Randy Burd

Hormesis and synergy: pathways and mechanisms of quercetin in cancer prevention and management

Quercetin is a unique dietary polyphenol because it can exert biphasic dose-responses on cells depending on its concentration. Cancer preventative effects of quercetin are observed at concentrations of approximately 1-40 microM and are likely mediated by quercetins antioxidant properties. Pro-oxidant effects are present at cellular concentrations of 40-100 microM. However, at higher concentrations, many novel pathways in addition to ROS contribute to its effects. The potent bioactivity of quercetin has led to vigorous study of this compound and revealed numerous pathways that could interact synergistically to prevent or treat cancer. The effect of intake and concentration on emerging pathways and how they may interact are discussed in this review.

Radiation-induced salivary gland dysfunction results from p53-dependent apoptosis.

PURPOSEnRadiotherapy for head-and-neck cancer causes adverse secondary side effects in the salivary glands and results in diminished quality of life for the patient. A previous in vivo study in parotid salivary glands demonstrated that targeted head-and-neck irradiation resulted in marked increases in phosphorylated p53 (serine(18)) and apoptosis, which was suppressed in transgenic mice expressing a constitutively active mutant of Akt1 (myr-Akt1).nnnMETHODS AND MATERIALSnTransgenic and knockout mouse models were exposed to irradiation, and p53-mediated transcription, apoptosis, and salivary gland dysfunction were analyzed.nnnRESULTSnThe proapoptotic p53 target genes PUMA and Bax were induced in parotid salivary glands of mice at early time points after therapeutic radiation. This dose-dependent induction requires expression of p53 because no radiation-induced expression of PUMA and Bax was observed in p53-/- mice. Radiation also induced apoptosis in the parotid gland in a dose-dependent manner, which was p53 dependent. Furthermore, expression of p53 was required for the acute and chronic loss of salivary function after irradiation. In contrast, apoptosis was not induced in p53-/- mice, and their salivary function was preserved after radiation exposure.nnnCONCLUSIONSnApoptosis in the salivary glands after therapeutic head-and-neck irradiation is mediated by p53 and corresponds to salivary gland dysfunction in vivo.

Quercetin as a systemic chemopreventative agent: structural and functional mechanisms.

There is a growing focus on diet and the use of naturally abundant compounds as supplements because their properties have many potential health benefits with minimal side effects. The flavonol-type flavonoid quercetin has increased in popularity because it is a highly studied, multidimensional bioactive compound that possesses both antioxidant properties and the ability to modulate signal transduction pathways. Direct antioxidant properties may play a role in the abrogation of both DNA damage, but potentially of more importance quercetin, can also target multiple signaling pathways associated with oncogenesis and tumor progression, which include DNA damage, inflammation and obesity. Quercetin can also upregulate proteins that abrogate free radical damage, such as p53. The concurrent targeting of quercetins multiple bioactivities presents a potent chemopreventative strategy, but because bioavailability of quercetin is poor it will be necessary to develop quercetin analogs to maximize the full chemopreventative potential of the compound. This review will explore the structural and mechanistic properties of quercetin as they relate to its ability to act as a chemopreventative compound. A better understanding of quercetins mechanistic properties could aid in the rational design of more potent or bioavailable flavonol-type compounds.

IGF1 activates cell cycle arrest following irradiation by reducing binding of ΔNp63 to the p21 promoter

Radiotherapy for head and neck tumors often results in persistent loss of function in salivary glands. Patients suffering from impaired salivary function frequently terminate treatment prematurely because of reduced quality of life caused by malnutrition and other debilitating side-effects. It has been previously shown in mice expressing a constitutively active form of Akt (myr-Akt1), or in mice pretreated with IGF1, apoptosis is suppressed, which correlates with maintained salivary gland function measured by stimulated salivary flow. Induction of cell cycle arrest may be important for this protection by allowing cells time for DNA repair. We have observed increased accumulation of cells in G2/M at acute time-points after irradiation in parotid glands of mice receiving pretreatment with IGF1. As p21, a transcriptional target of the p53 family, is necessary for maintaining G2/M arrest, we analyzed the roles of p53 and p63 in modulating IGF1-stimulated p21 expression. Pretreatment with IGF1 reduces binding of ΔNp63 to the p21 promoter after irradiation, which coincides with increased p53 binding and sustained p21 transcription. Our data indicate a role for ΔNp63 in modulating p53-dependent gene expression and influencing whether a cell death or cell cycle arrest program is initiated.

