Mepitel film for the prevention and treatment of acute radiation dermatitis in breast cancer: a systematic review and meta-analysis of randomized controlled trials.

PURPOSE: This systematic review and meta-analysis aimed to evaluate the efficacy of Mepitel film in preventing or treating acute radiation dermatitis (RD) in patients with breast cancer in randomized controlled trials (RCTs). METHODS: Embase, APA PsychInfo, Journals@Ovid Full Text, Ovid MEDLINE, PubMed, and Cochrane Trials were searched until December 12, 2022, to identify RCTs on the use of Mepitel film for preventing or treating acute RD from breast cancer radiotherapy. Per-protocol analysis was used to compare outcomes, calculate pooled effect sizes, odds ratio (OR), and 95% confidence intervals (CI), and to create forest plots using random effects analysis in RevMan 5.4. RESULTS: Three RCTs were included in this review. Mepitel film significantly reduced the incidence of grade 3 RD (OR 0.15 95% CI 0.06, 0.37, p<0.0001) and grade 2 or 3 RD (OR 0.16 95% CI 0.04, 0.65, p=0.01) as scored on either the CTCAE or the RTOG scale. Additionally, Mepitel film significantly reduced RISRAS mean scores assessed by patients and combined researcher and patient (standardized mean difference (SMD) -7.59, 95% CI -14.42, -0.76, p=0.03; SMD -15.36, 95% CI -30.01, -0.71 p=0.04) but not the researcher component of the assessment tool (SMD -17.55, 95% CI -36.94, 1.84, p=0.08). CONCLUSION: Mepitel film reduced the incidence of acute RD and improved patient-reported outcomes with minimal side effects, the main one being itchiness. Future research should assess the feasibility of Mepitel film with respect to specific patient-reported outcomes such as health-related quality of life issues associated with its use.

Standardized cranberry capsules for radiation cystitis in prostate cancer patients in New Zealand: a randomized double blinded, placebo controlled pilot study.

PURPOSE: Acute radiation cystitis, inflammation of the bladder, is a common side effect in men receiving external beam radiation for prostate cancer. Although several treatments provide symptomatic relief, there is no effective treatment to prevent or treat radiation cystitis. Cranberry products have been associated with urinary tract health. This study aimed to determine the effect of highly standardized cranberry capsules (containing 72 mg proanthocyanidins [PACS]) compared with that of placebo capsules on the incidence and severity of radiation cystitis. METHODS: Forty-one men with prostate cancer participated in a double blinded randomized placebo controlled study. Men took one capsule a day at breakfast during treatment and for 2 weeks after treatment completion. Severity of urinary symptoms and the bother these caused were measured using the individual items of the urinary domain of the Modified Expanded Prostate Index Composite (EPIC). RESULTS: The incidence of cystitis was lower in men taking cranberry capsules (65%) compared with those that took placebo capsules (90%) (p = 0.058); severe cystitis was seen in 30% of men in the cranberry arm and 45% in the placebo arm (p = 0.30). Overall, the incidence of pain/burning was significantly lower in the cranberry cohort (p = 0.045). Men on the low hydration regimen who took cranberry had less pain/burning (p = 0.038), stronger urine steam (p = 0.030) and used significantly fewer pads/liners (p = 0.042), which was significantly different from those on the high hydration regimen (p = 0.028). CONCLUSION: Men receiving radiation therapy for prostate cancer may benefit from using cranberry capsules, particularly those on low hydration regimens or with baseline urinary symptoms.

Polyphenol and glucosinolate-derived AhR modulators regulate GPR15 expression on human CD4+ T cells.

Diets high in fruit and vegetables are perceived to be beneficial for intestinal homeostasis, in health as well as in the context of inflammatory bowel diseases (IBDs). Recent breakthroughs in the field of immunology have highlighted the importance of the ligand-activated transcription factor aryl hydrocarbon receptor (AhR) as a critical regulator of mucosal immunity, including the intestinal trafficking of CD4+ helper T cells, an immune cell subset implicated in a wide range of homeostatic and pathogenic processes. Specifically, the AhR has been shown to directly regulate the expression of the chemoattractant receptor G Protein-Coupled Receptor 15 (GPR15) on CD4+ T cells. GPR15 is an important gut homing marker whose expression on CD4+ T cells in the peripheral circulation is elevated in patients suffering from ulcerative colitis, raising the possibility that, in this setting, the beneficial effect of a diet rich in fruits and vegetables may be mediated through the modulation of GPR15 expression. To address this, we screened physiologically-relevant polyphenol and glucosinolate metabolites for their ability to affect both AhR activity and GPR15 expression. Our complementary approach and associated findings suggest that polyphenol and glucosinolate metabolites can regulate GPR15 expression on human CD4+ T cells in an AhR-dependent manner.

