Targeting Glioma Cells with Nutraceuticals: Therapeutic Effects Based on Molecular Mechanisms, New Evidence and Perspectives.

Gliomas are the most common malignant cancers of the brain that have unregulated proliferation and are known as highly invasive tumors. Hence, their relapse rate is high, and the prognosis is low. Despite remarkable advances in neuroimaging, neurosurgery, and radiation therapy, they, especially glioblastoma, are highly resistant to treatments, including radiotherapy, surgery, and temozolomide chemotherapy. The average survival rate for patients with malignant glioma is still less than two years. Accordingly, the search for new treatment options has recently become an urgent need. Today, a number of nutraceuticals have been considered because of their special role in inhibiting the angiogenic process, metastasis, and apoptosis, resulting in the inhibition of tumor growth, including glioma. Nutraceuticals can disrupt cancer cells by affecting different pathways. In fact, these compounds can reduce the growth of cancer cells, inhibit their proliferation and angiogenesis, as well as induce apoptosis in these cells and play an important role in various stages of treatment. One of the key targets of nutraceuticals may be to regulate cellular signaling pathways, such as PI3K/Akt/mTORC1, JAK/STAT, and GSK-3, or to exert their effects through other mechanisms, such as cytokine receptors and inflammatory pathways, reactive oxygen species, and miRNAs. This review refers to the results of recent studies and target molecules as well as signaling pathways affected by some nutraceuticals in glioma cells. These studies indicated that clinical trials are imminent and new approaches can be beneficial for patients.

The efficacy of an unrestricted cycling ketogenic diet in preclinical models of IDH wild-type and IDH mutant glioma.

Infiltrative gliomas are the most common neoplasms arising in the brain, and remain largely incurable despite decades of research. A subset of these gliomas contains mutations in isocitrate dehydrogenase 1 (IDH1mut) or, less commonly, IDH2 (together called "IDHmut"). These mutations alter cellular biochemistry, and IDHmut gliomas are generally less aggressive than IDH wild-type (IDHwt) gliomas. Some preclinical studies and clinical trials have suggested that various forms of a ketogenic diet (KD), characterized by low-carbohydrate and high-fat content, may be beneficial in slowing glioma progression. However, adherence to a strict KD is difficult, and not all studies have shown promising results. Furthermore, no study has yet addressed whether IDHmut gliomas might be more sensitive to KD. The aim of the current study was to compare the effects of a unrestricted, cycling KD (weekly alternating between KD and standard diet) in preclinical models of IDHwt versus IDHmut gliomas. In vitro, simulating KD by treatment with the ketone body ß-hydroxybutyrate had no effect on the proliferation of patient-derived IDHwt or IDHmut glioma cells, either in low or normal glucose conditions. Likewise, an unrestricted, cycling KD had no effect on the in vivo growth of patient-derived IDHwt or IDHmut gliomas, even though the cycling KD did result in persistently elevated circulating ketones. Furthermore, this KD conferred no survival benefit in mice engrafted with Sleeping-Beauty transposase-engineered IDHmut or IDHwt glioma. These data suggest that neither IDHwt nor IDHmut gliomas are particularly responsive to an unrestricted, cycling form of KD.

Dietary-Induced Ketogenesis: Adults Are Not Children.

There is increasing interest in the use of a ketogenic diet for various adult disorders; however, the ability of adults to generate ketones is unknown. Our goal was to challenge the hypothesis that there would be no difference between adults and children regarding their ability to enter ketosis. METHODS: Two populations were studied, both treated with identical very low-carbohydrate high-fat diets: a retrospective series of children with epilepsy or/and metabolic disorders (2009-2016) and a prospective clinical trial of adults with glioblastoma. Dietary intake was assessed based upon written food diaries and 24-h dietary recall. Ketogenic ratio was calculated according to [grams of fat consumed]/[grams of carbohydrate and protein consumed]. Ketone levels (ß-hydroxybutyrate) were measured in blood and/or urine. RESULTS: A total of 168 encounters amongst 28 individuals were analyzed. Amongst both children and adults, ketone levels correlated with nutritional ketogenic ratio; however, the absolute ketone levels in adults were approximately one quarter of those seen in children. This difference was highly significant in a multivariate linear regression model, p < 0.0001. CONCLUSIONS: For diets with comparable ketogenic ratios, adults have lower blood ketone levels than children; consequently, high levels of nutritional ketosis are unobtainable in adults.

