method also affected drug contents and loading efficiency. According to 1H NMR using CDCl3 and D2O, specific peaks of the PCL block and drug appearing in CDCl3, disappeared at D2O, suggesting hydrophobic core with hydrophilic shell formed in water. atRA release was faster at smaller MW of copolymer and lower drug contents. Nanoparticles prepared in DMF showed faster release rate compared with those prepared in THF or acetone. Cytotoxicity of atRA against U87MG, U251MG and U343MG cell lines were increased by nanoencapsulation while empty nanoparticles of CE diblock copolymer were not significantly affected.

Differentiation-inducing activity of neomycin in cultured rat glioma cells

Induction of cellular differentiation is an attractive therapeutic strategy against glioma cell proliferation and tumorigenicity. Preliminary in vitro studies have indicated that neomycin inhibits the proliferation of cultured glioma cells and induces changes in cellular morphology, making it potentially useful as a therapeutic agent for gliomas. The purpose of this work was to expand on the preliminary research by investigating the differentiation effect of neomycin in rat C6 glioma cells, using glial fibrillary acidic protein (GFAP) staining as a reliable marker of differentiation for normal astrocytes and for tumors of astrocytic lineage. Cell cultures were grown in the absence or presence of 10 mM neomycin sulfate for 48 hours. Neomycin treatment produced changes in cell morphology and GFAP expression indicative of cellular differentiation. These results suggest that neomycin is an attractive differentiation agent for the treatment of gliomas.

Maintenance therapy with 13-cis retinoid acid in high-grade glioma at complete response after first-line multimodal therapy--a phase-II study

BACKGROUND

Approximately 5% of patients with malignant glioma achieve complete response (CR) after first-line combined modality treatment. Although these patients will invariably suffer from tumor recurrence, they usually do not receive any further treatment to maintain remission. According to in vitro and in vivo clinical studies, 13-cis retinoic acid (cRA) may be a promising agent for maintenance therapy in these patients.

OBJECTIVE

We initiated a clinical study to evaluate the feasibility and toxicity of high-dose cRA as maintenance therapy in patients with high-grade glioma in complete remission after first-line multimodal treatment.

METHODS

A prospective single-arm phase-II study in patients with CR after combined first-line therapy (neurosurgery, radio- and chemotherapy) was performed. Patients were treated with cRA at 60 mg/m2 BS from day 1 to 21 in four-weekly cycles with a dose escalation of up to 100 mg/m2 BS until tumor recurrence. Clinical controls were performed every 4 weeks, magnetic resonance imaging every 8 weeks.

RESULTS

Twenty-three patients (10, grade IV; 13, grade III) were evaluable using an intention-to-treat analysis. Treatment was well tolerated for up to 149 weeks with moderate dermatological symptoms in all patients. No grade 4 toxicities were observed. Median time to progression was 41 weeks, median overall survival 74 weeks after inclusion in the protocol.

DISCUSSION

There is an urgent need for strategies maintaining remission in patients with malignant glioma. Maintenance therapy with high-dose cRA is feasible and well tolerated over long periods of time. A controlled clinical trial to test the efficacy of cRA as a maintenance treatment in malignant glioma is warranted.