Bioenergetic and Metabolic Adaptation in Tumor Progression and Metastasis.

The ability of cancer cells to adjust their metabolism in response to environmental changes is a well-recognized hallmark of cancer. Diverse cancer and non-cancer cells within tumors compete for metabolic resources. Metabolic demands change frequently during tumor initiation, progression and metastasis, challenging our quest to better understand tumor biology and develop novel therapeutics. Vascularization, physical constraints, immune responses and genetic instability promote tumor evolution resulting in immune evasion, opportunities to breach basement membrane barriers and spread through the circulation and lymphatics. In addition, the unfolded protein response linked to the ubiquitin proteasome system is a key player in addressing stoichiometric imbalances between nuclear and mitochondrially-encoded protein subunits of respiratory complexes, and nuclear-encoded mitochondrial ribosomal protein subunits. While progressive genetic changes, some of which affect metabolic adaptability, contribute to tumorigenesis and metastasis through clonal expansion, epigenetic changes are also important and more dynamic in nature. Understanding the role of stromal and immune cells in the tumor microenvironment in remodeling cancer cell energy metabolism has become an increasingly important area of research. In this perspective, we discuss the adaptations made by cancer cells to balance mitochondrial and glycolytic energy metabolism. We discuss how hypoxia and nutrient limitations affect reductive and oxidative stress through changes in mitochondrial electron transport activity. We propose that integrated responses to cellular stress in cancer cells are central to metabolic flexibility in general and bioenergetic adaptability in particular and are paramount in tumor progression and metastasis.

The novel phloroglucinol PMT7 kills glycolytic cancer cells by blocking autophagy and sensitizing to nutrient stress.

The switch from oxidative phosphorylation to glycolytic metabolism results in cells that generate fewer reactive oxygen species (ROS) and are resistant to the intrinsic induction of apoptosis. As a consequence, glycolytic cancer cells are resistant to radiation and chemotherapeutic agents that rely on production of ROS or intrinsic apoptosis. Further, the level of glycolysis correlates with tumor invasion, making glycolytic cancer cells an important target for new therapy development. We have synthesized a novel redox-active quinone phloroglucinol derivative, PMT7. Toxicity of PMT7 was in part due to loss of mitochondrial membrane potential in treated cells with subsequent loss of mitochondrial metabolic activity. Mitochondrial gene knockout ρ0 cells, a model of highly glycolytic cancers, were only half as sensitive as the corresponding wild-type cells and metabolic pathways downstream of MET were unaffected in ρ0 cells. However, PMT7 toxicity was also due to a block in autophagy. Both wild-type and ρ0 cells were susceptible to autophagy blockade, and the resistance of ρ0 cells to PMT7 could be overcome by serum deprivation, a situation where autophagy becomes necessary for survival. The stress response class III deacetylase SIRT1 was not significantly involved in PMT7 toxicity, suggesting that unlike other chemotherapeutic drugs, SIRT1-mediated stress and survival responses were not induced by PMT7. The dependence on autophagy or other scavenging pathways makes glycolytic cancer cells vulnerable. This can be exploited by induction of energetic stress to specifically sensitize glycolytic cells to other stresses such as nutrient deprivation or potentially chemotherapy.

Review of the Accident Compensation Corporation's radiation therapy injury claims, 1 July 2009-30 June 2019.