Feasibility and Biological Activity of a Ketogenic/Intermittent-Fasting Diet in Patients With Glioma.

OBJECTIVE: To examine the feasibility, safety, systemic biological activity, and cerebral activity of a ketogenic dietary intervention in patients with glioma. METHODS: Twenty-five patients with biopsy-confirmed World Health Organization grade 2 to 4 astrocytoma with stable disease after adjuvant chemotherapy were enrolled in an 8-week Glioma Atkins-Based Diet (GLAD). GLAD consisted of 2 fasting days (calories <20% calculated estimated needs) interleaved between 5 modified Atkins diet days (net carbohydrates ≤20 g/d) each week. The primary outcome was dietary adherence by food records. Markers of systemic and cerebral activity included weekly urine ketones, serum insulin, glucose, hemoglobin A1c, insulin-like growth factor-1, and magnetic resonance spectroscopy at baseline and week 8. RESULTS: Twenty-one patients (84%) completed the study. Eighty percent of patients reached ≥40 mg/dL urine acetoacetate during the study. Forty-eight percent of patients were adherent by food record. The diet was well tolerated, with two grade 3 adverse events (neutropenia, seizure). Measures of systemic activity, including hemoglobin A1c, insulin, and fat body mass, decreased significantly, while lean body mass increased. Magnetic resonance spectroscopy demonstrated increased ketone concentrations (ß-hydroxybutyrate [bHB] and acetone) in both lesional and contralateral brain compared to baseline. Average ketonuria correlated with cerebral ketones in lesional (tumor) and contralateral brain (bHB R s = 0.52, p = 0.05). Subgroup analysis of isocitrate dehydrogenase-mutant glioma showed no differences in cerebral metabolites after controlling for ketonuria. CONCLUSION: The GLAD dietary intervention, while demanding, produced meaningful ketonuria and significant systemic and cerebral metabolic changes in participants. Ketonuria in participants correlated with cerebral ketone concentration and appears to be a better indicator of systemic activity than patient-reported food records. TRIAL REGISTRATION INFORMATION: ClinicalTrials.gov Identifier: NCT02286167.

Ketogenic Diet for Malignant Gliomas: a Review.

PURPOSE OF REVIEW: In this review, we examine the postulated mechanisms of therapeutic effect of ketogenic diets in the treatment of gliomas, review the completed clinical trials, and discuss further directions in this field. RECENT FINDINGS: Cancers including gliomas are characterized by derangements in cellular metabolism. In vitro and animal studies have revealed that dietary interventions to reduce glucose and glycolytic pathways in gliomas may have a therapeutic effect. Early trials in patients with malignant gliomas have shown feasibility, but are not robust enough yet to demonstrate clinical applicability. Therapies for malignant gliomas of the brain are increasingly using a multi-targeted approach. The use of ketogenic diets and its variants may offer a unique and promising anti-glioma treatment by exploiting metabolic alterations seen in cancers including gliomas seen at the cellular level, which may work in concert with other therapies.

Cerebral Ketones Detected by 3T MR Spectroscopy in Patients with High-Grade Glioma on an Atkins-Based Diet.