Restoration of radiation therapy-induced salivary gland dysfunction in mice by post therapy IGF-1 administration

BackgroundRadiotherapy for head and neck cancer results in severe and chronic salivary gland dysfunction in most individuals. This results in significant side effects including xerostomia, dysphagia, and malnutrition which are linked to significant reductions in patients quality of life. Currently there are few xerostomia treatment approaches that provide long-term results without significant side effects. To address this problem we investigated the potential for post-therapeutic IGF-1 to reverse radiation-induced salivary gland dysfunction.MethodsFVB mice were treated with targeted head and neck radiation and significant reductions in salivary function were confirmed 3 days after treatment. On days 4-8 after radiation, one group of mice was injected intravenously with IGF-1 while a second group served as a vehicle control. Stimulated salivary flow rates were evaluated on days 30, 60, and 90 and histological analysis was performed on days 9, 30, 60, and 90.ResultsIrradiated animals receiving vehicle injections have 40-50% reductions in stimulated salivary flow rates throughout the entire time course. Mice receiving injections of IGF-1 have improved stimulated salivary flow rates 30 days after treatment. By days 60-90, IGF-1 injected mice have restored salivary flow rates to unirradiated control mice levels. Parotid tissue sections were stained for amylase as an indicator of functioning acinar cells and significant reductions in total amylase area are detected in irradiated animals compared to unirradiated groups on all days. Post-therapeutic injections of IGF-1 results in increased amylase-positive acinar cell area and improved amylase secretion. Irradiated mice receiving IGF-1 show similar proliferation indices as untreated mice suggesting a return to tissue homeostasis.ConclusionsPost-therapeutic IGF-1 treatment restores salivary gland function potentially through normalization of cell proliferation and improved expression of amylase. These findings could aid in the rational design of therapy protocols or drugs for the treatment of radiation-induced salivary gland dysfunction in patients who have completed their anti-cancer therapies.

Quercetin Selectively Inhibits Bioreduction and Enhances Apoptosis in Melanoma Cells That Overexpress Tyrosinase

Abstract Tyrosinase is expressed in melanoma cells and catalyzes the formation of 3,3′,4′,5,7-pentahydroxyflavone (quercetin) into reactive quinone species and subsequent glutathionyl adducts. Therefore, we examined the effect of quercetin metabolism on the glutathione (GSH) bioreduction pathway and cell viability in DB-1 melanoma cells that express varying levels of tyrosinase (Tyr+). In a cell-free system, GSH was significantly decreased by quercetin, which coincided with the formation of glutathionyl adducts. In Tyr+ clones, quercetin decreased bioreduction capacity and increased reactive oxygen species (ROS) to a greater degree compared to control cells. The antioxidant/electrophile response element-induced enzymes, glutathione-S-transferase (GST), and nicotinamide adenine dinucleotide phosphate:quinone oxidoreductase 1 were expressed at high levels in Tyr+ cells and contributed to pro-oxidant quercetin metabolism. The basal level of ROS and apoptosis was higher in Tyr+ cells and were selectively increased after exposure to quercetin. The increase in apoptosis following quercetin exposure was p53/Bax mediated and correlated with a decrease in GST-driven bioreduction capacity and an increase in ROS. In conclusion, quercetin can selectively sensitize Tyr+ expressing melanoma cells to apoptosis and may serve as an adjuvant to chemotherapy by enhancing cell death and interfering with GST-mediated drug resistance.

Prevention of Radiation-Induced Salivary Gland Dysfunction Utilizing a CDK Inhibitor in a Mouse Model

Background Treatment of head and neck cancer with radiation often results in damage to surrounding normal tissues such as salivary glands. Permanent loss of function in the salivary glands often leads patients to discontinue treatment due to incapacitating side effects. It has previously been shown that IGF-1 suppresses radiation-induced apoptosis and enhances G2/M arrest leading to preservation of salivary gland function. In an effort to recapitulate the effects of IGF-1, as well as increase the likelihood of translating these findings to the clinic, the small molecule therapeutic Roscovitine, is being tested. Roscovitine is a cyclin-dependent kinase inhibitor that acts to transiently inhibit cell cycle progression and allow for DNA repair in damaged tissues. Methodology/Principal Findings Treatment with Roscovitine prior to irradiation induced a significant increase in the percentage of cells in the G2/M phase, as demonstrated by flow cytometry. In contrast, mice treated with radiation exhibit no differences in the percentage of cells in G2/M when compared to unirradiated controls. Similar to previous studies utilizing IGF-1, pretreatment with Roscovitine leads to a significant up-regulation of p21 expression and a significant decrease in the number of PCNA positive cells. Radiation treatment leads to a significant increase in activated caspase-3 positive salivary acinar cells, which is suppressed by pretreatment with Roscovitine. Administration of Roscovitine prior to targeted head and neck irradiation preserves normal tissue function in mouse parotid salivary glands, both acutely and chronically, as measured by salivary output. Conclusions/Significance These studies suggest that induction of transient G2/M cell cycle arrest by Roscovitine allows for suppression of apoptosis, thus preserving normal salivary function following targeted head and neck irradiation. This could have an important clinical impact by preventing the negative side effects of radiation therapy in surrounding normal tissues.