AIM: The aim of this study was to review and report on radiation therapy injury claims lodged with the Accident Compensation Corporation (ACC) in New Zealand in the last decade. METHODS: ACC's treatment injury database was used to identify injury claims decided between 1 July 2009 and 30 June 2019. The associated structured and unstructured data, including claim lodgement information and medical records, were reviewed. RESULTS: Of 121,168 treatment injuries, only 975 (0.8%) were radiation therapy injury claims, with 519 claims accepted for cover. Most declined claims were considered "ordinary consequences of treatment" rather than treatment injuries. Of the 519 accepted claims, ACC classified 21 as fatal and eight as serious, which indicates a need for lifelong ACC support. Injuries correlated with the age and gender of the most common cancers treated with radiation therapy in New Zealand. More treatment injury claims were submitted and accepted for New Zealand European patients compared with Maori and Pasifika patients. CONCLUSION: Radiation therapy injury claims make up a very small proportion of the total number of ACC treatment injury claims. A better understanding of the claim process may assist injured individuals better by improving appropriate claim lodgement and claim acceptance rates.

Practical Approach To Explore the Effects of Polyphenols on Aryl Hydrocarbon Receptor Regulated Immune Function.

The ligand-activated aryl hydrocarbon receptor (AhR) is an important molecular regulator of immune function, whose activity can be modulated by dietary glucosinolate- and tryptophan-derived metabolites. In contrast, the potential use of polyphenols as dietary regulators of AhR-dependent immunity remains unclear. In this perspective, we discuss how cellular metabolism may alter the net effect of polyphenols on AhR, thus potentially reconciling some of the conflicting observations reported in the literature. We further provide a methodological roadmap, across the fields of immunology, metabolomics, and gut microbial ecology, to explore the potential effects of polyphenol-rich diets on AhR-regulated immune function in humans.

Cranberry capsules are not superior to placebo capsules in managing acute non-haemorrhagic radiation cystitis in prostate cancer patients: A phase III double blinded randomised placebo controlled clinical trial.

PURPOSE: Acute radiation cystitis affects the quality of life of many prostate cancer patients. A previous pilot study suggested that cranberry capsules may decrease some of the symptoms of acute radiation cystitis. Here we further test their effectiveness in a multicentre double blinded placebo-controlled clinical trial. MATERIAL AND METHODS: A total of 108 prostate cancer patients were recruited at three New Zealand hospitals between September 2016 and January 2019. Out of this cohort, 101 patients provided datasets for analysis (51 men on cranberry capsules and 50 men on beetroot-containing placebo capsules). Patients took two capsules each morning during RT and for 2 weeks after completion of RT. Three measures were used to assess cystitis severity: modified RTOG, O'Leary interstitial cystitis scale and a sensitive novel radiation induced cystitis assessment scale (RICAS). Cystitis severity was scored at baseline and weekly thereafter during RT and for two weeks after completion of RT. Radiation protocols were stratified to conventional fractionation or hypo-fractionated radiation therapy (CHHiP) to the prostate or radiation to the prostate bed. RESULTS: Cranberry capsules performed significantly worse than placebo capsules with respect to day time frequency and bladder control, using the more sensitive RICAS scale. No significant difference in cystitis severity was seen between patients receiving hypofractionation and those receiving conventional fractionation to the prostate gland. CONCLUSION: Cranberry capsules were not superior to beetroot-containing placebo capsules in managing radiation cystitis in our prostate patient cohort. RICAS may be a useful tool for measuring radiation cystitis in future studies.

A simple indirect colorimetric assay for measuring mitochondrial energy metabolism based on uncoupling sensitivity.

PURPOSE: Cancer cells rapidly adjust their balance between glycolytic and mitochondrial ATP production in response to changes in their microenvironment and to treatments like radiation and chemotherapy. Reliable, simple, high throughput assays that measure the levels of mitochondrial energy metabolism in cells are useful determinants of treatment effects. Mitochondrial metabolism is routinely determined by measuring the rate of oxygen consumption (OCR). We have previously shown that indirect inhibition of plasma membrane electron transport (PMET) by the mitochondrial uncoupler, FCCP, may also be a reliable measure of mitochondrial energy metabolism. Here, we aimed to validate these earlier findings by exploring the relationship between stimulation of oxygen consumption by FCCP and inhibition of PMET. METHODS: We measured PMET by reduction of the cell impermeable tetrazolium salt WST-1/PMS. We characterised the effect of different growth conditions on the extent of PMET inhibition by FCCP. Next, we compared FCCP-mediated PMET inhibition with FCCP-mediated stimulation of OCR using the Seahorse XF96e flux analyser, in a panel of cancer cell lines. RESULTS: We found a strong inverse correlation between stimulation of OCR and PMET inhibition by FCCP. PMET and OCR were much more severely affected by FCCP in cells that rely on mitochondrial energy production than in cells with a more glycolytic phenotype. CONCLUSION: Indirect inhibition of PMET by FCCP is a reliable, simple and inexpensive high throughput assay to determine the level of mitochondrial energy metabolism in cancer cells.