BACKGROUND AND PURPOSE: Ketogenic diets are being explored as a possible treatment for several neurological diseases, but the physiologic impact on the brain is unknown. The objective of this study was to evaluate the feasibility of 3T MR spectroscopy to monitor brain ketone levels in patients with high-grade gliomas who were on a ketogenic diet (a modified Atkins diet) for 8 weeks. MATERIALS AND METHODS: Paired pre- and post-ketogenic diet MR spectroscopy data from both the lesion and contralateral hemisphere were analyzed using LCModel software in 10 patients. RESULTS: At baseline, the ketone bodies acetone and ß-hydroxybutyrate were nearly undetectable, but by week 8, they increased in the lesion for both acetone (0.06 ± 0.03 ≥ 0.27 ± 0.06 IU, P = .005) and ß-hydroxybutyrate (0.07 ± 0.07 ≥ 0.79 ± 0.32 IU, P = .046). In the contralateral brain, acetone was also significantly increased (0.041 ± 0.01 ≥ 0.16 ± 0.04 IU, P = .004), but not ß-hydroxybutyrate. Acetone was detected in 9/10 patients at week 8, and ß-hydroxybutyrate, in 5/10. Acetone concentrations in the contralateral brain correlated strongly with higher urine ketones (r = 0.87, P = .001) and lower fasting glucose (r = -0.67, P = .03). Acetoacetate was largely undetectable. Small-but-statistically significant decreases in NAA were also observed in the contralateral hemisphere at 8 weeks. CONCLUSIONS: This study suggests that 3T MR spectroscopy is feasible for detecting small cerebral metabolic changes associated with a ketogenic diet, provided that appropriate methodology is used.

Diet and risk of glioma: combined analysis of 3 large prospective studies in the UK and USA.

BACKGROUND: Available evidence on diet and glioma risk comes mainly from studies with retrospective collection of dietary data. To minimize possible differential dietary recall between those with and without glioma, we present findings from 3 large prospective studies. METHODS: Participants included 692 176 from the UK Million Women Study, 470 780 from the US National Institutes of Health-AARP study, and 99 148 from the US Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Cox regression yielded study-specific adjusted relative risks for glioma in relation to 15 food groups, 14 nutrients, and 3 dietary patterns, which were combined, weighted by inverse variances of the relative risks. Separate analyses by <5 and ≥5 years follow-up assessed potential biases related to changes of diet before glioma diagnosis. RESULTS: The 1 262 104 participants (mean age, 60.6 y [SD 5.5] at baseline) were followed for 15.4 million person-years (mean 12.2 y/participant), during which 2313 incident gliomas occurred, at mean age 68.2 (SD 6.4). Overall, there was weak evidence for increased glioma risks associated with increasing intakes of total fruit, citrus fruit, and fiber and healthy dietary patterns, but these associations were generally null after excluding the first 5 years of follow-up. There was little evidence for heterogeneity of results by study or by sex. CONCLUSIONS: The largest prospective evidence to date suggests little, if any, association between major food groups, nutrients, or common healthy dietary patterns and glioma incidence. With the statistical power of this study and the comprehensive nature of the investigation here, it seems unlikely we have overlooked major effects of diet on risk of glioma that would be of public health concern.

Effect of ketogenic diets on leukocyte counts in patients with epilepsy.

OBJECTIVES: Ketogenic diets (KDs) have long been used to treat epilepsy and are being explored in a variety of diseases. Preclinical data suggest KDs affect inflammation and cytokine release. It is unknown whether KDs affect white blood cell (WBC) counts over time. This is particularly important in clinical populations who may be immune-suppressed at baseline, such as those with cancer or autoimmune disorders. METHODS: A retrospective review of 125 consecutive adults seen at the Adult Epilepsy Diet Center (AEDC) was conducted. Clinical data regarding compliance, laboratory data, weights, and diet records were collected. A control cohort consisted of patients evaluated at the AEDC who elected not to complete a prescribed KD. RESULTS: In 52 adults on KDs, there was a small but statistically significant decrease in WBC and absolute neutrophil counts at 6 and 12 months into KD therapy. There was no effect on lymphocyte counts. This pattern was also seen in a small population of patients with gliomas (n = 10) on KDs, most (n = 8) of whom had also received chemotherapy and radiation, putting them at risk for bone marrow suppression. Across both glioma and non-glioma groups, patients with pre-existing lymphopenia did not have further worsening of their counts on the KD. CONCLUSIONS: In this retrospective case-control study, a small but significant decrease in total WBC and neutrophil counts was observed in patients with epilepsy treated with the KDs. These patterns are similar in patients with and without gliomas suggesting baseline immunosuppression does not worsen with KD. These findings provide data for prospective confirmatory studies.