Tyrosinase Overexpression Promotes ATM-Dependent p53 Phosphorylation by Quercetin and Sensitizes Melanoma Cells to Dacarbazine

Dacarbazine (DTIC) has been used for the treatment of melanoma for decades. However, monotherapy with this chemotherapeutic agent results only in moderate response rates. To improve tumor response to DTIC current clinical trials in melanoma focus on combining a novel targeted agent with chemotherapy. Here, we demonstrate that tyrosinase which is commonly overexpressed in melanoma activates the bioflavonoid quercetin (Qct) and promotes an ataxia telangiectasia mutated (ATM)-dependent DNA damage response. This response sensitizes melanoma cells that overexpress tyrosinase to DTIC. In DB-1 melanoma cells that overexpress tyrosinase (Tyr cells), the threshold for phosphorylation of ATM and p53 at serine 15 was observed at a low dose of Qct (25 μM) when compared to the mock transfected pcDNA3 cells, which required a higher dose (75 μM). Both pcDNA3 and Tyr DB-1 cells demonstrated similar increases in phosphorylation of p53 at other serine sites, but in the Tyr cells, DNApk expression was found to be reduced compared to control cells, indicating a shift towards an ATM-mediated response. The DB-1 control cells were resistant to DTIC, but were sensitized to apoptosis with high dose Qct, while Tyr cells were sensitized to DTIC with low or high dose Qct. Qct also sensitized SK Mel 5 (p53 wildtype) and 28 (p53 mutant) cells to DTIC. However, when SK Mel 5 cells were transiently transfected with tyrosinase and treated with Qct plus DTIC, SK Mel 5 cells demonstrated a more than additive induction of apoptosis. Therefore, this study demonstrates that tyrosinase overexpression promotes an ATM-dependent p53 phosphorylation by Qct treatment and sensitizes melanoma cells to dacarbazine. In conclusion, these results suggest that Qct or Qct analogues may significantly improve DTIC response rates in tumors that express tyrosinase.

The promise of digital (mobile) health in cancer prevention and treatment

Technological advances in how we exchange and analyze information are having a broad impact across all facets of modern medicine. Indeed, the mobile health (mHealth) paradigm is providing the format for instantaneous exchange of information between health providers and their patients, creating a potential virtual forum consisting of the patient’s medical team and expert opinion worldwide. This is particularly important in oncology where mHealth is promising to provide the platform upon which patients become more committed to cancer-preventative lifestyles. There is now a framework for a revolutionary dynamic to emerge within the patient care model that will improve self-health advocacy and, ultimately, clinical outcomes. Currently, mHealth is an indispensable modality for providing access to care in remote parts of the world and it is already being used to shore up inefficiencies in clinical trial management. The growing capacity to store and analyze large amounts of data is making the mHealth arsenal a necessary addition in the genomic age of clinical medicine. Digital networks will drive health

Autophagy Correlates with Maintenance of Salivary Gland Function Following Radiation

The current standard of care for head and neck cancer includes surgical resection of the tumor followed by targeted head and neck radiation. This radiotherapy results in a multitude of negative side effects in adjacent normal tissues. Autophagy is a cellular mechanism that could be targeted to ameliorate these side effects based on its role in cellular homeostasis. In this study, we utilized Atg5f/f;Aqp5-Cre mice which harbor a conditional knockout of Atg5, in salivary acinar cells. These autophagy-deficient mice display increased radiosensitivity. Treatment of wild-type mice with radiation did not robustly induce autophagy following radiotherapy, however, using a model of preserved salivary gland function by IGF-1-treatment prior to irradiation, we demonstrate increased autophagosome formation 6–8u2005hours following radiation. Additionally, administration of IGF-1 to Atg5f/f;Aqp5-Cre mice did not preserve physiological function. Thus, autophagy appears to play a beneficial role in salivary glands following radiation and pharmacological induction of autophagy could alleviate the negative side effects associated with therapy for head and neck cancer.