Mitochondrial DNA Affects the Expression of Nuclear Genes Involved in Immune and Stress Responses in a Breast Cancer Model.

Tumor cells without mitochondrial (mt) DNA (ρ0 cells) are auxotrophic for uridine, and their growth is supported by pyruvate. While ATP synthesis in ρ0 cells relies on glycolysis, they fail to form tumors unless they acquire mitochondria from stromal cells. Mitochondrial acquisition restores respiration that is essential for de novo pyrimidine biosynthesis and for mitochondrial ATP production. The physiological processes that underpin intercellular mitochondrial transfer to tumor cells lacking mtDNA and the metabolic remodeling and restored tumorigenic properties of cells that acquire mitochondria are not well understood. Here, we investigated the changes in mitochondrial and nuclear gene expression that accompany mtDNA deletion and acquisition in metastatic murine 4T1 breast cancer cells. Loss of mitochondrial gene expression in 4T1ρ0 cells was restored in cells recovered from subcutaneous tumors that grew from 4T1ρ0 cells following acquisition of mtDNA from host cells. In contrast, the expression of most nuclear genes that encode respiratory complex subunits and mitochondrial ribosomal subunits was not greatly affected by loss of mtDNA, indicating ineffective mitochondria-to-nucleus communication systems for these nuclear genes. Further, analysis of nuclear genes whose expression was compromised in 4T1ρ0 cells showed that immune- and stress-related genes were the most highly differentially expressed, representing over 70% of those with greater than 16-fold higher expression in 4T1 compared with 4T1ρ0 cells. The monocyte recruiting chemokine, Ccl2, and Psmb8, a subunit of the immunoproteasome that generates MHCI-binding peptides, were the most highly differentially expressed. Early monocyte/macrophage recruitment into the tumor mass was compromised in 4T1ρ0 cells but recovered before mtDNA could be detected. Taken together, our results show that mitochondrial acquisition by tumor cells without mtDNA results in bioenergetic remodeling and re-expression of genes involved in immune function and stress adaptation.

Mepitel Film is superior to Biafine cream in managing acute radiation-induced skin reactions in head and neck cancer patients: a randomised intra-patient controlled clinical trial.

INTRODUCTION: We previously showed that Mepitel Film decreased the severity of acute radiation-induced skin reactions in head and neck cancer patients. In the current study, we compared the effect of Mepitel Film and Biafine cream on skin reaction severity in a larger cohort of head and neck cancer patients. METHODS: A total of 44 head and neck cancer patients were recruited with 39 patients contributing full data sets for analysis. Patients received a dose of 50 Gy in 25 fractions to the bilateral lymph nodes in the neck. Left and right lymph node areas were randomised to either Mepitel Film or Biafine cream, applied prophylactically. Skin reaction severity was measured using Radiation-Induced Skin Reaction Assessment Scale (RISRAS) and expanded Radiation Oncology group (RTOG) grades. Skin dose was measured using gafchromic Film. RESULTS: Skin reaction severity (combined RISRAS score) underneath Mepitel Film was decreased by 30% (P < 0.001) and moist desquamation rates by 41% (P < 0.001). Skin dose underneath Mepitel Film and Biafine cream was similar (P = 0.925) and unlikely to have affected skin reaction severity. The vast majority (80%) of patients preferred Mepitel Film over Biafine cream. Negative aspects of Mepitel Film included poor adherence (11/39) and discomfort (16/39) during hot weather and showering and itchy skin underneath Mepitel Film (12/39). CONCLUSIONS: Mepitel Film was superior to Biafine cream in reducing the severity of acute radiation-induced skin reactions and moist desquamation incidence in our head and neck patient cohort.

The anti-cancer drug, phenoxodiol, kills primary myeloid and lymphoid leukemic blasts and rapidly proliferating T cells.