Treatment of malignant gliomas with ketogenic or caloric restricted diets: A systematic review of preclinical and early clinical studies.

BACKGROUND & AIMS: Patients with malignant gliomas have a poor prognosis. Diets that lower blood glucose, such as ketogenic or caloric restricted diets (KCRDs), are hypothesized to reduce tumor growth and improve survival. In this systematic review, we summarize preclinical and clinical data on KCRDs in gliomas. METHODS: We searched PubMed and Embase for preclinical and clinical studies on KCRDs in gliomas, and extracted data on surrogate and clinically relevant endpoints, in accordance with PRISMA statement. Quality assessment of clinical studies was performed with use of Cochrane Collaboration's tool. We performed Fisher's exact test to examine associations between surrogate and clinically relevant endpoints. RESULTS: We included 24 preclinical studies, seven clinical studies and one mixed study. Both preclinical and clinical studies were highly heterogeneous. Preclinically, KCRDs reduced tumor growth, but only a small majority of the in vivo studies found improved survival. These effects were stronger in groups with decreased blood glucose than in those with increased ketones, and also when other therapies were used concomitantly. Finally, KCRDs influence multiple molecular-biological pathways, including the PTEN/Akt/TSC2 and NF-kB pathway. In clinical studies, KCRDs seem to be safe and feasible in glioma patients. Clinical data were insufficient to draw conclusions regarding efficacy. CONCLUSIONS: KCRDs have positive effects on malignant gliomas in published preclinical studies. Preliminary clinical data suggest that KCRDs are safe and feasible. However, because of the paucity of clinical data, the efficacy of KCRDs for improving survival and quality of life of glioma patients remains to be proven in prospective studies.

Application of Bayesian evidence synthesis to modelling the effect of ketogenic therapy on survival of high grade glioma patients.

BACKGROUND: Ketogenic therapy in the form of ketogenic diets or calorie restriction has been proposed as a metabolic treatment of high grade glioma (HGG) brain tumors based on mechanistic reasoning obtained mainly from animal experiments. Given the paucity of clinical studies of this relatively new approach, our goal is to extrapolate evidence from the greater number of animal studies and synthesize it with the available human data in order to estimate the expected effects of ketogenic therapy on survival in HGG patients. At the same time we are using this analysis as an example for demonstrating how Bayesianism can be applied in the spirit of a circular view of evidence. RESULTS: A Bayesian hierarchical model was developed. Data from three human cohort studies and 17 animal experiments were included to estimate the effects of four ketogenic interventions (calorie restriction/ketogenic diets as monotherapy/combination therapy) on the restricted mean survival time ratio in humans using various assumptions for the relationships between humans, rats and mice. The impact of different biological assumptions about the relevance of animal data for humans as well as external information based on mechanistic reasoning or case studies was evaluated by specifying appropriate priors. We provide statistical and philosophical arguments for why our approach is an improvement over existing (frequentist) methods for evidence synthesis as it is able to utilize evidence from a variety of sources. Depending on the prior assumptions, a 30-70% restricted mean survival time prolongation in HGG patients was predicted by the models. The highest probability of a benefit (> 90%) for all four ketogenic interventions was obtained when adopting an enthusiastic prior based on previous case reports together with assuming synergism between ketogenic therapies with other forms of treatment. Combinations with other treatments were generally found more effective than ketogenic monotherapy. CONCLUSIONS: Combining evidence from both human and animal studies is statistically possible using a Bayesian approach. We found an overall survival-prolonging effect of ketogenic therapy in HGG patients. Our approach is best compatible with a circular instead of hierarchical view of evidence and easy to update once more data become available.

Role of ketogenic metabolic therapy in malignant glioma: A systematic review.