BACKGROUND: The redox-active isoflavene anti-cancer drug, phenoxodiol, has previously been shown to inhibit plasma membrane electron transport and cell proliferation and promote apoptosis in a range of cancer cell lines and in anti-CD3/anti-CD28-activated murine splenocytes but not in non-transformed WI-38 cells and human umbilical vein endothelial cells. DESIGN AND METHODS: We determined the effects of phenoxodiol on plasma membrane electron transport, MTT responses and viability of activated and resting human T cells. In addition, we evaluated the effect of phenoxodiol on the viability of leukemic cell lines and primary myeloid and lymphoid leukemic blasts. RESULTS: We demonstrated that phenoxodiol inhibited plasma membrane electron transport and cell proliferation (IC(50) 46 microM and 5.4 microM, respectively) and promoted apoptosis of rapidly proliferating human T cells but did not affect resting T cells. Phenoxodiol also induced apoptosis in T cells stimulated in HLA-mismatched allogeneic mixed lymphocyte reactions. Conversely, non-proliferating T cells in the mixed lymphocyte reaction remained viable and could be restimulated in a third party mixed lymphocyte reaction, in the absence of phenoxodiol. In addition, we demonstrated that leukemic blasts from patients with primary acute myeloid leukemia (n=22) and acute lymphocytic leukemia (n=8) were sensitive to phenoxodiol. The lymphocytic leukemic blasts were more sensitive than the myeloid leukemic blasts to 10 muM phenoxodiol exposure for 24h (viability of 23+/-4% and 64+/-5%, respectively, p=0.0002). CONCLUSIONS: The ability of phenoxodiol to kill rapidly proliferating lymphocytes makes this drug a promising candidate for the treatment of pathologically-activated lymphocytes such as those in acute lymphoid leukemia, or diseases driven by T-cell proliferation such as auto-immune diseases and graft-versus-host disease.

Cell surface oxygen consumption: a major contributor to cellular oxygen consumption in glycolytic cancer cell lines.

Oxygen consumption for bioenergetic purposes has long been thought to be the prerogative of mitochondria. Nevertheless, mitochondrial gene knockout (rho(0)) cells that are defective in mitochondrial respiration require oxygen for growth and consume oxygen at the cell surface via trans-plasma membrane electron transport (tPMET). This raises the possibility that cell surface oxygen consumption may support glycolytic energy metabolism by reoxidising cytosolic NADH to facilitate continued glycolysis. In this paper we determined the extent of cell surface oxygen consumption in a panel of 19 cancer cell lines. Non-mitochondrial (myxothiazol-resistant) oxygen consumption was demonstrated to consist of at least two components, cell surface oxygen consumption (inhibited by extracellular NADH) and basal oxygen consumption (insensitive to both myxothiazol and NADH). The extent of cell surface oxygen consumption varied considerably between parental cell lines from 1% to 80% of total oxygen consumption rates. In addition, cell surface oxygen consumption was found to be associated with low levels of superoxide production and to contribute significantly (up to 25%) to extracellular acidification in HL60rho(0) cells. In summary, cell surface oxygen consumption contributes significantly to total cellular oxygen consumption, not only in rho(0) cells but also in mitochondrially competent tumour cell lines with glycolytic metabolism.

Glycolytic metabolism confers resistance to combined all-trans retinoic acid and arsenic trioxide-induced apoptosis in HL60rho0 cells.

Glycolytic cancers are resistant to many forms of chemotherapy and some respond poorly to differentiation therapies. Here, we investigate the effects of exposure to all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) on differentiation and cell survival in the human leukemia cell line, HL60 and its mitochondrial gene knockout mutant, HL60rho0. Glycolytic HL60rho0 cells exposed to single and combined treatments expressed less CD15, in most cases, but produced a stronger respiratory burst than parental HL60 cells. HL60rho0 cells were also significantly more resistant to apoptosis after combined ATO+ATRA treatment compared with HL60 cells, and this was associated with failure to upregulate Fas expression.

Intercellular Communication in Tumor Biology: A Role for Mitochondrial Transfer.

Intercellular communication between cancer cells and other cells in the tumor microenvironment plays a defining role in tumor development. Tumors contain infiltrates of stromal cells and immune cells that can either promote or inhibit tumor growth, depending on the cytokine/chemokine milieu of the tumor microenvironment and their effect on cell activation status. Recent research has shown that stromal cells can also affect tumor growth through the donation of mitochondria to respiration-deficient tumor cells, restoring normal respiration. Nuclear and mitochondrial DNA mutations affecting mitochondrial respiration lead to some level of respiratory incompetence, forcing cells to generate more energy by glycolysis. Highly glycolytic cancer cells tend to be very aggressive and invasive with poor patient prognosis. However, purely glycolytic cancer cells devoid of mitochondrial DNA cannot form tumors unless they acquire mitochondrial DNA from adjacent cells. This perspective article will address this apparent conundrum of highly glycolytic cells and cover aspects of intercellular communication between tumor cells and cells of the microenvironment with particular emphasis on intercellular mitochondrial transfer.

Review of the patient positioning reproducibility in head-and-neck radiotherapy using Statistical Process Control.

BACKGROUND AND PURPOSE: A remarkable improvement in patient positioning was observed after the implementation of various process changes aiming to increase the consistency of patient positioning throughout the radiotherapy treatment chain. However, no tool was available to describe these changes over time in a standardised way. This study reports on the feasibility of Statistical Process Control (SPC) to highlight changes in patient positioning accuracy and facilitate correlation of these changes with the underlying process changes. MATERIALS AND METHODS: Metrics were designed to quantify the systematic and random patient deformation as input for the SPC charts. These metrics were based on data obtained from multiple local ROI matches for 191 patients who were treated for head-and-neck cancer during the period 2011-2016. RESULTS: SPC highlighted a significant improvement in patient positioning that coincided with multiple intentional process changes. The observed improvements could be described as a combination of a reduction in outliers and a systematic improvement in the patient positioning accuracy of all patients. CONCLUSION: SPC is able to track changes in the reproducibility of patient positioning in head-and-neck radiation oncology, and distinguish between systematic and random process changes. Identification of process changes underlying these trends requires additional statistical analysis and seems only possible when the changes do not overlap in time.

The effect of Mepitel Film on acute radiation-induced skin reactions in head and neck cancer patients: a feasibility study.

OBJECTIVE: Mepitel Film significantly decreases acute radiation-induced skin reactions in breast cancer patients. Here we investigated the feasibility of using Mepitel Film in head and neck cancer patients (ACTRN12614000932662). METHODS: Out of a total of 36 head and neck cancer patients from New Zealand (NZ) (n = 24) and China (n = 12) recruited between June 2015 and December 2016, 33 patients complied with protocol. Of these, 11 NZ patients followed a management protocol; 11 NZ patients and 11 Chinese patients followed a prophylactic protocol. An area of the neck receiving a homogenous radiation dose of > 35 Gy was divided into two equal halves; one half was randomized to Film and the other to either Sorbolene cream (NZ) or Biafine cream (China). Skin reaction severity was measured by Radiation Induced Skin Reaction Assessment Scale and expanded Radiation Therapy Oncology Group toxicity criteria. Skin dose was measured by thermoluminescent dosimeters or gafchromic film. RESULTS: Film decreased overall skin reaction severity (combined Radiation Induced Skin Reaction Assessment Scale score) by 29% and moist desquamation rates by 37% in the Chinese cohort and by 27 and 28%, respectively in the NZ cohort. Mepitel Film did not affect head movements but did not adhere well to the skin, particularly in males with heavy beard stubble, and caused itchiness, particularly in Chinese patients. CONCLUSION: Mepitel Film reduced acute radiation-induced skin reactions in our head and neck cancer patients, particularly in patients without heavy stubble. Advances in knowledge: This is the first study to confirm the feasibility of using Mepitel Film in head and neck cancer patients.

Plasma membrane electron transport: a new target for cancer drug development.

The view that mitochondrial electron transport is the only site of aerobic respiration and the primary bioenergetic pathway in mammalian cells is well established in the literature. Although this paradigm is widely accepted for most tissues, the situation is less clear for proliferating cells. Increasing evidence indicates that glycolytic ATP production contributes substantially to fulfilling the energy requirements of rapidly dividing somatic cells, many tumour cells, and self-renewing stem cells in hypoxic environments. Glycolytic cells have been shown to consume oxygen at the cell surface via plasma membrane electron transport (PMET), a process that oxidises intracellular NADH, supports glycolytic ATP production and may contribute to aerobic energy production. PMET, as determined by reduction of a cell-impermeable tetrazolium dye, is highly active in rapidly-dividing tumour cell lines, where it ameliorates intracellular reductive stress, originating from the mitochondrial TCA cycle. Thus, mitochondrial NADH production is linked to dye reduction outside the cell via the malate-aspartate shuttle. PMET activity increases several-fold under hypoxic conditions, consistent with the view that oxygen competes for electrons from this PMET system. In addition, rho(o) cells that lack mitochondrial electron transport are characterised by elevated PMET presumably to recycle NADH, a role traditionally assumed by lactate dehydrogenase. PMET presents an excellent target for developing novel anticancer drugs that exploit its unique plasma membrane localisation. We propose that PMET is a ubiquitous, high-capacity acute NADH redox-regulatory system responsible for maintaining the mitochondrial NADH/NAD+ ratio. Blocking this pathway compromises the viability of rapidly proliferating cells that rely on PMET.