BACKGROUND: Coined as the "Warburg effect" and a recognized hallmark of cancer, energy metabolism is aberrantly geared towards aerobic glycolysis in most human cancers, including malignant glioma. Ketogenic metabolic therapy (KMT), i.e. nutritional intervention with ketogenic or low-glycemic diets, has been proposed as an anti-neoplastic strategy in glioma patients. MATERIALS AND METHODS: We here review the rationale and existing data investigating KMT in management of patients with malignant glioma and discuss the promise and potential challenges of this novel strategy. Results from published clinical studies and ongoing clinical trials on the topic are systematically reviewed, including 6 published original articles and 10 ongoing clinical trials. Search criteria for this review entailed the databases MEDLINE, EMBASE, Cochrane CENTRAL, and Google Scholar, as well as ICTRP (WHO) and ClinicalTrials.gov (NIH) registries. RESULTS: A substantial amount of preclinical literature demonstrates KMT efficacy and safety in model systems of malignant glioma. Clinical literature indicates KMT safety and feasibility; 2 clinical studies suggest KMT-associated anti-neoplastic efficacy and clinical benefit. Ongoing clinical trials address KMT safety and metabolic impact, patient compliance, and patient clinical/survival benefit. CONCLUSIONS: While clinical evidence is still limited in this evolving field, increasing numbers of ongoing clinical trials suggest that KMT is emerging as a potential therapeutic option and might be combinable with existing anti-neoplastic treatments for malignant glioma. Emerging clinical data will help answer questions concerning safety and efficacy of KMT, and are aiming to identify the most promising KMT regimen, compatibility with other anti-cancer treatments, ethical aspects, and impact on quality of life of cancer patients.

Cyclooxygenase-2 Induction by Amino Acid Deprivation Requires p38 Mitogen-Activated Protein Kinase in Human Glioma Cells.

Glioblastomas (GBMs) are malignant brain tumors that can outstrip nutrient supplies due to rapid growth. Cyclooxygenase-2 (COX-2) has been linked to GBMs and may contribute to their aggressive phenotypes. Amino acid starvation results in COX-2 mRNA and protein induction in multiple human glioma cell lines in a process requiring p38 mitogen-activated protein kinase (p38-MAPK) and the Sp1 transcription factor. Increased vascular endothelial growth factor expression results from starvation-dependent COX-2 induction. These data suggest that COX-2 induction with amino acid deprivation may be a part of the adaptation of glioma cells to these conditions, and potentially alter cellular response to anti-neoplastic therapy.

A ketogenic diet increases transport and oxidation of ketone bodies in RG2 and 9L gliomas without affecting tumor growth.

BACKGROUND: The dependence of tumor cells, particularly those originating in the brain, on glucose is the target of the ketogenic diet, which creates a plasma nutrient profile similar to fasting: increased levels of ketone bodies and reduced plasma glucose concentrations. The use of ketogenic diets has been of particular interest for therapy in brain tumors, which reportedly lack the ability to oxidize ketone bodies and therefore would be starved during ketosis. Because studies assessing the tumors' ability to oxidize ketone bodies are lacking, we investigated in vivo the extent of ketone body oxidation in 2 rodent glioma models. METHODS: Ketone body oxidation was studied using (13)C MR spectroscopy in combination with infusion of a (13)C-labeled ketone body (beta-hydroxybutyrate) in RG2 and 9L glioma models. The level of ketone body oxidation was compared with nontumorous cortical brain tissue. RESULTS: The level of (13)C-beta-hydroxybutyrate oxidation in 2 rat glioma models was similar to that of contralateral brain. In addition, when glioma-bearing animals were fed a ketogenic diet, the ketone body monocarboxylate transporter was upregulated, facilitating uptake and oxidation of ketone bodies in the gliomas. CONCLUSIONS: These results demonstrate that rat gliomas can oxidize ketone bodies and indicate upregulation of ketone body transport when fed a ketogenic diet. Our findings contradict the hypothesis that brain tumors are metabolically inflexible and show the need for additional research on the use of ketogenic diets as therapy targeting brain tumor metabolism.

The Ketogenic Diet Alters the Hypoxic Response and Affects Expression of Proteins Associated with Angiogenesis, Invasive Potential and Vascular Permeability in a Mouse Glioma Model.