High Dose Ascorbate Causes Both Genotoxic and Metabolic Stress in Glioma Cells.

We have previously shown that exposure to high dose ascorbate causes double stranded breaks (DSBs) and a build-up in S-phase in glioblastoma (GBM) cell lines. Here we investigated whether or not this was due to genotoxic stress as well as metabolic stress generated by exposure to high dose ascorbate, radiation, ascorbate plus radiation and H2O2 in established and primary GBM cell lines. Genotoxic stress was measured as phosphorylation of the variant histone protein, H2AX, 8-oxo-7,8-dihydroguanine (8OH-dG) positive cells and cells with comet tails. Metabolic stress was measured as a decrease in NADH flux, mitochondrial membrane potential (by CMXRos), ATP levels (by ATP luminescence) and mitochondrial superoxide production (by mitoSOX). High dose ascorbate, ascorbate plus radiation, and H2O2 treatments induced both genotoxic and metabolic stress. Exposure to high dose ascorbate blocked DNA synthesis in both DNA damaged and undamaged cell of ascorbate sensitive GBM cell lines. H2O2 treatment blocked DNA synthesis in all cell lines with and without DNA damage. DNA synthesis arrest in cells with damaged DNA is likely due to both genotoxic and metabolic stress. However, arrest in DNA synthesis in cells with undamaged DNA is likely due to oxidative damage to components of the mitochondrial energy metabolism pathway.

Functional Mitochondria in Health and Disease.

The ability to rapidly adapt cellular bioenergetic capabilities to meet rapidly changing environmental conditions is mandatory for normal cellular function and for cancer progression. Any loss of this adaptive response has the potential to compromise cellular function and render the cell more susceptible to external stressors such as oxidative stress, radiation, chemotherapeutic drugs, and hypoxia. Mitochondria play a vital role in bioenergetic and biosynthetic pathways and can rapidly adjust to meet the metabolic needs of the cell. Increased demand is met by mitochondrial biogenesis and fusion of individual mitochondria into dynamic networks, whereas a decrease in demand results in the removal of superfluous mitochondria through fission and mitophagy. Effective communication between nucleus and mitochondria (mito-nuclear cross talk), involving the generation of different mitochondrial stress signals as well as the nuclear stress response pathways to deal with these stressors, maintains bioenergetic homeostasis under most conditions. However, when mitochondrial DNA (mtDNA) mutations accumulate and mito-nuclear cross talk falters, mitochondria fail to deliver critical functional outputs. Mutations in mtDNA have been implicated in neuromuscular and neurodegenerative mitochondriopathies and complex diseases such as diabetes, cardiovascular diseases, gastrointestinal disorders, skin disorders, aging, and cancer. In some cases, drastic measures such as acquisition of new mitochondria from donor cells occurs to ensure cell survival. This review starts with a brief discussion of the evolutionary origin of mitochondria and summarizes how mutations in mtDNA lead to mitochondriopathies and other degenerative diseases. Mito-nuclear cross talk, including various stress signals generated by mitochondria and corresponding stress response pathways activated by the nucleus are summarized. We also introduce and discuss a small family of recently discovered hormone-like mitopeptides that modulate body metabolism. Under conditions of severe mitochondrial stress, mitochondria have been shown to traffic between cells, replacing mitochondria in cells with damaged and malfunctional mtDNA. Understanding the processes involved in cellular bioenergetics and metabolic adaptation has the potential to generate new knowledge that will lead to improved treatment of many of the metabolic, degenerative, and age-related inflammatory diseases that characterize modern societies.