BACKGROUND: The successful treatment of malignant gliomas remains a challenge despite the current standard of care, which consists of surgery, radiation and temozolomide. Advances in the survival of brain cancer patients require the design of new therapeutic approaches that take advantage of common phenotypes such as the altered metabolism found in cancer cells. It has therefore been postulated that the high-fat, low-carbohydrate, adequate protein ketogenic diet (KD) may be useful in the treatment of brain tumors. We have demonstrated that the KD enhances survival and potentiates standard therapy in a mouse model of malignant glioma, yet the mechanisms are not fully understood. METHODS: To explore the effects of the KD on various aspects of tumor growth and progression, we used the immunocompetent, syngeneic GL261-Luc2 mouse model of malignant glioma. RESULTS: Tumors from animals maintained on KD showed reduced expression of the hypoxia marker carbonic anhydrase 9, hypoxia inducible factor 1-alpha, and decreased activation of nuclear factor kappa B. Additionally, tumors from animals maintained on KD had reduced tumor microvasculature and decreased expression of vascular endothelial growth factor receptor 2, matrix metalloproteinase-2 and vimentin. Peritumoral edema was significantly reduced in animals fed the KD and protein analyses showed altered expression of zona occludens-1 and aquaporin-4. CONCLUSIONS: The KD directly or indirectly alters the expression of several proteins involved in malignant progression and may be a useful tool for the treatment of gliomas.

The ketogenic diet for the treatment of malignant glioma.

Advances in our understanding of glioma biology has led to an increase in targeted therapies in preclinical and clinical trials; however, cellular heterogeneity often precludes the targeted molecules from being found on all glioma cells, thus reducing the efficacy of these treatments. In contrast, one trait shared by virtually all tumor cells is altered (dysregulated) metabolism. Tumor cells have an increased reliance on glucose, suggesting that treatments affecting cellular metabolism may be an effective method to improve current therapies. Indeed, metabolism has been a focus of cancer research in the last few years, as many pathways long associated with tumor growth have been found to intersect metabolic pathways in the cell. The ketogenic diet (high fat, low carbohydrate and protein), caloric restriction, and fasting all cause a metabolic change, specifically, a reduction in blood glucose and an increase in blood ketones. We, and others, have demonstrated that these metabolic changes improve survival in animal models of malignant gliomas and can potentiate the anti-tumor effect of chemotherapies and radiation treatment. In this review we discuss the use of metabolic alteration for the treatment of malignant brain tumors.

Targeting metabolism with a ketogenic diet during the treatment of glioblastoma multiforme.

Retrospective data suggests that low serum glucose levels during the treatment of glioblastoma multiforme (GBM) may improve clinical outcomes. As such, many patients are implementing a ketogenic diet (KD) in order to decrease serum glucose flux while simultaneously elevating circulating ketones during radiation therapy and chemotherapy for the treatment of GBM. With IRB approval, a retrospective review of patients with high-grade glioma treated with concurrent chemoradiotherapy and adjuvant chemotherapy was carried out from August 2010 to April 2013. Serum glucose and ketone levels, dexamethasone dose, and toxicity of patients undergoing a KD during treatment were also assessed. Blood glucose levels were compared between patients on an unspecified/standard diet and a KD. Toxicity was assessed by Common Terminology Criteria for Adverse Events version 4. In total, 53 patients were analyzed. Six underwent a KD during treatment. The diet was well tolerated with no grade III toxicity and one episode of grade II fatigue. No episodes of symptomatic hypoglycemia were experienced. Four patients are alive at a median follow-up of 14 months. The mean blood glucose of patients on a standard diet was 122 versus 84 mg/dl for those on a KD. Based on this retrospective study, a KD appears safe and well tolerated during the standard treatment of GBM. Dietary restriction of carbohydrates through a KD reduces serum glucose levels significantly, even in conjunction with high dose steroids, which may affect the response to standard treatment and prognosis. Larger prospective trials to confirm this relationship are warranted.

Short-term calorie and protein restriction provide partial protection from chemotoxicity but do not delay glioma progression.

Short-term starvation (STS) protects normal cells while simultaneously sensitizing malignant cells to high-dose chemotherapeutic drugs in mice and possibly patients. The fasting-dependent protection of normal cells and sensitization of malignant cells depends, in part, on reduced levels of insulin-like growth factor-1 (IGF-1) and glucose. Calorie restricted diets with defined macronutrient (carbohydrate, protein, fat) ratios were evaluated for the effects on stress sensitization markers and protection in mice treated with high-dose chemotherapy. We show that short-term CR significantly reduced both glucose and IGF-1 levels, but when specific macronutrient deficiencies were tested, only the complete lack of proteins reduced IGF-1 levels. Short-term 50% CR combined with either severe protein-deficiency or ketogenic diets improved chemotoxicity resistance similarly to the standard 50% CR, but did not result in the high protection caused by STS. Notably, a high protein diet reversed the beneficial effects of short-term CR. In a subcutaneous mouse model of glioma, feeding a low protein (4% calories from protein) diet for more than 20days did not delay tumor progression once the tumor became palpable. Also, cycles of short-term (3days) 50% CR did not augment the chemotherapy efficacy of cisplatin in a murine breast cancer model. These results indicate that the protection from chemotoxicity and retardation of the progression of certain tumors achieved with fasting is not obtained with short-term calorie and/or macronutrient restriction.

Blood DNA radiosensitivity may be predictive for efficacy of experimental glioma irradiation: an animal study.

OBJECTIVE: An animal study was conducted to evaluate the -association between blood DNA radiosensitivity, assessed by determining the original S-index, and the response of experimental gliomas to irradiation. Possible modifications of the latter after administration of iron-containing water (ICW) were also explored. METHODS: The study was performed on Wistar rats with subcutaneously implanted experimental glioma-35. The tumors were locally X-irradiated with a single 15 Gy dose. ICW (60-63 mg·Fe(2+)/l) was administered in the drinking water for 3 days before treatment. The animals underwent blood sampling for analysis of the DNA concentration and leukocyte count. DNA index was estimated 3 days before irradiation and 24 h thereafter. The S-index was evaluated within 4 h before irradiation. RESULTS: The mean initial S-index in the blood samples of glioma-bearing rats was 0.73 ± 0.05. Addition of ICW in vitro resulted in a significantly increased S-index in half of the samples. In general, the irradiated rats, which had been given pretreatment ICW and demonstrated an in vitro increase of the S-index to >1.0, showed the most marked inhibition of tumor progression and the smallest tumor volume 25 days after irradiation. They also exhibited the lowest rate of lesion growth and the longest survival. CONCLUSION: Determination of the biochemical S-index and evaluation of its changes in vitro caused by ICW may be predictive of the response of experimental glioma to irradiation. Because in vivo administration of ICW was associated with a somewhat better tumor response to treatment, it may be considered as a potential radiosensitizer.

The ketogenic diet is an effective adjuvant to radiation therapy for the treatment of malignant glioma.

INTRODUCTION: The ketogenic diet (KD) is a high-fat, low-carbohydrate diet that alters metabolism by increasing the level of ketone bodies in the blood. KetoCal® (KC) is a nutritionally complete, commercially available 4:1 (fat:carbohydrate+protein) ketogenic formula that is an effective non-pharmacologic treatment for the management of refractory pediatric epilepsy. Diet-induced ketosis causes changes to brain homeostasis that have potential for the treatment of other neurological diseases such as malignant gliomas. METHODS: We used an intracranial bioluminescent mouse model of malignant glioma. Following implantation animals were maintained on standard diet (SD) or KC. The mice received 2×4 Gy of whole brain radiation and tumor growth was followed by in vivo imaging. RESULTS: Animals fed KC had elevated levels of ß-hydroxybutyrate (p = 0.0173) and an increased median survival of approximately 5 days relative to animals maintained on SD. KC plus radiation treatment were more than additive, and in 9 of 11 irradiated animals maintained on KC the bioluminescent signal from the tumor cells diminished below the level of detection (p<0.0001). Animals were switched to SD 101 days after implantation and no signs of tumor recurrence were seen for over 200 days. CONCLUSIONS: KC significantly enhances the anti-tumor effect of radiation. This suggests that cellular metabolic alterations induced through KC may be useful as an adjuvant to the current standard of care for the treatment of human malignant gliomas.